Autonomic Nervous System

Question 1

All pre-ganglionic neurons use what neurotransmitter?

Answer 1

cholinergic = ACh – binds post-ganglionic nAChR

Question 2

What is the function of the autonomic nervous system?

Answer 2

controls all vegetative (involuntary) functions: heart rate, BP, GI motility, iris diameter.

separate from voluntary (somatic) motor system.

entirely efferent (conducting outwards or away from something), but is regulated by afferent inputs

Question 3

Where do the sympathetic nerves originate from?

Answer 3

originate from lateral horn of thoracic and lumbar region

Question 4

Which is fight or flight + rest and digest?

Answer 4

Fight or flight: sympathetic

Rest and digest: parasympathetic

Question 5

What is the sympathetic nerve structure?

Answer 5

Short pre-ganglionic, long post-ganglionic - Ganglia are located in paravertebral chain close to spinal cord

Question 6

Name the sympathetic receptors

Answer 6

Receptors –> a1, a2, b1, b2 (GCPRs)

Question 7

Where do the parasympathetic nerves originate from?

Answer 7

originate from lateral horn of medullary and sacral region

Question 8

What is the parasympathetic nerve structure?

Answer 8

Long pre-ganglionic, short post-ganglionic - Ganglia are located within innervated tissues

Question 9

What is the parasympathetic post-ganglionic neurotransmitter?

Answer 9

Post-ganglionic = cholinergic: ACh - bind muscarinic receptors (GPCR, M1, M2, M3)

Question 10

What is the sympathetic post-ganglionic neurotransmitter?

Answer 10

Post-ganglionic = noradrenergic NA - bind adrenergic receptors (GPCRs, A1, A2, B1, B2)

highly branching axonal network, numerous varicosities: specialized site for Ca2+-dependent noradrenaline release

Question 11

Name the parasympathetic receptors

Answer 11

Receptors –> M1, M2, M3 (GCPRs)

Question 12

Describe the ANS within the adrenal glands

Answer 12

Sympathetic post-ganglionic neurons diff to form neurosecretory chromaffin cells (prod noradrenalin) = can be considered as postganglionic sympathetic neurons that do not project to a target tissue.

Noradrenalin –> adrenaline (catalysed by phenylethanolamine N- methyltransferase)

Question 13

Outline the steps in neurotransmission

Answer 13

1) uptake of precursors
2) synthesis of transmitter
3) vesicular storage of transmitter
4) degradation of transmitter
5) depolarization by propagated action potential
6) depolarization-dependent influx of Ca2+
7) exocytotic release of transmitter
8) diffusion to post-synaptic membrane
9) interaction with post-synaptic receptors
10) inactivation of transmitter
11) re-uptake of transmitter
12) interaction with pre-synaptic receptors

Question 14

How is ACh synthesised?

Answer 14

acetyl CoA + choline –> ACh + coenzyme A (catalysed by choline acetyltransferase)

Question 15

How is ACh degraded?

Answer 15

ACh –> acetate + choline (catalysed by acetylcholinesterase)

Question 16

What is SLUDGE?

Answer 16

pathological side effects indicative of massive discharge of parasympathetic nervous system, Usually in drug overdose (mushrooms), Insecticides = covalently deactivate acetylcholinesterase = raise Ach.

S --> salivation 
L --> lacrimation 
U --> urination 
D --> defecation 
G --> gastrointestinal upset: diarrhoea 
E --> emesis: vomiting

Question 17

Outline 2 noradrenergic therapeutic interventions

Answer 17

β2-adrenoceptor-selective agonists (salbutamol) used in asthma to reverse/oppose bronchoconstriction, beta receptors in heart and lungs = selectivity important as it limits possible cardiovascular side-effects.

α1-adrenoceptor-selective antagonists (doxazosin) and β1-adrenoceptor-selective antagonists (atenolol) = treat cardiovascular disorders: hypertension

Question 18

Outline the pathophysiology of asthma

Answer 18

1) eosinophils accumulate/infiltrate bronchial smooth muscle = mucosal oedema
2) swelling = narrowing
3) release of cytotoxic mediators damage respiratory epithelial layer
4) damage = exposure of sensory nerves = bronchial hyper-responsiveness
5) = smooth muscle spasms = narrowing
6) Inflammation = hyper secretion of mucus = plug = further narrowing

Question 19

Describe the innervation of airways

Answer 19

Autonomic innervation of the airway = parasympathetic = Ach –> Stimulation of β 2 adenoceptors = activates AC, formation cAMP, activation PKA, low Ca2= conc = bronchodilation

Question 20

What is an asthma reliever?

Answer 20

bronchodilators: β agonists (salbutamol), montelukast blocks leukotriene D4 which is a major bronchoconstrictor mediator

Question 21

What is an asthma preventer?

Answer 21

anti-inflam drugs: glucocorticosteroids (dexamethasone): down regulate genes involved in mediating inflame response. Sodium cromoglicate: reduces release of histamine from mast cells

Question 22

How is hypertension regulated?

Answer 22

sympathetic NS, renin angiotensin aldosterone system RAAS

Question 23

How is hypertension treated?

Answer 23

1) ACE inhibitors –> medications that inhibit activity of enzyme ACE = decreases prod of angiotensin II = blood vessels dilate, BP reduced
2) Ca channel blockers –> prevent release of Ca stores = smooth muscle vasodilators
3) Diuretics –> increase Na and water loss, reduces ECF = lowers blood volume = lowers BP
4) β-adrenoceptors blockers (antagonist) –> reduce cardiac output (reduce ionotropy/force and chromotropy/ rate of heart), reduce renin production = less aldosterone = increase kidney secretion
5) α-adrenoceptor blockers (antagonist) –> vasodilator

Question 24

Where are the following receptor found: α1, α2, β1, β2, M1, M2, M3?

Answer 24

A1 = Smooth muscle cells of blood vessels. A2 = Liver cells, platelets, and the smooth muscle of blood vessels. B1 = Heart, Kidney. B2 = Bronchioles of the lungs and the arteries of the skeletal muscles. M1 = Exocrine glands. M2 = Heart. M3 = Lungs

Question 25

What is the function of the thyroid?

Answer 25

T3, T4: regulate metabolic rate. Low levels = hypo releases TRH –> pituitary releases TSH –> thyroid. High T3, T4 = -ve feedback = stops prod. Hypo = underactive. Hyper = overactive. Thyroid hormones upregulate the number of adrenoceptors in the body

Question 26

What is thyrotoxicosis and how is it treated?

Answer 26

Thyrotoxicosis = clinical symptoms due to high levels of thyroid hormone in blood. Treatment = propranolol non-selective β-adrenoceptor antagonist, IV given in thyrotoxic crisis (storm), Iodine = blocks release of hormones as reduces conversion of T4 to T3

Question 27

What are the 2 divisions of the ANS

Answer 27

sympathetic and parasympathetic

Question 28

What parasympathetic nerve regulates the heart?

Answer 28

vagus nerve

Question 29

What is the term for disorders of the ANS?

Answer 29

dysautonomia

Question 30

What are catecholamines disorders?

Answer 30

cancer cell release NA and adrenaline constantly = always fight or flight

Question 31

Activation of M2 receptors in the heart causes?

Answer 31

bradycardia

Question 32

Activation of B1 receptors in the heart causes?

Answer 32

tachycardia

Question 33

Activation of A1 receptors cause?

Answer 33

arteriolar contraction

Question 34

Explain what activation of B2 receptors causes?

Answer 34

bronchiole relaxation

Question 35

What is trimethaphan used for?

Answer 35

ganglion blocking cholinergic drug, given during surgery to sustain hypotension