Session 6 Flashcards
The sympathetic outflow to the whole body arises from the
Thoracolumbar portions T1-L2 of spinal cord (lateral horn)
Preganglionic sympathetic fibres on exiting spinal cord usually synapse with their
Post ganglionic nerve in a sympathetic chain ganglion
Sympathetic outflow to the head and neck region arises from
T1/T2 segments
Preganglionic fibres reaching the neck have to
ascend from thorax, up sympathetic chain to reach the neck
Synapse on one of the upper (cervical) ganglia of the chain
In superior and middle cervical ganglia
Post ganglionic sympathetic fibres reach their target tissues in the head and neck by
Hiking onto blood vessels
Parasympathetic outflow arises from
2 regions of CNS
Top and bottom of spinal cord
Cranial (brainstem) and sacral region- craniosacral outflow
Cranial portion supplies
Parasympathetic innervation to the head and neck, and thorax and abdomen via CN X
What are nuclei
Collections of preganglionic parasympathetic nerve cell bodies
Nuclei lie in
Brainstem, often in close proximity to the nuclei of cranial nerves
Hitch hike on them when leaving brainstem
Parasympathetic preganglionic nerves compared to sympathetic preganglionic nerves
Parasympathetic have longer preganglionic nerves
Travel longer distance before reaching their associated ganglia
Post ganglionic neurone is shorter
Parasympathetic outflow does not have a chain of ganglia but instead has
A number of discrete ganglia- 4
4 head and neck parasympathetic ganglia
Ciliary CN 3
pterygopalatine CN 7
submandibular CN 9
and otic CN 10
What happens once the post ganglionic parasympaethic fibres reach their ganglia
Jump ship and hitch hike onto branches of the trigeminal nerve, to reach the target tissues
The parasympaethic fibres associated with the vagus nerve do not have
A discrete ganglion within the head, but instead travel some distance with the vagus nerve down the neck and into the thorax
The parasympathetic fibres remain with the vagus nerve until the autonomic fibres meet and synapse in
Ganglia very close to or within its target effector tissues
E.g. mucous membrane glands, smooth muscle of larynx, pharynx, thorax abdomen and heart
Autonomic nervous system controls
Non-voluntary actions such as smooth muscle, cardiac muscle and glands
Sympathetic fight or flight response direct effect on target tissues (most important)
Smooth muscles in eyelid (superior tarsal muscle) = eyelid retraction
Smooth muscle in the iris (dilator pupillae) = dilates pupils
Sweat glands
Sympathies fight or flight response effect on target tissues (other)
Smooth muscle of blood vessels (skin and gut) = constricts
Smooth muscle of respiratory tract and gastrointestinal tract (bronchodilator airways and decrease gut motility)
Cardiac muscle (increased rate and force of contraction)
Parasympathetic effects on target tissues (most important)
Smooth muscle of iris (sphincter pupillae) = constricts pupil
Smooth muscle in ciliary body (makes lens fatter)
Lacrimal glands increase secretions
Salivary glands increase secretions
Parasympathetic effects on target tissues (other)
Mucosal gland secretions increase
Smooth muscle of respiratory and GI tract contracts
Cardiac muscle (decreased rate and force of contraction)
Difference between position of cell body in pre and post ganglionic
Sympathetic route to neck in detail up to post ganglionic
Sympathetic route from post ganglionic onwards
Points where sympathetic innervation to head and neck structures can be damaged
1st order neurone within CNS
2nd order neurone exiting CNS and within sympathetic chain
3rd order neurone running with blood vessels
Key anatomical relations to sympathetic nerves reaching H and N structures
Common carotid or internal carotid e.g. carotid artery dissection or aneurysm
Apical lung cancer e.g. Pancoasts tumour
Clinical manifestation of interruption of sympathetic innervation to face and eye
Why does interruption of sympathetic innervation lead to partial ptosis (not complete)
Levator Palpebrae Superioris LPS contracts to elevate (retract) the upper eyelid
2 muscle types within it contribute
Skeletal (somatic)- majority
Smooth muscle (autonomic)- smaller
What happens when you have light in left pupil
Parasympathetic associated with facial nerve reach target tissues via
Greater petrosal nerve (carries only pre-gang parasympathetic fibre)
Chorda tympani nerve
Parasympathetics associated with CN IX pathway
Branch supplying sensory to middle ear (tympanic nerve): pre-ganglionic parasympathetic fibres hitch hike with it
Pre-ganglionic parasympathetics associated with CN IX exit middle ear as
Lesser petrosal nerve which runs to otic ganglion (in infratemporal fossa)
Post ganglionic parasympathetics associated with CN IX exit ganglion to join with
Auriculotemporal nerve (Vc branch) to supply parotid gland
Parasympathetics associated with Vagus nerve pathway
Summary for parasympathetic innervation to head and neck
