Autonomic Innervation of the Head and Neck Flashcards
What is the autonomic nervous system part of?
The peripheral nervous system
Does the autonomic nervous system have any central control?
Yes
Where does the central control of the autonomic nervous system come from?
The hypothalamus of the brain
What does the autonomic nervous system do?
Controls body functions that are not under conscious control
What tissues does the autonomic nervous system act on?
- Smooth muscle
- Cardiac muscle
- Glands
Give two examples of locations of smooth muscle that the autonomic nervous system acts on
- Gut
- Blood vessels
Give 3 glands that the autonomic nervous system acts on
- Lacrimal
- Mucosal
- Salivary
What is the overall function of the autonomic nervous system?
Maintains and fine tunes the internal environment
What does the sympathetic nervous system act as in most cases?
An accelerator
What does the parasympathetic nervous system act as in most cases?
A brake
How are the neurones arranged in the autonomic nervous system?
Has a sequential two neurone arrangement, and an associated ganglion
Where does the pre-ganglionic nerve come from in the autonomic nervous system?
The spinal cord
Where do the neurones synapse in the autonomic nervous system?
Synapse in the ganglion
What is a ganglion?
A collection of cell bodies in the peripheral nervous system
Where do the neurones of the sympathetic nervous system arise from?
The thoracolumbar spinal cord
Where do the cell bodies of the pre-ganglionic sympathetic nerves sit?
In the lateral horn of the grey matter of spinal cord segments T1-L2
What happens to the pre-ganglionic neurone of the SNS once it has arisen from the spinal cord?
They enter the sympathetic chain and run up the spinal cord
Where do the pre-ganglionic neurones of the SNS synapse?
Don’t synapse at the first ganglion they encounter while running up the sympathetic chain, go up to the top ganglia in the neck
What are the top 3 paravertebral ganglia in the neck called?
Cervical ganglia
Where do most sympathetics to the head and neck synapse?
In the superior cervical ganglia (the top ganglion)
What happens to the sympathetic neurones supplying the head and neck from the sympathetic chain?
They hitch hike to where they need to be on blood vessels
What to the neurones form around the internal and external carotid arteries?
A carotid plexus
What happens to the neurones hitch hiking on the internal and external carotid arteries?
They follow the branches to the target tissues
What sympathetic fibres does the internal carotid arteries carry?
The eye
How to the sympathetic fibres get from the internal carotid artery to the eye?
Via the opthalmic artery
What sympthatic fibres does the external carotid artery carry?
Those going to sweat glands and smooth muscle in blood vessels of the face and neck
What is the result of the carotid plexus following the carotid arteries?
Any disease affecting the carotid artery could also affect the sympathetics of the face
What is in important anatomical relations to the sympathetic nerves innervating the head and neck?
The carotid arteries and lung apex
What can pathologies involving the carotid arteries and lung apex cause?
Autonomic dysfunction in the eye and face
What may apical lung tumorus cause?
Development of autonomic disruptio of the face and eye
What happens once sympathetic nerve fibres get close to the target tissue?
Sympathetic nerve fibres have to leave vessels and hitchhike on cranial nerves
What cranial nerve does the sympathetics of the tarsal muscle hitch-hike on?
The oculomotor nerve
What cranial nerve do the sympathetics of the dilator pupillae hitch-hike on?
The trigeminal nerve
What do the sympathetic nerves of the head and neck innervate?
- Smooth muscle of the blood vessels
- Smooth muscle of the eyelid (the tarsal muscle)
- Smooth muscle of the iris (dialtor pupillae)
- Arrector pili muscles
- Decreases secretion from salivary and lacrimal glands
What does the tarsal muscle do?
Retracts eyelid to keep eyes wide
What does the dilator pupillae do?
Causes the iris to dilate, and so cause the pupils to widen
What does Horners syndrome result from?
Interruption of the sympathetic nerve supply to the head and neck
What are the signs of Horners syndrome?
- Miosis
- Partial ptosis
- +/- anhydrosis
What is miosis?
Dilation of pupil
What do the possible diagnoses of Horners syndrome relate to?
Anatomical relations of sympathetic nerve supply on its route from the spinal cord to head
What are the possible causes of Horners syndrome?
- Apical lung cancer
- Carotid artery dissection
Where do the parasympathetic nerve fibres innervating the head and neck arise from?
The cranial outflow, arising from the brainstem
How do the parasympathetic nerves from the cranial outflow leave the brainstem?
From specific parasympathetic nuclei
What are parasympathetic nuclei?
Collections of cell bodies
What are the names of the parasympathetic nuclei?
- Edinger Westphal
- Superior salivary
- Inferior salivary
- Dorsal motor
What cranial nerves carry parasympathetic fibres from the brainstem?
- Oculomotor
- Facial
- Glossopharyngeal
- Vagus
Where does the oculomotor nerve arise from?
The brainstem
Where do the parasympathetic nerves that hitch-hike on the oculomotor nerve arise from?
The Edingere Westphal parasympathetic nuclei inside it
What course does the oculomotor nerve and associated sympathetic fibres take?
Runs through cavernous sinus and then through the superior orbital fissure
When do the parasympathetics leave the oculomotor nerve?
After it passes through the ciliary ganglion
What happens once the parasympathetic fibres have left the oculomotor nerve?
They hitch hike on small branches from V1/Va
What do the post-ganglionic parasympathetic nerves from the oculomotor nerve innervate?
- Ciliary body
- Sphincter pupillae
What is the sphincter pupillae responsible for?
The pupillary light reflex
What course does the facial nerve and its associated parasympathetics take?
Arises in brainstem, travels inside the petrous part of the temporal bone, and then branches into chora tympani and greater petrosal nerves
Where do the parasympathetics travelling on the greater petrosal nerve synapse?
At the pterygopalatine ganglion
Where do the parasympathetics travelling on the chorda tympani synapse?
Submandibular ganglion
Where do the nerves from the pteryogopalatine ganglion go?
To the lacrimal gland and mucosal glands in nasal/oral cavity
Where do the nerves from the submandibular ganglion go to?
The salivary glands; submandibular and sublingual
What is pathology of the facial nerve complex?
Because three branches of the facial nerve are given off in the petrous bone
What happens in pathology at or before the geniculate ganglion?
May involve all parasympathetic functions carried within CN VII
What happens in pathology after the geniculate ganglion?
Lacrimal glands are spared, as the pathology does not involve the greater petrosal nerve
What course does the glossopharyngeal nerve and its associated parasympathetics take?
Arises, goes through the jugular foramen, and then branches into the tympanic nerve, then divides into a plexus. The plexus exits from the petrous part of the temporal bone through the foramen ovale to the lesser petrosal nerve
What does the tympanic nerve supply?
Sensory to the middle ear
Where do the parasympathetics hitch-hiking on the glossopharyngeal nerve synapse?
Otic ganglion
What do the parasympathetics hitch-hiking on the glossopharyngeal nerve supply?
Parotid
Where does the vagus nerve arise from?
The medulla of the brainstem
Where do the parasympathetics hitch hiking on the vagus nerve synapse?
At a ganglino at, or in, the target tissue
What are the target tissues for parasympathetics of the vagus nerve?
Glands in larynx, respiratory tract, GI tract, etc
Where is the parasympathetic sacral outflow/
S2-4
What do the parasympathetics innervate in the head and neck?
- Smooth muscle of iris (sphincter pupillae)
- Smooth muscle of ciliary body
- Lacrimal glands
- Salivary and mucosal glands
What does the sphincter pupillae do?
Makes pupil smaller
What does the smooth muscle of the ciliary body do?
Controls thickness of the lens
