neuro - the senses

The Visual System

takes light from the environment, focuses it on the retina

in the visual system what does the light convert it into

into nerve signals, and sends it through the optic pathway to the occipital lobe

what does the occipital lobe do

the brain interprets what we see.

what is the retina

the thin layer of nervous tissue that lines the back inside wall of the eye.

what happens to the light in the retina

its changed into electrical signals that can travel to the brain.

retina function

Receive light Convert light into nerve signals Begin processing visual information

Send signals through the optic nerve, CN II, to the brain

retina pathway

Light enters the eye and reaches the retina. Then signals move through retinal cells:

Photoreceptors → bipolar cells → ganglion cells → optic nerve

The optic nerve, cranial nerve II, carries visual information from where

from the retina to the brain.

what is the optic nerve essential for

vision, visual fields, color vision, visual acuity, and the pupillary light reflex.

At the optic chiasm

Fibers from the nasal retina cross , Fibers from the temporal retina stay on the same side

The Visual Pathway

Light travels through retina, stimulates the rods and cones, bipolar cells, retinal ganglion (axons of the retinal ganglion radiate toward the optic disc where they become myelinated and emerge to form the optic nerve), Optic nerve passes posteromedial and unites to form the optic chiasm optic tracts pass posterolaterally, terminate on the lateral geniculate nuclei, exit as the optic radiation, fibers from optic radiation travel posteriorly to the occipital lobe

A visual field is the

full area you can see when your eyes are looking straight ahead

Central vision

what you see directly in front of you

Peripheral vision

what you see off to the sides, above, and below

Each eye sees both the

right and left visual fields

Homonymous hemianopsia is

loss of the same visual field on the same side in both eyes.

A lesion behind the optic chiasm causes what

homonymous hemianopsia.

A lesion behind the optic chiasm causes homonymous hemianopsia includes damage to the

Optic tract

Lateral geniculate nucleus, LGN

Optic radiations

Occipital lobe / visual cortex

Homonymous Hemianopsia common causes

Stroke

Traumatic brain injury

Brain tumor

Multiple sclerosis lesion

Optic radiation damage

Occipital lobe injury

The Anatomy of the Ear consists of what

External, Middle, Inner

how many parts are there to the ear

three

Auricle is in which section of the ear

external

what does the auricle do

gathers sound

External auditory Meatus is apart of what section of the ear

external

External auditory Meatus does what

amplifies and directs sound toward the tympanic membrane

Tympanic Membrane (eardrum) is apart of which section of the ear

external ear

Tympanic Membrane (eardrum) is set into motion by what

sound waves

what is the separation between the external and middle ear

Tympanic Membrane (ear drum)

Middle ear is what type of cavity

air filled cavity in the temporal bone

where is the middle bone found

temporal bone

the middle ear contains how many auditory ossicles

three

what are the three auditory ossicles

The malleus, the incus and the stapes

the middle ear contains two muscles to help control what

bone movement

What does The tensor tympani attached to the malleous Pull

the bone

How does The tensor tympani pull the bone

internally

what happens when the tensor tympani is pulled

dampening the sound

what is the The stapedius mm is attached to

stapes

how does the stapedius pull the stapes

away from the tympanic membrane

what happens when the stapes is pulled away from the membrane

thus decreasing sound intensity.

where is the inner ear located

in the temporal bone

the inner ear is made up of how many parts

two

what does the bony labyrinth contain

Perilymph

The membranous labyrinth is contained WITHIN what

the bony labyrinth

the membranous contains what

Endolymph

The spiral organ of corti is what

sensory receptor of the inner ear.

First Step of Hearing

Sound waves enter the outer ear

what does the pinna/auricle collect

sound waves

Sound travels through what

external auditory canal.

Second step of hearing

Sound waves hit the tympanic membrane

The tympanic membrane, or eardrum, vibrates in response to what

sound

3rd step of hearing

The ossicles vibrate

Vibrations move through how many bones of the middle ear

three

what are the three bones vibrations move through

Malleus Incus Stapes

4th step of hearing

The stapes pushes on the oval window

The stapes transfers vibration into what

the inner ear by moving the oval window

5th step of hearing

Fluid waves move through the cochlea

Movement at the oval window creates waves in

the fluid-filled cochlea

6th step of hearing

The basilar membrane moves

Fluid waves cause what to vibrate

basilar membrane

7th step of hearing

Hair cells in the organ of Corti bend

where does The organ of Corti sit

on the basilar membrane

Movement bends the stereocilia of the hair cells against

the tectorial membrane

8th step of hearing

Mechanical energy becomes electrical energy

Bending of stereocilia opens what

ion channels

Hair cellsdepolarize and release what

neurotransmitters

9th step of hearing

The cochlear nerve is stimulated

Signals travel through the

cochlear branch of cranial nerve VIII, the vestibulocochlear nerve.

10th step of hearing

Signals travel through the brainstem

Auditory information passes through what

Cochlear nuclei Superior olivary complex Inferior colliculus

11th step of hearing

The signal reaches the medial geniculate nucleus of the thalamus

12th step of hearing

Sound is processed in the auditory cortex

The signal reaches the primary auditory cortex where

temporal lobe

The brain interprets what

pitch, volume, location, and meaning of the sound

how many steps must you complete to hear

12

Conduction deafness

Interference with sound waves through the external and middle ear. Sound can still be conducted by the bones of the cranium

Nerve deafness

damage to the organ of corti or the cochlear nerve. This will result in ipsilateral deafness proportional to the amount of damage.

Auditory modulation:

information received will send back information to allow selective hearing.