S1: Anatomy of the Autonomic Nervous System

Question 1

How many pairs of spinal nerves do we have?

Answer 1

31

Question 2

Where do spinal nerves exit the CNS?

Answer 2

Vertebral foramen

The vertebral bodies are seperated by the intervertebral discs

Question 3

What are vertebral bodies seperated by?

Answer 3

The vertebral bodies are seperated by the intervertebral discs

Question 4

How many somatic nerve fibres make contact with NMJ?

Answer 4

1

Ach is used at Nicotinic receptors

Question 5

Explain how ANS efferent fibres are in a series

Answer 5

Preganglionic fibre synapses at an autonomic ganglion to (one of more) post ganglionic neurone

Question 6

What outflow does sympathetic fibres exit the spinal cord at?

Answer 6

Thoracolumbar outflow

Question 7

Where are sympathetic preganglionic cell bodies found?

Answer 7

In the spinal cord

Question 8

The sympathetic chain runs parallel to the spinal cord

What is its function?

Answer 8

It enables innervation to reach the rest of the body

Question 9

What outflow does sympathetic fibres exit at?

Answer 9

Cranio-sacral outdlow

Parasympathetic fibres leave the medulla (cranial nerves) and sacral regions

Question 10

What part of the brain controls the ANS?

Answer 10

Hypothalamus

Question 11

What vertebral level does thoracolumabar outflow have?

Answer 11

T1-L2/3

Question 12

What is the autonomic outflow?

Answer 12

Sympathetic preganglionic fibres exit the CNS

Question 13

Explain how sensory and motor fibres enter and exit the spinal cord

Answer 13

Sensory fibres enter into the posterior horn

Motor fibres exit out of the anterior horn

Question 14

What is the origin of preganglionic fibres?

Answer 14

The intermediolateral horn in the middle of the spinal cord and it is the origin of pre-ganglionic fibres (where sympathetic cell bodies are).

These then exit via the anterior horn

Question 15

What connects sympathetic chain to spinal nerve?

Answer 15

Grey and white communicantes which feed into the ganglion.

The white rami contain myelinated axons while the grey contain unmyelinted.

Question 16

Explain the course of a sympathetic pre-ganglionic fibre exiting the CNS to ganglion

Answer 16

A sympathetic pre-ganglionic fibre exits the CNS down the mixed spinal nerve and enter into the autonomic ganglion through the white ramus communicans.

The pre-ganglionic fibre synapses to the post-ganglionic fibre and this then exits via the grey ramus communicans rejoining the mixed spinal nerve then travels to its target structure.

However, the preganglionic nerve doesn’t have to synapse at first ganglion

Question 17

if the preganglionic fibre doesn’t synapse at the first ganglion, what are the three routes it can travel from the sympathetic chain?

Answer 17

It can travel up the sympathetic chain towards cervical ganglia

It can travel down towards lumbosacral ganglia

It can becomes part of the splanchic nerves that supply the gut

Question 18

What are the three main ganglia in the cervical region?

Answer 18

Superior cervical ganglion
Middle cervical gangion
Stellate ganglion (inferior)

Question 19

Describe the cervical ganglia (sympathetic supply to the head)

Answer 19

• Sym fibres travel in the internal carotid plexus (in the walls of arteries travelling to their target structure)

Superior cervical ganglion is the origin which innervates: dilator pupillae, superior tarsal muscle and facial sweat glands

Question 20

What is Horner’s Syndrome?

Answer 20

Loss of sympathetic supply to the head

• Side effects: Small pupil (myosis) and loss of sweating

Question 21

Explain sympathetic supply to abdominopelvic viscera

Answer 21

The abdominopelvic viscera (organs/tissue in this area) are supplied by the ‘splanchnic nerves’, the greater, lesser and least splanchnic nerves.

Pre-ganglionic fibres pass through the sympathetic chain (T6-T12) and terminate in the pre-aortic ganglia. These surround the major vessels (coeliac trunk, mesenteric arteries).

The post ganglionic fibres are then distributed with the arteries (they get into the wall of the arteries)

Question 22

What cranial nerve are parasympathetic?

Answer 22

III - occulomotor
VII - facial
IX- glossopharyngeal
X- Vagus

Question 23

What level is the sacral outflow?

Answer 23

S2 S3 S4

pelvis splanchic nerve