Module 5 - Thalamus, Brainstem, and Cranial Nerves

What is the thalamus?

The “mail person”

It receives information, processes information, and sends information to specific areas in the cortex

What are the groups of thalamic nuclei?

Relay nuclei, association nuclei, and nonspecific nuclei

What is relay nuclei

It conveys information by receiving input and sending it to other areas of the cerebral cortex

What is association nuclei?

It processes emotional and memory information, and it integrates and interprets different types of sensory information

What is nonspecific nuclei?

It regulates consciousness, arousal, and attention

What are the connections of the thalamus with other parts of the brain?

The thalamus is interconnected with the different cortexs’, basal ganglia, reticular formation, brainstem, spinal cord, and cerebellum

What does the brainstem control?

Autonomic and vegetative functions (HR, BP, breathing, reflexes)

What is the reticular formation?

A complex neural network within the brainstem; it helps regulate alertness and consciousness along with the thalamus and cerebral cortex. It also filters incoming sensory info and modulates nociceptive information (tune in or out pain)

What is cranial nerve 1 and what is its function?

Olfactory nerve; Function: afferents for olfaction (smell)

What is cranial nerve 2 and what is its function?

Optic nerve; Function: afferents for sight and vision, pupillary and accommodation reflexes, light and dark awareness, and orientation of head and eye movements 

What is cranial nerve 3, 4, and 6 and what is its function?

3: oculomotor

4: trochlear

6:abducens

Functions: all three are in charge of extra ocular eye movement (outside the eyeball); only CN 3 is an efferent branch of pupillary and accommodation reflexes

Think of pupillary light as your eye adjusting to changes in lighting; think about accommodation reflexes as your eyes adjusting to closeness of an object

What is cranial nerve 5 and what is its function?

Trigeminal nerve; Function: somatosensory, motor, and reflex

Somatosensory: face (tongue, jaw, teeth) and anterior ear

Motor: mastication (chewing)

Reflex: sensory afferents for corneal reflex (blinking)

What is cranial nerve 7 and what is its function?

Facial nerve; Function: somatosensory, motor, special sensory, and autonomic

Somatosensory: ear and external ear canal

Motor: facial expression and stapedius muscle (in inner ear for loud sounds), and its an efferent for corneal reflex

Special sensory: taste from anterior tongue

Autonomic: lacrimal (tears), nasal, salivary glands

Bells Palsy: damage to CN 7 

What is cranial nerve 8 and what is its function?

Vestibulocochlear; Function: vestibular and hearing, and sensory afferents for vestibulo-ocular reflex

What is cranial nerve 9 and what is its function?

Glossopharyngeal nerve; Function: somatosensory, motor, and special sensory

Somatosensory: pharynx, posterior tongue, soft palate, and it’s a sensory afferent for gag and swallow reflex

Motor: one muscle in the pharynx

Special sensory: taste (posterior tongue)

What is cranial nerve 10 and what is its function?

Vagus nerve; Function: somatosensory, motor, and autonomic

Somatosensory: palate and epiglottis (flap of cartilage at the top of the windpipe; crucial for airway and swallowing)

Motor: pharynx and larynx, motor for gag and swallow reflex

Autonomic: motor and sensory from thoracic and abdominal organs

What is cranial nerve 11 and what is its function?

Accessory nerve; Function: innervates trapezius and sternocleidomastoid (STM) muscles

What is cranial nerve 12 and what is its function?

Hypoglossal nerve; Function: tongue movement

What do lesions in CN 1 cause?

It causes amonia: loss of smell

What do lesions in CN 2 cause?

Lesion causes blindness

What do lesions in CN 3, 4, and 6 cause?

Lesions cause motor paresis/paralysis and diplopia (double vision); CN 3 will also have ptosis (droopy eyelids) and loss of reflexes

What do lesions in CN 5 cause?

Lesions cause facial paralysis

What do lesions in CN 7 cause?

Lesions cause decreased taste, loss of ipsilateral corneal reflex, and ipsilateral facial paralysis

What do lesions in CN 8 cause?

Lesions cause deafness, tinnitus (sounds in the ear that aren’t happening externally), decreased balance, vertigo, and nystagmus

What do lesions in CN 9 cause?

Lesions cause lack of gag and swallowing reflex, and dysphagia of taste

What do lesions in CN 10 cause?

Lesions cause dysphonia (hoarseness), dysphagia, dysarthria, asymmetric elevation of soft palate, and loss of gag and swallow reflex

What do lesions in CN 11 cause?

Lesions cause ipsilateral flaccid paralysis

What do lesions in CN 12 cause?

Lesions cause deviation of tongue, weakness and atrophy, dysarthria, and dysphagia

What is dysphagia?

Impaired swallowing

What is dysarthria?

Impaired speaking - can’t make sounds come out clearly

Ex: mumbling, slurred words

Think of chubby bunny challenge

What is diplopia?

Double vision

What is dysmetria?

Impaired ability to control distance of movements

What is brainstem ischemia?

Damage to cranial nerves that causes dysarthria, dysphagia, diplopia, dysmetria, nystagmus, vertigo, ipsilateral pain and temperature loss 

What are the categories of eye movements?

Gaze stabilization and direction of gaze

What types of eye movements are in the direction of gaze?

Saccade: fast eye movements to switch gaze from one object to a new target

Smooth pursuits: eye movements that follow a moving object

Vergence movements: movement of the eyes toward or away from midline, and aligning eyes on a new target

What are the types of gaze stabilization?

Vestibulo-ocular reflexes (VORs): keeping gaze on target during fast head movements; it requires vestibular input

Optokinetic nystagmus: keeps gaze on fixed target during slow, sustained head movements