Ans Flashcards
Give a brief overview of the ans
• Part of the
– Central control is from hypothalamus
• Controls body functions not under conscious control
• Maintains and fine tunes internal environment: accelerator and brake
• Has a sequential two neurone arrangement and an associated ganglion
– Pre ganglionic nerve -> ganglion -> post ganglionic nerve
• Target tissues are smooth muscle* (cardiac muscle in thorax) and glands (lacrimal and salivary)
*smooth muscle action is involuntary and frequently found in viscera (organs e.g. gut) hence ANS (symp/parasymp) is also known as “visceral efferent/motor”
Describe the autonomic outflow of the cns
Sympathetic: ‘thoracolumbar outflow’ - Segments T1- L2 of spinal cord only - Cell bodies within lateral horn of grey matter of spinal cord
Parasympathetic: ’craniosacral outflow’ - Cranial (four cranial nerves)
- Sacral (S2-S4)- pelvic splanchnics
Describe teh functions of sons vs pons
- Smooth muscle of blood vessels, eye lid (tarsal muscle) and iris (dilator pupillae)
- Sweat glands
- Arrector pili muscles (hair follicles)
- Decreases secretions from salivary and lacrimal glands (smaller volume but higher protein-more viscous)
- Smooth muscle of iris (sphincter pupillae) and muscle in ciliary body
- Lacrimal glands (tears)
- Salivary and mucosal glands
- Smooth muscle of the respiratory and gastrointestinal tract
Describe how sympathetics follow blood vessels
Most to head and neck synapse at superior cervical ganglion - cell bodies of post ganglionic sympathetic
It then hitch hikes on blood vessels. Has to go on blood cell ess are they run up neck to head structures.
Smth plexus
Sympathetic nerves destined for eye hitchhike on internal carotid artery . A branch of the CIA is the Opthalmic artery, which goes into orbit
Sympathetics to eye follow I ca, thru cavernous sinus, To Opthalmic into orbit
Once in orbit, blood vessel will only get so far - then will jump ship to cranial nerves destined for eyelid or structure inside th eye
CN iii carries motor fibre to lps - sympathetics follows them up there.
CN va - carries to deeper structures on the eye
In the eye, sympathetic innervation goes to superior tarsal muscle - small smooth muscle componen of lps.
Dilator pupillae - sns
ECA carries sympathetics to skin - sweat glands also provides vasoomotor tone - sympathetic - vasoconstriction - everythign on outside of head that isn’t eye or orbit aka, sweat glands, blood vessels
How can carotid artery and lung apex affect sympathetics
If ICA splits (dissects), can injure sympathetic plexus
Sympathetic symptoms and pain in neck - think - cold it be a ica dissection
Cancers in the apex of lung are close to where sympathetics exit spinal cord. - lung cancer can present with sympathetic signs in the eye
What is hornets syndrome
Consticted pupil - lost dilator pupillary - lost sympathetic - drooping tf eyelid (ptosis) and mitosis (constrictred pupil) anhydrosis (lack of sweating)
Hornets syndrome
Describe the route of the parasympathetic innervation to head and neck
Preganglionic parasympathetic in brain stem - close proximity to which ever cranial nerve will carry out with it
Occulomotor goes straight through. Parasympathetic hits a ganglion. The other fibres for a cranial nerve DO NOT SYNNApS HERE. This is an autonomic ganglion. Once the parasympathetic hit a ganglion . Become post ganglionic. They then leave the cranial nerve and will jump onto a branch of a trigeminal. Parasympathetic is NOT a function of the trigeminal as it did not Carr them out of the brain stem - they only hatchhike on very distal parts
What are the parasympathetic nuclei and ganglia
4 parasympathetic nuclei, 4 cns, that carry them out 4, 4 parasympathetic nuclei - remember designer Westphalia - relates to parasympathetics relating to cn iii see slide
What ae teh are functions
Smooth muscle (sphincter pupillae -pupil constrictor) and ciliary muscle (controls lens) • Lacrimal gland • Mucosal glands in nasal/oral mucosa/ resp. tract • Salivary glands
Describe the route of parasympathetic following cn iii
Brainstem (EWN)
Parasympathetic fibres emerge with CN III fibres
Ciliary ganglion
Hitch hikes on small branches from (CN Va)
Eye-
Ciliary body: lens Constrictor of the pupil
Why do both pupils constrict when a light is shoe in one
Sensory - optic nerve , chiasm, send a branch that communicates with midbrain (goes to occipital lobe too but also communicate with midbrain). At midbrain, signal come in from left eye, left optic nerve, gives abranch into brain stem, that afferent limb will communicate with EWN on left side, but also on right side - connects to both sides. That triggers the parasympatheticoutput to run out on occulomotor nerve, caring the parasympathetics which run to pupil to eye that shone the light in, but also to the other eye as well
Sensory afferent from left retina (CN II)
Some branches leave CN II to enter midbrain
Connection with EDW nuclei (left and right!)
Parasympathetic fibres from EDW leave brainstem with CN III (left and right)
Pass via ciliary ganglion
Reach sphincter pupillae
Direct left reflex, consensual right
What are the 2 main brainces of the facial nerve that the parasympathetics hitch hike onto
Parasympathetics reach target tissues via two main branches of the facial nerve that arise in petrous bone
• Greater petrosal nerve
• Chorda tympani nerve
• Two associated parasympathetic ganglia RESPECTIVELY
• Pterygopalatine ganglion
• Submandibular ganglion
• These ganglia =cell bodies of post ganglionic parasympathetic nerves
Decsribe how parasympathetics hitch hike on cn vii
See slide
Decsribe teh parasympathetics tat ollow cn ix
• Parasympathetic fibres arise from brainstem and exit with CN IX
• Exits through jugular foramen but at this point splits into no. of branches
— sensory oropharynx
— taste + gs post 1/3 tongue
— carotid sinus
— stylopharynngeus
— Tympanic nerve which to supply sensory to middle ear
• Parasympathetic fibres run with the tympanic nerve initially
• Then parasympathetics exit middle ear as lesser petrosal nerve
• Synapses in otic ganglion (in infratemporal fossa)
• (Postganglionic parasympathetics then hitch hike on branch of CN Vc )
• Parotid gland
Descrbe tha parasympathetics that follow cn x
Brainstem (medulla) Parasympathetics exit with CN X
Parasympathetic fibres run with CN X and its branches
Meet ganglion at or in target tissue:
- Glands in laryngopharynx, larynx; glands and smooth muscle of oesophagus and trachea
- Heart
- Smooth muscle and glands within respiratory and gastrointestinal tract
