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Lecture

PHGY 209 Immunology.doc


Department
Physiology
Course Code
PHGY 209
Professor
Ann Wechsler

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Body Fluids
Physiology: Study of how living organisms work.
Includes the study of individual molecules.
Includes the complex processes that depend on the interplay of many widely
separated organs in the body.
Physiological Genomics: Integration of molecular biology with physiology.
Pathophysiology: Integration of medicine with physiology. Many disease states are
also physiology gone wrong. It is important for pathologists to understand and know
physiology to deal with disease.
Cells: Simplest structural units into which a complex multicellular organism can be
divided and still retain the functions characteristic of life.
Certain fundamental activities are common to all cells.
All cells exchange materials with their immediate environment.
200 different types of cells
4 categories of functions:
Muscle
Nerve
Epithelial
Connective
Cell Differentiation: The transformation of an unspecialized cell into a specialized
cell.
Muscle cells: Generate the mechanical forces that produce movement.
Surround may tubes in the body. When contracted, they change the diameter
of these tubes.
3 categories:
Skeletal
Cardiac
Smooth
Nerve cells: Initiate and conduct electrical signals, often over long distances.
Provide a major way of controlling the activities of other cells.
Epithelial cells: Responsible for the selective secretion and absorption of ions and
organic molecules and for protection.
Located primarily at:
Cover the body or individual organs
Line the walls of carious tubular and hollow structures within the body.
Rest on an extracellular protein layer called the basement membrane.
Form the boundaries between compartments and function as selective barriers
regulating the exchange of molecules.
Cells at the surface of the skin form a barrier that prevents most substances in
the external environment from entering.
Found in glands that form from the invagination of epithelial surfaces.

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Connective tissue cells: Connect, anchor and support the structures of the body .
Found in the loose meshwork of cells and fibres underlying most epithelial
layers.
Types:
Fat-storing, bone, red blood, white blood
Tissues: Aggregation of specialized cells.
4 types:
Muscle
Nerve
Epithelial
Connective
The immediate environment that surrounds each individual cell in the body is
the extracellular fluid.
Fluid is all between a complex extracellular matrix which is made up
of a mixture pf protein molecules.
The matrix has two main functions:
Allows for cells to attach
Transmits information in the form of chemical messengers to the cells to
help regulate their activities, migration, growth and differentiation.
Consists of collagen fibres and elastin fibres
Collagen constitutes 1/3 of all the body's protein.
They are the communicational links between extracellular chemical
messengers and the cells.
Organs:
Composed of four different types of tissues.
Organized into small, subunits called functional units who perform the
organ's function.
Organ system: Collection of organs that perform an overall function
10 organ systems in the body
Refer to page 4 for systems
Extracellular Fluid: The fluid present in blood and in the spaces surrounding cells.
20% of the fluid portion in blood is plasma.
80% is the interstitial fluid.
Plasma exchanges stuff with the interstitial fluid as it flows by so
concentrations in both mediums are virtually the same.
However!! Protein concentration in plasma is much greater than in the
interstitial fluid!
Extracellular fluid may be considered as homogeneous though
Intracellular Fluid: The fluid present inside the cells.
Cells regulate their activities by maintaining differences between the two
fluids.
Fluids in the body are compartmentalized.

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Water
The most important and predominant fluid in the body.
60% of an adult male weighing 70kg.
2/3 is intracellular and 1/3 is extracellular.
Compartmentalization is created by putting barriers around the compartments.
Homeostasis: State of reasonably stable balance between physiological variables.
It is dynamic.
Every organ and organ system contributes in keeping homeostasis.
Everything is interdependent so if 1 system is nonhomeostatic then other
system will begin to fail as well.
Physiology=Homeostatic
Pathophysiology=Lack of homeostasis
It is important to record data over a 24-hour period as many homeostatic
systems vary throughout the day. Ex: Repeated blood measurements. Or a 24
hour cumulative urine sample.
Voluntary behavioural responses are crucial events in homeostasis.
Some homeostatic systems are more important than others so some will be
altered to keep the more important ones constant.
Homeostatic control systems perform regulatory response.
Steady state: System in which a particular variable is not changing however energy
is added continuously to maintain this constancy.
Equilibrium: Variable is not changing but no energy is added.
Set point: The point at which the steady state stops at. For ex: 37C is the set point
for the thermoregulatory system.
Can be reset adaptively. Ex: during a fever, body temperature set point is
raised to kill off pathogens.
Negative feedback system: an increase or decrease in the variable being
regulated brings about responses that tend to move the variable in the opposite
direction.
May occur at the organ, cellular or molecular level.
Regulate many enzymatic processes.
Positive feedback system: Accelerates a process.
Less common than negative feedback.
Feedforward regulators: Regulators that anticipate change and act upon it quickly
to help the body achieve homeostasis quicker.
Ex: Faster heartbeat before athletic competitions.
Reflex: Specific involuntary response to a stimuli.
Can be learned or acquired.
Usually associated with a negative feedback system but not necessarily.
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