Lecture 6: Autonomic Nervous System

Question 1

What does the autonomic nervous system control?

Answer 1

Controls non-skeletal peripheral function:

• cardiac muscle (heart)
• smooth muscle
• internal organs
• skin

Question 2

What is the autonomic nervous system a sub-division of?

Answer 2

The peripheral nervous system (motor/efferent division –> visceral motor)

Question 3

What is the ANS split into?

Answer 3

• parasympathetic (rest and digest - PNS)

- sympathetic (fight and flight - SNS)

Question 4

What sort of effects does the PNS have on the body?

Answer 4

• constricts pupil
• increases secretion in salivary gland
• decreases heart rate/contractility
• constricts lungs
• increases motility and secretions in GIT
• increases bile release in liver
• contracts bladder

Question 5

What sort of effects does the SNS have on the body?

Answer 5

• dilates pupils
• decreases secretion in salivary glands
• increases heart rate/contractility
• dilates lungs
• decreases motility and secretions in GIT
• increases glucose release in liver
• relaxes bladder

Question 6

What is an exception to the antagonistic effects of the PNS and SNS?

Answer 6

SNS controls blood vessel tone - both constriction and dilation (due to diff receptors)

Question 7

What does the ANS react to?

Answer 7

sensory information received in the integrating centre (hypothalamus)

Question 8

Where do the visceral motor nuclei originate?

Answer 8

in the hypothalamus

Question 9

What is a ganglion?

Answer 9

a nerve cell cluster or group of nerve cell bodies

Question 10

What 2 types of neurones do autonomic neurones consist of?

Answer 10

a pre-ganglionic and a post-ganglionic neurone

Question 11

What type of ganglion would you find in the PNS?

Answer 11

• long pre-ganglionic fibres
• ganglions close to (or embedded within) effector tissues
• short post-ganglionic fibres

Question 12

What type of ganglion would you find in the SNS?

Answer 12

• short pre-ganglionic fibres
• ganglions close to originating site of pre-ganglionic fibre
• long post-ganglionic fibres
  (sympathetic nerves often work together)

Question 13

What is the one exception to the 2 neurone arrangement in the ANS?

Answer 13

• adrenal gland (only 1 sympathetic nerve)

Question 14

In which synapses is acetylcholine released?

Answer 14

• pre- and post-ganglionic nerve fibres of parasympathetic

- pre-ganglionic nerve fibre of sympathetic

Question 15

In which synapse is noradrenaline released?

Answer 15

post-ganglionic nerve fibre of sympathetic

Question 16

What does the adrenal gland secrete instead of neurotransmitter and where does this substance go?

Answer 16

• hormone (adrenaline) and some noradrenaline that is secreted into bloodstream rather than a synapse

Question 17

How does the sympathetic nervous system influence lung function?

Answer 17

• by adrenal gland producing adrenaline which affects lung rather than neurotransmitter

Question 18

What does the ANS respond to?

Answer 18

sensory input

Question 19

What is unusual about the nerves going to the lungs?

Answer 19

There are parasympathetic nerves innervating the lung tissue but no sympathetic neurons innervating the lung tissue.

Question 20

Where does the enteric nervous system work?

Answer 20

In GIT

Question 21

What type of receptor would you want at autonomic ganglia?

Answer 21

acetylcholine receptor (nicotinic acetylcholine receptor - ion channel linked receptor)

Question 22

What do nicotinic acetylcholine (nACh) receptors do?

Answer 22

• mediate responses to ACh released from preganglionic fibres at ALL autonomic ganglia
• also mediate response to ACh released by sympathetic nerves innervating adrenal medulla (adrenal gland)

Question 23

Which receptors are used for the post-ganglionic neurones in the PNS?

Answer 23

muscarinic receptors (G-protein coupled) - for ACh

Question 24

Which receptors are used for the post-ganglionic neurones in the SNS?

Answer 24

adrenergic receptors (G-protein coupled) - for noradrenaline (NA) or adrenaline via blood

Question 25

Outline the general biosynthesis and metabolism of neurotransmitter.

Answer 25

1. Precursor enzymatically converted to neurotransmitter
2. packaged into vesicles
3. action potential causes Ca2+ influx and exocytosis
4. exocytosis and neurotransmitter release
5. receptor activation
6. removal of NT from synapse via uptake into pre-synaptic terminal or glial cells. can be metabolised in synapse prior to uptake.

Question 26

Where does the precursor for neurotransmitters usually come from?

Answer 26

usually from diet

Question 27

How is acetylcholine produced?

Answer 27

choline + acetyl CoA enzymatically converted by choline acetyl transferase

Question 28

What receptors may acetylcholine bind to?

Answer 28

muscarinic (G-coupled) or nicotinic (ion channel)

Question 29

What happens to acetylcholine after it’s been used to activate receptors on the post-synaptic terminal?

Answer 29

• ACh rapidly degraded by acetylcholinesterase in the synapse
• Choline taken up into presynaptic terminal by choline uptake protein

Question 30

What would happen if you blocked acetylcholinesterase?

Answer 30

over accumulated ACh

Question 31

How is noradrenaline produced?

Answer 31

• tyrosine converted to DOPA by tyrosine hydroxylase
• DOPA converted to dopamine by DOPA decarboxylase
• dopamine packaged into vesicles and dopamine B hydroxylase produces noradrenaline

Question 32

What receptor does noradrenaline bind to?

Answer 32

adrenergic

Question 33

How is adrenaline produced?

Answer 33

noradrenaline converted to adrenaline in the cytoplasm by phenylethanol methyl transferase

Question 34

What happens once adrenaline is released into the synaptic cleft?

Answer 34

Adrenaline diffuses into capillary and is transported to tissues in the blood

Question 35

What happens to noradrenaline after it has activated receptors on the post-synaptic terminal?

Answer 35

It is transported back to pre-synaptic neuron via reuptake channels and then metabolised.