Autonomic Control

Question 1

Skeletal muscle nerve pathway

Answer 1

On target organ, nicotinic receptors (N1) that are stimulated by acetylcholine

Question 2

Parasympathetic

Answer 2

Ganglion is located near target organ
Pre ganglionic neurons: acetylcholine on to N2 recptors (nicotinic)
Postganglionic: aetylcholine on muscarinic receptors

Question 3

Sympathetic

Answer 3

Preganglionic: acetylcholine at N2 receptors
Postganglionic: norepinephrine at alpha and beta adrenergic receptors.

Question 4

Sympathetic via adrenal gland

Answer 4

N2 cells respond to acetylcholine at adrenal medulla
chormaffin cells cause release of epinephrine into the blood stream which will act on these adrenergic receptors (mostly beta??)

Question 5

What is atropine?

Answer 5

It is a muscarinic receptor antagonist

Blocks parasympathetic activity so increases heart rate.

Question 6

Where are alpha and beta receptors often found?

Answer 6

Alpha: In the smooth muscle of the vasculature
Beta: heart cells (note some B2 in smooth muscle)

Question 7

What is special about the alpha 2 receptor?

Answer 7

Once noradrenaline has binded, it then inhibits noradrenaline release. (found on the postganglionic cell, not the target organ)

Question 8

What are the binding affinities of the two types of receptors?

Answer 8

Alpha :noradrenaline > adrenaline > isoproteronol
Beta: isoproteronol > adrenaline > noradrenaline (more sensitive to the circulating epinehphrine, so heart responds as well as circulating to cause vasodilation)

Question 9

What are the important subtypes of these adrenergic receptors?

Answer 9

B1: found in the heart, will increase rate and force of contraction
B2: SM relaxation
A1: smooth muscle (in vasculature) contraction (phenylehprine is A1 agonist)
A2: inhibition of further noradrenaline release

Question 10

Describe the broad schematic of the autonomic nervous system (CVS) and where the parts go

Answer 10

Parasympathetic: Vagus nerve and innervates the atria (SA and AV nodes)
Sympathetic: Down the sympathetic trunk ganglia to the heart (SA node, AV node and ventricles) as well as the periphery so blood vessels and the adrenal glands

Question 11

What i respiratory sinus arrythmia driven by?

Answer 11

Vagus nerve. Demonstrates that the parasympathetic nervous system acts faster than the sympathetic

Question 12

At the SA node how do P/S and S systems affect it

Answer 12

P/S: Ach will increase the Ik and decrease the If, prolonging hyperpolarization, slowing HR

S: NAdr will increase the If and the Ica, increasing rate of spontaneous depolarization, increasing HR

Question 13

In terms of cardiac muscle physiology how does NAdr play a role in ventricular myocytes?

Answer 13

Acts on Beta receptors (B1) and this will increase the intracellular calcium aswell as increase cAMP activity, increase PKA, more phsopholamban (more SERCA), more SR release as well as more troponin more cross bridge cycling e yes!!!

Question 14

What are beta blockers?

Answer 14

Block beta recptors, eg atenolol, labetalol

They prevent arrythmias, and reduce workload (during heart failure)

Also used for performance anxiety, glaucoma and migranes

Question 15

Describe the dive reflex

Answer 15

peripheral vasoconstriction causes a raise in BP(symp. activity)
bradycardia p/s activity

Initiated in response to: cold water / pressure stimulating 10th cranial nerve, central and peripheral chemoreceptors and central command