MFAC1501 Lecture Notes - Lecture 28: Pituitary Gland, Amylopectin, Thermoregulation
27 May 2018
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Department
Course
Professor
Foundations MFAC1501 Topical Key Points
Physiology 1
Body Compartments
• Intracellular compartments à fluid inside of cells, includes RBCs and WBCs
• Extracellular compartments
- Interstitial space à env. of most cells; ie surrounding area
- Transcellular àpools of special fluids with specific functions; cerebral spinal fluid (CSF),
synovial fluid of joints etc
- Plasma à fluid blood
• Function of compartments
- Compartmentalization; such that different metabolic pathways can occur simultaneously
- Maintaining gradients for movement of substances:
A) passive transport: osmosis, diffusion à follows concentration gradient
Osmosis:
- Based on concentration differences of solute molecules which causes a net movement of
water molecules
- Presence of semi-permeable membrane
- With reference to water molecules; ie water moves from region of more less negative water
potential to more negative water potential
- In hypertonic solution, water moves out of cell à crenation of cell
- In hypotonic solution, water moves into cell à if no cell wall, cell may rupture but if cell wall
present (eg in plants) plasmolysis occurs
- Capillary exchange depends on the balance of hydrostatic and osmotic pressure
- Osmoles = number of moles of all solute particles
- Osmolarity = number of osmoles per litre of solution
Diffusion:
- Based on Brownian motion; random movement of each molecule where each molecule has
the same probability of crossing membrane à until equilibrium is reached
- Simple vs facilitated diffusion
- Does not require ATP
- Challenges:
à some molecules too large to pass through membrane
à molecules are hydrophilic/do not dissolve easily into membrane
B) active transport à usage of ATP to move substances against concentration gradient
C) bulk movement à via cell signaling
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Physiology 2
Cell and Molecular Physiology
Diffusion
Active Transport
Bulk movement
Simple
Facilitated
The movement of molecules
across a membrane against
the concentration gradient
with the use of ATP
- sodium-potassium
pumps
- endocytosis
- exocytosis
- pinocytosis
- phagocytosis
Where a molecule
passes through a
membrane without
the aid of an
intermediary such as
an integral membrane
protein
Where molecules are
moved across a
membrane via specific
protein carrier or
channel molecules;
but does not require
ATP
• Membrane potential
- Defined as the difference in charge distribution across a membrane based on the number of
ions on each side of the membrane
- Resting Membrane Potential (RMP) = -70mV; usually refers to membrane of a neuron or of
all excitable cells à usually due to K+ ions leaving cell via leaky K+ channels
- Essential for cell signaling
• Depolarization
- Membrane become less polarized à value becomes less negative
- Result of more cations or less anions in cell à Na+ influx/ less K+ efflux/ Cl- efflux
• Hyperpolarization
- Membrane potential moves in negative direction à follows repolarization; as a result of lag
time taken for K+ gated channels to close more negative membrane potential than RMP
Action Potential
Synaptic Potential
Receptor Potentials
Graded Potentials
Rapid response of
about 100mV à
causes depolarization
à requires a
threshold stimulus to
elicit response (all or
nothing) à usually
results in muscle
contractions
Nerve response to
neurotransmitter à
can cause either
depolarization or
hyperpolarization
Response to sensory
stimuli in specialized
sensory receptors à
eg skin receptors;
Pacinian corpuscle
A depolarization that
is proportional to
stimulus à larger
potential = larger
response
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Physiology 3
Cardiovascular System
• Function
- Transportation; gaseous exchange, nutrients, fluid and electrolytes, waste, hormones
- Defense against infection
- Delivery of platelets for clotting
- Thermoregulation
A) Arteries
- Transportation of blood at high pressure; away from heart to rest of body
- More elastic fibres than veins to withstand high pressure
- Large lumen
B) Arterioles
- Resistance vessels; controls flow to individual tissue beds à hydraulic filter
- Relatively smaller lumen, but still has thick wall
C) Capillaries
- Exchange vessels; oxygenated to deoxygenated blood
- Thin walls for effective gaseous exchange
D) Venules/Veins
- Returns blood from rest of body to heart; capacitance vessels à stsytemic veins store the
largest vol of blood at rest
- Less elastic fibres than arteries
• Cardiac Output (CO)
- amount of blood pumped each minute
- CO = SV (stroke vol) x HR (heart rate)
- Stroke vol = vol pumped per beat
Systemic
Pulmonary
Flow
Same
Pressure diff
Large
Small
Resistance
High
Low
Pressure
High
Low
• Flow vs Velocity
- Blood flows in the same direction as the decreasing pressure gradient: arteries to capillaries
to veins
- Velocity varies inversely with the total cross-sectional area of the blood vessel
- CA increase, velocity decreases
Basic Theory of Circulatory Function
1. Rate of blood flow to each tissue is almost always precisely controlled in reaction to the
tissue need
2. CO is controlled mainly by sum of all local tissue flows
3. Generally, arterial pressure in controlled independently of either local blood flow control or
CO control
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Intracellular compartments fluid inside of cells, includes rbcs and wbcs: extracellular compartments. Interstitial space env. of most cells; ie surrounding area. Transcellular pools of special fluids with specific functions; cerebral spinal fluid (csf), synovial fluid of joints etc. Plasma fluid blood: function of compartments. Compartmentalization; such that different metabolic pathways can occur simultaneously. Maintaining gradients for movement of substances: passive transport: osmosis, diffusion follows concentration gradient. Based on concentration differences of solute molecules which causes a net movement of water molecules. With reference to water molecules; ie water moves from region of more less negative water potential to more negative water potential. In hypertonic solution, water moves out of cell crenation of cell. In hypotonic solution, water moves into cell if no cell wall, cell may rupture but if cell wall present (eg in plants) plasmolysis occurs. Capillary exchange depends on the balance of hydrostatic and osmotic pressure. Osmoles = number of moles of all solute particles.
