6 - Autonomic Flashcards
What is the autonomic nervous system?
Part of peripheral nervous system that controls smooth muscle and glands, under central control from hypothalamus
Describe sympathetic outflow from the CNS
Thoracolumbar outflow - T1-L2
cell bodies within lateral horn of grey matter of spinal cord
Describe parasympathetic outflow from the CNS
Craniosacral outflow - 4 cranial nerves and S2-S4 pelvic splanchnics
Cell bodies in brainstem or grey matter of sacral spinal cord
Describe the effect of autonomic stimulation on the eye
Sympathetic: Dilates pupil
Parasympathetic: Constricts pupil, contracts ciliary muscle allow lens to thicken for near vision
Describe the effect of autonomic stimulation on the skin
Parasympathetic: None
Sympathetic: Arrector muscles of hair, cause hair to stand on end
Causes vasoconstriction of peripheral blood vessels, lips and fingers turn bluw
Promotes sweating
Describe the effect of autonomic stimulation on the lacrimal and salivary glands
Sympathetic: Decreases secretion, makes more viscous
Parasympathetic: Increases secretion, makes more watery
Which muscles in/around the eye receive sympathetic innervation?
Superior tarsal muscle, retracts eyelid
Dilator pupillae
Where do sympathetic fibres originate?
T1-T6
Describe the path of sympathetic fibres after they leave the spinal cord
Enter sympathetic chain, travel till reach superior/middle/inferior cervical ganglia
Hitch-hike with common carotid, then its branch to its target tissue
What are the target tissues and effects of sympathetic innervation?
Dilator pupillae - Pupil dilation
Superior tarsal muscle - Assists lid retraction
Blood vessles - vasoconstriction
Sweating
Which blood vessel will sympathetic fibres targeting the face/sweat glands hitch hike along?
External carotid artery
Which blood vessel will sympathetic fibres targeting the eye hitchhike along and what structures will they pass through?
Internal carotid artery Base of skull Cavernous sinus Opthalmic artery Orbit Can hitchhike with Occulomotor (III)/opthalmic nerve (V1)
What symptoms constitute Horner’s syndrome?
Partial ptosis - drooping of upper eyelid, as superior tarsal muscle is paralysed
Miosis - constriction of pupil due to paralysis of dilator pupillae
Anhydrosis - lack of sweating on one side of face
What causes Horner’s syndrome?
Pancoast tumour (cancer of apex of the lung)
Internal carotid artery pathology
Spinal cord lesion
Which cranial nerves carry parasympathetic fibres from the brainstem?
Oculomotor
Facial
Glossopharyngeal
Vagus
What are the target tissues of parasympathetic innervation?
Constrictor pupillae Cillary muscle Lacrimal gland Mucosal glands Salivary glands
Describe the route taken by parasympathetic fibres innervating the ciliary body
Edinger-Westphal nucleus in brainstem
Hitchhikes on oculomotor (III) nerve fibres
Cillary ganglion
Hitchhikes on branches of opthalmic nerve
Cillary body
What is the consensual light reflex?
Where both pupils constrict, even though only one is stimulated because the optic (I) nerve sends afferent signal sent through Edinger-Westphal nucleus, whose axons run to both occulomotor (III) nerves
Describe what happens when the retina is stimulated by light into the left eye
Sensory afferent from optic (II) nerve
Fibres return to midbrain, to connect to edinger-westphal nucleus
Parasympathetic fibres leave edinger-westphal nucleus
Hitchhike on occulomotor (III) fibres
Ciliary ganglion
Reach sphincter pupillae - left eye causing direct light reflex, right eye causing consensual light reflex
Describe the route of parasympathetics to the lacrimal/nasal/palatine glands
Exits brainstem with facial nerve (VII)
Into petrous bone
At level of geniculate ganglion, travels with greater petrosal nerve
Pterygopalatine ganglion
Hitchhike with maxillary (V2) nerve to reach target tissues
Describe the route of the parasympathetics to the sublingual/submandibular glands
Exits brainstem with facial nerve (VII) Into petrous bone Hitchhikes with chorda tympani (VII) Crosses through middle ear cavity Exits via base of skull Synpases with submandibular ganglion Branches of trigeminal (V) nerve, hitchhikes to target tissue
Describe the route of the parasympathetics to the parotid gland
Exit brainstem with glossopharyngeal (IX) via the jugular foramen
Enters petrous bone
Hitchhikes with tympanic nerve (IX) and tympanic plexus
Hitchhikes with lesser petrosal nerve (IX) and exits via foramen ovale
Synapses with otic ganglion
Hitchhikes onto mandibular (V3) till it reaches the parotid gland
Describe the route of the parasympathetics to glands/smooth muscle in upper gi and resp tract and heart
Exit the brainstem with vagus (X) nerve fibres
Meets its ganglia at the target organ (so no post ganglionic hitchhike with trigeminal (V) fibres) to target tissues
What are the target tissues associated with the vagus (X) nerve?
Smooth muscle of oesophagus and trachea
Glands within laryngopharynx
Heart
