ANS Flashcards
What part of the nervous system is the ANS part of?
Peripheral nervous system that controls smooth muscle and glands
Describe the neuronal arrangement of the ANS
Pre-ganglionic N – ganglion – post ganglionic N
What is a ganglion?
Collection of cell bodies
What is the equivalent of a ganglion in the CNS?
nuclei
What is the location of the autonomic outflow?
Sympathetic = thoracolumbar, T1-L2, cell bodies in lateral horn of grey matter of spinal cord
Parasympathetic = craniosacral, brainstem, S2-S4, cell bodies (nuclei) in brainstem or grey matter of sacral spinal cord
How do sympathetics reach structures in the head and neck?
Axon leaves spinal cord (mainly T1/2) = meets sympathetic chain (chain of ganglion) = doesn’t synapse but ascends up sympathetic trunk = now in the superior CERVICAL ganglion = pre-ganglionic N meets cell body of post ganglionic N = hitch hikes on common carotid – internal/external = through base of the skull via carotid canal =
internal carotid A to the ophthalmic A to the eye = can also travel along the oculomotor and trigeminal Ns (superior tarsal muscle, dilator pupillae)
external carotid A to the sweat glands and blood vessels of face/neck
Top 3 ganglion in the cervical chain are called?
The cervical ganglion = due to location in the neck
What is the carotid plexus?
Sympathetic Ns having arisen from the ganglion making their way up the neck by associating with the carotid artery
How can pathology involving the apex of the lung cause autonomic dysfunction in the eye and face?
Lung cancer – pancoast tumour = interrupt sympathetic supply as the axons leave the spinal cord - to the face/eye
Clinical appearance = partial ptosis, constricted pup (miosis), anhidrosis (lack of sweating) = Horners syndrome
What is horners syndrome?
Interruption of the sympathetic nerves to 1/2 face/eye
Clinical appearance = partial ptosis, constricted pup (miosis), anhidrosis (lack of sweating) = Horners syndrome
Causes = lung apex cancer, pathology of the carotid artery
Which cranial nerves carry parasympathtic fibres from the brainstem?
Oculomotor
Facial
Glossopharngeal
Vagus
How do parasympathetic fibres reach the head and neck?
Arise from brainstem
Hitch-hike on 1 of 4 CNs
Ganglion
Synapse with post-ganglionic parasympathetic axon
Hitch-hike on trigeminal N
To target tissue = constricting smooth muscle in iris, ciliary muscle, lacrimal gland, mucosal gland, salivary glands
Name the parasympathetic ganglion
Ciliary = oculomotor N
Submandibular = facial N
Pterygopalatine = facial N
Otic = glossopharyngeal
What is the name of the important parasympathetic nuclei?
Edinger westphal
Outline the pupillary-light reflex
1) Light in L pupil
2) Sensory afferent OPTIC N from L retina
3) Some branches leave the optic nerve to enter midbrain
4) Connect with edinger-westphal nuclei L and R
5) Parasympathic fires from EDW leave brainstem
6) Hitch-hike on OCCULOMOTOR N L and R
7) Pass via ciliary ganglion
8) Reach sphincter pupillae
9) Direct light reflex L pupil, consensual light reflex R pupil
Outline how the parasympathetic Ns travel the oculomotor N
Brainstem – edinger westpahl nucleus
Pre-ganglionic hitch-hikes on oculomotor N
Ciliary ganglion
Post-ganglionic hitch-hikes on trigeminal
Ciliary body (constrictor of pupil)
Outline how the parasympathetic fibres travel the facial N
Parasympathetic pre-ganglionic emerges from brainstem hitch hiking on facial N
Into petrous bone
At point of geniculate ganglion
1) greater petrosal N leaves = to pterygopalatine fossa containing pterygopalatine ganglion – post-ganglionic parasympathetics hitch-hikes via trigeminal N to lacrimal/nasal/palatine glands
2) chorda tympani N leaves = crosses middle ear cavity, exiting base of skull – submandibular ganglion – post-ganglionic parasympathetics hitch hike via trigeminal N to tongue/sublingual/submandibular glands
Outline how the parasympathetic fibres travel the glossopharngeal N
Parasympathetic pre-ganglionic emerges from brainstem hitch-hiking on glossopharngeal N
Through jugular foramen
Gives off tympanic N (sensory to middle ear)
Travel inside the petrous bone
Exits as the lesser petrosal N
Synapse with otic ganglion
post-ganglionic parasympathetics hitch hike via trigeminal N to parotid gland
Outline how the parasympathetic fibres travel the vagus N
Parasympathetic pre-ganglionic emerges from brainstem hitch-hiking on Vagus N
Meets ganglion in target tissues
Post ganglion fibres inside
1) glands
2) heart
3) smooth muscle in resp/GI
Which branches of the facial N arise within the petrous part of the temporal bone?
greater petrosal N
chorda tympani branch
nerve to stapedius
If there is a small tumour of the vestibulocochlear N in the area of the internal acoustic meatus, which other cranial N may be affected?
CN 7 - facial N
