6 - Autonomic

Question 1

What is the autonomic nervous system?

Answer 1

Part of peripheral nervous system that controls smooth muscle and glands, under central control from hypothalamus

Question 2

Describe sympathetic outflow from the CNS

Answer 2

Thoracolumbar outflow - T1-L2

cell bodies within lateral horn of grey matter of spinal cord

Question 3

Describe parasympathetic outflow from the CNS

Answer 3

Craniosacral outflow - 4 cranial nerves and S2-S4 pelvic splanchnics
Cell bodies in brainstem or grey matter of sacral spinal cord

Question 4

Describe the effect of autonomic stimulation on the eye

Answer 4

Sympathetic: Dilates pupil
Parasympathetic: Constricts pupil, contracts ciliary muscle allow lens to thicken for near vision

Question 5

Describe the effect of autonomic stimulation on the skin

Answer 5

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

Question 6

Describe the effect of autonomic stimulation on the lacrimal and salivary glands

Answer 6

Sympathetic: Decreases secretion, makes more viscous
Parasympathetic: Increases secretion, makes more watery

Question 7

Which muscles in/around the eye receive sympathetic innervation?

Answer 7

Superior tarsal muscle, retracts eyelid

Dilator pupillae

Question 8

Where do sympathetic fibres originate?

Answer 8

T1-T6

Question 9

Describe the path of sympathetic fibres after they leave the spinal cord

Answer 9

Enter sympathetic chain, travel till reach superior/middle/inferior cervical ganglia
Hitch-hike with common carotid, then its branch to its target tissue

Question 10

What are the target tissues and effects of sympathetic innervation?

Answer 10

Dilator pupillae - Pupil dilation
Superior tarsal muscle - Assists lid retraction
Blood vessles - vasoconstriction
Sweating

Question 11

Which blood vessel will sympathetic fibres targeting the face/sweat glands hitch hike along?

Answer 11

External carotid artery

Question 12

Which blood vessel will sympathetic fibres targeting the eye hitchhike along and what structures will they pass through?

Answer 12

Internal carotid artery 
Base of skull
Cavernous sinus
Opthalmic artery
Orbit 
Can hitchhike with Occulomotor (III)/opthalmic nerve (V1)

Question 13

What symptoms constitute Horner’s syndrome?

Answer 13

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

Question 14

What causes Horner’s syndrome?

Answer 14

Pancoast tumour (cancer of apex of the lung)
Internal carotid artery pathology
Spinal cord lesion

Question 15

Which cranial nerves carry parasympathetic fibres from the brainstem?

Answer 15

Oculomotor
Facial
Glossopharyngeal
Vagus

Question 16

What are the target tissues of parasympathetic innervation?

Answer 16

Constrictor pupillae 
Cillary muscle
Lacrimal gland 
Mucosal glands 
Salivary glands

Question 17

Describe the route taken by parasympathetic fibres innervating the ciliary body

Answer 17

Edinger-Westphal nucleus in brainstem
Hitchhikes on oculomotor (III) nerve fibres
Cillary ganglion
Hitchhikes on branches of opthalmic nerve
Cillary body

Question 18

What is the consensual light reflex?

Answer 18

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

Question 19

Describe what happens when the retina is stimulated by light into the left eye

Answer 19

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

Question 20

Describe the route of parasympathetics to the lacrimal/nasal/palatine glands

Answer 20

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

Question 21

Describe the route of the parasympathetics to the sublingual/submandibular glands

Answer 21

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

Question 22

Describe the route of the parasympathetics to the parotid gland

Answer 22

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

Question 23

Describe the route of the parasympathetics to glands/smooth muscle in upper gi and resp tract and heart

Answer 23

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

Question 24

What are the target tissues associated with the vagus (X) nerve?

Answer 24

Smooth muscle of oesophagus and trachea
Glands within laryngopharynx
Heart