Autonomic Nervous System Flashcards
What is the autonomic nervous system?
Part of the PNS that controls smooth muscle and glands
What is the sympathetic outflow from the CNS?
Thoracolumbar - T1-L2 segments
Where are the cell bodies of preganglionic sympathetic nerves?
Within lateral horn of grey matter of spinal cord
What is the parasympathetic outflow from the CNS?
Craniosacral - cranial (4 CNs) or sacral (S2-S4) - pelvic splanchnics
Which muscles do sympathetic nerves contract?
Smooth muscle of blood vessels, eyelid (tarsal muscle) and iris (dilator pupillae)
Which muscles do parasympathetic nerves contract?
Smooth muscle of iris (sphincter pupillae) and ciliary body
SM of respiratory and gastrointestinal tract
Which muscle in the eyelid is controlled by sympathetics?
Superior tarsal muscle
Which muscle in the iris is controlled by sympathetics?
Dilator pupillae
What is lost in partial ptosis?
Only lost action of sympathetics - still got oculomotor nerve
What happens to the eye if sympathetic innervation is lost?
Partial ptosis (superior tarsal muscle lost) Constricted pupil (dilator pupillae lost)
Pathology involving the apex of the lung and internal carotid artery can cause what syndrome?
Horner’s syndrome
Which cranial nerves carry parasympathetic fibres from the brainstem?
Oculomotor
Facial
Glossopharyngeal
Vagus
What do sympathetic nerves to the head and neck hitch hike on to?
Blood vessels
Post ganglionic parasympathetics hitch hike onto branches of what nerve?
CN V (trigeminal)
What is the Edinger Westphal nucleus?
The parasympathetic pre-ganglionic nucleus that innervates the iris sphincter muscle and the ciliary muscle.
Why do you get constriction of both pupils even if you shine a light in just one eye?
Optic nerve sense light, sends signal to brain
COmmunication from optic nerve into midbrain
Communicates with EW on same side as well as the EW nucleus on opposite side
What are the target tissues of parasympathetics in the head and neck?
Smooth muscle in iris (constrictor) Ciliary muscle (controls lens) Lacrimal gland Salivary glands Mucosal glands in nasal/oral mucos/resp tract
Which ganglion do parasympathetic fibres of the oculomotor nerve pass through?
Ciliary ganglion
On which part of the nerve do parasympathetic fibres run?
On the outside
From what nucleus do parasympathetic fibres of the oculomotor nerve emerge?
Edinger Wesphal nucleus
What are the four parasympathetic nuclei?
Edinger Westphal
Superior salivary
Inferior salivary
Dorsal motor
What are the four ganglia associated with parasympathetics in the head and neck?
Ciliary
Submandibular
Pterygopalatine
Otic
After the ciliary ganglion, what do the postganglionic parasympathetic fibres of CN III hitch hike onto?
Branches of the trigeminal nerve (as do all postganglionic PS fibres)
What do parasympathetics of the oculomotor nerve do to the iris?
Constricts it
What is the consensual light reflex?
Response on one side of the body when the other side has been stimulated
Why does the consensual light reflex happen?
Because the afferent signal sent through one optic nerve connects to the Edinger-Westphal nucleus, whose axons run to both the right and the left oculomotor nerves.
What do parasympathetics of the oculomotor nerve do to the lens?
Fatten it - contract ciliary muscle
After passing through the internal auditory meatus, where do parasympathetics of the facial nerve enter?
Petrous bone, where it gives off a few branches
What are the two main branches of parasympathetics given off by the facial nerve in the petrous bone?
Greater petrosal nerve and chorda tympani
At which point does the greater petrosal nerve branch off?
At the point of geniculate ganglion
What is the target tissue of the greater petrosal nerve?
Lacrimal gland, palatine and nasal glands
Where is the pterygopalatine ganglion?
In the pterygopalatine fossa
What is the ganglion associated with the greater petrosal nerve?
Pterygopalatine ganglion
After passing through the pterygopalatine ganglion, what do postganglionic fibres of the facial nerve jump onto?
Branches of the trigeminal nerve
What ganglion is associated with the chorda tympani nerve?
Submandibular ganglion
How do parasympathetics get to the salivary glands (submandibular and sublingual)?
Join the chorda tympani nerve to the submandibular ganglion and then join branches of the trigeminal nerve
What can facial nerve lesions cause?
Dry eye
Dry mouth
Loss of taste
Loss of muscles of facial expression
What branch of the glossopharyngeal nerve gives sensory to the middle ear?
Tympanic nerve
What is the target tissue of parasympathetics of the glossopharyngeal nerve?
Parotid gland
How do parasympathetics of the glossopharyngeal nerve reach the parotid gland?
Runs with tympanic nerve through petrous bone in middle ear, exits via lesser petrosal nerve, goes to otic ganglion, postganlionic fibres hitch hike onto CN V to reach parotid gland
What is the vagus nerve in as it runs down the length of the neck?
Carotid sheath
