Midterm 1 (Unit 1-3)

Physiology is the science of ———, physical, bioelectrical, and ——— functions of an organism in ——— health, their organs, and the cells they are composed.

mechanical, biochemical, good

Function refers to ——— the system exist/the event occurs.

Process refers to ——— the system works → physiological ———.

why, how, mechanisms

Homeostasis is the maintenance of a relatively stable internal environment, especially ——— ———^.

extracellular fluid

Failure to compensate for change and return to homeostasis leads to ——-.

The study of failure to compensate is called ———.

disease, pathophysiology

What is the key difference between local vs. reflex control?

local control - cells that are near the site of change initiates the response

reflex control - cells at a distant site controls the response

What are the components of the response loop (7)?

stimulus, sensor, input signal, integrating centre, output signal, target, response

What are the 3 feedback mechanisms?

negative feedback, feedforward, positive feedback

Negative feedback ——— variables.

Feedforward control ——— change.

Positive feedback ——— stimulus.

stabilizes, anticipates, reinforces

Which of the following is true?

a) Negative feedback is homeostatic, but positive feedback is not.

b) Both negative feedback and positive feedback are homeostatic.

c) Positive feedback is homeostatic, but negative feedback is not.

a

In cell-cell communication, ——— signals involves changes in membrane potential. While ——- signals are secreted into extracellular fluid by all cells.

electrical, chemical

Electrical signals are restricted to nerve and muscle cells. T/F

T

——— refers to when chemicals (i.e. hormones) are released into the bloodstream and distributed throughout the body → long-range cell-cell communication.

endocrine

Endocrine and neural are both considered long-range communication. T/F

T

In neural communication, ——— signal travels down a neuron, and when it reaches the end, the signal is translated to a ——- signal (neurotransmitter) to communicate with the next cell.

electrical, chemical

In neuroendocrine communication, the electrical signal travels down a neuron → reaches the end → secreted into ——-.

blood

Endocrine, neural, and neuroendocrine refers to ——— the signal gets to the ——— cell.

how, target

Only cells that have receptors for a particular signal will respond to it. The signal molecule that binds to a particular receptor is its ——-.

ligand

Receptors are proteins that…

a) project to outside of the membrane

b) are within the cell (in the cytoplasm)

c) all of the above

d

Water-soluble ligands often bind to ——- receptors, while water-insoluble receptors often bind to ——— receptors.

surface, intracellular

One ligand may have several different types of receptors. T/F

T - this explains how the same signal can have different effects in different cells

Receptors enhibit s———, s——-, and c——- for their ligands (and molecules similar to their ligands).

saturation, specificity, competition

Give an example of receptors enhibting specificity for their ligands.

relative affinities of adrenergic receptors for epinephrine vs. norepinephrine

Give an example of receptors exhibting competition for their ligands (and molecules similar to their ligands).

agonists and antagonists competing with endogenous ligands

Cells can change their response to signals by changing receptor n——- or s———.

number, sensitivity

Explain how cells are able to increase and decrease the number of receptors they exhibit.

increase → increase gene expression (up-regulate)

decrease → internalize surface receptors (down-regulate)

Give an example on how cells can change their receptor sensitivity.

phosphorylation → conformation change → increase/decrease receptor’s affinity for its ligand or its ability to initiate downstream signaling

Give an example of a ligand that has more than one receptor.

ligand = epinephrine

α-receptor on intestinal blood vessel → vasoconstriction

β₂-receptor on skeletal muscle blood vessel → vasodilation

Agonists and antagonists are structurally ——- molecules that compete for receptor binding sites.

similar

An ——- is a molecule that’s similar to the ligand that activates receptor (binds and trigger downstream events).

agonist, analogue, mimic

An ——- is a molecule that is similar enough to the native ligand that binds to the receptor, but does not activate it (does not trigger downstream events).

antagonist, blocker

What is the physiological effect of cholera toxin?

blocks the enzyme activity of G proteins → cell keeps making cAMP

Explain the activation of G-protein coupled receptor (GPCR).

1. ligand binds to surface receptor → G-protein binds to surface receptor

2. α subunit configuration change to have lower affinity for GDP, higher affinity for GTP

3. activated α subunit (now bound to GTP) and βγ complex dissociates from each other and from surface receptor

4. α-subunit goes to activate a target protein

Explain the deactivation of G-protein coupled receptor (GPCR).

1. α subunit hydrolyze GTP (intrinsic GTPase activity of Gα) → dissociates from the target protein

2. inactive α subunit reassembles with βγ complex to reform an inactive G-protein

Explain the effect of cholera toxin on the inactivation of Gα subunit.

chlolera toxin blocks to intrinsic GTPase activity of Gα → Gα persistently bound to target protein (adenylyl cyclase)

Cannon’s Postulates:

1. The ——— system has a role in maintaining “fitness” of the internal environment - coordinates responses that regulate blood volume, blood pressure, osmolarity, body temp, etc.

2. Some systems are under ——- control

3. Some systems are under ——— control

4. One chemical signal can have different effects in different tissues

nervous, tonic, antagonistic

Tonic control involves ——- regulatory signal(s) that modulate the activity of a target tissue or organ by varying the intensity (frequency or level) of the signal.

a single

Give an example of a system that is under tonic control.

blood vessel diameter is controlled by the sympathetic nervous system

• low level of norepinephrine (low signal frequency) → vasodilation

• increase norepinephrine (high signal frequency) →vasocontriction

Antagonistic control involves ——- opposing signal(s) that work against each other to regulate a process.

two or more

Give an example of a system that is under antagonistic control.

heart rate

sympathetic nervous system → increase heart rate via norepinephrine

parasympathetic nervous system → decrease heart rate via acetylcholine

opposing signals to control heart rate

Sensors/detectors/receptors are specialized cell types that are often found in extracellular fluid. T/F

T