Sympathetic nervous system

Question 1

Where do preganglionic sympathetic axons terminate? (3)

Answer 1

1. Paravertebral sympathetic chains
2. Prevertebral ganglia/plexuses - abdominal cavity: coeliac, superior mesenteric and hypogastric
3. Adrenal medulla - 10th & 11th segment

Question 2

Describe the sympathetic ganglionic structure:

Answer 2

Preganglionic fibres are SHORT, post ganglionic fibres are LONG

Question 3

What is the receptor and neurotransmitter on the sympathetic prevertebral ganglion? (same as PS NS)

Answer 3

Receptor: Nicotinic
Neurotransmitter: ACh

Question 4

Where is the preganglionic nerve located?

Answer 4

Thoraco-lumbar spinal cord

Question 5

What is the most common receptor and neurotransmitter on the postganglionic axon to effector?

Answer 5

Receptor: Adrenoreceptors
Neurotransmitter: Noradrenaline

Question 6

What releases noradrenaline?

Answer 6

Varicosities

Question 7

What are the steps in noradrenaline synthesis and use? (6)

Answer 7

1. Tyrosine
2. NA synthesis (enzymes)
3. MAO is released (monoamine oxidase)
4. NA is packaged into vesicles
5. Varicosities are evaded
6. Released by exocytosis

Question 8

What are the receptors on the post synaptic cell?

Answer 8

Alpha and Beta adrenoreceptors

Question 9

What receptor causes inhibition of NA on presynaptic cell and how does it work?

Answer 9

Alpha 2 receptors act as a brake, recycling the NA to be reused

Question 10

What are the uptakes on post and presynaptic cleft for?

Answer 10

They reduce levels in the synaptic cleft which stops perpetual activation

Question 11

What type of receptors are a and b adrenoreceptors?

Answer 11

Metabotrophic receptors

Question 12

What does a metabotrophic receptor do? (4)

Answer 12

1. Attaches to a G protein
2. Activates a 2nd messenger system
3. Enzyme activation/ion transport
4. Response (change in shape)

Question 13

What receptors can be found on the post synaptic cleft?

Answer 13

a1, a2, b1, b2, b3

Question 14

What receptors can be found on the pre synaptic cleft?

Answer 14

ONLY a2

Question 15

What receptors are AGONISTS and what can they be used for? (3)

Answer 15

1. a1 - decongestant, eye drops, mydriasis (constrict blood vessels)
2. b2 - salbutamol (asthma inhaler) relaxes airways
3. b1 - enhance cardiac muscle contraction

Question 16

What receptors are ANTAGONISTS and what can they be used for? (2)

Answer 16

a1 - antihypertensive

b - beta blockers, can slow HR

Question 17

At a synapse, how would a AGONISTIC a2 receptor affect NA?

Answer 17

Would reduce NA release as it would uptake more to the presynaptic cell

Question 18

At a synapse, how would a ANTAGONISTIC a2 receptor affect NA?

Answer 18

Would increase NA release as it would lower the uptake

Question 19

How does SNS control pupil diameter? (3)

Answer 19

1. Sympathetic nerve activation
2. Radial muscle contraction (ciliary) or relaxing
3. Pupil dilation or pupil decreases in size

Question 20

What receptor is used at the eye?

Answer 20

Muscarinic 3 (M3)

Question 21

What can mydriatic drugs be used for?

Answer 21

Eye inspection and surgery - dilation

Question 22

What can anti glaucoma drugs be used for?

Answer 22

Miosis, pupil constricts and releases pressure

Question 23

What is neuropeptide Y and what does it do? (3)

Answer 23

Nueromodulator that:

1. Prejunctional - decreases NA & ATP release
2. Post junctional - increases NA action
3. Acts with ATP for VASCONSTRICTION

Question 24

What is adenosine 5’-triphosphate and what does it do? (3)

Answer 24

ATP

1. Directs actions - P2 receptors
2. Neuromodulator - P1 receptors
3. Acts with NPY for VASOCONSTRICTION