Sympathetics of head and neck Flashcards
Where does the sympathetic innervation to the head and neck arise from?
T1-L2 of spinal cord
How does the sympathetic pre-ganglionic nerve fibre reach the superior cervical ganglion?
Travels to the sympathetic chain at its spinal level
then travels up the sympathetic chain
Where does the sympathetic pre-ganglionic nerve fibre synapse with the sympathetic post-ganglionic nerve fibre?
In the superior cervical ganglion
What is the superior cervical ganglion?
Most superior ganglion of sympathetic chain
What structures in the head and neck are innervated by the sympathetic nervous system?
Smooth muscle of blood vessels
Superior tarsal muscle
Dilator pupillae muscle
Sweat glands
Arrector pili muscles
Lacrimal and salivary glands
What type of muscle is the superior tarsal muscle made up of?
Smooth muscle
Where is the superior tarsal muscle located?
Eyelid
What is the action of the superior tarsal muscle?
Retracts the eyelid
What type of muscle is the dilator pupillae muscle?
Smooth muscle
What is the action of the dilator pupillar muscle?
Dilates the pupil
What effect does sympathetic innervation have on the lacrimal and salivary glands?
Decreases volume of secretions
makes them more viscous
How do the sympathetic post-ganglionic nerve fibres reach the blood vessels in the head and neck that they supply?
From the superior cervical ganglion, run around the carotid arteries, forming the carotid plexus
How do the sympathetic post-ganglionic nerve fibres reach the sweat glands in the head and neck that they innervate?
Run around the external carotid artery
which supplies the face and scalp
How do the sympathetic post-ganglionic nerve fibres reach the muscles in the eye that they innervate?
Run around internal carotid artery, opthalmic artery
which supplies the eye
May also join the CN3 oculomotor nerve and the opthalmic branch of the CN5 trigeminal nerve
which supply the eye
What is Horner syndrome?
Group of signs and symptoms that result due to damage to the sympathetic trunk
What are the signs and symptoms of Horner’s syndrome?
Partial ptosis - droopy eyelid
Miosis - constricted pupil
Anhydrosis - decreased sweating
Why is partial ptosis seen with Horner’s syndrome?
Loss of sympathetic innervation to superior tarsal muscle
loss of retraction of eyelid
Partial because levator palpabrae superioris muscle which is innervated by the CN3 oculomotor nerve are both still functional
Why is miosis seen with Horner’s syndrome?
Loss of sympathetic innervation to dilator pupillae muscle
loss of dilation of pupil
Why is anhydrosis seen with Horner’s syndrome?
Loss of sympathetic innervation to sweat glands in face
loss of sweat production
What are some the causes of Horner’s syndrome?
Lung apex pancoast tumour
Internal carotid artery dissection
