Lecture 1 - Introduction to the ANS

Question 1

What are the two general functions of the sympathetic and parasympathetic nervous systems?

Answer 1

Sympathetic - Fight or flight

Parasympathetic - Rest and digest

Question 2

Is the liver largely sympathetic or parasympathetic and what effects are altered by the stimulation?

Answer 2

Largely sympathetic

Glycogenolysis and gluconeogenesis are increased by stimulation as available glucose needed during sympathetic response

Question 3

What organ do arterial baroreceptors have a large influence over the autonomic control of?

Answer 3

The heart

Question 4

What are the two branches of the autonomic nervous system (ANS)?

Answer 4

Sympathetic

Parasympathetic

Question 5

How do sympathetic and parasympathetic nerves affect the heart?

Answer 5

Sympathetic - stimulatory effect, increase rate and contractility
Parasympathetic - inhibitory effect, decrease rate and contractility

Question 6

What do baroreceptors detect and produce a response to?

Answer 6

Blood pressure

Question 7

How do baroreceptors influence autonomic control of responses to changing blood pressure?

Answer 7

Baroreceptors are stimulatory to parasympathetic nerves and inhibitory to sympathetic nerves to the heart.
When baroreceptors fire due to increased blood pressure, they activate the parasympathetic limb and inhibit the sympathetic limb thus leading to reduced heart rate and contractility, thus reducing blood pressure until they stop firing.

Question 8

Which limb of the ANS dominates the heart at rest?

Answer 8

Parasympathetic (rest and digest)

Question 9

Which limb of the ANS dominates the heart during exercise?

Answer 9

Sympathetic (fight or flight)

Question 10

How are the arterioles innervated regarding presence of sympathetic/parasympathetic fibres?

Answer 10

No parasympathetic innervation of arterioles

JUST sympathetic

Question 11

What neurotransmitters are used pre and post-ganglion in parasympathetic neurones?

Answer 11

Acetylcholine in both cases

Question 12

Difference in pre-ganglionic neurones in sympathetic and parasympathetic nervous systems?

Answer 12

Parasympathetic - Long pre-ganglionic

Sympathetic - Short pre-ganglionic

Question 13

What neurotransmitters are used pre and post-ganglion in sympathetic neurones?

Answer 13

Acetylcholine pre-ganglion

Noradrenaline, Adrenaline, Acetylcholine post-ganglion

Question 14

How do the sympathetic and parasympathetic responses differ in localisation and how wide they reach?

Answer 14

Sympathetic - Coordinated and divergent (happen same time in multiple organs with one pre-ganglionic fibre resulting in multiple post-ganglionic fibres)
Parasympathetic - Discrete and localised (1:1 ratio pre to post-ganglionic fibres, very focused response single target)

Question 15

How is the somatic nervous system different to the others?

Answer 15

Not influenced by the ANS at all, entirely voluntary, neurones don’t have ganglia, just single neurone from brain to muscle releasing acetylcholine

Question 16

Where are nicotinic receptors found and what neurotransmitter are they receptive to?

Answer 16

Found at ALL autonomic ganglia

Acetylcholine

Question 17

How do nicotinic receptors work in relaying signal and how fast are they?

Answer 17

They are Type 1 ionotropic - linked to an ion channel

ACh binds, ion channel opens which allows sodium/calcium influx and transmission of the signal - VERY FAST

Question 18

Where are muscarinic receptors found and what neurotransmitter are they receptive to? (what is the exception to the usual rule for these receptors?)

Answer 18

Found in any tissue innervated by post-ganglionic parasympathetic fibre
(exception are sweat glands which are sympathetically innervated)

Question 19

How do muscarinic receptors work in relaying signal and how fast are they?

Answer 19

They are Type 2 G-protein Coupled
G-protein handle relay of transmission
Much slower than nicotinic

Question 20

What are the subtypes of muscarinic receptors and where are they generally found/what do they do?

Answer 20

M1 - Neural
M2 - Cardiac
M3 - Exocrine and smooth muscle
M4 - Periphery
M5 - Striatal dopamine release
All found in the brain to some degree

Question 21

Where are adrenoceptors found and what are the different types?

Answer 21

Found at the end of the sympathetic nervous system on the effector organs.
Four subtypes, a1, a2, b1, b2

Question 22

What do the adrenoceptors control and what do the different types do specifically?

Answer 22

Control vasculature

• Alpha 1 constricts
• Beta 2 dilates

Question 23

What are adrenoceptors stimulated by and what are they linked to?

Answer 23

Stimulated by noradrenaline and adrenaline

G-Protein Coupled

Question 24

What is the 8 step process for the synthesis, release and metabolism of acetylcholine?

Answer 24

1) Acetyl CoA + Choline (catalysed by choline acetyl transferase) produces ACh + CoA
2) ACh packaged into vesicles
3) Ca2+ influx stimulates vesicle movement and fusion
4) Vesicle fuses and ACh released
5) ACh moves across synapse
6) ACh binds with receptor on post-synaptic membrane
7) ACh broken down in the synapse by acetylcholinesterase into Choline + Acetate
8) Choline moves back into pre-synaptic neurone to be recycled into step 1

Question 25

What is the 8 step process for the synthesis, release, reuptake and metabolism of noradrenaline?

Answer 25

1a) Tyrosine enters presynaptic neurone and is converted to DOPA by tyrosine hydroxylase
1b) DOPA is converted to dopamine by DOPA decarboxylase (still in neurone)
1c) Dopamine is packaged into vesicles
2) Dopamine is converted to noradrenaline by dopamine beta hydroxylase
3) Ca2+ influx stimulates vesicle movement and fusion
4) Vesicle fuses and NA is released
5) NA moves across synapse
6) NA binds to receptor on postsynaptic membrane.
7) NA reuptake via Uptake 1 transport protein into presynaptic neurone or Uptake 2 transport protein into extraneuronal tissue.
8) NA degraded by COMT in extraneuronal tissue or metabolised by Monoamine Oxidase A (MAO-A) in presynaptic neurone or returns to vesicle for recycling