L19 The Autonomic Nervous System

Question 1

Effectors of the autonomic nervous system

Answer 1

Cardiac muscles, smooth muscles, glands

Question 2

Neurotransmitters of ANS pre/post ganglionic neurons

Answer 2

ACh/nAChR; ACH/mAChR and norepinephrine α1, α2, β1, β2

Question 3

Sympathetic division function

Answer 3

“Fight or flight” (Response to fear, difficult, dangerous situations)

Question 4

Autonomic division function

Answer 4

“Rest-and-Digest” (salivation, lacrimation, urination, etc)

Question 5

Sympathetic neurons

Answer 5

Preganglionic: cell bodies in the thoracolumbar regions (T1-L2)
Postganglionic: cell bodies in the paravertebral ganglia (sympathetic chain) or in the prevertebral/collateral ganglia (celiac, mesenteric, superior, and inferior)

Question 6

Length of pre and post ganglionic axons:
sympathetic vs parasympathetic

Answer 6

S: pre = short, post = long
P: pre = long, post = short

Question 7

Adrenal gland, ganglia location and cell types

Answer 7

Cell bodies of preganglioic cells in the thoracic spinal cord (T5-T9).
Axons pass through the sympathetic chain and the celiac ganglion towards the adrenal medulla to synapse on chromaffin cells.

Question 8

Chromaffin cell function

Question 9

Parasympathetic neurons

Answer 9

Preganglionic: nuclei of the cranial nerves (III, VII, IX, X) and in the sacral region of the spinal cord.
Postganglionic: within or very close to the effector organs.

Question 10

Arrangement and innervation of neuromuscular junctions

Answer 10

Discrete, organised motor end plates.
A skeletal muscle fiber is innervated by a single motoneuron.Store neurotransmitters at the terminal.

Question 11

Arrangement and innervation of neuroeffector junctions

Answer 11

Diffuse branching networks.
target tissues may be innervated by many postganglionic neurons.
Store neurotransmitters in varicosities.

Question 12

Ganglia of the parasympathetic, sympathetic, and adrenal medulla use ______ and __________ (NT/R).

Answer 12

Acetylcholine and nicotinic acetylcholine receptors

Question 13

Transmitter/receptors for the parasympathetic NS effectors

Answer 13

ACh/mAChR

Question 14

Transmitters/receptors for the sympathetic NS effectors

Answer 14

Norepinephrine; ACh/α1, α2, β1, β2 and mAChR

Question 15

Transmitter/receptors of the adrenal medulla effectors

Answer 15

Epinephrine and norepinephrine/ α1, α2, β1, β2

Question 16

Molecular function of Gs

Answer 16

Stimulates adenylyl cyclase, increasing cAMP and PKA. Stimulated by β1, β2 receptors.

Question 17

Molecular function of Gi

Answer 17

Inhibits adenylyl cyclase, decreasing cAMP. Stimulated by α2 receptors.

Question 18

Molecular function of Gq

Answer 18

Activates PLC, increase IP3/DAG and PKC/Ca2+ release.
Stimulated by α1 receptors.

Question 19

Physiological function and location for Gs proteins (β1)

Answer 19

Function:
- Increase heart rate, conduction velocity, and contractility
- Increase secretion of saliva, renin, and lipolysis
Location:
- SA node, AV node and ventricular hear muscles.
- Salivary glands, kidneys, adipose tissue

Question 20

Physiological function and location for Gs proteins (β2)

Answer 20

Function:
- Relaxation or dilation
Location:
- Vascular smooth muscle or skeletal muscle
- Walls of the GI tract and bladder
- Bronchioles

Question 21

Physiological function and location for Gi proteins (α2)

Answer 21

Function: Relaxation
Location: Vascular smooth muscle and certain blood vessels.

Question 22

Physiological function and location for Gq proteins (α1)

Answer 22

Function: contraction
Location:
- Vascular smooth muscle (skin, skeletal, sphlanchnic)
- Sphincters on the GI tract and bladder
- Radial muscles of the iris.

Question 23

Auto receptors

Answer 23

Present on sympathetic presynaptic regions, use a negative feedback loop to inhibit release of norepinephrine from the same terminals.

Question 24

Heteroreceptors

Answer 24

Present of parasympathetic presynaptic regions. Inhibit release of acetylcholine from the postganglionic PS terminals.

Question 25

Muscarinic cholinoreceptors, location, mechanism of action, blocked by

Answer 25

Effector organs of the parasympathetic NS (and sympathetic for sweat glands).
Coupled to PLC via Gq, act upon ion channels.
Blocked by atropine.

Question 26

Nicotinic cholinoreceptors, location, mechanism of action, blocked by

Answer 26

Postganglionic neurons of the ANS, chromaffin cells and MEPs.
Operates as a K+ channel.
Blocked by Curare.

Question 27

Mechanism of pupillary mydriasis

Answer 27

Sympathetic
Increase NE release and α1 activity in pupillary dilator (radial) muscle leading to dilation.

Question 28

Mechanism of pupillary miosis

Answer 28

Parasympathetic
Increase ACh release and mAChR activity in the pupillary constrictor (sphincter) muscle causing constriction.

Question 29

Servomechanism

Answer 29

A control system that uses a negative feedback mechanism to operate another system. Eg, the vasomotor centre in blood pressure regulation.

Question 30

Hypothalamic receptors regulate:

Answer 30

Food intake (glucoreceptors), water intake (osmoreceptors), and temperature (thermoreceptors)

Question 31

Determinants of physiologic functions

Answer 31

Diversity: different transmitters, different receptors.
Specificity: same NT/receptor, but different functions depending on tissue and cell type.