The Autonomic Nervous System

Question 1

Where do the fibres of the PNS emerge from?

Answer 1

The medulla - cranial nerves oculomotor, facial, glossopharyngeal and vagus
Sacral region of spinal cord - the Nervi Egentes

Question 2

Where do the fibres of the SNS emerge from?

Answer 2

The thoracic and lumbar regions of the spinal cord.

Question 3

What are the features of ganglionic PNS fibres?

Answer 3

The ganglia are nearby the effector of the organ, so the postganglionic fibres tend to be short

Question 4

What are the features of ganglionic SNS fibres?

Answer 4

The ganglia are far away from the target so the postganglionic fibres are long

Question 5

Outline the transmitters involved in the PNS

Answer 5

Preganglionic fibres release ACh onto nACh receptors

Postganglionic fibres release Ach onto mACh receptors

Question 6

Outline the transmitters involved in the SNS

Answer 6

Preganglionic fibres release ACh onto nACh receptors.

Postganglionic fibres release Noradrenaline. Those innervating sweat glands release mACh receptors.

Question 7

Give an example of Heterotropic Interaction in the ANS

Answer 7

In the myenteric plexus of the gut, release of NA by the SNS inhibits release of ACh by PNS

Question 8

Give an example of Homotropic interaction in the ANS

Answer 8

Noradrenaline acts on pre-synaptic alpha 2 receptors which inhibit further NA release

Question 9

What are the effects of the co-transmitters Substance P and LHRH?

Answer 9

They have a slow excitatory effect as they decrease K+ permeability (preganglionic)

Question 10

What are the effects of Opioid Peptides?

Answer 10

They have a slow inhibitory effect via the M2 autoreceptors as they cause an increase in K+ permeability (preganglionic)