1 - introduction to the 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

Question 2

Which limb of the autonomic nervous system dominates the lungs and the eyes at rest? What effects does this cause from the lungs/eyes?

Answer 2

Parasympathetic
Lungs – causes partial bronchoconstriction - so it can further constricted and dilated
Eyes – allows near vision - partially constricted so it can be both constricted and dilated

Question 3

What nerve is the major parasympathetic nerve?

Answer 3

vagus

Question 4

In the baroreceptor reflex, what structures do the sympathetic and the parasympathetic separately act on?

Answer 4

parasympathetic - heart
(there is no parasympathetic innervation of arterioles)
sympathetic - heart and vessels (arterioles and veins)

Question 5

What is the relationship between the baroreceptors and parasympathetic and sympathetic nerves?

Answer 5

• positively coupled to parasympathetic nerves (stimulatory)

- negatively coupled to sympathetic nerves (inhibitory)

Question 6

Draw out diagram showing the different branches of the ANS ganglion neurones and what neurotransmitter is used at synapses

Answer 6

(one Note)

Question 7

Where do all sympathetic post-ganglionic neurones project out from?

What does this indicate about the sympathetic response?

Answer 7

the sympathetic trunk

sympathetic responses are coordinated and divergent

Question 8

Describe the differences between sympathetic responses and parasympathetic responses.

Answer 8

Sympathetic – coordinated and divergent

Parasympathetic – discrete and localised

Question 9

Name the two plexi of the enteric nervous system

Answer 9

submucosal and myenteric

Question 10

Describe the pathway and role of neurones in the enteric nervous system

Answer 10

• sensory neurone connected to mucosal receptors and stretch receptors detect chemical substances in the gut wall caused by food
• interneurones relay information to the myenteric and submucosal plexi
• motor neurones release ACh or substance P to contract smooth muscle or vasoactive intestinal peptide or NO to relax smooth muscle

Question 11

How is the somatic nervous system different to the autonomic in terms of efferent nerves?

Answer 11

it has just ONE motor neurone innervating a muscle and releasing ACh (no pre- and post-ganglionic neurones)

Question 12

Where are nicotinic and muscarinic receptors found in the autonomic NS?

Answer 12

nicotinic - on ALL post-ganglionic membranes

muscarinic - on any tissue innervated by a parasympathetic post ganglionic fibres (and on sympathetic sweat glands)

Question 13

What type of receptor are nicotinic receptors?

Answer 13

Type 1 – ionotropic receptors

They are VERY fast

Question 14

What type of receptor are muscarinic receptors?

Answer 14

Type 2 – G-protein coupled receptors

Slower than Type 1 receptors

Question 15

Describe the difference in the transmission through nicotinic and muscarinic receptors.

Answer 15

Nicotinic is much faster

Question 16

What would the effect of blockage of the nicotinic ACh receptors by on the heart?

Answer 16

(nicotinic - on ALL post-ganglionic membranes)
therefore, both sympathetic and parasympathetic arms would be affected

at rest, parasympathetic is dominant - blockade would result in a increase in heart rate
during exercise, sympathetic dominate - blockade would result in an decrease in heart rate

Question 17

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

Answer 17

Lungs – partial bronchoconstriction
Gut – increased gut motility
Bladder – increased urinary frequency
Eyes – short-sightedness

Question 18

Describe what would happen is the parasympathetic NS was blocked (lungs, sweat gland, gut, bladder and eyes)

Answer 18

o	Bronchodilation
o	Reduced sweat production 
o	CONSTIPATION - reduced gut motility 
o	Decreased urinary frequency 
o	Long-sightedness

Question 19

Why would giving a ganglion blocker at rest cause constipation?

Answer 19

At rest the parasympathetic nervous system is dominant, which increases gastric motility. This means that a ganglion blocker will knock out this effect and cause constipation.

Question 20

Where are the three types of muscarinic receptor found?

Answer 20

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

Question 21

What are adrenoreceptors generally found?

Answer 21

receptors at the end of efferent sympathetic pathway

Question 22

Explain how the SNS can control vasculature by itself?

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

Answer 22

This is because of the nature of adrenoreceptors - mainly alpha 1 and beta 2
Alpha 1 – constriction
Beta 2 – dilation

Question 23

What type of receptors are adrenoreceptors?

Answer 23

g-protein coupled receptors

Question 24

Describe the synthesis and metabolism of acetylcholine.

Answer 24

It is formed from acetyl CoA and choline by choline acetyltransferase
It is broken down by acetyl cholinesterase into choline and acetate

Question 25

Describe the synthesis of Noradrenaline.

Answer 25

• Tyrosine -> DOPA
  (enzyme: tyrosine hydroxylase)
• DOPA -> dopamine
  (enzyme: DOPA decarboxylase)
• Dopamine -> Noradrenaline
  (enzyme: dopamine β-hydroxylase)
  This last step takes place in a vesicle

Question 26

What are the two uptake and breakdown mechanisms of noradrenaline?

Answer 26

NOTE: breakdown does not occur in the synapse, but only once uptake has occurred
Uptake 1 – neuronal tissue – mainly Monoamine Oxidase breakdown (MAO)
Uptake 2 – extraneuronal tissue – mainly Catechol-O-Methyl Transferase (COMT)

Question 27

What is basal heart rate?

Answer 27

50-70 bpm

Question 28

Only one arm of the ANS effects the lens of the eye (i.e. the ciliary muscle)? Which arm is this?

Answer 28

parasympathetic arm of the ANS - causes contraction of the ciliary muscle

Question 29

What is unusual about the ANS innervation of the lungs?

Answer 29

there are no sympathetic nerves present int he lungs - dilation is stimulated through adrenaline from the adrenal medulla

Question 30

What is unusual about the ANS innervation of the liver?

Answer 30

the liver ONLY has sympathetic control

Question 31

What is unusual about the ANS innervation of blood vessels?

Answer 31

sympathetic nerve carry out all the effects - can have opposing effects on different blood vessels