6.1 Autonomic Innervation Of Head And Neck Structures Flashcards
What are the 2 major components of the peripheral nervous system?
- Autonomic nervous system - unconscious control
2. Somatic nervous system - conscious control
What are the main target tissues for ANS in the head and neck?
Smooth muscle (blood vessels and eye) and glands (sweat, lacrimal and salivary)
Where does the sympathetic outflow arise from?
Thoracocolumbar portion (T1 to L2) Lateral horn
Where do the sympathetic preganglionic nerves synapse?
In the Sympathetic chain. May travel superiorly or inferiorly from the level of their spinal cord origin before synapsing.
At what spinal level does the sympathetic outflow to the head and neck arise from?
T1/T2
Where do preganglionic sympathetic nerves to the head and neck synapse?
Superior cervical ganglia
sometimes middle cervical ganglia
How do postganglionic sympathetic fibres reach their target tissues in the head and neck?
Hitch hiking onto blood vessels ( internal carotid artery and the external carotid artery)
Where does parasympathetic outflow arise from?
Craniosacral outflow
What structures are supplied by the parasympathetic fibres from the cranial portion?
Structures of the head and neck.
Structures of the thorax and abdomen (via the vagal nerve)
Where do the nuclei of the preganglionic parasympathetic fibres lie?
In the brain stem.
What structures do the preganglionic parasympathetic fibres travel with when leaving the brain stem?
Cranial nerves
What are the 4 discrete ganglia associated with the parasympathetic outflow to the head?
ciliary ganglia
Pterygopalatine ganglia
Submandibular ganglia
Otic ganglia
Which cranial nerves are parasympathetic fibres associated with?
CN III
CN VI
CN IX
CNX
What structures are the postganglionic parasympathetic fibres associated with?
Trigeminal Nerve
Where is the central control of the ANS?
In the hypothalamus
How many neurones are in series in the autonomic nervous system?
2 - preganglionic and postganglionic
What 2 muscles of the head and neck are under sympathetic innervation?
Eye lid (tarsal muscle) Iris (dilator pupillae )
What are the 2 muscles of the eye that have parasympathetic innervation?
Iris (sphincter pupillae)
Muscle in the ciliary body (control thickness of the lens)
Where are the cell bodies of the sympathetic preganglionic neurones?
Lateral horn of the grey matter of the spinal cord
What sympathetic ganglion are located in the neck?
The top 3 ganglion in the sympathetic chain are located in the neck and are known as the cervical ganglion.
Superior cervical ganglion
Middle cervical ganglion
Inferior cervical ganglion
What are the target tissues in the head and neck of the sympathetic neurones?
Sweat glands of the forehead
Smooth muscles of the eyelid
Pupil
Sweat glands of the face
Pathology to what structures of the head and neck can cause autonomic dysfunction to the eye and face?
Apex of the lung (tumours)
Common carotid artery
How will a patient with disrupted sympathetic innervation to the face present?
Partial Ptosis
Myosis
Absence of sweating on half of face ipsolateral with lesion (anhydrosis)
Why in Horner’s Syndrome, is the Ptosis only partial?
Only partial Ptosis as the skeletal muscle of the Levator Palpebrae muscle is still working to open the eyelid.
Levator palpebrae superioris opens the eye lid and has both skeletal and smooth muscle components. The skeletal muscle component is stronger and innervated by the motor fibres of the oculimotor nerve. The small smooth muscle component of the LPS known as the superior tarsal is innervated by the sympathetic nerves and is paralysed in Horners Syndrome.
In an occulomotor nerve lesion, why is the Ptosis experienced not partial?
As the occulomotor nerve innervates the skeletal muscle of the Levator palpebrae muscle. The skeletal muscle makes up the bulk of the LPS and if paralysed the smooth muscle is not strong enough to elevate the eyelid.
How would the pupil differ in Horner’s Syndorme compared to an oculomotor nerve lesion?
Horners syndrome = miosis
CN III lesion = Mydriasis
What is Anhydrosis?
Lack of sweating