Introduction to ANS

Question 1

Which limb of the autonomic nervous system has more of an effect on the Liver?

Answer 1

Sympathetic – causes hepatic gluconeogenesis and glycogenolysis to increase blood sugar levels for ‘Fight or Flight’ response

Question 2

Which limb of the autonomic nervous system dominates the lungs and the eyes at rest?

Answer 2

Parasympathetic
Lungs – causes partial bronchoconstriction
Eyes – allows near vision

Question 3

Describe the relationship between baroreceptor firing and parasympathetic discharge.

Answer 3

Baroreceptors are stimulatory to the parasympathetic nerves i.e. an increase in baroreceptor firing stimulates an increase in parasympathetic firing

Question 4

Describe the differences between sympathetic responses and parasympathetic responses.

Answer 4

Sympathetic – coordinated and divergent (Thoracolumbar)
Parasympathetic – discrete and localised
(Cranialsacral)

Question 5

What type of receptor are nicotinic receptors?

Answer 5

Type 1 – ionotropic receptors

They are very fast and always the receptor present at ganglions

Question 6

What type of receptor are muscarinic receptors?

Answer 6

Type 2 – G-protein coupled receptors
Slower than Type 1 receptors, but found at effector organs because second messangers can cause many effects within target cells.

Question 7

What effect does parasympathetic dominance at rest have on the: lungs, gut, bladder and eyes?

Answer 7

Lungs – partial bronchoconstriction
Gut – increased gut motility
Bladder – increased urinary frequency
Eyes – Ability to near focus

Question 8

Where are the three types of muscarinic receptor found?

Answer 8

M1 – neural tissue
M2 – heart
M3 – exocrine and smooth muscle

Question 9

Which adrenergic receptors are responsible for the sympathetic control of vasculature?

Answer 9

Alpha 1 – constriction

Beta 2 – dilation

Question 10

What type of receptor are all adrenergic receptors?

Answer 10

G-protein coupled (Serpentine, 7TM)

Question 11

Describe the synthesis of acetylcholine.

Answer 11

Acetyl CoA + Choline -> Acetylcholine

(enzyme) = choline acetyltransferase

Later broken down by acetyl cholinesterase

Question 12

Describe the synthesis of Noradrenaline.

Answer 12

Tyrosine -> DOPA
(enzyme: tyrosine hydroxylase)

DOPA -> dopamine
(enzyme: DOPA decarboxylase)

Dopamine -> Noradrenaline - Occurs in vesicles
(enzyme: dopamine beta-hydroxylase)

Question 13

What are the two uptake and breakdown mechanisms of noradrenaline?

Answer 13

Uptake 1 – neuronal tissue – mainly Monoamine Oxidase breakdown (MAO)

Uptake 2 – extraneuronal tissue – mainly Catechol-O-Methyl Transferase (COMT)

Both require use of Transfer proteins in the synaptic cleft.