Lecture 41 - Cranial Nerves Flashcards
Organization of the cranial nerves
forebrain: olfactory and optic
midbrain: oculomotor, trochlear
Pons: trigeminal
pontomedullary junction: abducens, facial, vestibulocochlear, glossopharyngeal
medulla: vagus, accessory, hypogossal
Which cranial nerve is the only one to exit dorsally in the brain instead of ventrally
Trochlear nerve
Mnemonics to memorize cranial nerves and if sensory, motor, or both
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Olfactory tract sits in the
olfactory sulcus of the frontal lobe
What is the function of the olfactory tract
Olfaction/Smell
Is olfactory nerve sensory or motor
Special sensory
What is the pathway of the olfactory nerve
T or F: The olfactory nerve is the only nerve where sensory information is not first relayed through the thalamus
T
What 4 structures does the primary olfactory cortex project to
- Amygdala
- Hippocampus
- Piriform Cortex
- Secondary olfactory cortex
Anosmia
Lose sense of smell (injury, lesion, tumor)
What are the 4 cranial nerves associated with the visual system and what do they control
Vision transmitted by: Cranial Nerve II (optic nerve)
Eye movements are controlled by:
- Oculomotor (CNIII)
-Trochlear (CNIV)
-Abducens (CNVI)
Is the optic nerve sensory or motor
Special sensory
T or F: The optic nerve is susceptible to diseases at numeral locations and the visual defect is associated with site of injury
T
T or F: the optic nerve is capable of regeneration following a lesion
false, it is part of the CNS so it cannot regenerate
What are the 6 extrinsic ocular muscles that control movement
-Four recti
-2 oblique
Eyelid control is regulated by which muscle
Levator palpebrae superioris
visual fields are controlled
Contralaterally, so some crossover at optic chiasm, some do not (right visual field coming in the left eye stays on left side)
The pathway of the oculomotor nerve
midbrain -> superior colliculus -> superior orbital fissure -> divides to inferior and superior branches
All cranial nerves that control eye movements pass through
the superior orbital fissure (III, IV, VI)
What 5 muscles does the oculomotor nerve control through motor control and their function
- Levator Palpebrae Superioris: Raise eyelids
4/6 muscles that move the eye:
2. Superior rectus: elevates eyeball
3. Inferior rectus: Depresses eyeball
4. Medial rectus: Adducts eyeball
5. Inferior oblique: Elevates, abducts, and laterally rotates eyeball
What are the muscle functions of the 6 eye muscles (primary, secondary, and tertiary)
obliques abducted when they work together,
superior & inferior rectus adduct when they work together
What 2 muscles does the oculomotor nerve control parasympathetically and their function
- Sphincter pupillae: Constricts pupil and is responsible for pupillary light reflex
- Ciliary Muscles: Contracts (affect lens shape) and focusses lens on short-range objects
What 3 structures are affected by oculomotor nerve palsy and describe what occurs
- Eyelid (Ptosis): dysfunction of levator palpebrae
- Pupil (Mydriasis): Parasympathetic loss of ciliary function
- Eyeball Position: Down and out, and unopposed action of lateral rectus and superior oblique
Is the trochlear nerve motor or sensory
Motor
Where does the trochlear nerve emerge from
At level of midbrain (decussates here) and emerges from dorsal surface
Where does the trochlear nerve exit
Superior orbital fissure
What does the trochlear nerve innervate and its functions
Contralateral superior oblique muscle: Intorsion, depression and abduction of the eye
What 3 characteristics define trochlear nerve palsy
1 Eye position moves up and out
2. Head position compensates causing to tilt head away from affected side
3. Vertical diplopia
Can affect reading, doing stairs, balance = risk of falls
Is the abducens nerve motor or sensory
Motor
Where does the abducens nerve originate, exit and innervate
Originates: Pons (near pontomedullary junction
Exits: Superior orbital fissure
Innervates: Lateral rectus muscle
How can abducens nerve palsy occur
When any structure causes pressure on brainstem (space occupying lesion)
What are 2 effects caused by abducens nerve palsy
- Eye resting in adduction
- Diplopia (double vision)
What is the largest cranial nerve
Trigeminal nerve
Is the trigeminal nerve motor or sensory
Both
What 3 functions is the trigeminal nerve responsible for (are they motor or sensory)
- Biting and chewing (motor)
- Dampen tympanic membrane (motor)
- Sensation in face (Sensory)
Where does the trigeminal nerve exit
Ventral surface of the pons
What does the trigeminal nerve control through motor movement
- Muscles associated with mastication = chewing (temporalis, masseter, lateral and medial pterygoid, mylohyoid, and belly of digastric -> Dont memorize muscles)
- Dampens tympanic membrane via tensor tympani for protective function
What are the 3 sensory branches of the trigeminal nerve
- Ophthalmic
- Maxillary
- Mandibular
What are 4 sensory functions the trigeminal nerve is responsible for
- Discriminative touch
- Proprioception
- nociception
- Temperature
** all of the face
What is a disorder associated with damage to trigeminal nerve and what does it cause
Facial Hemianesthesia: Loss of sensation of face on one side (contralateral)
Where does the facial nerve emerge from
The pons (pontomedullary junction)
What 2 portions make up the facial nerve
Intracranial portion and extracranial portion
Is the facial nerve responsible for motor or sensory
Motor, sensory, special sensory, and parasympathetic
Where does the facial nerve exit
- Internal acoustic meatus
- Stylomastoid foramen
Stapedius of facial nerve function
dampens sound so if damaged = hypersensitivity to sound
Is the stapedius motor or sensory and is it intracranial or extracranial
Intracranial and motor
Hyperacusis
Hypersensitivity to sound
Chorda Tympani of facial nerve is
Responsible for taste
What are the 2 major landmarks of the facial nerve
What are the 4 muscles that make up the extracranial portion of the facial nerve
- Posterior auricular nerve
- Digastric muscle
- Stylohyoid muscle
- Motor root of facial nerve
The function of the posterior belly of digastric and stylohyoid and is it motor or sensory
Motor -> swallowing
Facial nerve is responsible for (4)
1) Facial expressions through facial muscles
2) ear dampening
3) swallowing
4) anterior 2/3 taste
What are the 5 branches of the facial muscles and function (don’t need to know -Mackeely confirm)
- Temporal: Rase eye brows
- Zygomatic: Close eye
- Buccal: smiling and whistling
- Mandibular: Pout
- Cervical: frowning
The upper facial muscles are controlled
Bilaterally
The lower facial muscles are controllled
Contralaterally
Damage to UMN of facial nerve results in
Contralateral weakness to lower facial muscles
Damage to LMN of facial nerve results in
Bell’s Palsy
What structure of the facial nerve is responsible for sensory and special sensory
Anterior 2/3 of tongue
What structure of the facial nerve is responsible for parasympathetic
Glands of the neck
Is the vestibulocochlear nerve sensory or motor
Sensory
What is the vestibular portion of the vestibulocochlear nerve responsible for
- Balance
- Vestibulo-Ocular Reflex
What is the cochlear portion of the vestibulocochlear nerve responsible for
Hearing
Where does the vestibular portion of the vestibulocochlear nerve arise from
Vestibular nuclei (pons/medulla)
Where does the cochlear portion of the vestibulocochlear nerve arise from
Ventral and dorsal cochlear nuclei (inferior cerebellar nuclei)
What can damage the vestibulocochlear nerve
Whiplash from MVA
The glossopharyngeal nerve originates in the
Medulla
The glossopharyngeal nerve exits the
cranium via jugular foramen
The glossopharyngeal nerve is responsible for sensory or motor
Sensory, Motor, special sensory, and parasympathetic
What is the motor muscle that the glossopharyngeal nerve controls
Stylopharyngeus muscle
What occurs if the glossopharyngeal nerve is damaged (in terms of the stylopharyngeus muscle)
Dysphagia (swallowing difficulties)
What sensory structures does the glossopharyngeal nerve control
- Middle ear and eustachian tube
- Tonsil and pharynx
- Carotid body and sinus
What special sensory structures does the glossopharyngeal nerve control
Taste for posterior 1/3 of tongue
What special sensory structures does the glossopharyngeal nerve control
Parotid Salivary Gland
What nerve is responsible for the gag reflex
Glossopharyngeal nerve (sensory info)
What nerve control the gag reflex
Cranial Nerve 9 (glossopharyngeal) does sensory info and Cranial Nerve 10 does motor (Vagus)
The vagus nerve originates in the
Medulla
The longest cranial nerve is the
Vagus nerve
The vagus nerve exits the
Jugular foramen
Is the vagus nerve responsible for motor or sensory
Motor, Sensory, Special sensory, parasympathetic
What are the motor structures innervated by vagus nerve
- Pharynx
- Soft palate
- Larynx
What are the sensory structures innervated by vagus nerve
- External acoustic meatus
- Larynx and laryngopharynx
- Heart
- Abdominal Viscera
What are the special sensory structures innervated by vagus nerve
Taste sensation to epiglottis and root of tongue
What are the parasympathetic structures innervated by vagus nerve
- Trachea, Bronchi
- GI Tract
- Regulates heart rhythm
What are 6 affects of damage to vagus nerve
- Gag reflex
- Dysphonia and aphonia
- Dysphagia
- Deviation of uvula (damage to vagus nerve on right = deviate to left)
- Loss of vagal tone of heart
- Unusal heart rate
What occurs if there is overstimulation of the vagus nerve
Vasovagal Syncope (fainting because blood vessels dilate too much or heart beat slows so not enough blood is going to brain)
Is the accessory nerve sensory or motor
Motor
The accessory nerve innervates
The trapezius and the sternocleidomastoid muscles
What are the 2 components of the accessory nerve
- Spinal Component
- Cranial Component
Where does the spinal component of the accessory nerve arise from and its pathway
Arise: C1-C6 nerve roots
Pathway: Foramen magnum -> Jugular Foramen -> Muscles
Where does the cranial component of the accessory nerve arise from and its pathway
Arise: Medulla
Pathway: Exits via jugular foramen -> contacts spinal component -> Combines with vagus nerve
SCM (Sternocleidomastoid) Function
Lateral flexion, rotation unilaterally, and extension of neck bilaterally
What is torticollis
Damage to accessory nerve resulting in loss of function of SCM
Trapezius function
Upper - elevate scapula and rotate
Middle: Retract scapula
Lower: Pull scapula inferiorly
Iatrogenic Nerve palsy
Accessory nerve damage resulting in loss of function of trapezius and atrophy
Is the hypoglossal nerve motor or sensory
Motor
Where does the hypoglossal nerve originate from
Medulla
Where does the hypoglossal nerve innervate
Extrinsic and intrinsic muscles of the tongue
Where does the hypoglossal nerve pass
Inferiorly to angle of mandible
Hypoglossal Nerve Palsy
Loss of movement in tongue