Autonomic Nervous System

Question 1

Where are the ganglia found in the sympathetic nervous system?

Answer 1

In the paravertebral ganglion chain.

Question 2

What parts of the spine do the sympathetic nerve fibres derive from?

Answer 2

The thoracolumbar region

Question 3

What are of the spine do the parasympathetic nerve fibres derive from?

Answer 3

The cervical and sacral spine.

Question 4

What part of the each vertebrae of the spine do autonomic fibres derive from?

Answer 4

The lateral horn of the medulla.

Question 5

What is a feature of post-ganglionic fibres?

Answer 5

They tend to be Unmyelinated.

Question 6

State the type of transmission which occurs at preganglionic synapses.

Answer 6

This is cholinergenic transmission and the post ganglionic nerve cells have nicotinic acetyl choline receptors.

Question 7

What are nicotinic acetylcholine receptors?

Answer 7

These are ligand gated ion channels.

Question 8

Describe the nature of a parasympathetic post ganglionic synapse.

Answer 8

This will have Muscarinic acetylcholine receptors, and these are linked to G proteins.

Question 9

Describe a sympathetic post ganglionic synapse.

Answer 9

At these, there are adrenoceptors which link to GPCRs. The exception to this is sweat glands which have cholinergenic innervation.

Question 10

What is a chromaffin cell?

Answer 10

This is in the adrenal glands and are innervated by the sympathetic nervous system via nicotinic acetylcholine receptors. When stimulated, they release adrenaline into the blood stream for activation of other sympathetic receptors.

Question 11

Name some molecules which can be coreleased at nerve terminals.

Answer 11

ATP, NO, 5-hydroxyhyptamine, neuropeptides.

Question 12

What is sludge?

Answer 12

This is an acronym for functions of the parasympathetic nervous system: salivation, lacrimation, urination, defaecation, gastrointestinal upset, emesis (vomitting)

Question 13

What is the action of the parasympathetic nervous system in the heart?

Answer 13

It acts on the SA node causing bradycardia, and it acts on the AV node to slow conduction rate.

Question 14

What is the carotid body?

Answer 14

This is a chemoreceptors at the carotid artery bifurcation which relays information to the CNS via the glossopharyngeal nerve.

Question 15

What leads to chemically induced vomitting?

Answer 15

Visceral information is input onto the medulla oblongata, and input from area postiema detects toxins in the blood and spinal fluid.

Question 16

Explain the release of neurotransmitter into synaptic clefts.

Answer 16

Neurotransmitter is synthesised and then packaged into vesicles. On membrane depolarisation, Ca influx occurs which causes exocytosis of these vesicles.

Question 17

What three actions in the synaptic cleft can we target drug actions against?

Answer 17

Interaction with receptors, inactivation of neurotransmitter and neurotransmitter reuptake.

Question 18

Explain why is is hard to target acetylcholine receptors.

Answer 18

Nicotinic receptors exist in both the sympathetic and parasympathetic nervous system so are not a good target for a specific response. There is some possibility of targeting to muscarinic receptors.

Question 19

What is the action of choline acetyl transferase?

Answer 19

Acetyl~coA + choline –> acetylcholine + coA

Question 20

How is acetyl choline degraded in the synaptic cleft?

Answer 20

This is by acetylcholine esterase and this produces acetate and choline. Choline is reuptake not for synthesis of acetylcholine again.

Question 21

What is an AChE inhibitor?

Answer 21

These block the action of acetylcholine esterase and so there is a more prolonged response because more acetyl choline remains in the synaptic cleft for a longer period of time.

Question 22

Name two AChE inhibitors

Answer 22

Donepezil and pyridostigmine

Question 23

What is the problem associated with non-specificity of cholinergic drugs?

Answer 23

They tend to cause unwanted side effects by reducing pulse rate, increasing bronchoconstriction and stimulating exocrine glands.

Question 24

What functions are mAChR agonists used for?

Answer 24

Pilocarpine/bethanechol are used to treat glaucoma and also stimulate bladder emptying.

Question 25

What is the purpose of varicosities?

Answer 25

These are close to effector tissues, and so a coordinated response occurs as many synapses are controlled by the same action.

Question 26

What is released at a varicosity?

Answer 26

Noradrenaline is released by a Ca2+ dependant method.

Question 27

What is the pathway for noradrenaline synthesis?

Answer 27

Tyrosine - DOPA - Dopamine - Noradrenaline

Question 28

Where do vesicles of NA take this up from?

Answer 28

They take up newly synthesised NA as well as Na recycled from the synaptic cleft.

Question 29

What is the fate of NA in the synaptic cleft?

Answer 29

It is either reuptake not or it is metabolised

Question 30

What two enzymes metabolise NA in the synaptic cleft?

Answer 30

Catechol-O-methyltransferase and monoamine oxidase

Question 31

How is NA reuptaken into presynaptic terminal?

Answer 31

NA is reuptaken by a high affinity transporter (which is sodium dependant) and also by a low affinity, non-neuronal mechanism

Question 32

Explain how NA release is controlled by presynaptic GPCRs.

Answer 32

On presynaptic terminal is a a1 adrenoceptor which can inhibit the VOCC channel when activated. This activation occurs when there is high NA in synaptic cleft and leads to less exocytosis because this is calcium dependant and the calcium channel has been blocked.

Question 33

What are sympathomimetic agents?

Answer 33

These are up taken into NA vesicles, displacing NA which leaks into the synaptic cleft causing action on receptors.

Question 34

What are tricyclic antidepressants?

Answer 34

These are nor-adrenaline re-uptake inhibitors, and these exert a major action in the CNS.