9 - ANS

Question 1

What is the anatomical structure of the parasympathetic nervous system?

Answer 1

S2 to S4

Question 2

What is the anatomical structure of the sympathetic nervous system?

Answer 2

Question 3

What neurotransmitters and receptors are involved in each synapse?

Answer 3

Question 4

What is the main difference between nAchR and mAchR?

Answer 4

nAChR = LGIC

mChR = GPCR

Question 5

What neurotransmitter is released from sympathetic post-ganglionic neurones?

Answer 5

• Mainly noradrenaline

- In sweat glands and hair follicles it is ACh

Question 6

Are there other neurotransmitters to NA and ACh?

Answer 6

Question 7

What could be classified as the third divsion of the autonomic nervous system?

Answer 7

Enteric in GI tract

Thousands of neurones in microcircuit

Question 8

What is the hormonal part of the sympathetic nervous system?

Answer 8

• Post-ganglionic neurones are chromaffin cells in adrenal medulla that synthesise adrenaline
• Whole cell depolarised by pre-ganglionic neurone, vesicles contain A fuse with membrane and release adrenaline into blood stream to act on adrenoreceptors

Question 9

Summarise the neurotransmitters in the somatic and autonomic nervous system.

Answer 9

Question 10

Why are beta 2 receptors classed as part of the sympathetic nervous system?

Answer 10

Dilate airways allowing more air and therefore more oxygen for respiration into the body

Question 11

Where does NO generation occuring and what is it used to stimulate?

Answer 11

Locally

Causes penile erection, iris sphincter and cilliary muscles

Question 12

What is dysauntomia?

Answer 12

Umbrella term for malfunctions of the ANS. Can be primary or occur secondarily to another condition (e.g to Parkinson’s)

Question 13

What is NCS, POTS and MSA?

Answer 13

- Neurocardiogenic Synope - Fainting spells

- Postural Orthostatic Tachycardia Syndrome - Lightheaded, tachycardia, fainting, chest pains, temperature sensitivity. Mainly in young women who look healthy

- Multiple System Atrophy - Fatal dysautonomia in adults over 40. Neurodegenerative disease with similarities to Parkinson’s. Bed ridden after 2 years of diagnosis and dead in 5-10 years. Very rare

Question 14

What are the clinical abnormalities in asthma?

Answer 14

• Bronchospasms
• Excess production of secretions

Question 15

What are the basic steps of neurotransmission and highlight the steps that can be targeted by drugs?

Question 16

How is acetylcholine synthesised and degraded?

Answer 16

Question 17

What drugs can target AChR?

Answer 17

• Targets skeletal muscle and pre-ganglionic neurones

- Trimethapan (ganglion blocking drug) used in hypertensive emergencies and controlled hypotension in surgery. Nicotinic antagonist

Question 18

What is the issue with developing drugs to act on the parasympathetic nervous system?

Answer 18

5 Muscarinic ACh receptors and hard to make drugs that are selective so drug will bind to all receptors, causing unwanted side effects

Question 19

What is sludge syndrome?

Answer 19

Pathological effects of overstimulation of muscarinic AChR’s in the parasympathetic nervous system.

Usually caused by:

• Drug overdose
• Organophospphorous insecticides (parathion) and nerve gases (sarin)
• Ingestion of magic mushrooms

Question 20

What is the treatment for SLUDGE syndrome?

Answer 20

• Agents covalently bind to AChE to irreversibly deactive enzyme and raise ACh levels
• Need drugs that either block muscarinic receptors or reverse covalent modification of AChE

- Atrophine and Pralidoxime

Question 21

What are some muscarinic agonists and antagonists?

Answer 21

Administered locally not systemically

Agonists:

• Pilocarpine (glaucoma)
• Bethanechol (stimulate bladder emptying)

Antagonists:

- Ipratropium (asthma but only certain causes)

• Tiotropium (COPD)
• Tolterodine, Darifenacin and Oxybutynin (overeactive bladder)

Question 22

What are sympathetic post-ganglionic neurones like?

Answer 22

• Noradrenaline release
• One neurone has lots of varicosities that are specialised for Ca2+ dependent noradrenaline release
• Allows coordinate control over a large area

Question 23

How is noradrenaline and adrenaline synthesised?

Answer 23

Question 24

What happens to Noradrenaline/Adrenaline once it has been released?

Answer 24

1. Reuptake by noradrenaline transport proteins (NET)

- Uptake 1: Uptake back into pre-synaptic neurone via a Na dependent high affinity transporter

- Uptake 2: Low affinity transporter

2. Metabolism (10%)

• Monoamine Oxidase (MAO)
• Catechol-O-methlytransferase (COMT)

Can produce drugs that inhibit these enzymes so NA not broken down

Question 25

What receptors does NA interact with?

Answer 25

**- Pre-synaptic adrenoreceptors:** To feedback and regulate processes in nerve terminal like NA release **- Post-synaptic adrenoreceptors:** Pass on message and then rapidly removed by NET

Question 26

Why is salbutamol such a good asthma treatment?

Answer 26

Relieves asthma no matter what has caused it

Question 27

Why would you use selective adrenoreceptor agonists?

Answer 27

To limit side effects, like cardiovascular side effects, as non-selective will act on both beta adrenoreceptors

Question 28

What are two drugs used to treat hypertension and other cardiovascular disorders?

Answer 28

Atenolol: B₁ antagonist Doxazosin: A₁ antagonist Bisprolol Fumarate: B1 antagonist

Question 29

What is thyrotoxicosis and how is it treated?

Answer 29

- Excess of thyroid hormone in the body causing lots of symptoms - Beta agonists used to combat some of the symptoms, e.g high b.p. - Propanolol, Attenolol, Nadaolol - Methimazole and Propylthiouracil stop thyroid overproducing hormone