Neuro Lecture 9 (pt. 1): Brainstem, Cranial Nerves, CN V & VII

What 3 structures does the brainstem consist of?

- Midbrain

- Pons

- Medulla

What are the main components of the brainstem (5)?

- Corridor between brain and body

- Long tracts

- Reticular formation

- Cerebellar circuits

- CN nuclei and related structures

What are the dorsal long tracts running in the brainstem?

- DCML

- Anterolateral spinothalamic tract

What are the ventral long tracts running in the brainstem?

Lateral corticospinal tract

What is the only cranial nerve to exit on the dorsal side?

CN IV (trochlear)

What is the main blood supply to the midbrain?

Posterior cerebral artery (PCA)

What is the main blood supply to the pons?

- Basilar artery

- Anterior inferior cerebellar artery (AICA)

What is the main blood supply to the medulla?

Vertebral artery

What is a neuron?

A single sensory or motor cell

What is a nerve?

A bundle of neurons (neuronal fibers)

How are cranial nerves defined?

A bundle of neurons that consist of a combination of motor/sensory neurons

How many types of sensory neurons are there?

3

How many types of motor neurons are there?

3

What is a ganglion?

Nerve cell bodies in PNS, with a few exceptions (ex. basal root ganglion in CNS)

What is a nuclei?

Collection of nerve cell bodies in the CNS

What are the 3 types of sensory neurons?

- General

- Special

- Visceral

What information are general sensory neurons responsible for?

- Touch

- Pain

- Temperature

Which cranial nerves carry general sensory information (4)?

- CNV

- CN VII

- CN IX

- CN X

What information are special sensory neurons responsible for?

- Smell

- Vision

- Hearing

- Equilibrium

- Taste

Which cranial nerves carry special sensory information (5)?

- CN I

- CN II

- CN VIII

- CN VII

- CN IX

What information are visceral sensory neurons responsible for?

- Viscera

- GI tract

- Trachea

- Bronchi

- Lungs

- Heart

Which cranial nerves carry visceral sensory information (2)?

- CN IX

- CN X

What are the 3 types of motor neurons?

- Somatic

- Branchial

- Visceral

What do somatic motor neurons innervate?

Skeletal muscles

Which cranial nerves carry somatic motor information (4)?

- CN III

- CN IV

- CN VI

- CN XII

What do branchial motor neurons innervate?

- Muscles derived from branchial arches

- Muscles of mastication, facial expression, palate, pharynx, larynx, traps, SCM

Which cranial nerves carry branchial motor information (6)?

- CN V

- CN VII

- CN IX

- CN X

- CN XI

What do visceral motor neurons innervate?

Involuntary (smooth) muscle or glands and parasympathetic pathways

CN I is also known as...

Olfactory nerve

What is the function of CN I?

Olfaction

CN II is also known as...

Optic nerve

What is the function of CN II?

Vision

CN III is also known as...

Oculomotor nerve

What is the function of CN III?

- Eye movements

- Pupil constriction

CN IV is also known as...

Trochlear nerve

What is the function of CN IV?

Eye movements

CN V is also known as...

Trigeminal nerve

What is the function of CN V?

- Facial sensation

- Muscles of mastication

CN VI is also known as...

Abducens nerve

What is the function of CN VI?

Eye movements

CN VII is also known as...

Facial nerve

What is the function of CN VII?

- Muscles of facial expression

- Taste

- Lacrimation

- Salivation

CN VIII is also known as...

Vestibulocochlear nerve

What is the function of CN VIII?

- Hearing

- Equilibrium sense

CN IX is also known as...

Glossopharyngeal nerve

What is the function of CN IX?

- Pharyngeal muscles

- Carotid body reflexes

- Salivation

- Taste

CN X is also known as...

Vagus nerve

What is the function of CN X?

- Parasympathetics to most organs

- Laryngeal muscles (voice)

CN XI is also known as...

Spinal accessory nerve

What is the function of CN XI?

- Head turning

- Trapezius and SCM

CN XII is also known as...

Hypoglossal nerve

What is the function of CN XII?

Tongue movement

What detects odors (CN I)?

- Chemoreceptors

- Located in nasal epithelium

Where do short olfactory nerves exit (CN I)?

- Bipolar

- Cribriform plate

How many short olfactory nerves are there (CN I)?

- 9-15 nerves

- Unmyelinated

What is the first step in the pathway of the olfactory nerve (CN I)?

Synapse in olfactory bulb

What is the second step in the pathway of the olfactory nerve (CN I)?

- Travel in olfactory tract

- Reach olfactory processing centers

What is the third step in the pathway of the olfactory nerve (CN I)?

Anterior olfactory nuclei

What is orthonasal smell responsible for (CN I)?

Normal olfaction

What is retronasal smell responsible for (CN I)?

Odors from food and drink

What are lateral olfactory striae responsible for (CN I)?

- Perceive olfactory stimuli

- Perceptions of smell and memory

What are medial olfactory striae responsible for (CN I)?

- Connect with limbic system

- Emotional responses to smell

What are other functions of olfaction (CN I)?

- Safety

- Pleasure finding mates

- QOL

What is anosmia (CN I)?

Inability to smell

What can cause anosmia (CN I)? (8)

- Nasal congestion

- Polyps

- Viral infections

- Head trauma

- Aging

- Parkinson's and Alzheimer's

- Cocaine abuse

- Medications

What is hyperosmia (CN I)?

Enhanced olfactory sensitivity (ex. pregnancy)

What are 3 major divisions of the trigeminal nerve (CN V)?

- V1 Ophthalmic division

- V2 Maxillary division

- V3 Mandibular division

Is the V1 ophthalmic division sensory or motor (CN V)?

Sensory

Is the V2 maxillary division sensory or motor (CN V)?

Sensory

Is the V3 mandibular division sensory or motor (CN V)?

- Sensory to face

- Anterior 2/3 of tongue (general sensory)

- Small motor rootlet for muscles of mastication/tensor tympani muscle

What does a lesion to the trigeminal nerve result in (CN V)?

- Ipsilateral sensory loss

- Synapses in trigeminal nucleus THEN crosses over

What is trigeminal neuralgia also known as (CN V)?

Tic douloureux

What causes trigeminal neuralgia (CN V)?

- Usually unknown

- Prevalent with MS

What triggers trigeminal neuralgia (CN V)?

- Irritation of trigger zones

- Chewing, shaving, touch, etc.

What are signs of trigeminal neuralgia (CN V)?

- Brief recurring episodes of severe pain

- Lasting seconds to minutes in V2/V3

How does trigeminal neuralgia affect facial sensation (CN V)?

- Normal

- Ipsilateral, usually unilateral involvement

What are 2 components of the facial nerve (CN VII)?

- Facial nerve proper

- Nervus intermedius

What type of nerve is facial nerve proper (CN VII)?

Branchial motor

What muscles is facial nerve proper responsible for (CN VII)?

- Facial expression

- Platysma and digastric

- Stapedius (inner ear)

What type of nerve is nervus intermedius (CN VII)?

- Parasympathetic

- Special sensory

- General somatosensory

What is the parasympathetic aspect of nervus intermedius responsible for (CN VII)?

- Lacrimal gland (tears)

- Salivary gland

What is the special sensory aspect of nervus intermedius responsible for (CN VII)?

Taste to anterior 2/3 of tongue

What is the general somatosensory aspect of nervus intermedius responsible for (CN VII)?

Sensation to external auditory meatus (ear canal)

What tests could an OT do for the facial nerve (CN VII)?

- Puff cheeks

- Smile

- Raise eyebrows

- Frown

What type of innervation does CN VII supply to the forehead?

Bilateral

What type of innervation does CN VII supply to below the eyes?

Contralateral

What does an UMN lesion to CN VII result in?

- Contralateral

- Weakness/paralysis below eyes

- Muscles of forehead unaffected (ipsilateral)

What does a LMN lesion to CN VII result in?

- Ipsilateral

- Facial paralysis (whole side)

What causes Bell's Palsy (CN VII)?

Viral/inflammatory (unknown)

What are signs of symptoms of Bell's Palsy (CN VII)?

- Unilateral facial weakness of LMN type

- Loss of taste on ipsilateral tongue

What tests could an OT do for Bell's Palsy (CN VII)?

- Smile

- Puff cheeks out

- Clench eyes tight

- Wrinkle brow

- Look for asymmetry

What signs would help you rule out Bell's Palsy (CN VII)?

- Hand weakness

- Sensory loss

- Dysarthria

- Aphasia

- UMN lesion is NOT Bell's Palsy