S6) Autonomic Innervation of the Head and Neck

Question 1

What is the autonomic nervous system?

Answer 1

The autonomic nervous system is the part of the peripheral nervous system that controls smooth muscle and glands

Question 2

How is the ANS controlled?

Answer 2

Central control is from the hypothalamus

Question 3

State 2 functions of the ANS

Answer 3

• Controls body functions not under conscious control
• Maintains and fine tunes internal environment (accelerator and brake)

Question 4

State 2 target tissues of the ANS

Answer 4

• Smooth muscle
• Glands (lacrimal & salivary)

Question 5

Describe the arrangement of neurones and ganglions in the ANS

Answer 5

Question 6

What are the two types of autonomic outflow from the CNS?

Answer 6

• Sympathetic: ‘thoracolumbar outflow’
• Parasympathetic: ‘craniosacral outflow’

Question 7

State the origins and location of cell bodies (nuclei) in the sympathetic nervous system

Answer 7

• Originates from T1 ‐ L2 segments of spinal cord

‐ Cell bodies are within lateral horn of grey matter of spinal cord

Question 8

State the origins of cell bodies in the sympathetic nervous system for the head and neck structures

Answer 8

T1 - T2

Question 9

Identify the ganglia involved in the sympathetic innervation of head & neck structures

Answer 9

Ganglia in cervical portion of sympathetic chain:

• Superior cervical ganglion
• Middle cervical ganglion (neck and chest structures)

Question 10

Which structures do the post ganglionic sympathetic ganglia hitch-hike onto to innervate their effector tissues?

Answer 10

• Blood vessels e.g. ICA, ECA, opthalmic artery
• Branches of CN V (very distally)

Question 11

Identify 4 effector tissues of the SNS in the structures of the head and neck

Answer 11

• Eye (dilator pupillae)
• Eye lid (superior tarsal muscle)
• Blood vessels
• Sweat glands

Question 12

State 4 responses of the SNS in the head and neck structures

Answer 12

• Pupillary dilation
• Assists eyelid retraction
• Vaso‐constriction
• Stimulates sweating

Question 13

Explain why carotid arteries and the lung apex are important anatomical relations to sympathetic nerves innervating head and neck

Answer 13

Pathology involving the apex of lung and internal carotid artery can cause autonomic dysfunction in the eye and face e.g. Horner’s syndrome

Question 14

Horner’s syndrome can result from a pancoast tumour in the apex of the lung.

Identify 3 symptoms of this clinical condition

Answer 14

• Partial ptosis
• Miosis (constricted pupil)
• Anhidrosis

Question 15

What is the most likely cause of Horner’s syndrome?

Answer 15

A pancoast tumour on the apex of the lung which impinges on the sympathetic chain

Question 16

State the origins and location of cell bodies (nuclei) in the parasympathetic nervous system

Answer 16

• Cranial segment originates from 4 CN’s

‐ Sacral segment originates from S2 ‐ S4 (pelvic splanchnics)

‐ Cell bodies are in brainstem / within grey matter of sacral spinal cord

Question 17

Parasympathetic preganglionic fibres for the head and neck structures arise from 4 nuclei in the brainstem.

Identify one

Answer 17

Edinger Westphal

Question 18

State the 4 cranial nerves which are associated with the pre-ganglionic fibres of the PNS

Answer 18

• Oculomotor nerve (CN III)
• Facial nerve (CN VII)
• Glossopharyngeal nerve (CN IX)
• Vagus nerve (CN X)

Question 19

State the 4 ganglia in the PNS innervation of head and neck structures

Answer 19

• Ciliary
• Submandibular
• Pterygopalatine
• Otic

Question 20

Which cranial nerve fibre is associated with the post ganglionic parasympathetic nerve fibres in the head and neck?

Answer 20

Branches of trigeminal nerve (CN V)

Question 21

Identify 4 effector tissues of the PNS in the head and neck

Answer 21

• Iris (sphincter pupillae) & ciliary muscles (controls lens)
• Lacrimal gland
• Mucosal glands (nasal/oral mucosa/ resp. tract)
• Salivary glands

Question 22

State 3 responses of the PNS in the head and neck structures

Answer 22

• Constrict pupil
• Accommodation reflex (lens shape)
• Glandular (salivary and mucosal) secretions

Question 23

Describe the anatomical course of CN III and the parasympathetic fibres from the brainstem via the ciliary ganglion

Answer 23

⇒ Preganglionic fibres emerge from EDW nuclei with CN III

⇒ Ciliary ganglion

⇒ Postganglionic fibres merge with CN V_a

⇒ Acts on sphincter pupiliae & lens

Question 24

in 8 steps, describe the pupillary light reflex for the left eye

Answer 24

⇒ Light in left pupil

⇒ Sensory afferent from left retina (CN II)

⇒ Some branches of CN II enter midbrain

⇒ Connection with EDW nuclei (left and right)

⇒ Preganglionic parasympathetic fibres leave brainstem

⇒ Fibres merge with CN III (left and right)

⇒ Fibres pass via ciliary ganglion

⇒ Postglangionic parasympathetic fibres reach sphincter pupillae

Question 25

For the diagram below, explain the types of light reflexes one will observe:

Answer 25

- **Left**: direct light reflex - **Right**: consensual light reflex

Question 26

How does the facial nerve enter the cranial cavity from the brainstem?

Answer 26

Through the **petrous temporal bone**

Question 27

Identify the two main branches of the facial nerve arising inside the petrous bone

Answer 27

- Greater petrosal nerve - Chorda tympani nerve

Question 28

Parasympathetics arising with CN VII have two associated parasympathetic ganglia. Identify them

Answer 28

- Pterygopalatine ganglion - Submandibular ganglion

Question 29

In 5 steps, describe the anatomical course of CN VII and the parasympathetic fibres from the brainstem via the greater petrosal nerve and pterygopalatine ganglion

Answer 29

⇒ Preganglionic fibres emerge with **CN VII** ⇒ Pass through **petrous temporal bone** ⇒ At the geniculate region, **greater petrosal nerve** enters pterygopalatine fossa ⇒ Fibres reach **pterygopalatine ganglion** ⇒ Postganglionic fibres act on **lacrimal, nasal & palatine glands**

Question 30

In 5 steps, describe the anatomical course of CN VII and the parasympathetic fibres from the brainstem via the chorda tympani nerve and submandibular ganglion

Answer 30

⇒ Preganglionic fibres emerge with **CN VII** ⇒ Pass through **petrous temporal bone** ⇒ Fibres join **chorda tympani nerve** & cross through middle ear cavity ⇒ Fibres exit via base of skull & reach **submandibular ganglion** ⇒ Post ganglionic fibres act on **sublingual & submandibular glands**

Question 31

How does the glossopharyngeal nerve enter the cranial cavity?

Answer 31

Through the **jugular foramen**

Question 32

In 6 steps, describe the anatomical course of CN IX and the parasympathetic fibres from the brainstem via the tympanic nerve and plexus

Answer 32

⇒ Preganglionic fibres emerge with **CN IX** ⇒ Pass through **jugular foramen** ⇒ Fibres join **tympanic nerve** & tympanic plexus ⇒ Fibres join **lesser petrosal nerve** & exit via foramen ovale ⇒ Fibres reach **otic ganglion** (in infratemporal fossa) ⇒ Postganglionic fibres then merge with CN V_c & act on **parotid gland**

Question 33

In 4 steps, describe the anatomical course of CN X and the parasympathetic fibres from the brainstem to the respective effector tissues

Answer 33

⇒ Parasympathetic fibres emerge with **CN X** ⇒ Preganglionic fibres meets ganglion **at or in target tissue** ⇒ Postganglionic fibres act on **smooth muscle and glands** of GI & resp tract ⇒ Postganglionic fibres act on **heart**

Question 34

Explain how Horner's syndrome produces its characteristic symptom of partial ptosis

Answer 34

- Sympathetic innervation of **superior tarsal muscle muscle** stops - Parasympathetic innervation of **levator palpabrae superioris** (through oculomotor nerve) still functions - Eyelid retraction is present but cannot be assisted = **partial ptosis**

Question 35

Explain how Horner's syndrome produces its characteristic symptom of miosis

Answer 35

- Sympathetic innervation of **dilator pupillae stops** = pupils constrict - Parasympathetic innervation of **sphincter pupillae dominates** = pupils constrict