Week 1: Vasoconstrictors and Direct Vasodilators

Question 1

SNS

Thoracolumbar origin (T1-L2)
Preganglia near spinal cord
Post ganglia secrete ______ -adrenergic fibers

Answer 1

Norepinephrine

Question 2

Norepinephrine:

_______ converts dopamine to NE

Answer 2

Dopamaine beta hydroxylase

An action potential releases NE for synaptic vessel

Question 3

NE signal termination:

Answer 3

• reuptake

- dilution by diffusion

Question 4

NE is metabolized by:

Answer 4

Monamine Oxidase (MAO) and Catechol-o-methyltranserase (COMT)

Question 5

Adrenergic Receptors: SNS

Alpha 1 receptors stimulates:

Answer 5

Periphery

Post synaptic receptor:

• activation increases intracellular Ca
• smooth muscle contraction (vessel constriction)
• Peripheral vasoconstriction
• Bronchoconstriction (Beta 2 overrides)
• inhibits insulin secretion (beta 2 overrides)
• stimulates glycogenolysis and gluconeogenesis (SNS)
• Mydriasis (dilated pupils)
• GI relaxation (stops parastalsis)

Question 6

Adrenergic Receptors: SNS

Alpha-2 receptors stimulates:

Answer 6

Negative feedback loop

Presynaptic in PNS

• decreases entry of Ca into the cell
• limits the release of NE

Post synaptic in CNS

• sedation
• decreased sympathetic outflow
• decreased BP
• platelet aggregation

Question 7

Adrenergic Receptors: SNS

Beta-1 receptors stimulates:

Answer 7

Postsynaptic Receptor:

• increases HR
• increases conduction velocity
• increases myocardial

Question 8

Adrenergic Recptors: SNS

Beta-2 receptors stimulates:

Answer 8

Postsynaptic receptor:

• stimulation leads to smooth muscle relaxation
• perpherial vasodilation
• decreases BP
• BRONCHODILATION
• increases insulin secretion
• increases glycogenolysis and gluconeogenesis
• decreases GI mobility

Question 9

Parasympathetic NS: Cholinergic

Craniosacral (Brain & Butt) origin:

Postganglia secrete______

Answer 9

Cranial Nerves: III, V, VII, X
Sacral nerves 2,3,4

Preganglia near organs of innervation

ACETYLCHOLINE (ACH)

Question 10

______ activates BOTH arms of the SNS

Answer 10

Acetylcholine (ACH)

Choleine+AetylCoA –> acetylcholine
(Choline acetyltranserase)

Calcium medicated action potential

Question 11

Acetylcholine is deactivted/broken down by:

Answer 11

Acetylcholinesterase–> Choline and acetate

Question 12

Cholinergic receptors (PNS):

Answer 12

Nicotinic

Muscarinic

Question 13

Up-Regulation:

Answer 13

Chronic depletion of catecholamines or use of antagonists increases the number of receptors, but not their sensitivity.

May account for withdrawal syndrome with beta blockers

Question 14

Down-Regulation:

Answer 14

Extended exposure to agonists reduces the number of receptors, but not their sensitivity.

Results in tachyphylaxis.

Question 15

Receptor desensitization/ Down-regulation:

Receptor uncoupling:

Answer 15

Desensitization is the reduction in a physiologic response over time to a stimulus that remains constant.

Un-coupling:

• occurs rapidly (takes seconds to minutes)
• inability to the receptor to bind G protein (alter function of the receptor)

Uncouples the receptor from the signal transduction system. Caused by the phosphorylation of the receptor and possibly the G protein.

Question 16

Receptor desensitization/ Down-regulation:

Sequesteration:

Answer 16

• occurs more slowly (minutes to hours)
• movement of receptors from the cell surface to intracellular compartments

Receptors moved from cells membrane to intracellular compartments are not accessible to hydrophilic ligands

Question 17

Receptor desensitization/ Down-regulation:

Down-regulation:

Answer 17

• prolonged process (hours to days)
• Movement of receptors from the cell surface to intracellurlar compartments, but then destroyed.

Receptors are not available for recycling to the cell surface. New receptor protein must be made from RNA to replace lost receptors.