Session 10 - The ANS

Question 1

How does the post-ganglionic innervation of the adrenal glands differ from others?

Answer 1

• Sympathetic postganglionic neurones are the chromaffin cells of the adrenal gland which secrete adrenaline directly
• Activated by stimulation of NA from preganglionic fibre of SNS

Question 2

What are the results of parasympathetic innervation to the heart?

Answer 2

-Bradycardia (SA node)
-Reduced conduction velocity (AV node)
M2 activation (Gai)

Question 3

What are the locations and the result of parasympathetic innervation of smooth muscle?

Answer 3

-Bronchiolar contraction
-Increased intestinal mobility (increased contraction)
-Bladder contraction (detrusor)
-Bladder relaxation (sphincter)
-Penile erection
M3 receptor (Gaq)

Question 4

What is the result of parasympathetic innervation of glandular tissue?

Answer 4

-Increased sweat, salivary, lacrimal secretion

M1/M3 (gaq)

Question 5

What is the effect of sympathetic innervation of the heart?

Answer 5

-Positive chronotropy (SAnode)
-Positive inotropy (ventricles)
b1 (some B2)

Question 6

What are the locations and effects of sympathetic innervation of smooth muscle?

Answer 6

• Arteriolar/venous contraction (a1)
• Arteriolar vasodilation in liver, skeletal and myocardium (b2)
• Bronchiolar, intestinal and uterine relaxtion (b2)
• Bladder sphincter contraction

Question 7

What is the effect of sympathetic innervation to the kidney?

Answer 7

-Renin release

Question 8

What effect does angiotensin II have on the brain and adrenal cortex?

Answer 8

• Stimulates ADH release from brain to upregulate aquaporin channels
• Stimulates aldosterone release from cortex

Question 9

Name a glucocorticoid receptor antagonist used to decrease aldosterone release?

Answer 9

-Spironolactone

Question 10

Describe the autonomic innervation of the prostate gland

Answer 10

Parasympathetic -> stimulates secretion from epithelia

Sympathetic-> smooth muscle contraction

Question 11

What enzyme is responsible for the synthesis of acetylcholine?

Answer 11

-Choline acetyltransferase

Question 12

What AchE inhibitor is used to treat myasthenia gravis?

Answer 12

-Pyridostigmine

Question 13

Why is the use of cholinergic drugs limited?

Answer 13

-They lack selectivity and often produce many unwanted side effects

Question 14

Name an muscarinic agonist used in glaucoma

Answer 14

-Pilocarpine

Question 15

Name a muscarnic antagonist used to treat asthma

Answer 15

-Ipratropium

Question 16

What is a variscosity?

Answer 16

-A vesicle in neurones which contains everything necessary for NA synthesis, store and release

Question 17

What is NA synthesised from?

Answer 17

-Tyrosine

Question 18

Briefly outline NA synthesis

Answer 18

Tyrosine -> DOPA (tyrosine hydroxylase)
DOPA-> Dopamine (DOPA decarboxyase)
Dopamine -> NA (Dopamine b-hydroxylase)

Question 19

How is NA removed from a synaptic cleft?

Answer 19

-Noradrenaline transporter proteins Uptake 1 and Uptake 2 facilitate re-uptake into presynaptic terminal

Question 20

What ion are uptake 1 and uptake 2 dependant upon?

Answer 20

-Na+

Question 21

How is NA not cleared by uptake 1 and 2 removed from the synpatic cleft?

Answer 21

-Metabolised by MAO (monoamine oxidase) and COMT (catechol-O-methyltransferase)

Question 22

How is NA release modulated from pre-synaptic neurones?

Answer 22

• a2-adrenoreceptors present on the pre-synaptic terminal membrane
• Activation of a2 causes dissociation of bg which binds to VOCC
• Reduces Ca influx of ca2+ and thus decreased neurotransmitter release

Question 23

How do indirect sympathomimetic agents work?

Answer 23

• Enter presynaptic terminal by uptake 1
• Mimic NA and are taken up into neurotransmitter vesicles with higher affinity
• Cause NA to leak from vesicle and into the synaptic cleft by a mechanism other than Ca2+ dependant exocytosis

Question 24

What are the three drugs used to treat HF?

Answer 24

• B-blocker
• ACE inhibitor
• Diuretic

Question 25

Name some other neurotransmitters which can be co-released with NA/Ach

Answer 25

• ATP
• NO
• 5-HT
• Neuropeptides (Vasoactive Intestinal Peptide)