W20-L4: Cranial Nerves Flashcards
Which Cranial nerves are purely sensory?
CNI, CNII, CNVIII
Which Cranial nerves are purely motor?
CN III, IV, VI, XI and XII
Which Cranial nerves are mixed?
CN V, VII, IX, X
Where is the somatic motor nerve column?
Most medial
Where are the nuclei in the somatic motor nerve column?
Midbrain: Oculomotor, trochlear
Pons: Abducens
Medulla: Hypoglossal
Where is the brachial motor nerve column?
2nd from the medial line
Where are the nuclei in the brachial motor nerve column?
Pons: Trigeminal motor nucleus (V3), Facial nucleus
Medulla: Nucleus ambiguus (CN IX, X)
Spinal cord: accessory nucleus
What is the function of the visceral efferents and where is the column?
Most lateral of the motor columns (medial 3), function is motor innervation to smooth muscles (autonomic)
Where are the nuclei in the visceral efferents column?
Midbrain: Edinger-Westphal nucleus
Pons: Superior salivatory nucleus (CN VII)
Medulla: Inferior salivatory nucleus (CN IX), Dorsal motor nucleus of the vagus
Where is the visceral afferent sensory column?
Most medial of the sensory columns
Where are the nuclei in the visceral afferent sensory column?
Extends from pons to level of nucleus gracilis: nucleus of the solitarus tract (CN VII, IX, X)
What are the parts of the nucleus solitarius?
Rostral: Gustatory nucleus (CN VII, IX, X)
Caudal: Visceral sensory division (IX, X)
Where is the somatic sensory column?
Middle of the three sensory lateral columns
Where are the nuclei in the somatic sensory column?
Midbrain: Mesencephalic trigeminal nucleus
Pons: Principle sensory trigeminal nucleus
Pons to spinal cord: Spinal trigeminal tract (CN V, VII, IX, X)
Where is the special sensory column?
Most lateral of all the columns
Where are the nuclei in the special sensory column?
Pons and medulla: More medial is vestibular nuclei
Pons: Lateral is cochlear nuclei
What is a cause of CN I disruption that causes a noxious smell?
Meningoma that impinges on the nerve
What does the oculomotor nerve do?
• Motor: – Extrocular muscles: MR, SR, IR, IO – Elevates eyelid-via levator palpebrae superioris • PS to eye: – Iris (pupils) – Ciliary muscle (focussing)
Where does CN III, IV and VI pass through together and why is this important?
Cavernous sinus and superior orbital fissure, so lesion in this area could affect them all
Where does CN III and VI go through together?
common tendinous ring
Pupillary light reflex
Sensory inputs to brain from retina via CNII.
Motor outputs to Sphincter Pupillae muscle in iris:
-PS fibres from Edinger Westphal nucleus.
Tests midbrain function
What does CN V do?
– Sensory: input from face and also inside of mouth
– Motor: Muscles of mastication and Tensor tympani (inner ear)
What are the principle sensory and spinal trigeminal nucleus analogous to in the spinal cord?
Dorsal column & Anterolateral system.
What does the mesencephalic trigeminal nucleus do?
Proprioception of the face
How does the trigeminal nerve exit the brainstem?
Two roots: motor and sensory
What is the difference in the two roots of the trigeminal nerve?
Sensory forms the trigeminal ganglion, motor travels under the ganglion
Corneal blink reflex
- Sensory inputs to brainstem are mediated via CNV1.
- Motor outputs to eyelid (Orbicularis oculi) are mediated by CNVII.
- Used as a test of pontine function
What does the facial nerve do?
Motor (facial nerve proper):
– Innervates the muscles of facial expression.
– Stapedius muscle (ear) which dampens sounds
Parasympathetic:
• Lacrimal & sublingual and submandibular salivary glands
Taste:
• from anterior 2/3rds of tongue and soft palate
Sensation:
• from a small region near the external auditory meatus.
What is the course of the facial nerve?
Gives off branch to tear ducts, stapedius and tongue then exits stylomastoid foramen and gives off posterior auricular and then T, Z, B, M and C branches
What does CN IX do?
Sensory: from tongue (post. 1/3), pharynx, middle ear and carotid body.
Taste: post. 1/3 tongue
Visceral motor: PS to parotid
Motor: stylopharyngeus
What is the course of CN IX?
CN IX exits skull via jugular foramen lateral to and in front of CNX, CNXI and forms the Superior and inferior ganglia. Then Follows the stylopharyngeus to reach the oropharynx and tongue.
What does the vagus nerve do?
• Motor: to many striated muscles – soft palate, pharynx, larynx, upper oesophagus and 1 tongue muscle. • PS to many organs, – from pharynx to upper abdomen. • Sensory: – from pharynx, larynx oesophagus • Visceral: – Input from baro and chemorecptors of the Aortic arch
Gag reflex
- Sensory inputs: IX-sensory to pharynx
- Motor outputs: X-motor to pharynx
- Used as a test of medulla function
What is the course of CN XI?
Spinal accessory nucleus is in the upper 5-6 of cervical spinal cord. Nerve enters cranium via Foramen magnum. Then travels with X roots and exits jugular foramen.
What is the function of CN XI?
Provides motor input to sternomastoid and upper part of trapezius.
A lesion of CN XI on one side will cause an inability to turn to which side?
Contralateral side
