Chp 12 - Brainstem

What are the 3 main parts of the brainstem?

Midbrain, pons, medulla

What does the brainstem do with information?

Carries all information between the brain and the remainder of the body

What is the brainstem the corridor to?

All the major sensory, motor, cerebellar, and cranial nerve pathway

The brainstem has nuclei that do what?

That control cranial nerves, consciousness, muscle tone, posture, and vital functions

What can small lesions in the brainstem cause?

Small lesions can result in substantial deficits 

What nerves do not emerge from the brainstem?

CN I Olfactory and CN II Optic nerves connect directly to the forebrain

Where do the olfactory nerves (CN1) enter?

They enter the olfactory bulbs and olfactory tracts that run along the ventral frontal lobe

How do the nerves exit the brainstem?

The foramina

Where do the optic nerves meet?

They meet at the optic chiasm forming the optic tracts

What are nuclei?

Clusters of nerve cells

How are the brainstem nuclei organized?

2 columns motor and sensory with 3 nuclei in each

Where are the motor columns located?

Closer to the center

What are the 3 nuclei in the motor column?

Somatic motor, branchial motor, and parasympathetic

What is the function of the Somatic motor nuclei?

Extraocular muscles and intrinsic tongue muscles

What is the function of the branchial motor nuclei?

Muscles in the face, jaw, and neck (including larynx)

What is the function of the parasympathetic nuclei?

Glands, smooth muscles, and cardiac muscles

Where are the sensory columns located?

Toward the outsides

What are the 3 nuclei in the sensory column?

Visceral sensory, general somatosensory, special somatic sensory

What is the function of the visceral sensory nuclei?

taste, cardiorespiratory, and digestive functions

What is the function of the general somatosensory nuclei?

Basic touch, pain, temperature, vibration sense for face, sinuses, and meninges

What is the function of the special somatic sensory nuclei

Olfaction, vision, hearing, balance (vestibular sense), and taste

What are the benefits of the brainstem nuclei having a columnar layout?

Allows the brainstem to efficiently process multiple types of information simultaneously and keeps related functions grouped together

What cranial nerves are purely motor?

CN III, IV, VI, XI, XII

What cranial nerves are both motor and sensory?

CN V, VII, IX, X

What cranial nerves are purely sensory?

CN I, II, VIII

What is the function of the olfactory nerve?

Olfaction, nose to brain

What is the olfactory nerve CN I process?

Stimuli are detected by chemoreceptors on sensory neurons → axons travel the olfactory nerves to synapse in the olfactory bulbs → from the bulbs info. travels via the olfactory tracts to neural processing areas

What can happen when things go wrong in the olfactory nerve CN I?

anosmia - olfactory loss

How can you acquire anosmia?

Congenital (from birth) or acquired through head trauma, viral infection (like COVID), and brain damage

What is the function of the optic nerve CN II?

Vision

What is the optic nerve CN II process?

The retinal ganglion cells (start of the optic nerve) carry info. to the optic chiasm which carries info. to the optic tract which carries info to the neural processing areas (LGN, occipital lobe, etc.)

What is the function of the oculomotor nerve CN III?

Pupil constriction and move eye upward

What is the function of the trochlear nerve CN IV?

Move eye inward and down

What is the function of the abducens nerve CN VI?

Move eye out - away from nose

What sort of path/highway are the nerves that have to do with eye movement?

One way highway - brain to muscles

What is oculomotor nerve palsy?

Oculomotor nerve CN III damage, abnormal eye movement towards nose, may lie in a “down and out” position at rest

What is abducens nerve palsy?

Abducens nerve CN VI damage, abnormal movement away from nose - can cause “lazy eye”

What is the sensory function of the Trigeminal nerve CN V?

Provides sensory innervation to the face (facial sensation not expression), touch, pain, temp, joint position, vibration of part of tongue + nasal sinuses + meninges

What is the motor function of the Trigeminal nerve CN V?

Controls jaw (mastication) muscles

What are the 3 branches of the Trigeminal nerve CN V?

Ophthalmic decision (V1), maxillary division (V2), and mandibular division (V3)

What is the sensory component of the Ophthalmic division (V1) of the Trigeminal nerve CN V?

sensation for forehead, upper eyelid, scalp, and nose tip → like feeling a headband across your forehead

What is the sensory component of the Maxillary division (V2) of the Trigeminal nerve CN V?

Sensation cheek, upper lip, upper teeth/gums, nose sides → feeling the wind on your cheek or pain from an upper tooth cavity

What is the sensory component of the Mandibular division (V3) of the Trigeminal nerve CN V?

Sensation lower jaw, lower lip, lower teeth/gums, chin, part of ear → feeling your chin rest in your hand

Upper motor neuron control reaching the trigeminal motor nucleus is predominantly ___ ?

bilateral

In relation to the Trigeminal nerve CN V, unilateral lesions cause what?

Nothing - usually no deficits

What is the main function of the facial nerve CN VII?

To control the muscles of facial expression

What does the branchial motor component of facial nerve CN VII do

Controls facial expression and middle ear muscles

What are the 3 sensory components of the facial nerve CN VII?

Parasympathetic, visceral sensory, and general somatosensory

What is the role of the parasympathetic sensory component of the facial nerve CN VII?

Tears and salivation

What is the role of the visceral sensory component of the facial nerve CN VII?

Taste (from chemoreceptors to the brain)

What is the role of the general somatosensory component of the facial nerve CN VII?

External ear (touch, pain, and temperature)

What is Bell's palsy?

The divisions of facial nerve CN VII are impaired within a few hours or days, and then gradually recover → cause is unknown

What are the 2 pathways in the vestibulocochlear nerve CN VIII?

Vestibulo (balance and rotation) and the cochlear (hearing)

What is the function of the vestibulo component of the nerve CN VIII?

Rotation and acceleration transduced in inner ear

What is the function of the cochlear component of the nerve CN VIII?

Sound vibration transduced from physical to electrical energy in inner ear

What are the 3 sensory components of the glossopharyngeal nerve CN IX?

General somatic, visceral somatic, general visceral

What is the role of the general somatic component of the glossopharyngeal nerve CN IX?

Sensation from middle ear, back ⅓ of tongue, and back of throat

What is the role of the visceral sensory component of the glossopharyngeal nerve CN IX?

Taste from back ⅓ of tongue (especially bitter)

What is the role of the general visceral sensory component of the glossopharyngeal nerve CN IX?

Conveys inputs from baroreceptors and chemoreceptors in the carotid body (including blood and oxygen levels)

What are the 2 motor components of the glossopharyngeal nerve CN IX?

Branchial motor and parasympathetic

What is the role of the branchial motor component of the glossopharyngeal nerve CN IX?

Swallowing assistance

What is the role of the parasympathetic component of the glossopharyngeal nerve CN IX?

Saliva production

What is glossopharyngeal neuralgia?

A rare disorder that causes severe intense pain  in the throat, tongue, tonsils, and ear

What is the role of the general somatic sensory component of the vagus nerve CN X?

Sensation for the small area of outer ear

What is the role of the general visceral sensory component of the vagus nerve CN X?

Sensation for abdominal pain and thoracic organs (blood chemistry, pressure, pain)

What is the role of the special visceral sensory component of the vagus nerve CN X?

Taste from epiglottis and pharynx

What is the role of the branchial motor component of the vagus nerve CN X?

Pharyngeal muscles (swallowing) and laryngeal muscles (voices)

What is the role of the parasympathetic component of the vagus nerve CN X?

“Rest and digest” - cardiovascular function, respirations, and digestion

What is the function of the spinal accessory nerve CN XI?

Turning head to opposite side (tilting head) and upper trapezius (movement and stabilization of scapula and upper limb movement- elevating the shoulder)

What is the function of the hypoglossal nerve CN XII?

Tongue intrinsic (in the tongue) and extrinsic (attached to the tongue) muscles → speech swallowing process, food manipulation in the mouth