Special Somatic Afferent - Auditory, Vestibular, Vision

1. optic nerve
2. optic chiasm
3. optic tract

bilateral

Ech eye influences ______ occipital lobes

Yes

Do axons in each optic nerve cross to enter the opposite optic tract

caudally toward the thalamus

Where do the optic tracts course

via ther laterlal geniculate nucleus (LGN)

How does the optic tract reach the thalamus

concious and unconcious pathways

Impulses from the optic tract are used for ________ and ____________ pathways

rentinogeniculostraite pathway

Another name for the concious perception pathway

concious perception of vision

Function of the rentinogeniculostraite pathway

occipital cortex

Where does the rentinogeniculostraite (concious) pathway project after the LGN

Menace response pathway

The rentinogeniculostraite pathway is also ulitized for the

through the thalamus for perceptions fo light at the occipital lobe

Where is most of the stimuli from the optic tract relayed

response, reflex

Menace respons is a _________ not a __________

normal vision via CNII and facial muscle function via CN VII

What is required for a the menace response

failure during the pathway to the cerebellum

What may also cause the failure of the menace response

1. stimulus is passed from the retina to the occipital lobe via the rentinogeniculostraite pathway
2. axons travel to the frontal lobe with tell us to blink
3. axons are sent from the frontal lobe to the cerebellum to coordinate the eyelid movement

Pathway of blinking to a menace response

1. retinopretectal pathway
2. retinotectal pathway
3. retinohypothalamic pathway

3 unconcious pathways

1. pupillary ligh reflex (PLR)
2. accomodation

2 functions of the retinopretectal pathway

near and far sight

What is visual accomodation

via pretectalnucleii

How does the retinopretectal pathway generate a unconcious PLR and accomidation

1. tectobublar pathway
2. tectospinal pathway

2 pathways associated with the retinotectal pathway

Rostal colliculus -> extrinsic eye mm.

Route of the tectobulbar pathway

Rostal colliculus -> neck mm. (for head movement)

Route of the tectospinal pathway

allows us to move head and eye to tract movement

What is the function of the retinotetcal pathway

circadian rhythams

Function of retinohypothalamic pathway

roof of the midbrain, rostal bodies of the copora quadrigemina

Where is the tectum located

Roof

What does tectum mean?

No

Is visual perception required for the unconcious reflexes of the optic tacts

LGN, brainstem

Whe unconcious optic tracts will bypass the ________ and synapse at the ___________

1. pretectalnuclei -> junction of thalamus and midbrain
2. rostal colliculi

2 locations of the brainstem where the unconcious optic tracts synapse

PLR and visual acommodation

The synpase in the pretectanuclei is the pathway for

somatic motor responses involving eye tracking and head movement

The synpase in the rostral colliculi is the pathway for

Afferent: CN II
Interneuron
Efferent: CN III

Afferent and Efferent nerves involved in the direct and indirect PLR

1. afferent cn II travels to the LGN
2. axons get passed to the pretectal nuclei
3. pretectal nuclei send exons to the Edinger-westphal nuclei of CN III
4. CNIII fibers travel from the EWN to the ciliary ganglia at the iris to cause pupillary constriction

Pathway of the direct pupillary light reflex

Menace
use of a maze
strabismus

Another way to determine damage to CN II and CNIII

will cause lateral strabismus since the patients resting tone of CN VI on the lateral rectus will still be intract

If a patient has damage to CN III, how will this effect strabismus

retinotectal reflexes

Reflex used to visually track an object

CN III
CN IV
CN VI

Movement fo the eyes involved what 3 nerves

Trochlear -> dorsal oblique

CN IV and what it controls

Abducens-> lateral rectus, retractor bulbi mm

CN VI and what is controls

Oculomotor -> ventral oblique, medial/dorsal/ventral rectus

CN III and what it controls

CN XI and cervical spinal nerves

What is involved in movement of the head

Light enters through CN II -> bypasses LGN -> enters suprachiasmatic nucleus (SCN) -> triggers output rhythms like physiology and behavior

Route of Retinohypothalamic pathway

1. stapes moves against the vestibular window -> movement of fluid in the cochlea
2. movement of the fluid causes movement of the hair cells
3. hair cells induce stimulus of cochlear portion of CN VIII

Mechanism of triggering the cochlear n. of CN VIII

1. cochlear hair cells of CN VIII
2. cochlear nuclei
3. thalamus
4. internal capsule
5. audirtory cortex

Route of percieving sound

1. cochlear hair cells of CN VIII
2. cochlear nuclei
3. caudal colliculus
4. CN VIII reflexes

Route for reflexes associated with CN VIII

fast motor response elicited by sudden onset of tactile, vestibular, or acoustic stimulus that exceeds certain intesity threshold

What is the startle reflex

LMNs of almost all skeletal muscles of the limbs

What do descending pathways of this reflex stimulate

1. overriding of concious behavioral patterns
2. protection from physical impact
3. fight/flight response

3 things facilitated by the startle reflex

1. conductive
2. sensorineural

2 types of hearing loss

obstruction of the passage of sound waves from the external ear to the inner ear

Conductive hearing loss

pathology of the receptor organ or the neurons of CN VIII

Sensorineural hearing loss

organ that senses balance and acceleration

Function of the vestibular system

the maintenance of a stable oritentation relative to gravity and motion

What does the vestibular system aid in

within muscles, tendons, and joints

Where are proprioceptors for the vestibular system located

motor pathways to coordinate position of the head with the body

Motor pathway influences by the vestibular system

Most vestibular pathways are independent of the cortex

Does the vestibular pathat relie on the cortex

hair cells are displaced with the fluid movement in the semicircular ducts

How does the vestibular system sense changes in movement

both, both

__________ ears send vestibular information to ______ hemispheres

it will drive the reflexes to re-orient the body

What will occur if there is any asymmetry of the signal from the bilateral vestibular system

toward the lesion

Compensatory tilting and turning of the head and body will occur

with a fast phase away from the lesion and a slow pahse towrd the lesion

Compensatory eye movement will occur

the body and head will be moving towars the left side while the fast phase of the eye will be moving to the right

What will you see if there is a left side vestibular VIII lesion and a normal right side

senses that there is movement toward the intact side

During a unilateral vestibulospinal lesion what will the patient be

rapid involuntary eye movement that consists of a slow and fast phase

What is nystagmus

1. physiological nystagmus
2. pathological nystamus

2 types of nystagmus

normal movement of the eyes in repsonse to head movement

physiological nystagmus

abnormal eye movement that is visualized when the head is not moving

Pathologival nystagmus

Movement of the head stimualtes the vesibular nucleus which will cause the eye to move in the opposite direction of the head in order to maintain focus on a given focal point followed by a catch up with the head in a rapid manner

What is the vestibulo-ocular reflex

horizontal
vertical
rotary

Types of nystagmus that can be visualized with central venstibular system disorders

horizontal
rotary

Types of nystagmus that can be visualized with peripheral venstibular system disorders

vertical nystagmus
nystagmus may change direction when the body changed position (i.e. recumbency)

2 signs that are present in central vestibular system disorders and not peripheral

controls eye movement in response to vestibular input

Function of the vestibulo-ocular path

to skeletal muscle for control of posture and balance

Function of the vestibulospinal tract

Concious perception of balance

Thalamocortical pathway

emetic center -> motion sickness

What center does the vestibular nuclei also project to