18 - Cranial Nerves 2 Flashcards
Role of CNI (olfactory nerve).
Sense of smell (special sensory)
Where does CNI exit the skull?
Cribiform plate
Role of CNII (optic nerve)
Vision (special sensory)
Where does CNII exit the skull?
Optic canal
Where do visual afferents cross over?
Optic chiasm
Number of extraocular muscles
Six
Extraocular muscles
1 - 6
Rectus muscles Superior rectus, inferior rectus Medial rectus, lateral rectus Oblique muscles Superior oblique Inferior oblique
Where do CNIII, IV and VI exit the skull?
Superior orbital fissure (CNV also travels through here)
Role of CNVI (abducent)
Moves eyes laterally (abducts)
Role of CNIII
Constriction of pupil.
Gives parasympathetic innervation to these muscles.
Innervates superior, inferior and medial rectus muscles of eye and inferior oblique muscle of eye.
Levator palpebrae superioris (elevates eyelid)
Type of nerve that CNIII is
Somatic nerve.
Visceral motor.
Role of CNIII
Motor - extraocular muscles, elevates eyelid.
Parasympathetic innervation to eye - Iris (pupillary constriction), ciliary muscle (focussing)
Muscle that elevates eyelid
Levator palpebrae superioris
Do nerve nuclei in the brain stem serve one or more purposes?
One. EG: motor nerves from one nucleus, sensory nerves from one nucleus. These do not emerge from a single nucleus.
CN exiting skull through cribiform plate
CNI
CN exiting skull through optic canal
CNII
CNs exiting skull through superior orbital fissure
CNIII, IV, VI, V(1)
CN exiting skull through auditory canal
CNVII, VIII
CN exiting skull through jugular foramen
CN IX, X, XI
CN exiting skull through hypoglossal formaen
CNXII
Pupillary light reflex
•Sensory inputs to brain from retina via CNII.
•Motor outputs to Sphincter Pupillae muscle in iris:
– Parasympathetic fibres from Edinger Westfal nucleus (CNIII).
Where does VZV sit dormant?
Sensory ganglia (dorsal rot ganglia, trigeminal nerve ganglia)
CNV is what type of nerve?
Somatic sensory and brachial motor
Role of CNV
1
2
3
Sensory input from the face, inside mouth.
Muscles of mastication (motor)
Tensor tympani (middle ear)
Number of branches of trigeminal nerve
Three
Length of trigeminal nuclei
Run from midbrain to upper spinal cord
Four nuclei making up trigeminal nuclei
1) Mesencephalic (sensory)
2) Chief sensory (sensory)
3) Spinal trigeminal nucleus (STN) (sensory)
4) Motor nucleus (in motor column in pons)
Mesencephalic nucleus
More related to proprioception (contributes to trigeminal nerve)
Chief sensory nucleus
More related to pain (contributes to trigeminal nerve)
How do the sensory fibres of the trigeminal nerve exit the skull?
•Exits brainstem as two roots: Motor and sensory
•Sensory root travels to trigeminal ganglion
– Three branches
•Motor: travel with the mandibular division
–Muscles of mastication
–Tensor tympani (inner ear)
•Exit skull via three foramina: SRO
–V1: Superior orbital fissure;
–V2: Foramen Rotundum
–V3: Foramen Ovale
Three branches of the sensory root of the trigeminal nerve
- V1-Ophthalmic division
- V2-Maxillary division
- V3-Mandibular division
Foraminae through which branches of the trigeminal nerve exit skull
–V1: Superior orbital fissure;
–V2: Foramen Rotundum
–V3: Foramen Ovale
Path of the motor division of the trigeminal nerve
Travels on inferior part of sensory fibres.
Innervates muscles of mastication.
Example of a test of pontine function
Corneal blink reflex
Corneal blink reflex
1
2
3
- 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
CNVII nerve type
Brachial motor.
Visceral efferent (parasympathetic, to the lacrymal gland)
Visceral sensory (taste)
Somatic sensory
CNVII roles
1
2
- Motor (facial nerve proper)
–Innervates the muscles of facial expression.
–Stapedius muscle (ear)
•Remember “Trigeminal for Tensor tympani and Seventh for Stapedius “
–Part of digastric muscle
2) Sensory
–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.
Role of stapedius muscle
Contracts to dampen loud sounds.
Role of tensor tympani
Eliminates sound of chewing
Divisions of CNVII
Facial nerve proper (motor) Nervus intermedius (parasympathetic, taste, sensation)
*Course of the facial nerve
FACIALNERVE
Structure that facial nerve (CNVII) passes through, but does not innervate
Parotid gland
Common cause of acquired hearing loss, progressing to balance problems.
Abnormal growth of glial cells impinging on vestibulocochlear nerve (CNVIII).
If grows too serious, can impinge on trigeminal nerve.
An ‘acoustic neuroma’
Nuclei of CNVIII (vestibulocochlear)
Dorsal and ventral cochlear nuclei.
Four vestibular nuclei.
Where does CNVIII exit the skull?
Internal acoustic meatus
Role of CNVIII
Hearing and balance
Role of CNIX (glossopharyngeal nerve) 1 2 3 4 5 6
1) Receives general sensory fibres (ventral trigeminothalamic tract) from the tonsils, the pharynx, the middle ear, and the posterior 1/3 of the tongue.
2) Receives special sensory fibres (taste) from the posterior 1/3 of the tongue.
3) Receives visceral sensory fibres from the carotid bodies, carotid sinus.
4) Supplies parasympathetic fibres to the parotid gland.
5) It supplies motor fibres to stylopharyngeus muscle, the only motor component of this cranial nerve.
6) It contributes to the pharyngeal plexus.
Where does CNIX exit the skull?
Through the jugular foramen
Pathway of the glossopharyngeal nerve
1
2
3
1) CNIX exits skull via jugular foramen lateral to and in front of CNX, CNXI.
2) Superior and inferior ganglia (contain afferent components of nerve).
3) Follows the stylopharyngeus to reach the oropharynx and tongue.
CNX is which type of nerve? 1 2 3 4 5
–Branchial motor –Visceral motor (PS) –Somatic sensory –Visceral sensory (special) taste –Visceral sensory (general)
Motor component of CNX
Motor: to many striated muscles
– soft palate, pharynx, larynx, upper oesophagus and 1 tongue muscle.
Parasympathetic innervation of CNX
–from pharynx to upper abdomen (eg heart, lung, GI).
Sensory components of CNX
–from pharynx, larynx, oesophagus
Visceral components of CNX
–Input from baro and chemorecptors of the Aortic arch
–Taste from epiglottis and pharynx.
Roles of CNX 1 2 3 4
1) Motor
2) Autonomic (parasympathetic)
3) Sensory
4) Visceral
Medullary test
Gag reflex
Gag reflex
1
2
3
- Sensory inputs: IX-sensory to pharynx
- Motor outputs: X-motor to pharynx
- Used as a test of medulla function
Path of CNXI
Spinal accessory nucleus is in ~C1-C5 of cervical spinal cord. Nerve enters cranium via Foramen magnum. Then travels with X roots and exits jugular foramen.
Role of CNXI
Provides motor input to sternomastoid and upper part of trapezius (shrug shoulders, turn head)
CNXII is which type of nerve?
Somatic motor
Role of CNXII
Motor innervation to intrinsic & extrinsic muscles of the tongue (except palatoglossus-CNX).
Where does CNXII (hypoglossal nerve) exit the skull?
Hypoglossal foramen
Appearance of a lesion of hypoglossal nerve
Tongue deviates to side where the lesion is
