ACh And Noradrenaline

Question 0

In what sympathetic response does noradrenaline not act?

Answer 0

Sweating

Question 1

Where does noradrenaline act?

Answer 1

At the neuroeffector junction of sympathetic post-ganglionic fibres

Question 2

What are the sympathetic effects on the heart?

Answer 2

Positive chronotropy (increased heart rate)
Positive ionotropy (increased force of contraction)

Question 3

What nerves and receptors in the heart are stimulated by the sympathetic nervous system?

Answer 3

Accelerator nerves

B1 adrenoceptors on the SA node, AV node and myocardium

Question 4

Where are a1-adrenoceptors found and what G-protein are they coupled to?

Answer 4

Vascular smooth muscle cells, skin, liver

G-alpha-q

Question 5

Where are a2-adrenoceptors found and what G-protein are they coupled to?

Answer 5

Brain, salivary gland

G-alpha-i

Question 6

Where are B1-adrenoceptors found and what G-protein are they coupled to?

Answer 6

Heart, kidney, adipose tissue

G-beta-s

Question 7

Where are B2-adrenoceptors found and what G-protein are they coupled to?

Answer 7

GI tract, bladder, bronchi, skeletal muscle, liver, uterus

G-beta-s

Question 8

Where is NA broken down?

Answer 8

It is taken back into the presynaptic axon by symport transporter with Ca, and broken down there.

Question 9

How is ACh produced?

Answer 9

Choline + Acetyl CoA -> Acetylcholine + CoA

Enzyme: Choline acetyl transferase

Question 10

Where does ACh act?

Answer 10

In the parasympathetic branches at the pre-ganglionic synapse and at the post-ganglionic target tissue junction.
In the sympathetic branches at the pre-synaptic synapse only (exception is sweating where ACh also acts at post-ganglionic junction).

Question 11

How is the ACh signal terminated?

Answer 11

Broken down by acetylcholinesterase in the synaptic cleft to choline and acetate.
Choline molecules taken back into pre-synaptic cell, acetate molecules diffuse into surrounding medium.

Question 12

What effect does the parasympathetic NS have on the heart?

Answer 12

Negative chronotropy (decreased heart rate)
Negative ionotropy (decreased conduction velocity)

Question 13

What nerves and receptors in the heart are stimulated by ACh?

Answer 13

Vagus nerve

M2 receptors on SA node and AV node

Question 14

Where are nicotinic receptors found?

Answer 14

At ganglionic junctions

Question 15

What type of receptors are nicotinic receptors?

Answer 15

Ligand-gated ion channels

Question 16

Where are muscarinic receptors found?

Answer 16

The parasympathetic neuroeffector junctions

Question 17

What type of receptor are muscarinic receptors?

Answer 17

G-protein coupled

Question 18

Where are M1 found and what G-protein are they coupled to?

Answer 18

Some glands

G-alpha-q

Question 19

Where are M2 found and what G-protein are they coupled to?

Answer 19

Heart, parasympathetic nerve terminals

G-alpha-i

Question 20

Where are M3 found and what G-protein are they coupled to?

Answer 20

Bronchi, bladder, glands

G-alpha-q

Question 21

How is noradrenaline synthesised?

Answer 21

Tyrosine -> Dopa -> Dopamine -> Noradrenaline
Tyrosine hydroxylase (rate limiting)
Dopamine B-hydroxylase (in the neurotransmitter vesicles)

Question 22

How can glaucoma be treated by stimulation of the parasympathetic NS and what drugs do this?

Answer 22

Pilocarpine activates M3 receptors on ciliary muscles, causing construction. Trabecular meshwork opens up, aqueous humour drains, decreasing intraoccular pressure.
Acetylcholinesterase inhibitors mean ACh is in the synaptic cleft for longer so increased stimulation of M3 receptors.

Question 23

How can glaucoma be treated by inhibition of the sympathetic NS and what drug does this?

Answer 23

Brimonidine blocks a2-adrenoceptors, decreasing dilation of ciliary muscle