Biology 1080- Post Midterm Reading Notes Only!
(other notes from before midterm are written out, lecture notes will be written out)
3A(iv)- The Endocrine System
Functions and Mechanisms of Hormones
Our bodies contain two types of glands: exocrine glands and endocrine glands.
Endocrine glands- are made of secretory cells that release their products called hormones
Hormones move from the cells that produced them to the fluid just outside the cells, where the diffuse directly into
Endocrine system- consists of endocrine glands and of organs that contain some endocrine tissue; these also have
Major endocrine glands: pituitary gland, thyroid gland, parathyroid gland, adrenal glands, pineal gland.
Organs with endocrine tissues: hypothalamus, thymus, pancreas, ovaries, testes, heart and placenta (also
organs of the digestive and urinary systems such as stomach, small intestine and kidneys)
The main function of the endocrine system is like the nervous system, to regulate and coordinate other body
systems and thereby maintain homeostasis. It is the more leisurely system, often coordinating and regulating
longer term processes such as growth, development and reproduction (the nervous system is the rapid system of
Parts of the Endocrine System
Posterior Lobe of the Pituitary Gland (Adrenal Cortex)
Antidiuretic hormone (ADH) Glucocorticoids
Promotes water reabsorption by the kidneys Stimulate glucose synthesis and conservation
Oxytocin (OT) Inhibit the inflammatory response
Stimulates milk ejection from the breasts Mineralcorticoids
Stimulates uterine contractions during childbirth Increase sodium reabsorption by kidneys
Anterior Lobe of the Pituitary Gland
Increase potassium excretion by kidneys
Growth hormone (GH) Gonadocorticoids
Stimulates growth Insignificant effects in adulthood, relative to secretion
Stimulates breakdown of fat by gonads
Prolactin (PRL) (Adrenal Medulla)
Stimulates synthesis and release of thyroid hormones Epinephrine
Thyroid-stimulating Hormone (TSH) Fight or flight response to stress
Stimulates synthesis and release of thyroid hormones Norepinephrine
Adrenocorticotropic hormone (ACTH) Fight or flight response to stress
Stimulates synthesis and release of hormones from Thyroid Gland
adrenal glands Thyroid hormone (TH)
Follicle-stimulating hormone (FSH) Regulates metabolism and heat production
Stimulates gamete production Promotes development and function of nervous,
Stimulates secretion of estrogen by ovaries muscular, skeletal and reproductive systems
Lutenizing hormone (LH) Calcitonin (CT)
Causes ovulation and stimulates ovaries to secrete Decreases blood levels of calcium and phosphate
estrogen and progesterone Pancreas
Stimulates testes to synthesize and secrete Glucagon
testosterone Increases blood glucose level
Pineal Gland Insulin
Melatonin Decreases blood glucose level
Reduces jet lag and promotes sleep Testis
Parathyroid Glands Testosterone/Androgens
Parathyroid hormone (PTH) Develop male secondary sex characteristics
Increases blood levels of calcium Uterus
Thymus Gland Contains plecenta when pregnant
Thymopoietin thymosin Ovary
Promote maturation of white blood cells Estrogen and progesterone
Adrenal Gland Develop female secondary sex characteristi
Hormones as Chemical Messengers
Hormones- Chemical messengers of the endocrine system They are released in very small amounts by the cells of endocrine glands and tissues and enter the bloodstream to
travel throughout the body. They come in contact with A LOT of cells, but only affect a target cell. Target cells have
receptors- protein molecules that recognize and bind to specific hormones. Once a hormone binds to its specific
receptor, this hormone receptor complex begins to target its effects on cells. Other cells that don’t have these
hormone-specific receptors are not affected by the hormone.
Hormones are either lipid soluble or water soluble. Lipid soluble hormones include steroid hormones
derived from cholesterol (ovaries, testes and adrenal glands are the main organs that secrete steroid hormones).
Lipid soluble hormones move easily through any cell’s plasma membrane because it is a lipid bilayer. Once inside a
target cell, a steroid hormone combines with receptor molecules in the cytoplasm then moves into the nucleus
where it attaches to DNA and activates certain genes. Usually, this leads to the target cell to synthesize specific
proteins including enzymes that stimulate or inhibit particular metabolic pathways.
Water-soluble hormones such as protein or peptide hormones, cannot pass through the lipid bilayer and therefore
cannot enter target cells themselves. Instead, the hormone (in this situation is called a first messenger) binds to a
receptor on the plasma membrane of the target cell. This binding activates a molecule- called the second
messenger- in the cytoplasm. Second messengers are molecules within the cell that influence the activity of
enzymes and the overall activity of the cell, to produce the effect of the hormone. Cyclic adenosine
monophosphate (cAMP) is a common second messenger. Binding of epinephrine to a receptor on the plasma
membrane of a liver cells prompts the conversion of ATP to cAMP within the cell. cAMP then activates an enzyme
within the cell (a protein kinase) which in turn activates another enzyme, and so on. The end result of this enzyme
cascade is the activation of an enzyme that catalyzes the breakdown of glycogen to glucose within the liver cell.
These hormones instead of inhibiting or stimulating the synthesis of proteins by a cell, activate proteins that are
already present in the cell.
Feedback Mechanisms and Secretion of Hormones
Stimuli that cause endocrine glands to manufacture and release hormones include other hormones, signals from
the nervous system and changes in the levels of certain ions (Ca+) or nutrients (glucose) in the blood.
Recall that homeostasis keeps the body’s internal environment relatively constant. Such constancy most
often is achieved through negative feedback mechanisms, which the outcome of a process feeds back to the
system, shutting the process down. These mechanisms regulate the secretion of some hormones. Typically, a gland
releases a hormone, then rising blood levels of that hormone inhibit its further release.
Secretion of some hormones is sometimes regulated by positive feedback loops in which the outcome of a process
feeds back to the system and stimulates the process to continue. For example, childbirth, the pituitary gland
releases the hormone oxytocin which stimulates the uterus to contract which then stimulates the release of more
oxytocin, which stimulates even more contractions. Stimulates rather than inhibits. Eventually, some change breaks
the positive feedback cycle.
Sometimes the nervous system overrides the controls of the endocrine system. For example, during times of
exreme stress the nervous system overrides the mechanism controlling the release of insulin. The nervous system
permits levels of blood glucose to rise much higher than normal. This response gives cells access to the large
amounts of energy needed to cope with stress.
Interactions between Hormones
Interactions may be antagonistic, synergistic or permissive. When the effect of one hormone opposes that of
another hormone, the interaction is antagonistic. Example, glucagon and insulin. Glucagon increases the glucose
level and insulin decreases it.
During synergistic, the response of a tissue to combination of two hormones is much greater than its response to
either individual hormone. Example, epinephrine and glucagon both prompt the liver to release glucose and when they act together, the amount of glucose released by the liver is greater than the combined amount released by
each hormone acting alone.
During permissive, one hormone must be present for another hormone to exert its effects. For example, thyroid
hormone must be present for aldosterone to stimulate reabsorption of sodium within kidney tubules.
Pituitary gland is a stalk that connects the pituitary gland to the hypothalamus, the area of the brain that regulates
physiological responses like body temperature. The pituitary gland has two lobes (looks like balls) the anterior and
posterior lobes, which differ in size and release different hormones.
The anterior lobe is larger. A network of capillaries runs from the base of the hypothalamus through the
stalk. The capillaries connect to veins that lead into more capillaries in the anterior lobe. This circulatory connection
allows hormones of the hypothalamus to control the secretion of hormones from the anterior lobe. Nerve cells in
the hypothalamus synthesize and secrete hormones that travel by the blood stream to the anterior lobe, where
they stimulate or inhibit hormone secretion. Substances produced by the hypothalamus that stimulate hormone
secretion by the anterior pituitary are called releasing hormones and those that inhibit are called inhibiting
hormones. The anterior pituitary responds to releasing and inhibiting hormones from the hypothalamus by
modifying its own synthesis and secretion of six hormones, growth hormone (GH), prolactin (PRL), thyroid-
stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle stimulating hormone (FSH) and lutenizing
The primary function of growth hormone is to stimulate growth through increases in cell size and rates of
cell division. Target cells are quite diverse. Most susceptible are cells of bone, muscle and cartilage. GH also plays a
role in glucose conservation by making fats more available as a source of fuel. Two hormones of the hypothalamus
regulate the synthesis and release of GH. GHRH stimulates the release and GHIH inhibits it. Through the actions of
these two hormones, the levels of GH in the body are normally maintained within an appropriate range. Excesses
or deficiencies can dramatically affect growth (gigantism, acromegaly (widening) both decrease life span and
dwarfism). Can be caused by tumours on anterior pituitary.
Prolactin (PRL) stimulates the mammary glands to produce milk (oxytocin secreted from the posterior
causes the ducts of the mammary glands to eject milk). It interferes with female sex hormones and can cause
lactating mothers to not get their period. Growth of the pituitary gland may cause excess PRL causing infertility in
females. In males, PRL appears to be involved in the production of mature sperm.
A hormone produced by endocrine gland that influences another endocrine gland is a tropic hormone. Two
such hormones are thyroid stimulating hormone (TSH) and adrenocortocotropic hormone (ACTH). TSH acts on
the thyroid gland in the neck to stimulate the synthesis and release of thyroid hormones. ACTH controls the
synthesis and secretion of glucocorticoid hormones from the outer portion of the adrenal glands.
Two other tropic hormones secreted by the anterior pituitary gland influence the gonads (ovaries and
testes). Follicle stimulating hormone (FSH) promotes development of egg cells and secretion of hormone estrogen
in females. Luteinizing hormone (LH) causes ovulation, the release of a future egg cell by the ovaries in females. LH
also stimulates the ovaries to secrete estrogen and progesterone. These two prepare the uterus for implantation of
a fertilized ovum and the breasts for production of milk. In males, FSH promotes maturation of sperm and LH
stimulates cells within the testes to produce and secrete testosterone.
The connection between the hypothalamus and the posterior is neural (not circulatory). Oxytocin (OT) and
antidiuretic hormone (ADH) are produced by the hypothalamus and move along the axons of nerve cells to the
posterior pituitary where they are stored and released.
It doesn’t produce any hormones of its own. Neurons of the hypothalamus manufacture antidiuretic hormone and
oxytocin and these travel down the nerve cells into the posterior pituitary, where they are stored and released. Antidiuretic hormone (ADH) is to conserve body water by decreasing urine output by prompting the kidneys to
remove water from the fluid destined to become urine. The water is then returned to the blood. Alcohol inhibits
ADH causing increased urine flow causing dehydration and a hangover. Dehydration from peeing too much is
caused by damage to these areas and is called diabetes insipidus.
Oxytocin (OT) is the second hormone produced in the hypothalamus. It stimulates uterine contractions during
childbirth and stimulates milk ejection from mammary glands.
Inside it has small spherical chambers called follicles. Cells line the walls of the follicles and produce thyroglobulin,
the substance from which thyroxine (T4) and triiodothyronine (T3) are made- thyroid hormone (TH). Nearly all
body cells are the target cells for TH so it has broad effects. TH regulates the body’s metabolic rate and production
of heat. It also maintains blood pressure and promotes normal development and functioning of several organ
systems. TH affects cellular metabolism by stimulating protein synthesis, the breakdown of lipids and the use of
glucose for ATP production. Falling levels of TH prompt the hypothalamus to secrete a releasing hormone which
stimulates the anterior pituitary to secrete TSH which in turn causes the thyroid to release more TH.
Iodine is needed for production of TH. A diet deficient in iodine can produce a simple goiter (an enlarged thyroid
gland). When iodine intake is low, TH is low and low level of TH triggers secretion of TSH which stimulates the
thyroid gland to increase production of thryoglobin (which is low if TH is low). Undersecretion of TH uring fetal
development or infancy causes cretinism, a condition characterized by dwarfism and delayed mental and sexual
development. Oral doses of TH can prevent. Undersecretion of TH in adulthood causes myxedema where fluid
accumulates in facial tissues.
Oversecretion of TH causes Graves disease, an autoimmune disorder in which a persons own immune system
produces Y-shaped proteins called antibodies that mimic the action of TSH. The antibodies stimulate the thyroid
gland causing it to enlarge and overproduce hormones. Increased metabolic rate, heartrate, sweating, nervousness.
Many people with Graves have exopthalamos, protruding eyes caused by swellings.
Calcotonin (CT) secreted by the parafollicular cells of the thyroid helps regulate the concentration of calcium in the
blood to ensure the proper functioning of muscle cells and neurons. Ca+ binds to the protein troponin, leading to
changes in other muscle proteins and eventually causing muscle contractions and also releases neurotransmitters
into the synaptic cleft and is therefore critical in neuron communication. When Ca+ is high, CT stimulates the
absorption of calcium by the bone thereby lowering calcium in blood. Also increase calcium in urine.
Parathyroid glands secrete parathyroid hormone (PTH). PTH increases levels of calcium in the blood. Low levels
stimulate the parathyroid to secrete PTH which causes calcium to move from bone and urine into the blood. PTH
exerts its effects by (1) bone-destroying cells called osteoclasts that release calcium from the bone into the blood,
(2) the removal of calcium from urine and return to blood,
(3) rate at which calcium is absorbed into the blood from the gastrointestinal tract
Oversecretion of PTH pulls calcium from bone tissue, causing increased blood calcium and weakened bones. High
levels of calcium in the blood can lead to kidney stones, calcium deposits in soft tissue and decreased nervous
Adrenal Glands- two of them, located on the tops of the kidneys. Outer region is the adrenal cortex which secretes
more than 20 different lipid soluble (steroid) hormones (groups gonadocorticoids, mineralcorticoids and
glucocorticoids). The inner region is the adrenal medulla, which secretes water soluble hormones, epinephrine and
Adrenal Cortex The gonadocorticoids are male and female sex hormones known as androgens and estrogens. Secrete both in
both genders. In females, the ovaries and placenta also produce estrogen, although during menopause, the ovaries
decrease secretion of estrogen and eventually stop secreting it. The gonadocorticoids from the adrenal cortex may
alleviate the effects of decreased ovarian estrogen in menopause.
The mineralcorticoids secreted by the adrenal cortex affect mineral homestasis and water balance. The primary
mineralcorticoid is aldosterone, a hormone that acts on cells of the kidneys to increase reabsorption of sodium ions
into the blood. The reabsorption prevents depletion of sodium ions and increases water retention. It also acts on
the kidney cells to promote the excretion of potassium ions in the urine. Addisons’s disease is a disorder caused by
the undersecretion of aldosterone and the glucocorticoid cortisol. It is an autoimmune disorder where the bodys
own immune system perceives cels of the adrenal cortex as foreign and destroys them. This causes weight loss,
fatigue, poor appetite.
The glucocorticoids are hormones secreted by the adrenal cortex that affect glucose levels. Act on the liver to
promote conversion of fat and protein to intermediate substances that are ultimately converted into glucose. Also
act on adipose tissue to prompt the breakdown of fats to fatty acids and released into blood stream. Conserve
glucose by inhibiting uptake in muscle and fat tissue. Also inhibit inflammatory response by slowing the movement
of white blood cells to the injury site. Inhibit wound healing (cortisol, corticosterone and cortisone). Cushings
syndrome- prolonged exposure to high levels of cortisol. Body fat is redistributed and fluid accumulates in the face.
Produces adrenaline and nonadrenaline (responsible for fight or flight response) body’s sympathetic nervous
system in emergencies. Heart rate, blood pressure and breathing increase but blood vessels dealing with digestive
tract constrict because it is not important at that time. Blood, oxygen and glucose reach the brain in greater
amounts to increase alertness.
Located in the abdomen just behind the stomach. It contains both endocrine and exocrine cells. The endocrine cells
occur in small clusters known as pancreatic islets containing three types of hormone producing cells (one produces
glucagon, insulin and somatostatin). Glucagon increases the level of blood sugar by prompting cells of the liver to
increase conversion of glycogen to glucose. It also stimulates the liver to form glucose from lactic acid and amino
acids. The liver releases glucose into bloodstream.
Insulin decreases glucose in the blood (antagonistic with glucagon). Stimulates transport of glucose into muscle
cells, white blood cells, connective tissue. Insulin also inhibits the breakdown of glycogen to glucose. Also, prevents
conversion of amino acids and fatty acids. Insulin promotes protein synthesis, fat storage and glucose for energy.
Type 1 diabetes mellitus: insulin dependent. Immune system attacks cells of the pancreas responsible for insulin
production (need insulin injected). Underweight
Type 2 diabetes: non insulin dependent. Adults. Overweight, decreased sensitivity to insulin.
The thymus gland decreases in size as we age. Secretes thymopoietin and thymosin. These promote the
maturation of white blood cells called T lymphocytes. Precursor cells from the bone marrow travel by way of the
bloodstream to the thymus gland where they mature into T cells to become a part of the body’s defense
Pineal gland secretory cells produce melatonin. This hormone is greater at night than at daylight hours because of
input of visual pathways. Influences daily rythms (circadian), sleep and season changes in mood influenced by
melatonin. (also pigment melanin inhabitation). May also slow aging processes. Seasonal Affective Disorder (SAD) .
Depression in winter when short day length and decreased light exposure.
Locally Acting Chemical Messengers Local signally molecules act near the site of their release on adjacent target cells within mseconds. Communication
via these occurs much more rapidly than by hormones which travel to distant sites in the body. (fight or flight may
take 30secs). Examples are prostaglandins and nitric oxide. Prostaglandins are lipid molecules continually released
by the plasma membrane of most cells. Diverse effects, influencing blood clotting, regulation of body temp. Also
effect reproductive system, menstrual cramps. Act on smooth muscle of the uterus causing muscle contraction and
pain. Found in semen too. Growth factors are peptides or proteins that when present in the fluid outside target
cells, stimulate those cells to grow develop and multiply. Nitric oxide leads to dilation of blood vessels.
3a(v) The Local Support and Defense System
The Body’s Defense System
Targets: organisms that cause disease, infection or cells that turned cancerous
Pathogens: Bacteria, viruses, protazoans, fungi, parasitic worms and infectious proteins that cause disease
Many bacteria are beneficial (flavor cheese, get rid of corpses (decomposition) and interact with other bacteria).
Recycle nutrients to support new life.
A cancer cell was once a normal body cell, but because of changes in its genes it cannot regulate its cell division
(multiplying and taking over the body). This upsets balance, chokes pathways, causes pain and death.
Three Lines of Defense
Three strategies to defend against foreign organisms and cancer cells
1. Keep the foreign organisms or molecules out of the body in the first place (first line of defense-chemical
and physical surface barriers).
2. Attack any foreign organism or cancer cell inside the body (second line of defense- internal cellular and
chemical defenses that become active when surface barriers are penetrated)
3. Destroy a specific type of foreign organism or cancer cell (third line of defense- immune response which
destroys specific targets, usually disease causing organisms and remembers those targets so quick that a
response can be mounted again if enters again (immunity)). This is if pathogen survives nonspecific
Therefore the first and second lines consist of nonspecific mechanisms that are effective against any foreign
material and the third line, the immune response, is a specific mechanism of defense.
First Line of Defense- Physical and Chemical Barriers
Formed by the skin and mucous membrane. Physical and chemical barriers act as nonspecific defenses against any
threats and collectively prevent many invading organisms from entering the body, or confine them to a local
region, kill them or remove them or slow their growth.
unbroken skin protects body from pathogens by providing a barrier. A layer of dead cells forms the tough outer
layer of skin. These cells are filled with fibrous protein- keratin- which waterproofs the skin and makes it resistant
to the disruptive toxins and enzymes of most invaders. Some of this strength is from the tight connection of cells.
Dead cells continuously shed and replaced and as they flake off they take any microbes that latch on with them.
Mucous membrane lines the digestive and respiratory passages, producing sticky mucus that traps any microbes
and prevents them from fully entering the body. The cells of the mucous membrane in upper resp. pathways have
cilia which beat constantly, moving contaminated mucus to the throat which is eliminated by coughing, swallowing
Sweat and oil wash away microbes. Acidity of secretions slows bacterial growth and the oils contain chemicals that
kill some bacteria. Lining of the stomach produces HCl and protein digesting enzymes that destroy pathogens. Also,
womans vagina has acidic environment. Urine acts as chemical because acidic and physical because it pushes
microbes out. Saliva and tears have lysozyme which disrupts cell walls of bacteria. Tears- wash away irritating substances and microbes, lysozyme kills many bacteria
Saliva- washes microbes from the teeth and mucous membranes in mouth
Respiratory Tract- mucus traps organisms, cilia sweep away trapped organisms
Bladder- Urine washes microbes from urethra
Stomach- acid kills bacteria
Skin- physical barrier, acidic ph discourages growth of organisms, sweat and oil glands
Large intestine- normal bacterial inhabitants keep invaders in check
Second Line of Defense: Defensive Cells and Proteins, Inflammation and Fever
Second line consists of nonspecific internal defenses against any pathogen that breaks through the physical and
chemical barriers and enters the body.
Specialized “scavenger” cells called phagocytes engulf pathogens, damaged tissue or dead cells by phagocytosis.
When a phagocyte meets a foreign particle, cytoplasmic additions flow from the phagocytic cell, bind to the particle
and pull it inside the cell. The particle is enclosed within a membrane bound vesicle and quickly destroyed by
digestive enzymes. Types include neutrophils which arrive at the site of attack before other cells and consumes
pathogens, especially bacteria, by phago. Other white blood cells leave the vessels of the circulatory system and
enter the tissue fluids, where they develop into large macrophages. They have hearty appetites and attack and
consume anything not recognized. Eosinophils attack large pathogens that cannot be phagocytosized, such as
parasitic worms. They get close to the parasite and discharge enzymes that destroy. Macrophages clean the debris.
Natural Killer Cells
Third type of white blood cell that roams the body in search for abnormal cells and quickly orchestrates their death.
Respond to any suspicious behavior including a cell whose membrane has been altered by the addition of proteins
that are unfamiliar. Prime targets are cancer cells and cells with viruses. Cancer cells routinely form but are quickly
destroyed and prevented from spreading.
As soon as it touches a cell with abnormal surface, NK cell attaches itself and delivers a kiss of death in the form of
proteins that create many pores which make the target cell leaky, so it can no longer maintain a constant internal
environment and bursts.
Slow the viral reproduction. Before certain virally infected cells die, they secrete small proteins called interferons to
help undamaged cells. These act to slow the spread of viruses already in the body (saving good cells). Interfere with
viral activity. First, they help rid the body of virus infected cells by attracting macrophages and NK cells that destroy
the infected cells immediately. Then interferons protect uninfected cells. Interferons diffuse to neighboring cells
and stimulate them to produce proteins that prevent viruses from replicating in those cells (all viruses, not just
Until these proteins are activated by infection, they circulate in the blood in an inactive state. Once activated, these
proteins enhance both nonspecific and specific defense mechanisms. The effects of complement include:
Destruction of pathogen: Act directly by punching holes in target cells membrane (discussed above)
Enhancement of phagocytosis: Compliment proteins attract macrophages and neutrophils to the site of infection
to remove foreign cells. Also, one of the compliment proteins binds to the surface of the microbe making it easier
for macrophages and neutrophils to get a grip on the intruder and devour it
Stimulation of Inflammation: Compliment causes blood vessels to widen and become more permeable. This
provides increased blood flow to the area and increased access for white blood cells
Defense Example Function
Defensive cells Phagocytic cells such as neutrophils and macrophages Engulf organisms
Eosinophils Kill parasites Natural Killer cells Kill many invading organisms and cancer cells
Defensive Interferons Slow the spread of viruses in the body
Complement System Stimulates histamine release; promotes
proteins phagocytosis; kills bacteria; enhances
Inflammation Widening of blood vessels and increased capillary Brings in defensive cells and speeds healing
permeability, leading to redness, heat, swelling and
Fever Abnormally high body temp Slows the growth of bacteria, speeds up body
When the bodys tissues are injured or damaged, a series of events called the inflammatory response or rection
occurs. The four cardinal signs of inflammation that occur at the site of a wound are redness, heat, swelling and
pain. These announce that certain cells and chemicals have combined efforts to contain infection, clean up
damaged area and heal the wound.
Redness: occurs because blood vessels dilate in the damaged area, causing blood flow in this area to increase. The
dilation is caused by histamine a substance that is also released during allergic reactions by small connective tissue
cells called mast cells in response to chemicals from damaged cells. This increased blood flow to the site of injury
deliver phagocytes, blood clotting proteins and defensive proteins. This increased blood flow also washes away
dead cells and toxins
Heat: increased blood flow elevates temperature of the injury area. The increased temperature increases metabolic
rate of the body cells in the region and speeds healing. Also increases activity of defensive cells
Swelling: Histamine makes capillaries more permeable than usual so area swells. Fluid seeps in the tissues from the
bloodstream, bringing with it beneficial substances. Blood clotting factors enter the injured area and begin to wall
off the region, helping to protect surrounding areas from injury and prevent excessive blood loss. Seepage also
increases the oxygen and nutrient supply to cells. If swelling on a joint, hampers movement to rest and recover.
Pain: such as excessive fluid that has leaked into tissue presses on nerves. Pain can also be caused by bacterial
toxins, which kill body cells. Injured cells also release pain causing chemicals such as prostaglandins.
Because of all these, phagocytes begin to swarm the site, attracted by chemicals released when tissue is damaged.
Within minutes, the neutrophils squeeze through capillary walls into the fluid around cells and begin engulfing
pathogens, toxins and dead body cells. As recovery from infection, dead cells and phagocytes begin to ooze from
wound as pus.
A fever is an abnormally high body temperature cause by pyrogens, chemicals that rais the thermostat in the brain
to a higher set point. Bacteria release toxins that act as pyrogens but body also produces its own. Raise set point so
that physiological responses such as shivering, are initiated to raise body temperature. Thus we have chills. When
set point is lowered, fever breaks and perspiration reduces body temperature until reaches new set point.
A mild or moderate fever helps the body fight bacterial infections by slowing the growth of bacteria ad stimulating
body defense responses. This is because a fever causes the liver and spleen to remove iron from the blood and
many bacteria need iron to reproduce. Fever also increases cells metabolism, speeding up defensive responses.
Very high fever can inactivate enzymes needed for biochemical reactions necessary
Third Line of Defense: Immune Response
When the body’s first and second lines fail, the bodys specific defenses respond and target the specific pathogen,
cancer cell, etc. Third line of defense is the immune system which provides the specific responses and memory.
The organs of the lymphatic system are important components of the system because it produces various cells
responsible for immunity. The immune system is not an organ system, but it recognizes and destroys specific
pathogens or foreign molecules. First the immune system is directed at a particular pathogen then acts to immobilize, neutralize or destroy it.
Second the immune system has a memory so it remembers the pathogen and destroys it quickly.
Distinguishing Self from Nonself
To defend against a foreign molecule, body must be able to distinguish it from a body cell and recognize it is
foreign. This ability depends on the fact that each cell in your body has special molecules embedded in the plasma
membrane that label the cell as self. The molecules called MHC markers are flags that declare the cell as a friend.
The self labels on your cells are different from others as ell as those of other organisms, including pathogens.
Immune system uses the labels to attack unrecognized cells.
A nonself substance that triggers an immune response is called an antigen. are large molecules such as proteins,
etc. Often found on surface of an invader embedded in the plasma membrane or a part of the protein coat of a
virus. Each antigen is recognized by its shape.
Certain white blood cells, called lymphocytes, are responsible for both the specifity ad memory of immune system.
There are B and T lymphocytes. Both types form in bone marrow, but mature in different organs of the body. T cells
mature in thymus gland and B cells mature in bone marrow.
As the T lymphocytes mature, they develop the ability to distinguish between cells that belong in the body and
those that do not. T cells must be able to recognize specific MHC self markers and not respond vigourously to cells
bearing that marker. Once they are mature, they circulate through the body, bumping into other cells and checking
to be sure they have the correct marker.
Both T and B lymphos are programmed to recognize one particular antigen (specifity). Each lymphocyte develops
its own particular receptors on its surface. Thousands of identical on same one, but all different on others. When
an antigen fits into a lymphos receptors, the body’s defenses target that particular antigen. When an antigen is
detected, T and Bs receptors able to respond to that specific invader are stimulated to divide repeatedly, forming
two lines of cells. One line- effector cells- carry out attack on the enemy and only live for a few days. After invader
killed, number of effector cell lowers. Other line is memory cells- long lived and remember particular invaders and
mount a rapid intense response. (chicken pox).
Antibody-Mediated Responses and Cell-Mediated Responses
Antibody- mediated immune responses defend primarily against antigens found travelling freely in intercellular
and other body fluids. The warriors of this branch of the immune system are the effector B cells (plasma cells) and
their weapons are Y shaped proteins called antibodies which neutralize and remove potential threats from the
body. Antibodies are programmed to recognize and bind to the antigen posing the threat
Cell-mediated immune responses protect against cellular pathogens or abnormal cells, including body cells that
have become infected with viruses. The lymphocytes responsible for cell-mediated immune responses are T cell
type called cytotoxic T cell. Once activated, cytotoxic T cells quickly destroy the cellular pathogen, infected body
cell by causing them to burst.
Steps of Immune Response
Step 1: THREAT: immune response begins when a molecule (antigen) lacking the MHC marker manages to evade
the first two lines of defense and enters the body
Step 2: DETECTION: Recall that macrophages are phagocytic cells that roam the body, engulfing any foreign
material or organisms. Within the macrophage, the engulfed material is digested into smaller pieces.
Step 3: ALERT: macrophage then alerts the immune system’s commander, a helper T cell (on switch), that an
antigen is present. The macrophage accomplishes this task by transporting some of the digested pieces to its own
surface where they bind to the MHC self markers on the macrophage membrane. The self marker acts as a secret
password that identifies the macrophage as a friend. The antigen bonded to the self markers function as a wanted
poster, telling the lymphocytes that there is an invader and revealing how it can be detected. Thus, macrophage is
a antigen-presenting cell (APC). The macrophages present the antigen to a helper T cell, the kind of T cell that
serves as the main switch for the entire immune response. The macrophage must alert the right kind of helper T
cell- one that bears receptors that recognizes the specific antigen being presented. Macrophage wanders through the body until it bumps into an appropriate helper T cell. The encounter occurs in the lymph nodes because they
Step 4:ALARM- within hours, an activated helper T cell begins to secrete its own chemical messages. The helper T
cells message calls into active duty the appropriate B and T cells.
Step 5: BUILDING SPECIFIC DEFENSES- when the appropriate B and T cells are activated, they begin to divide
repeatedly. The result is a clone specialized to protect against the particular target antigen. The process by which
this specialized clone is produced, called clonal selection, underlies the entire immune response. (tremendous
variety of B cells. Each B cell has receptors for diff antigen on its surface. This B cell has receptors specific for this
particular antigen. The antigen binds to the B cell with appropriate receptors. The selected B cell divides, producing
a clone of cells all bearing receptors for particular antigen. Memory cells remain to bring about a quick response to
that antigen in the future---Clonal selection). Your body produces samples of many lymphocutes, a given
lymphocyte responds to one antigen. When an antigen selects the appropriate lymphocyte, the body produces
many additional copies of the lymphocyte chosen by that particular antigen.
Step 6: DEFENSE- the antibody mediated response. Activated B cells divide. Effector cells they produce through
clonal selection, plasma cells, secrete antibodies into the bloodstream to defend against antigens free in the blood
or bound to the cell. Antibodies are Y shaped proteins that recognize a specific antigen by its shape. Each antibody
is specific for one antigen. Each antibody can link to two identical antigens (two arms). Antibodies can only bind to
antigens that are free in body fluids or attached to the surface of a cell. Their main targets are toxins and
extracellular microbes, including bacteria. Antibodies help defend against these pathogens in several ways that can
be rememberd by PLAN
Precipitation: antigen-antibody binding causes antigens to clump together and precipitate, enhancing
phagocytosis by making antigens easier for phagocytic cells to capture and engulf.
Lysis: certain antibodies activate the complement system, which then pokes holes through the membrane of the
target cell and causes it to burst.
Attraction: antibodies attract phagocytic cells to the area. Phagocytes then engulf and destroy the foreign material.
Neutralization: Antibodies bind to toxins and viruses, neutralizing them and preventing them from causing harm.
There are five classes of antibodies each with a special role. Antibodies are also called immunoglobulins (Ig): IgG,
IgA, IgM, IgD and IgE. Y shape is monomer.
Step 6: DEFENSE- The cell mediated response. The cytotoxic C cells are the effector T cells responsible for the cell-
mediated immune response, which destroys antigen bearing cells. A cytotoxic T cell becomes activated to destroy a
target cell when (1) it encounters an antigen-presenting cell such as a macrophage and (2) a helper T cell must
release a chemical to activate thr T cell. When activated, it divides producing memory and effector cytotoxic T cells.
An effector cytoT cell releases perforins, which cause holes to form in the target cell membrane which are large
enough to release cells contents and destroy it. CytoT cell deatches from the target cell and seeks another cell
having the same antigen.
Step 7: CONTINUED SURVEILLANCE- the first time an antigen enters the body, only a few lymphocytes can
recognize it. As a result of built up army, the primary response, the one that occurs during the first encounter, is
slow. A lapse of several days occurs before the antibody concentration begins to rise and peaks at 1-2 weeks.
Following subsequent exposure to the antigen, the secondary response is strong and swift. Memory cells. The
number of effector cells rises quickly during secondary and reaches a higher peak in shorter 2-3 days than primary.
Step 8: WITHDRAWAL OF FORCES- as the immune system begins to conquer the invading organism and the level of
antigens declines, suppressor T cells release chemicals to dampen activity of both B and T cells, turning off immune
response when the antigen no longer poses a threat. Prevents overreaction and harming healthy body cells.
Active and Passive Immunity Two types of immunity: active immunity- the body actively defends itself by producing memory B and T cells
following exposure to an antigen. Happens naturally when person gets an infection. Can develop through
vaccination (immunization) which introduces a harmless form of an antigen into the body to stimulate immune
responses against that antigen. Only the protein (not the antigen) is injected so doesn’t cause disease. Microbes
are killed or weakened. It leads to the production of memory cells and is long lived. The first dose of vaccine causes
the primary immune response and antibodies and some memory cells are generated. Sometimes, may forget
though so need regular shot.
Passive immunity: the protection that results when a person receives antibodies produced by another person or
animal. Some antibodies produced by pregnant women, cross placenta, causing immunity until baby can produce
its own. People can be vaccinated and experience passive, but has to have antibodies produced by person or
animal. Effects are immediate but short lived.
Groups of identical antibodies that bind to one specific antigen. Pregnancy tests.
Occur when the immune system fails to distinguish between self and nonself and attacks tissues and organs of the
body. Lymphocytes that cannot detect MHC markers are destroyed, but some unfortunately are not and attacks
bodys cells. Organ specific (T cells) and nonspecific (B cells). Occur because portions of the disease causing
organisms resemble proteins found on normal body cells. Mistake bodys antigens for foreign antigens. Rheumatic
fever, lupus (lymphocytes attack the bodys connective tissue throughout the body, causing butterfly rash,
Hay fever is allergic rhinitis caused by pollen, mold spores, animal dander, feces of dust mites in the nasal cavity
lining. Causes sneezing and congestion. It is an allergy
Allergy is an overreaction by the immune system to an antigen (called an allergen). Allergen is not harmful to the
body, it is the overreaction of the immune system. Most common is hay fever (allergies). Immediate allergic
reactions occur when person is exposed to allergen and primary immune response is launched. Soon, plasma cells
churn out antibody IgE which binds to basophils or mast cells. In subsequent exposures to the allergen, allergen
binds to IgE antibodies on the surface of those cells and releases histamine which causes swelling and redness, etc.
Blood vessels widen, slowing blood flow and causing redness. Vessels also become leaky, causing swelling. Also
causes runny nose and smooth muscle contraction. Anaphylaxis. Antihistamines block effects of histamine.
3b(i) The Cardiovascular and Lymphatic Systems
Functions of Blood
Blood serves as a transport system. It carries vital materials to all the cells of the body and carries away the cell
waste. White blood cells help protect us against disease and its clotting mechanisms help protect us from excessive
blood loss in a damaged vessel. Blood also regulates body temperature by absorbing heat in metabolic active
regions and distributing it to cooler regions. Therefore, transportation, protection and regulation are the functions
Composition of the Blood
Blood is thicker than water because it contains cells. Blood is classified as connective tissue because it has cellular
elements suspended in its matrix. The liquid matrix is called the plasma.
Plasma is a straw coloured liquid that makes up 55% of the blood and serves as the medium which materials are
transported by the blood. Almost every substance transported by the blood is dissolved in the plasma such as
nutrients (simple sugars, amino acids, lipids, vitamins), ions (CO2, N, O2) and every hormone. Plasma also carries
away waste such as urea from protein breakdown and uric acid from nucleic acid breakdown are carried to the kidneys where they can be removed from the body. Blood transports CO2 from the cells where it is produced to the
lungs for release.
Most of the dissolved substances in the blood are plasma proteins, which help balance water flow between the
blood and the cells. Water moves by osmosis across biological membranes from an area of lesser concentration to
an area of greater concentration. Without plasma proteins, water would be drawn out of the blood by proteins in
the cells. As a result, fluid would accumulate in the tissues, causing swelling.
General categories include: albumins, globulins and clotting proteins. Albumins make up more than half of the
plasma proteins and are most important in the bloods water balancing ability. The globulins transport lipids (fats
and cholesterol) and fat soluble vitamins, act as antibodies that provide protection against many diseases. An
example of a plasma protein is fibrinogen.
This includes platelets, white blood cells and red blood cells. Red bone marrow, a porous connective tissue that fills
the cavities within many bones, is the birthplace for formed elements. Spongelike frame supports fat cells and
undifferentiated cells called blood stem cells that divide and give rise to all the formed elements.
Type of formed Cell Function Description Life span
Platelets Play role in blood clotting and contain Fragments of megakaryocyte (formed in 5-10 days
substances important in stopping loss of red bone marrow); small, purple stained
blood granules in cytoplasm
White Blood Cells Removing wastes and toxins and are also fighters against disease. Counts are used as a way to index
(leukocytes) infection because number increases when body repsonds to microbes. These are nucleated.
Circulate the blood stream. Squeeze through neighbouring cells that form the walls of blood vessels,
so they can leave the circulatory system and move to a site of infection. Gather in areas of damaged
tissue (attracted to damaged cells).
Granulocytes 1) Consume bacteria by phagocytosis thus 1) Multilobed nucleus, clear-staining 1) 6-72
curbing infection spread. Dead-makes pus cytoplasm, inconspicuous granules hours
2) Eosinophils 2) Consume antibody-antigen complex by 2) Large, pink staining granules in 2) 8-12
3) Basophils phagocytosis; attack parasitic worms. Also cytoplasm, bilobed nucleus days
reduce severity of allergies 3)Large, purple staining cytoplasmc 3) 3-72
3) Release histamine, which attracts white granules, bilobed nucleus hours
blood cells to the site of inflammation and
widens blood vessels, increasing blood
flow to affected area
Agranulocytes 1) Give rise to macrophages, which 1) Gray-blue cytoplasm with no 1) months
1)Monocytes consume bacteria, dead cells and cell parts granules; U shaped nucleus 2) years
2) Lymphocytes by phagocytosis 2) Round nucleus that almost fills the
2) Attack damaged or diseased cells or cell
disease causing organisms and produce
Red Blood cells Transport oxygen and CO2 (picks up Biconcave disk with no nucleus 120 days
(erythrocytes) oxygen in the lungs and brings it to cells,
picks up CO2 from cells and brings it to
lungs to export).
Granulocytes have granules in their cytoplasm and the granules are sacs containing chemicals that are used as
weapons to destroy invading pathogens, especially bacteria.
Agranulocytes lack cytoplasmic granules.
Red Blood Cells and Transport of Oxygen
Red blood cells (RBCs) are called erythrocytes and transport oxygen. Their shape maximizes the surface area of the
cell which allows the oxygen to enter the cell faster. It is flexible and can squeeze through capillaries. Each RBC is
packed with hemoglobin, the oxygen binding pigment that is responsible for the red colour. Each hemoglobin molecule can carry up to four molecules of oxygen. Body cells use the oxygen to boost the energy extracted from
food molecules in cell resp. As oxygen is used, CO2 is produced which travels to the lungs, dissolved in plasma, but
some binds to hemoglobin. If CO and O2 molecules were equal in inhaled air, for every 1 molecule of hemoglobin
that binds to O2 molecules, 200 molecules of hemoglobin bind to CO. This is deadly, it blocks oxygen from binding
to it, preventing blood from carrying life giving oxygen to cells.
Once hemoglobin is packed in, nucleus is pushed out. Leaves red bone marro at maturity after change of shpe. Liver
and spleen are areas where worn out red blood cells are removed. Macrophages destroy them, hemoglobin goes to
liver and degreades into its protein (globin). Remaining part is excreted by the liver in bile, bile is released into the
small intestine where it assists in fat digestion. Also reason for colour of poop and bruises.
Yellow or brown colour is when tiny blood vessels are ruptured and blood leaks into surrounding tissue and as the
tissue uses up the oxygen, the blood becomes darker (black and blue). Gradually the red blood cells degenerate,
releasing hemoglobin and make the bruise appear yellow.
Blood Cell Disorders
Red Blood Cells
Anemia- bloods ability to carry oxygen is reduced due to lack or hemoglobin or too few red blood cells (fatigue,
dizziness, paleness, faster heart rate). Insufficient iron by diet or by inability to absorb iron from digestive system or
blood loss. Sickle cell anemia, has abnormal hemoglobin, misshaping the cells, making them more fragile and
White Blood Cells
Infectious mononucleosis (mono) is a viral disease of the lymphocytes. Causes an increase of lymphocytes that have
Leukemia is a cancer of white blood cells that causes uncontrollable multiplication. The cells remain immature and
unable to defend the body against infection and take over the bone marrow, preventing development of normal
blood cells. Cure by destroying bone marrow then implanting a donors.
The body’s immediate response to blood vessel injury is for the vessel to constrict (squeeze shut). The next
response is to plug the hole. Platelets form a plug. The platelet plug is formed when platelets cling to cables of
collagen, a protein fibre on the torn blood vessel surface. When attached, the platelets swell, form many cellular
extensions and stick together, they also produce a chemical that attracts other platelets to the wound and makes
them stick together more. Aspirin prevents the formation and inhibits clot formation, thus prescribed to prevent
formation of blood clots that could block vessels nourishing heart tissue and thus cause death of heart cells (heart
The next step is through the damaged blood vessel forming the clot itself. Begins when clotting factors are released
from injured site and form platelets. At the site of the wound, the clotting factors convert an inactive blood protein
to prothrombin activatior, which then converts prothrombin, a plasma protein produced by the liver, to an active
form, fibrinogen which forms long strands of fibrin which makes a web and traps blood cells, forming a clot. The
clot is a barrier that prevents additional blood loss through the wound in the vessel.
Vitamin K is needed for the liver to synthesize prothrombin and three other clotting factors.
Hemophilia is where the affected person bleeds excessively owing to a fault in on of the genes involved in
producing clotting factors.
A blood clot in an undamaged vessel is thrombus and a blood clot that drifts to the circulatory system is embolus.
When the tiny vessels that nourish the heart or brain become blocked with a clot, this can lead to a severe stroke or
heart attack. Plasmin destroys clots.
Consists of the heart and blood vessels. The blood delivers a continuous supply of oxygen and nutrients to the cells
and carries away metabolic wastes so they cannot poison cells.
It is the body’s transportation system. Blood Vessels
Do not form a single long tube, but are arranged in branching networks.
This is the circ. System!
The hollow interior of a blood vessel, where blood flows, is called the lumen. The inner lining of that comes into
contact with the blood flowing through the lumen is composed of simple epithelium. This lining, called the
endothelium, provides a smooth surface that minimizes friction so that the blood flows easily.
Are muscular tubes that transport blood away from the heart, delivering it rapidly to the body tissues. Outside the
endothelium is a middle layer with circular layers of smooth muscle and elastic fibres, which allow an artery to
stretch and then return to normal shape. The smooth muscle enables the artery to contract.
The elastic fibres in the middle layer of the artery have two important functions: (1) they help the artery tolerate
the pressure shock caused by blood surging into it when the heart contracts and (2) they help maintain a relatively
even pressure within the artery. When the heart contracts and sends blood into the aorta, the bodys main artery.
Elastic walls of the artery stretch with each wave of blood and return to their original size when done; this results in
a continuous stream of blood rather than waves.
Pulse rate is heart beat, where the expansion and recoil of arteries create a pressure wave (you can feel your pulse
When the middle layer of the arterial wall with smooth mucles contracts and the diameter of the lumen becomes
narrower, it is called vasoconstriction and blood flow to the artery is reduced. When it relaxes, becomes wider and
When the artery becomes weakened due to disease, injury, inflammation,etc, it may cause the wall to swell
outward like a balloon, forming an aneurysm. Aneurysm can burst, causing blood loss and the tissues serviced by
that vessel will be deprive of oxygen and nutriemts. It can also cause a clot that travels and then blocks small
arteries. Tobacco does this.
Smallest arteries are arterioles and their walls have the same three layers found in arteries. They are the prime
controllers of blood pressure which is the pressure of blood against the vessel walls. When the muscle in arteriole
walls contracts, blood pressure increases. Greater number of arterioles contract, the higher blood pressure.
Relaxation lowers blood pressure. They also serve as gatekeepers to capillary networks which can be open or
closed, depending on whether the smooth muscle in the walls of the arteriole leading to it allows blood through.
Are small microscopic blood vessels that connect arterioles and venules. They exchange the materials between the
blood and body cells. Capillary walls are only one cell layer thick and so substances move easily between the blood
and the fluid surrounding the cells outside the capillary. The plasma membrane of the capillarys endothelial cell is a
selective barrier that determines which substances cross. Some substances only pass between adjacent endothelial
The network of the capillaries network is a capillary bed to deliver nutrients and oxygen to particular place.
Precapillary sphincter surrounds the capillary where it branches off the arteriole and regulates blood flow into it.
They act as valves that open and close the capillary beds. Ie when you are on the beach after finishing a lunch, the
capillary beds servicing the digestive organs will open and nutrients will be absorbed. If you start swimming, the
capillary beds of the digestive organs will close down and those in the skeletal muscles will open. Collectively, the capillaries provide a tremendous surface area for the rapid exchange of materials between body
and blood. Capillary beds bring capillaries very close to every cell. Capillaries are so narrow that red blood cells
squeeze through single file. Large cross section where blood flows much more slowly through them than through
the arteries or veins. The slower rate allows more time for exchange of materials.
Capillaries move into the smallest kind of vein, a venule, which then join to larger veins which are blood vessels that
return blood to the heart. Walls are made of the same as capillaries, but veins are thinner (walls) and the lumen is
bigger. Thin walls and large lumen allow veins to hold a large volume of blood. Veins hold a lot of blood.
Three mechanisms move blood from lower parts toward the heart
1. Valves in veins prevent backflow of blood- One way and allow blood to move toward the heart but
prevent backwards movement.
2. Contraction of skeletal muscle squeezes veins- when a skeletal muscle contracts, it squeezes nearby veins.
This pressure pushes blood past the valves towards the heart. When skeletal muscles relax, any blood that
moves backwards fills the valves and as they fill, they extend further into the lumen of the vein, closing the
vein and preventing the flow of blood from reversing direction. Thus, the skeletal muscles are always
squeezing the veins and driving blood toward the heart.
3. Breathing causes pressure changes that move blood toward the heart-The chest cavity increases in size
when we inhale. The expansion reduces pressure within the thoracic cavity and at the same time increases
pressure in the abdominal cavity. Thus, reduced pressure in thoracic cavity that comes with each breath
pulls blood back toward the heart and increased pressure in abdominal cavity squeezes veins, forcing blood
back to the heart
Size of a fist but is an incredible muscular pump that generates the force needed to circulate blood. The healthy
heart does not fatigue. It has three layers, each one contributing to the hearts ability to function as a pump. The
wall of the heart, myocardium, is mostly cardiac muscle tissue. Its contractions are responsible for the pumping
actions. The endocardium is a thin lining in the cavities of the heart. By reducing friction, the endocardium’s
smooth surface lessens the resistance to blood flow through the heart. The pericardium is a thick, fibrous sac that
holds the heart in the center of the chest cavity and slides over the surface of the heart without hampering its
The heart has two halves. Right side of the heart pumps blood to the lungs, where it picks up oxygen. The left side
pumps blood to the body cells. Halves separated by the septum. Each half consists of two chambers: an upper
chamber called an atrium and the lower is a ventricle. The two atria function as receiving chambers for the blood
returning to the heart. The two ventricles are the main pumps of the heart. Contraction of the ventricles forces
blood out of the heart under great pressure. Ventricles are much larger and thicker.
Two pairs of valves ensure that blood flows in only one direction through the heart. The first pair is the
atrioventricular (AV) valves, each leading from an atrium to a ventricle. The AV valves are connective tissue flaps,
called cusps, anchored to the wall of the ventricle by strings of connective tissue. These strings prevent AV valves
from flapping back into the atria under the pressure developed when the ventricles contract. The AV valve on the
right ?side of the heart has three flaps and is called the tricuspid valve. The one on the right has two, called the
Each of the second pair of valves, called semilunar valves, is located between a ventricle and its connecting artery,
either the aorta or the pulmonary artery. When the pressure in the arteria becomes greater than the pressure in
the ventricles, the valves fill up with blood and the semilunar valves prevent the backflow of blood into the
ventricles from the aorta or pulmonary artery.
Two Circuits of Blood Flow
In both circuits, blood moves through the arteries, arterioles, capillaries and venules before returning to the heart
via the veins. Left and right have separate routes though. The right side pumps blood through the pulmonary circuit, which transports blood to and from the lungs. The left side pumps blood through the systemic circuit, which
transports blood to and from body tissues. This prevents oxygenated blood from mixing with blood with low
The pulmonary circuit begins in the right atrium, as veins return oxygen-poor blood from the systemic circuit. The
blood then moves from the right atrium to the right ventricle. Contraction of the right ventricle pumps poorly
oxygenated blood to the lungs through the pulmonary trunk which divides to form the left and right pulmonary
arteries. In the lungs, oxygen diffuses into the blood and CO2 diffuses out. The now oxygen rich blood is delivered
to the left atrium through four pulmonary veins, two from each lung. Pulmonary circulation is an exception to the
rule that arteries carry oxygen rich blood and veins carry oxygen poor blood. Exactly the opposite is true of vessels
in the pulmonary circulation. The pathway of blood pumped through the pulmonary circuit by the right side of the
AV valvle Right Pulmonary Pulmonary Pulmonary Pulmonary
Right atrium (tricuspid) ventricle sevalvear trunk arteries Lungs Veins Left atrium
The systemic circuit begins when oxygen rich blood enters the left atrium. Blood then flows to the left ventricle.
When the left ventricle contracts, oxygenated blood is pushed through the largest artery in the body, the aorta. The
aorta arches over the top of the heart and gives rise to smaller arteries that eventually feed the capillary beds of
the body tissues. The venous system collects the oxygen-depleted blood and eventually culminates in veins that
return the blood to the right atrium. These veins are the superior vena cava which delivers blood from regions
above the heart, and the inferior vena cava, which returns blood from regions below the heart. Pathway on the left
side (systemic) is:
AV Aortic Inferior
Left (bicuspid) Left semilunar Aorta Body Vena Cava Right
atrium valve ventricle valve tissues or atrium
The lub sound of the heart is produced by the turbulent blood flow when the AV valves snap shut as ventricles
begin to contract. The higher pitched second heart sound (dub) is produced by the turbulent blood flow when
closure of the semilunar valves and the beginning of ventricular relaxation occur.
Heart murmurs are swooshing heart beat sounds other than lub dub, and are created by disturbed blood flow. Can
be in healthy people but can also indicate a problem. In these cases, the heart is strained because it has to work
harder to move blood.
An extensive network that services the tissues of the heart (nourishment). The first two arteries that branch off the
aorta are the coronary arteries. These give rise to numerous branches, ensuring the heart receives a rich supply of
oxygen and nutrients. After passing through the capillary beds that nourish heart tissue, blood enters the cardiac
veins and eventually flows into the right atrium
The two atria work at once, then the two ventricles work at once. Each beat of the heart involves a contraction,
which is called systole and relaxation, called diastole. All the events associated with the flow of blood through the
heart chambers during a heartbeat is called the cardiac cycle.
1. All chambers relax (diastole) and blood passes through the atria and enters the ventricles
2. When the ventricles are 70% full, the atria contract (atrial systole) and push their contents into the
3. The atria then relax (atrial diastole) and the ventricles begin their contraction phase (ventricular systole)
4. After this, the whole heart relaxes again. More time relaxing than contracting
Internal Conduction System
Heart doesn’t rely on outside conditions, its keeps beating even if outside. Heart cells twitch independently but if
they touch, will go in to rhythm. The cell membranes of adjacent cardiac muscle cells interweave with one another
at specialized junctions called intercalated disks. Cell junctions in these disks mechanically and electrically couple the connected cells. Adjacent cells are held together so tightly they do not rip apart during contraction but instead,
transmit the pull of contraction from one cell to the next. At the same time, the junctions permit electrical
communication between adjacent cells, allowing the electrical events responsible for contraction to spread rapidly
over the heart by passing from cell to cell.
The tempo of the heartbeat is set by a cluster of specialized cardiac muscle cells, called the sinoatrial (SA) node.
Because the SA node sends out the impulses that initiate each heartbeat, it is reffered to as the pacemaker. About
70 times a minute, the SA node sends out an electrical signal that spreads through the muscle cells of the atria,
causing them to contract. The signal reaches another cluster of specialized muscle cells called the atrioventricular
(AV) node, located in the partition between the two atria, and stimulates it. He AV node then relays the stimulus by
a bundle of specialized muscle fibres, called the atrioventricular bundle, which then divides into many other
specialized cardiac muscle cells and penetrate the walls of the ventricles.
When the conduction system is fault, cells may begin to contract independently. This can result in rapid, irregular
contractions of the ventricles, which render the ventricles useless as pumps and stop circulation. Electric shock, the
SA node will once again begin to function normally (defibrillator). Can also be treated by an artificial pacemaker
implanted below the skin. Pace of the heartbeat changes constantly in response to activity or excitement. The ANS
and certain hormones make adjustments.
The electrical events that spread through the heart with each heartbeat actually travel throughout the body,
because the body fluids are good conductors. Electrodes placed on the body surface detect this, transmitting them
so that cause deflections in the trcing made by a recording device. An electrocardiogram is an image of the electric
activities of the heart, generated by a recording device. It consists of thee distinguishable deflection waves. The
first wave, P wave, accompanies the spread of the electrical signal over the atria and atrial contraction that follows.
The next wave, QRS, reflects the spread of the electrical signal over the ventricles and ventricular contraction. The
third wave, T wave, represents the return of the ventricles to the electric state that preceded contraction. Can
indicate heart problems
Blood pressure is the force exerted by the blood against the walls of the blood vessels. When the ventricles
contract, they push blood into the arteries under great pressure. This pressure is the driving force that moves blood
through the body, but it also pushes outward against vessel walls. It is highest during the contraction of the
ventricles (ventricular systole), when blood is being forced into the arteries. The optimal systolic pressure, the
highest pressure in the artery during each heartbeat is 110-120mm. Blood pressure is lowest when the ventricles
are relaxing (diastolic). Diastolic pressure optimum is 70-80. 120/80 (systolic, diastolic). Measure by
sphygmomanometer which consists of an inflatable cuff that wraps around your upper arm.
Biggest killer. Heart attacks.
High blood pressure: hypertension (aka). Silent killer because it can cause fatal problems including heart, brain and
blood vessels. Hypertension damages the heart primarily by causing the heart to work harder to keep the blood
moving. In response, the heart muscle thickens, and the heart enlarges. The enlarged heart works less efficiently
and has difficulty keeping up with the bodys needs. Increased workload increases the hearts need for oxygen and
nutrients. Heart attack results if this cannot be accommodated.
Kidneys can be blamed, if they have impaired ability to handle sodium, the resulting fluid retention increases blood
pressure by increasing blood volume. Or sympathetic nervous system can respond to strongly to stress. Thus more
blood per minute is pumped through vessels that provide greater resistance.
Diuretics decrease blood volume by increasing excretion of sodium and fluids, reducing blood pressure by reducing
blood volume. Other drugs cause blood vessels to dilate. Can also treat by controlling weight, exercise regularly, do
not smoke and limit dietary salt.
Atherosclerosis Is a buildup of fatty substances in the walls of arteries, fueled by an inflammatory response. In some cases, the
deposits narrow the artery causing problems because it reduces blood flow through the vessles, choking off vital
blood supply. The inflammatory response thought to cause atherosclerosis is the same that wards off infection
when you scrape your knee. The damaged cells begin to pick up low density lipoproteins (LDLs), the bad form of
cholesterol. The accumulation of LDLs is most likely to occur when the concentration in blood is high. The plaque
can buldge into the artery channel, blocking blood flow. Fat filled cells weaken the cap and a small break in the cap
can allow the plaque to rupture, causing blood clots, starving and killing the cells. Heart attack or stroke. Coronary
artery disease is major cause of heart attacks.
Consists of lymph, which is a fluid identical to interstitial fluid; of lymphatic vessels through which lymph flows.
1. Return excess interstitial fluid to the blood stream: If it was not returned and the surplus interstitial fluid
was not drained, it would cause tissue to swell; a volume of blood would drop to potentially fatal levels;
and blood would become too viscous for the heart to pump (elephantiasis- parasitic worms block lymphatic
vessels and causes buildup of fluid followed by growth of connective tissue resulting in massive swelling,
darkening and thickening of the skin)
2. Transport products of fat digestion from the small intestine to the bloodstream: products of fat digestion
are too large to be absorbed in the capillaries of the small intesyine and instead, enter the lymphatic vessel
and travel there to be returned to the blood circ system
3. Help defend against disease causing organisms
Differ from blood capillaries by (1) ending bluntly (unlike continuous and drainage only moves in one direction) and
(2) they are much more permeable so they can absorb digestive products of fats and interstitial fluids. Lymph flows
slowly through the lymphatic vessels which by contractions near skeletal muscles compressing on lymphatic
vessels, pushing lymph along. One way valves prevent backflow.
Lymphatic vessels are studded with lymph nodes that cleanse the lymph as it filters through. They contain
macrophages and lymphocytes. Increased number of lymphocytes causes the lymph nodes to swell, thus swollen
and painful lymph nodes (glands) sign for infection.
Other lymphatic organs are the tonsils which form a ring around the entrance to the throat to help protect against
disease organsms. The thymus gland helps the maturation of lymphocytes that protect us from disease in
childhood. The spleen clears the blood of old and damaged red blood cells and platelets. Peyers patches keep
bacteria from reaching the intestinal wall. The red bone marrow where white blood cells and other formed
elements are produced, is an organ found in the ends of long bones, ribs and vertebrae.
3b(ii) The Digestive System
The digestive system takes the food we eat and breaks the complex organic molecules into their chemical subunits.
The subunits are molecules small enough to be absorbed into the blood stream and delivered to the body cells
where they either provide fuel or growth and repair of the body or they provide energy for daily activities.
The digestive system consists of a long hollow tube called the gastrointestinal (GI) tract into which various
accessory glands release their secretions. It begins at the mouth and continues to the esophagus, stomach, small
intestine and large intestine.
4 basic layers:
Mucosa: the innermost layer which is moist and secretes mucus. Mucus lubricates the lumen allowing food
to slide through easily. Also helps to protect cells in the lining of the GI tract from rough substances in the
food and digestive enzymes.
Submucosa: consists of connective tissue containing blood vessels, lymph vessels and nerves. The blood
supply maintains the cells of the digestive system and picks up and transports products of digestion. Nerves
coordinate contractons of the next layer Muscularis: responsible for movement of materials through the GI tract and for mixing ingested materials
with digestive secretions. Mostly double layered smooth muscle. Longitudinal muscles shorten the GI tract
when they contract, inner muscles cause contraction. The muscle layers churn the food until it is liquefied,
mix the result with enzymes and propel food along the GI tract in a process called peristalsis. Segmental
contractions mix intestinal contents and also assist absorption of digested food by moving intestinal
contents over the intestinal wall –two ways and allows mixing
Serosa: a thin layer of epithelial tissue supported by connective tissue and wraps around the GI. It secretes
fluid that lubricates the outside of the GI tract to reduce friction with other parts.
One aspect of processing food is mechanical digestion, the physical breakdown of food into smaller pieces and
another, the chemical digestion, where the breaking of chemical bonds so that complex molecules are taken apart
into smaller subunits. Produces molecules that can be absorbed into the bloodstream and used by the cells.
Specialized Compartments for Food Processing
Food moves along the GI tract, it passes through the mouth, pharynx, esophagus, stomach, small intestine, and
large intestine. The salivary glands, liver, and pancreas add secretions. Nutrients absorbed by small intestine.
Additional water is absorbed in large intestine. Undigested and indigestible materials pass out the anus.
Soft palate prevents food from entering the nose when swallowing. The mouth begins mechanical and some
chemical digestion and it monitors food quality, also it moistens and manipulates foods so it call be swallowed.
Teeth and salivary glands and tongue help.
As we chew, our teeth break solid foods down into smaller fragments to swallow and digest. Sharp incisors slice
food. Pointed canines tear the food, the food is then crushed and pulverized by molars. Teeth are alive, in the
center of each tooth is pulp which has blood vessels that nourish the tooth and nerves that sense heat, cold,
pressure and pain. Dentin surrounds the pulp. The crown of the tooth is covered in enamel, nonliving material that
is hardened with calcium salts. The root is covered with calcified yet living sensitive connective tissue called
cementum. Root canal is where the nerves reach the pulp.
Tooth decay is caused by acid produced by bacteria living in the mouth. Bacteria are nourished by sugars stuck in
teeth. As they dgest the sugar, acid is produced that erodes the enamel and causes cavities. Blood vessels in pulp
widen in response allowing greater numbers of white blood cells to reach the area and fight infection. The widened
blood vessels may press on nerves causing a tooth ache. When the enamel has been penetrated, bacteria can
invade the softer dentin. Bacteria can then infect the pulp. Plaque, an invisible film of bacteria, mucus and food
particles, promotes tooth decay because it holds the acid against the enamel. Daily brushing and flossing helps.
Gingivitis is an early sign of gum disease which occurs when plaque has formed along the gum line and causes gums
to be inflamed and swollen. Gums aren’t as tight, making it easier to trap plaque. Attacks bone and soft tissue
(bacteria) called periodontitis.
Salivary Glands and Chemical Digestion
As we chew, food is mixed with saliva and the water in saliva moistens food and mucus binds food particles
together, making it easier for the food to pass through the GI tract. Saliva also contains enzymes called amylase
that begins to chemically digest starches into shorter chains of sugar.
Tongue: Taste and Food Manipulation
Once food molecules are dissolved in saliva, the chemicals in food stimulate receptors in taste buds. Information
from taste buds, along with olfactory receptors in the nose, helps monitor food quality. Tongue moves food to
position for crushing. Turned into bolus to be easily swallowed. Tongue initates swallowing
Is a passageway commonly called the throat which is a part of the resp and digestive system. When we swallow,
food is pushed through the pharynx and into the esophagus which connects the stomach and pharynx. Swallowing
consists of voluntary component followed by an involvuntary one. When a person begins to swallow, the tongue
pushes the bolus of softened and moistened food into the pharynx. Once the food is there, it is too late to change your mind and sensory receptors in the wall of pharynx detect the presence of food and stimulates involuntary
swallowing reflex. Reflex movements of the soft palate prevent food from entering nose. Other involuntary muscle
contractions push the larynx (adams apple, voice box) upward and causes the epiglottis to move, covering the
opening to airways of the resp system, preventing food from entering. Food is then pushed into the esophagus.
Muscular tube that conducts food from the pharynx to the stomach. Food is moved along the esophagus and all the
rest of the GI tract by rhythmic waves of muscle contraction called peristalsis. This is produced by the two layers of
muscle in the muscularis. The muscles of the inner layer circle the tube causing a constriction when they contract.
The muscles in the outer layer run lengthwise, causing a shortening of the regions of contraction. The presence of
food sretches the walls of one region triggering the contraction of circular muscles in the region of the tube
immediately behind food mass. When they contract, that region os the tube pinches inward, pushing food forward.
At the same time, longitudinal muscles in front of the food contract and shorten the region to widen its walls and
receive food. Gravity is not important.
Is a muscular sac that (1) stores food and regulates the release of food to the small intestine (2) liquefies food and
(3) carries out initial chemical digestion of proteins.
Storage of Food and Regulation of the Release of Food to the Small Intestine
Stomach is expandable and has openings that can close to seal the contents within as well as open for filling and
emptying. When empty, the stomach is small J shaped sac that can hold only 50ml without stretching. When fully
expanded, as after a large meal, the stomach can hold several liters of food. Bands of circular muscle called
sphincters guard the openings at each end of the stomach and regulate the release of food to the small intestine.
Contraction of a sphincter closes the opening and relaxation of a sphincter allowes material to pass through.
Liquefaction of Food
Food is generally stored and processed within the stomach for 2-6 hours. The stomach wall has three layers of
muscle. Knead and compress stomach contents, breaking food into smaller pieces. Food is churned and mixed with
secretions produced by glands of the stomach until it is chyme.
Initial Chemical Digestion of Proteins
Chemical ingestion in the stomach is limited to the initial breakdown of proteins. The lining of the stomach has
millions of gastric pits, within which are gastric glands containing several types of secretory cells. Some produce
HCl which kills most of the bacteria swallowed with food or drink. It also breaks down the connective tissue of meat
and activates pepsinogen. Once activated by HCl, pepsinogen becomes pepsin, a protein digesting enzyme. Gastric
juice is peptin and HCl and pepsin begins the chemical digestion of protein in food. Mucus protects the stomach
from gastric juice. Intrinsic factor is secreted by gastric glands, a protein necessary for the absorption of vitamin
B12 from the small intestine.
Various things needed to keep stomach from digesting itself (gastric juice is able to attack stomach). One is mucus
which forms a thick, protective coat that prevents gastric juice from reaching the cells of the stomach wall. Mucus
neutralizes the HCl. Another protection is pepsinogen that cannot digest the cells that produce it (inactive form).
Neural and hormonal reflexes regulate the production of gastric juise so that little is release unless food is present
to absorb and dilute it. If stomach lining is damages, the high rate of cell division in the stomach fixes it (new
stomach lining every 3 days). Alcohol and aspirin are absorbed fast, especially if no food to dilute it.
Has two major functions: chemical digestion and absorption. Food passes through the duodenum, jejunum and
ileum. Chyme enters the duodenum, the first region, in squirts so that only a small amount enters. Digestive juices
also enter from the pancreas and liver. Most chemical digestion and absorption occurs in the jejunum and ileum.
Chemical Digestion within the Small Intestine Enzymes in the small intestine chemically digest carbs, proteins, fats and nucleic acids. Most digestion in small
intestine is actually performed by pancreatic enzymes. Fats are insoluble in water. Lipase, which breaks down fats,
is soluble in water and not in fats. As a result, lipase can only work at the surface of a fat globule. Large fat globules
have less combined surface area than smaller droplets so digestion proceeds slower.
Bile is a mixture of water, ions, cholesterol, bile pigments and salts that plays a role in digestion of fats. The salts
keep fats separated into small droplets that disperse in liquid. The separation exposes a larger combined surface
area to lipase making the digestion faster. Bile is produced by the liver, stored in the gallbladder and acts in the
Structure of the Small Intestine
Small intestine is the primary site of absorption and is extremely effective because it is long and specialized. First,
the entire lining of the small intestine is pleated into circular folds with increase the surface area for absorption and
cause chyme to flow through the small intestine in a spiral. The spiral helps mix the chyme with digestive enzymes
and increases its contatct with the absorptive surfaces. Covering the entire lining is villi which give increases the
surface area of the intestine. Each villis contain projections (microvilli) which increase the surface area of the small
intestine more. Very large surface area. The core of each villus is penetrated by a network of capillaries and a
lacteal, which is lymphatic vessel. As substances are absorbed from the small intestine, they cross only two cell
layers: epithelial cells of the villi and wall of either a capillary or lacteal.
Accessory Organs: Pancreas, Liver and Gallbladder
Not part of the GI tract but play a role in digestion by releasing their secretions into the small intestine.
Pancreatic juce drains from the pancreas which fuses with the common bile duct from the liver just before entering
the duodenum. Pancreatic juice has enzymes, water and ions important in neutralizing the acid in chyme when it
emerges from the stomach. Break nutrients: proteins to amino acids, carbs to monosaccharides and triglycerides to
fatty acids and glycerol.
Primary role is to produce bile. It also controls glucose level of the blood, either removing excess glucose and
storing it as glycogen or breaking down glycogen to raise blood glucose levels. The liver also packages lipids with
protein carrier molecules to form lipoproteins which transport lipids in the blood. After the liver adjusts blood
composition, blood is returned to circulation through hepatic veins. Liver stores vitamins A, D, E, K, B12 and folate.
Liver also removes poisonous substances. Hepatitis is inflammation of the liver caused by viruses. Healthy liver cells
remove bilirubin from the bloodstream and use it to make bile. Injured liver stops filtering it and accumulating
bilirubin is deposited in the skin and turns eyes yellow..
Bile is stored and modified in the gallbladder. When chyme enters the small intestine, a hormone causes the
gallbladder to squirt it into the duodenum. Bile is rich in cholesterol. Sometimes, if the balance of dissolved
substances in bile becomes upset, a tiny crystal particle precipitates out and cholesterol can build up around to
form a gallstone.
The material that was not absorbed in the small intestine moves into the large intestine. Functions: (1) to absorb
most of the water remaining in the indigestible food residue, thereby adjusting the consistency of the waste
material or feces, (2) to store the feces and (3) to eliminate them from the body. Home to many bacteria, some
Regions of the Large Intestine
Four regions: cecum, colon, rectum, anal canal. Extending from the cecum is the appendix which has no digestive
function. Appendicitis is inflammation of the appendix caused by infection after it is blocked by a piece of hardened
stool from the cecum, food or tumor. Largest region of the large intestine is the colon, where material entering is liquid. Colon absorbs 90% of the remaining water and ions. The material left after passing the colon is feces, which
consists of undigested food and epithelial cells and bacteria. Brown colour is from bile pigments. Bacteria here is
beneficial and not disease causing. E. coli. Metabolic processes of bacteria release gas when they eat undigested
food. Eventually food is pushed into the rectum, stretching the rectal wall and initiating defecation reflex. Nerve
impulses from the stretch receptors travel to the pnal cord, sending motor impulses back to the rectal wall,
stimulating muscles to contract and propel feces into the anal canal. Two rings of muscles, called sphincters, must
relax to allow the expulsion of feces. The internal sphincter relaxes automatically as a part of the reflex. The
external sphincter is under voluntary control, allowing the person to decide whether to defecate.
Water absorption that occurs in the colon adjusts the consistency of feces. When material passes through the colon
too rapidly, too little water is absorbed, feces is liquid. Too slowly, constipation.
Nerves and Hormones in Digestion
Because the body is composed of many of the same substances found in food, digestive enzymes should not be
released until food is present. Food spends little time in the mouth so to be effective, saliva must be secreted
quickly. Nervous stimulation is faster than hormonal. Nervous system controls salivation. Some saliva is released
before food even enters the mouth (thoughts). While food is being chewed, neural reflexes stimulate the stomach
lining to begin secreting gastric juices and mucus. Distention of the stomach by swallowed food, along with the
presence of partially digested proteins, stimulates cells in the stomach lining to release gastrin which enters the
bloodstream and circulates throughout the body and back to the stomach, where it increases the production of
gastric juice. (second brain)
The presence of acidic chyme triggers local nerve reflexes and is the most important stimulus for the release of
enzymes. It also causes the small intestine to release several hormones that are responsible for the release of
digestive enzymes and bile.
Ted Talk Video
Bacteria are the oldest living organisms on earth. Are one cell and have one piece of DNA. They consume nutrients
from their environment, grow and divide. Ten trillion bacterial cells (more bacterial than human cells). 100x more
bacterial genes on you all your life. 1% human. Coat us in armour, digest our food, make vitamins, educate immune
system. Vital for keeping us alive. A lot of unwanted bacteria that make you sick. Little squid lives in shallow water
and is nocturnal, needs vibrio fischerae bacteria for bioilluminesence. Squid doesn’t make a shadow so predators
cant see it. Pump in circadian rhythm that pumps out 95% of bacteria. All bacteria have protein enzymes that make
molecules and pump them out then attach to receptors. Virulence is important to us, they get in us and wait, then
grow and recognize that when they have enough, they all eject at once and attack us. Bacteria don’t live by
themselves. Multilingual. Intra and inter species communication. Are able to count and decide what tasks are
carried out by populations. Current antibiotics make bacteria stronger because the mutant survivors reproduce.
Want to make it so bacteria cant count, cant communicate, etc. Jamming recognition. Quorum sensing.
Future treatment options should include targeting unique metabolic niches found within bacterial biofilms in
addition to the enzymes or compounds that inhibit biofilm accumulation molecules and/or interact with quorum
sensing and intercellular bacterial communication.
3b(iii)- The Energy Distribution
Carbohydrates, Amino Acids and Lipids as sources of energy
All living organisms need to have a source of energy to do metabolic or physical work and animals depend on their
diets for chemical energy; substrates such as carbs, fats and protein are catabolized in reactions to capture some of
the energy in the form of ADP which is then used to power most cell functions. Some energy will be lost as ATP is
made and more will be lost as it is used. This energy is lost as heat which challenges body temperature control.
A kilocalorie (kcal), or Calorie (Cal), is the amount of energy required to raise the temperature of a liter of water by
1 degree C. (bomb calorimeter) to find out the greatest amount of energy that food could provide if consumed. We state this in terms of calories and once we correct for predi