Lecture 11- Autonomic innervation of the head and neck Flashcards
The autonomic (visceral) nervous system made up of
Sympathetic and parasympathetic nervous system
autonomic (visceral) nervous system is part of
- of the peripheral nervous system
- Central control from hypothalamus
autonomuc nervous system controls
unconscious control
examples of unconscious control
- Controls body functions not under conscious control e.g. vasoconstriction and pupil reflex (smooth muscle)
- Maintains and fine tunes internal environment
- Accelerator and brake
Neurone arrangement
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pre-ganglionic autonomic neurone starts in the CNS and synapse with post ganglionic nerve either in the sympathetic chain or at the organ itself
- Sympathetic neruones preganglionic nerves synapse with post ganglionic neurones in the
- vertical arrangement of autonomic ganglion
paraympathetic neruones preganglionic nerves synapse with post ganglionic neurones in the
- Target tissue
- Smooth muscle
- Cardiac muscle
- Glands (lacrimal, mucosal and salivary)
Sympathetic
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- Flight or flight
- Smooth muscles of blood vessels (constriction), eye lid (tarsal muscle) and iris (dilator pupillae)
- Just not in resp and GI
- Sweat glands (NOT USUALLY SALIVARY)
- Arrector pili muscles (hair follicles)
- Decrease secretions from salivary and lacrimal glands (smaller volume but higher protein-more viscous)
Parasympathetic
- Parasympathetic and sympathetic leave the CNS in
discrete regions
sympathetics leave the CNS via
thoracolumbar outflow
- All sympathetic nerves leaves the CNS from segments T1-L2 ONLY
- then enter sympathetic chain
Parasympathetic leave the CSN via
Craniosacral outflow
- Cranial (4 cranial nerves)
- Sacral (S2-S4)
- pelvic splanchnics
nerve sthat come out of T1/T2 are
destined for head and neck
thoracolumbar t1-T2 (sympathetic innervation to the head and enck) follow
routes of blood vessles (hitchhike on the exteranl surface of blood vessels)
outline how thoracolumbar T1/T2 provide symapthetic innervation to the head an enck
- Pre-ganglionic sympathetic nerves exit the spinal cord T1/T2
- Joins the sympathetic chain (one on either side of the vertebral column)
- Top 3 ganglion (cervical ganglion) at the top of the vertebral chain (in the neck)
- Superior ganglion
- Middle
- Inferior
- Superior cervical ganglion most important when thinking of head and neck
- When the pre-ganglionic nerve meets the superior cervical ganglion we meet the cell body of the post-ganglionic sympathetic nerve
- Post ganglionic sympathetic nerve will join the common carotid artery and follow the external carotid artery as it distributes branches across the face and the internal carotid artery as it runs through the base of the skull through the cavernous sinus and a branches into the orbit (think of the route of the carotid artery= route of sympathetic nerve)
- Follows ophthalmic artery (branch of internal carotid) into the eye
- To the smooth muscle of the eyelid
- Pupil
- Follows external carotid to the
- Sweat glands of the forehead
- Sweat glands of face
think of the route of the carotid artery=
route of sympathetic nerve
post ganglionic sympathetic nerve joins the
common carotid artery and follows the……
- external carotid artery as it distirbutes branches across the face
- internal carotid artery as it runs through the base of the skull through the cavernous sinus and branche sinto the orbit -carotid canal
- Follows ophthalmic artery (branch of internal carotid) into the eye and innervates
- Small smooth muscle portion of the levator palpebrae superioris muscle which opens the eye called the superior tarsal muscle
- Pupil- ciliary muscles= pupil dilation
The …………….is the only muscle involved in raising the superior eyelid- innervated by oculomotor CN III.
levator palpebrae superioris (LPS)
A small portion of this muscle contains a collection of smooth muscle fibres – known as the superior tarsal muscle. In contrast to the LPS, the superior tarsal muscle is innervated by the sympathetic nervous system.
- Post ganglionic sympathetic fibres follows external carotid to the
- Sweat glands of the forehead
- Sweat glands of face
the common carotid arteires and its branches and the lung apex
important relations to sympathetic nerves innervating head and neck
- A number of areas in the neck and body that if we have pathology it may manifest itself in signs in the face and the eye
- E.g. ptosis or partial ptosis, pupil constriction (miosis) à due to interruption to sympathetic innervation to the eye
Why in Horner’s syndrome, is the ptosis only partial- compared to the more severe ptosis seen in an oculomotor nerve lesion?
- Smooth muscle (innervated by sympathetic nerve) part of the Levator Palpebrae Superioris Muscle (LPS), called the superior tarsal muscle, is only a small component LPS, which is innervated by the oculomotor nerve which uses skeletal muscle
- therefore if the sympathetic nerve has a lesion then only a small part of the LPS (superior tarsal) will be affected= partial pstosis
full ptosis
- If you lose oculomotor nerve (and not sympathetic nerve), you would still get full ptosis due to the smooth muscle (superior tarsal) not being strong enough to open the eye
Horner’s syndrome refers to a
Triad of symptoms produced by damage to the sympathetic trunk in the neck:
- Partial ptosis (drooping of the upper eyelid) – Due to denervation of the superior tarsal muscle.
- Miosis (pupillary constriction) – Due to denervation of the dilator pupillae muscle.
- Anhidrosis (absence of sweating) on the ipsilateral side of the face – Due to denervation of the sweat glands.
Horner’s syndrome can represent serious pathology, such as a tumour of the apex of the lung (Pancoast tumour), aortic aneurysm or thryoid carcinoma.
How would the pupil differ in a Horner’s syndrome compared to an oculomotor nerve lesions?
Horners (sympathetic lesion)- constricted pupil (miosis)
Oculomotor lesion- dilated pupil (mydriasis)
Miosis in horners sundroem
mydriasis in CN III lesion
dilated pupil
interruption to the parasymapthetic innervation (carried by mydriasis) to the constrictor muscle of the pupil, leaving unopposed sympathetic innervation to dilaotr muscle of pupil
- Causes of Horners syndrome
- Sympathetic route comes from inside the chest?
- Patients with apical lung cancer can have sympathetic interference e.g.
- Pancoast tumour
- Patients with anerysms or dissected blood vessels into the neck
- Patients with apical lung cancer can have sympathetic interference e.g.
2 main ganglia (cell bodies of post ganglionic neurone) of the sympathetic innervation to the head and neck
top of sympathetic chain
- superior cervical ganglion (head)
- middle cervical ganglion (neck and chest)
sympathetic nerve hitch hike on the
common carotid artery and then external and internal carotid artery
sympathetic flight or flight response in the head and neck
pupillary dilation
assists eyelid retraction
vaso-constriction
sweating
