2017 Physiology 1 - Signal Transduction

Question 1

Primary NT for sympathetics

Answer 1

Epinephrine and Norepinephrin

Question 2

Primary NT for parasympathetics

Answer 2

Acetylcholine (ACh)

Question 3

G Protein Signaling and Cyclin, steps

Answer 3

1. Signal molecule binds to G-protein
2. Receptor/protein complex allows GTP to displace GDP from alpha-subunit
3. Binding of GTP causes dissociation into free alpha and beta+gamma subunits
4. Alpha subunit interacts to cause secondary messengers
5. Alpha unit has intrinsic GTPase activity to turn GTP into GDP
6. Cycle repeats

Question 4

Examples of secondary messengers

Answer 4

cAMP, IP3, DAG

Question 5

Function of Gs class of G-Protein Receptors

Answer 5

Stimulatory towards Adenylate Cyclase which increases cAMP activity which has downstream affects on Protein Kinase A (PKA)

Question 6

Function of Gi class of G-Protein Receptors

Answer 6

Inhibitory towards Adenylate Cyclase which lowers cAMP activity

Question 7

Function of Gq class receptors?

Answer 7

Activate Phospholipase C (PLC)

Question 8

What is Phospholipase C and what does it do?

Answer 8

Membrane bound enzyme that converts phosphatidyl inositol (1,4) bisphosphate (aka. PIP2) into Inositol (1,4,5) triphosphate (aka. IP3) and Diacylglycerol (DAG)

Question 9

What does IP3 do?

Answer 9

formed in plasma membrane by PLC, binds to IP3 receptors on the ER causing release of intracellular Ca++ stores

Question 10

What does DAG do? Effect on Protein Kinase C (PKC)

Answer 10

Made by PLC, remains membrane bound.
Protein Kinase C (PKC) translocates from cytosol to membrane and is activated by DAG.
Activated PKC then phosphorylates other proteins to alter function.

Question 11

What is Guanylate Cyclase and what is it’s function?

Answer 11

Can be membrane bound or soluble; forms cGMP from GTP when receptor site is activated.

Question 12

How is NO produced in the cell and what is it’s function?

Answer 12

Produced from the aa. Arginine

Activated soluble, cytosolic guanylate cyclase -> thus increasing cGMP.

Question 13

Special features of NO as secondary messenger?

Answer 13

Membrane soluble, which allows it to diffuse to nearby cells.
Of importance between vascular endothelial cells and nearby smooth muscle cells.

Question 14

Phosphodiesterases function?

Answer 14

Breakdown cGMP and terminate it’s action

Question 15

Types of Cholernergic Receptors?

Answer 15

Nicotinic (N1/Nm and N2/Ng)

Muscarinic (M1-M5)

Question 16

Types of Nicotinic Receptors

Answer 16

Skeletal Muscle - N1/Nm

Autonomic Ganglia - N2/Ng

Question 17

Types of Muscarinic Receptors

Answer 17

M1,M3,M5 - activate PLC via Gq receptors. PLC leads to increase in intracellular Ca++ (via IP3)

M2,M4 - inhibit adenylate cycle via Gi receptors.

Question 18

Types of Adrenergic Receptors and function of each:

Answer 18

Beta - stimulate adenylate cyclase - produces cAMP and Activates PKA. Gs mediated.

Alpha 1 - increase IP3 and DAG. Presumably Gq mediated and involve PLC activation.

Alpha 2 - inhibition of adenylate cyclase. Presumably Gi mediated.