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Head, neck and introduction to neuroanatomy > Session 6 > Flashcards

Session 6 Flashcards

1
Q

What is the autonomic nervous system?

A
  • Divided into parasympathetic and sympathetic nervous systems
  • Part of the peripheral nervous system
  • Controls non-voluntary actions of smooth muscle, cardiac muscle and glands
  • Maintains and fine-tunes internal environment
  • Many structures receiving autonomic innervation are dually innervated with sympathetic and parasympathetic fibres
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2
Q

What are the actions of the sympathetic nervous system?

A
  • Retract eyelids
  • Dilates pupils
  • Increases activity of sweat glands
  • Constricts smooth muscle of blood vessels in skin and gut
  • Bronchodilates airways
  • Decreases gut motility
  • Increases rate and force of contraction of cardiac muscle
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3
Q

What are the actions of the parasympathetic nervous system?

A
  • Constricts pupil
  • Makes lens fatter (smooth muscle in ciliary body)
  • Increases activity of lacrimal glands
  • Increases activity of salivary glands
  • Increases activity of mucosal glands
  • Increases contraction of smooth muscle of respiratory and GI tract
  • Decreases rate and force of contraction of heart
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4
Q

Where are pre-ganglionic neurones found?

A
  • Cell bodies (nuclei) within CNS
  • Axons exit CNS to synapse with another autonomic neurone
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5
Q

Where are post-ganglionic neurones found?

A
  • Cell body lies within a ganglion outside of CNS
  • Axon exits ganglion to synapse with tissues
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6
Q

Where do sympathetic fibres exit the CNS?

A
  • Thoracolumbar outflow
  • T1-L2 spinal segments only
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7
Q

Where do parasympathetic fibres exit the CNS?

A
  • Craniosacral outflow
  • Brainstem x4 cranial nerves
  • Sacral S2-S4 pelvic splanchnics
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8
Q

Outline how 1st, 2nd, and 3rd order neurones reach the structures of the head and neck?

A
  • 1st order neurone descends via brainstem into spinal cord
  • Synapses onto cell body of 2nd order neurone
  • 2nd order neurone exits at T1/T2 level in thoracolumbar region of spinal cord
  • Then enters and ascends in sympathetic chain up into the neck
  • At superior cervical ganglion 2nd order neurone synapses onto 3rd order neurone
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9
Q

How do 3rd order neurones travel in the head and neck?

A
  • Hitch-hike onto blood vessels
  • Runs on outside of CCA and then along ICA and ECA to reach target tissues
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10
Q

How do 3rd order sympathetic neurones to the eye and orbit reach their targets?

A
  • Run with ICA
  • Then into orbit
  • Run alongside ophthalmic artery and distal branches of Va
  • Increase retraction of upper eyelid
  • Dilate the pupil
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11
Q

How do 3rd order sympathetic neurones to the sweat glands of the face and neck reach their targets?

A
  • Run with branches of the ECA
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12
Q

What are the points where sympathetic innervation to the head and neck can be damaged?

A
  • 1st order neurones - within the CNS
  • 2nd order neurones - exiting the CNS and within the sympathetic chain
  • 3rd order neurones - running with blood vessels
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13
Q

Which pathologies/injuries affect the sympathetic nerves reaching the head and neck?

A
  • Pathology/injury to CCA or ICA - e.g. carotid artery dissection or aneurysm
  • Apical lung cancer e.g. Pancoast’s tumour (can interrupt sympathetic innervation to head and neck and involve structures relating to eye)
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14
Q

What is the clinical manifestation of interruption of sympathetic innervation to face and eye?

A
  • Horner’s syndrome:
    1. Partial ptosis
    2. Miosis (constricted pupil)
    3. Anhidrosis (ability to sweat is lost on affected side of face)
    4. Apparent enophthalmus
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15
Q

Why does interruption of sympathetic innervation lead to partial ptosis, not a complete or severe ptosis?

A
  • Levator palpabrae superioris contracts to elevate (retract) upper eyelid
  • Two muscle types within it contribute different amounts
  • Skeletal muscle innervated by CN III (somatic) has major contribution
  • Smooth muscle innervated by sympathetics has smaller contribution
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16
Q

Which cranial nerves carry parasympathetic fibres with them?

A
  • Oculomotor (III)
  • Facial (VII)
  • Glossopharyngeal (IX)
  • Vagus (X)
  • Remember 1973
17
Q

Describe the cranial outflow of parasympathetic innervation to the head and neck

A
  • Parasympathetic nuclei in brainstem
  • Preganglionic axons exit brainstem with 1 of 4 cranial nerves
  • Parasympathetic ganglia (cell body of post-ganglionic neurone)
  • Post-ganglionic axons after exiting ganglia run with the very distal branches of CN V (a, b or c)
  • To target tissues
18
Q

Outline the parasympathetic route starting at the Edinger-Westphal nucleus to head and neck

A
  • Edinger-Westphal nucleus (most important nucleus)
  • Parasympathetic fibres exit with CN III
    -Ciliary ganglion
  • Target tissues are sphincter pupillae (constricts pupil) and ciliary muscle (fattens lens)
19
Q

Outline the parasympathetic route starting at the superior salivary nucleus to head and neck

A
  • Superior salivary nucleus
  • Exits with CN VII
  • Pterygopalatine ganglion and submandibular ganglion
  • Target tissues are lacrimal glands (tears), nasal and mucosal glands (mucus) and salivary glands (submandibular and sublingual)
20
Q

Outline the parasympathetic route starting at the inferior salivary nucleus to head and neck

A
  • Inferior salivary nucleus
  • Exits with CN IX
  • Otic ganglion
  • Target tissue is salivary gland (parotid gland)
21
Q

Outline the parasympathetic route starting at the dorsal motor nucleus to head and neck

A
  • Dorsal motor nucleus
  • Exits with CN X
  • No named ganglion - sits very close to or within target tissues
  • Target tissues are mucosal glands and smooth muscle within respiratory tract and most of GI tract and cardiac muscle
22
Q

Outline the pupillary light reflex (light in left pupil)

A
  1. Light enters left eye
  2. Optic nerve is sensory afferent from left retina
  3. Some branches leave optic nerve to enter midbrain on left and synapse on pre-tectal nucleus
  4. Connection with EDW nuclei is on left and right side
  5. Pre-ganglionic parasympathetic fibres from EDW leave brainstem with oculomotor nerve fibres
  6. Pre-ganglionic fibres synapse in ciliary ganglion; become post-ganglionic
  7. Reach sphincter pupillae muscle of iris to make both pupils constrict
23
Q

What are the 2 pupillary light reflexes?

A
  • Direct light reflex (pupil into which light shone constricts)
  • Consensual light reflex (other pupil also constricts)
24
Q

Outline the relationship of parasympathetics associated with the facial nerve to the facial nerve

A
  • Parasympathetic nuclei in close proximity to facial nerve nuclei
  • Parasympathetic preganglionic axons exit brainstem with other axons forming facial nerve
  • Run with facial nerve into petrous bone
25
Q

Which branches of the facial nerve do parasympathetic fibres run with?

A
  • Greater petrosal nerve (associated with pterygopalatine ganglion)
  • Chorda tympani nerve (associated with submandibular ganglion)
26
Q

Outline the relationship of parasympathetics associated with the glossopharyngeal nerve to the glossopharyngeal nerve

A
  • Pre-ganglionic nuclei in close proximity to nuclei of CN IX
  • Axons exit brainstem with axons of CN IX
  • Pre-ganglionic parasympathetic fibres hitch-hike with tympanic nerve (branch of CN IX)
  • Pre-ganglionic parasympathetic fibres exit middle ear as lesser petrosal nerve which runs to Otic ganglion
  • Post-ganglionic parasympathetics exit ganglion and join with auriculotemporal nerve
  • Supply parotid gland
27
Q

Outline the relationship of parasympathetics associated with the Vagus nerve to the Vagus nerve

A
  • Pre-ganglionic parasympathetic fibres exit with other axons forming CN X
  • Run within CN X and its branches
  • Meet ganglion at or in target tissues
28
Q

What are the target tissues of the parasympathetics associated with the Vagus nerve?

A
  • Heart
  • Mucosal glands in pharynx/larynx and smooth muscle of oesophagus and trachea
  • Smooth muscle and mucosal glands within rest of respiratory and GI tract

Head, neck and introduction to neuroanatomy (11 decks)

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