Autonomic Innervation

Question 1

What is a nucleus?

What is a ganglion?

Answer 1

Nucleus - collection of cell bodies within the CNS

Ganglion - collection of cell bodies outside of the CNS

Question 2

Why is parasympathetic outflow termed ‘craniosacral’?

Answer 2

Parasympathetic innervation stems from four of the cranial nerves and from the S2-S4 pelvic splanchnics

Question 3

Why is sympathetic outflow termed ‘thoracolumbar’?

Answer 3

Outflow comes from the T1-L2 spinal cord segments

Question 4

Describe the pathway sympathetic innervation to the head and neck takes

Answer 4

Hypothalamus - spinal cord - cell body of 2nd order neurone at the lateral horn (T1/2) - Exits spinal cord - ascends sympathetic chain - synapses to 3rd order neurone at the superior cervical ganglion - runs with branches of common carotid artery to target tissues.

Question 5

The internal carotid artery carries sympathetic innervation to which target tissues?

Answer 5

Dilator pupillae,

Levator palpabrae superioris (note this is also innervated by cranial nerve III).

Question 6

The external carotid artery carries sympathetic fibres to which target tissues?

Answer 6

Sweat glands of the face and neck.

Question 7

What sort of injuries can disrupt sympathetic innervation to the head and neck?

Answer 7

Carotid artery dissection, cancer of the apical lung.

Question 8

What three features are associated with Horners syndrome?

Answer 8

Partial ptosis (drooping of the eye),
Miosis (contracted pupil),
Anhydrosis (lack of sweating).

Question 9

Why is ptosis only partial in horners syndrome?

Answer 9

Levator palpabrae superioris is mainly innervated by the occulomotor nerve and as such only the smooth muscle fibres are lost in horners syndrome.

Question 10

What signs differentiate Horners syndrome from a CNIII lesion?

Answer 10

In CNIII lesion:
Pupil is dilated not constricted,
Eye assumes down and out position.

Question 11

Which cranial nerves carry parasympathetic fibres from the brainstem?

Answer 11

Occulomotor (III),
Facial (VII),
Glossopharyngeal (IX),
Vagus (X).

Question 12

Describe the route of parasympathetic innervation to the head and neck

Answer 12

Arise via brainstem from parasympathetic nuclei - run with one of the 4 cranial nerves - synapse with parasympathetic ganglia - join distal branches of CN V.

Question 13

Which parasympathetic nucleus is associated with the occulomotor nerve?

Which parasympathetic ganglion?

Answer 13

Endinger Westphal nucleus,

Ciliary ganglion.

Question 14

Which two parasympathetic ganglions synapse with the facial nerve?

What do they innervate?

Answer 14

Pterygopalatine - lacrimal glands

Mandibular - salivary glands (bar parotid) and nasal mucosal glands

Question 15

Which intrapetrous branch of the facial nerve is the pterygopalatine ganglion associated with?

Answer 15

Greater petrosal nerve

Question 16

Which branch of the facial nerve is the submandibular parasympathetic ganglion associated with?

Answer 16

Chorda tympani nerve

Question 17

Which parasympathetic ganglion is associated with the Glossopharyngeal nerve?
What does it supply?

Answer 17

Otic ganglion

Parotid gland

Question 18

What structures does the vagus nerve carry fibres from the dorsal motor nuclei to?

Answer 18

Mucosal glands and smooth muscle of the larynx, respiratory tract and GI tract,
The heart.

Question 19

What are the four parasympathetic ganglia?

Answer 19

Ciliary - occulomotor
Pterygopalatine - facial
Submandibular - facial
Otic - Glossopharyngeal

Question 20

What is the direct pupillary light reflex?

What is the consensual pupillary light reflex?

Answer 20

Direct - bright light stimulates constriction of the pupil in the ipsilateral eye
Consensual- bright light stimulates constriction of the pupil of the contralateral eye