Bio 30 Section 14

Biology 30 Section 14: Sensory information, eyes, and ears

Sensory Adaptation

Sensory Adaptation

Neurons slow/stop firing in presence of continued stimuli.

Getting used to the stimulus (smells, clothes, rings.)

Taste receptor

Chemical stimulus

Smell receptor

Chemical stimulus

Pressure receptor

Mechanical stimulus

Propioreceptor

Mechanical stimulus

Balance receptor

Mechanical stimulus

Audio receptor

Sound stimulus

Visual receptor

Light stimulus

Thermoreceptor

Temp change stimulus

Taste

Detected based on shape and charge

Each receptor is specialized for one thing but all buds work together.

Salty Taste

Na+ ions

Sweet Taste

Sugars (glucose)

Sour Taste

H+ ions

Bitter taste

Alkaloids

Umami (Savory) Taste

Glutamic acid (MSG)

Taste + Smell + Irritation =

Flavour

Smell and Taste

Work together

Things like colds and COVID affect both.

Layers of The Eye (and functions)

Sclera

• Protection

Choroid

• focus light

Retina

• detect light

Cornea

In Sclera

Shiny layer that only covers pupils and iris.

Protects iris and pupil

Begins to focus light entering eye onto lens

Gets oxygen from tears and nutrients from aqueous humor.

Pupil

In choroid

Light enters the eye

Iris

In choroid

Uses muscle to control how much light enters eye

Eye colour.

Lens

Transparent, double convex lens

Small ciliary muscles change the shape to focus the image onto retina

Light passes through vitreous humor

Retina

Blood vessels make the red-eye effect.

Light converges

The wall at back is packed with photo-receptors

Receives flipped image of what we see

Converts light into an impulse for the brain

Cross over and convergence

Four Layers

Four layers of Retina

Pigmented Epithelium (Prevent Scattering)

Light Sensitive Cells (Rods and Cones)

Bipolar Cells (Relay to optic nerve)

Optic Nerve (Transmit to brain)

Optic Nerve —> Thalmus —> Primary Visual Cortex —> Visual Association Cortex

Photo-receptors

Rods and Cones

Rods

Detect light

Work well in the dark

At the edge of retina (peripheral vision)

18x as many as cones

Cones

Detect colour

Doesn’t work well in the dark

Comes in three kinds (red, green, blue)

Concentrated at fovea centralis

Optic Nerve

The path information takes from eyes to get to the brain

Information from each side of the eye goes to the opposite side of the brain.

Brain reads information and makes the image you understand right-side-up.

Chemistry of Vision

Rods contain rhodopsin (retinal and opsin)

Photon causes isomeric change in retinal —> opsin shape changes

Causes

1. Activate phosphodiesterase

2. Destroy Cyclic GMP (Stop Na+ in)

3. Build electrochemical gradient

4. Action Potential

Rhodopsin maintained by vitamin A levels.

Afterimages

When your RBG cones fatigue over time

White contains all the colors so when you see “white” it fills in all the colors that aren’t fatigued

Accommodations

When the ciliary muscles adjust shape of the lens for objects at different distances.

Close: Muscles contracts and lens thickens

Far: Muscles relax and lens is thin

6 meters nothing changes

Lens flexibility gets worse with age making these worse.

Glaucoma

Drainage canal becomes blocked.

Pressure builds up causing optic nerve damage.

“Halo” vision

Can be helped with drugs or surgery

Cataracts

When lens becomes cloudy

More likely develops with age and diabetes

Lens scatters light not focusing it.

Can be helped by replacing the lens or giving strong glasses.

Astigmatism

Blurry vision caused by irregularly shaped cornea or lens (more horizontal curve than vertical)

Can be helped with glasses, contacts, or LASIK surgery.

Nearsightedness

Myopia

Image focused in front of retina

Eye is too long with more of a oval shape.

Corrected with concave lens

Farsightedness

Hyperopia

Image focus behind retina

Eye is too short.

Corrected with biconvex lens

Outer Ear

Pinna

Auditory Canal

Tympanic membrane

Pinna

Ear flap

Capture the sound

Auditory Canal

Carries sound and protects

Is the sweat glands and wax

Tympanic Membrane

Eardrum

Transmits sound

Middle Ear

Tympanic membrane to oval window

Ossicles: Malleus, incus, stapes

Eustachian tubes

Ossicles

Malleus, Incus, and Stapes

Is where sound vibration is concentrated

Stapes strikes oval window and amplifies sound

Eustachian Tubes

Links middle ear to mouth/nose

Equalizes air pressure

Prevents eardrum rupture

Helps prevent pressure changes; infections which cause discomfort, deafness, and poor balance.

Inner Ear

Vestibule

Semicircular Canal

Cochlea

Vestibule

Has utricle/saccule

Allows awareness for head position

Semicircular Canal

Fluids inside detects body movement

Cochlea

Contains hair cells

Converts sounds to nerve impulses.

Hearing

Sound waves on eardrums —> Ossicles amplify —> Oval window moves in —> waves in cochlea —> round window moves out —> Basilar membrane vibrates —> Organ of corti: hair cells respond at target frequency —> hair cell movement stimulates nerve —> info to temporal lobe

High Pitch sound

At the base of hairs in the cochlea

Low Pitch sound

At the top of hairs in cochlea

Head Injury Hearing

causes the hairs in ear to move producing a ringing sound.

Static Balance

Standing still

Saccule, Utricle, and otoliths

Otoliths respond to gravity and head position

Dynamic Balance

Moving around

Semicircular Canals

Semicircular canals detect movement in ampulla (hair cells)

Motion Sickness

Fluid movement in canals

Conductive Hearing Loss

Sound entry issue

(wax, eardrum damage, infection etc)

Sensorineural Hearing Loss

Nerve or cochlear hair cell damage

(Aging, loud noise, trauma, genetics)

Hearing Aids

Amplify Sound

Patient has to have been able to hear before

Cochlear Implants

Converts sound to electrical impulses in ________

Microphone —> speech processer —> transmitter —> receiver —> electrodes —> nerve —> brain