Unit 10: Senses and Eye

Chapter 14: Sensory Perception

OpenStax: Ch 14

What if you could taste colors and

see music?

Synesthesia is a perceptual

phenomenon in which stimulation of one

sensory or cognitive pathway leads to

automatic, involuntary experiences in a

second sensory or cognitive pathway. Ideasthesia – Letters and

numbers evoke colorsGeneral Senses = receptors found throughout the body,

including joints and organs

Special senses = specialized receptors found in the head

(eyes, ears, mouth)Sensations & Receptors

Sensation = feeling that occurs when

a brain interprets a sensory nerve

impulse

Projection = the brain causes a

feeling to stem from a source

Sensory adaptation = sensory

receptors stop sending signals when

they are repeatedly stimulated

What do you think is going

on in this picture?

Sensory Deprivation is a technique initially

used by neuro-psychiatrists designed to

deliberately reduce or completely remove

stimuli from one or all of the senses.Receptor cells in the PERIPHERAL NERVOUS SYSTEM

are activated by stimuli in the environment

Receptor cells can be classified into types on the basis of

three different criteria:

cell type, position, and functionStructure Receptor Types

Free Nerve Endings -

dendrites embedded in

tissue as receivers

Respond to pain and

temperature

Encapsulated - embedded

in connective tissue to

increase sensitivity

(pressure and touch)

Specialized - receptors in

the retina of the eyeLocation-Based Receptor Types

Exteroreceptor environment (skin)

Interoreceptor - located near external

- interprets stimuli from internal

organs

Proprioreceptor - located near moving body parts,

interprets positionFunctional Receptor Types

Chemoreceptor - chemicals, mostly found in nose/mouth

Osmoreceptor - respond to solutes in body fluids

Thermoreceptor - temperature

Mechanoreceptor - pressure, vibration, body position

Nocireceptor - pain (chemicals released when tissue is

damaged)Sense of Pain

Visceral Pain - occurs in visceral tissues

such as heart, lungs, intestine

Referred pain - feels as though it is

coming from a different part (heart pain

may be felt as pain in arm or shoulder)

Acute Pain - originates from skin, usually

stops when stimulus stops (needle prick)

Chronic Pain - dull aching sensationUse the universal pain assessment tool to assess the pain level for each event.

Stubbed toe

Burn from stove

Slamming finger in a door

Paper cut

Sprained ankle

Sore throat

MigraineHow can you measure pain in babies and young children?

Face, Legs, Activity, Cry, Consolability

scale or FLACC scaleThe Rising Tide of Prescription Abuse

2.6 million people

nationwide now regularly

use prescription pain pills

for recreational purposes.

Taken in small doses,

painkillers produce

feelings of euphoria with

no hangover.An overview of how opioids

work to block pain and why

they become less effective

the longer you use them.

1. Nerve sends signal

2. Opioids slow/block signal

3. Limbic system (emotions)

and reward pathway are

stimulatedWhat is the responsibility of the government with regard to drug use and overdose?

What strategies can reduce the number of overdose deaths?Special Senses

Olfactory (smell)

Gustatory (taste)

Hearing & Equilibrium

SightSense of Smell (Olfactory)

Odor -->

Receptor Cell -->

Olfactory bulb -->

Olfactory Tract

--> LIMBIC SYSTEM

Why do smells trigger

memories?Olfactory Bulb on Sheep BrainSense of Taste (Gustatory)

Papillae = taste budsTaste Sensations

Imagine the taste of:

Sweet

Sour

Bitter

Salty

Savory (Umami)

Strawberries

Cheetos

Banana

French Fries

ChocolateUmami - a savory taste, is one of the five basic tastes,

together with sweet, sour, bitter and salty. A loanword from the

Japanese umami can be translated "pleasant savory taste".

Bacon, cheddar and beef all have

umami, and together they

“synergize the umami effect.”

Toss in sautéed mushrooms and

you’ve struck an umami mother

lode. Umami, he says, “alters our

perception of other tastes, making

salt, saltier, sweet sweeter, and

bitter and sour less biting.” It is a

taste that can’t be duplicated with

any of the other four tastes.Do we all experience taste in the same way?

Genetics may play a role in whether you like certain foods.

Does cilantro taste like soap to you?Sense of Hearing

External Ear

Auricle (pinna) - outer ear

Auditory Canal

(external auditory meatus)

- opening to the eardrumEar movement is common in

many mammals, including cats,

dogs and horses, and usually

serves to swivel the ear towards

the direction of a sound. A

group of muscles called the

are responsible for

this movement.

auriculares Ear wiggling is considered a

VESTIGIAL trait - a trait that no

longer functions but is part of our

evolutionary past.Middle Ear (tympanic cavity)

malleus

Eardrum (tympanum)

Auditory Ossicles - malleus,

incus, stapes - transmit

vibrations and amplify the signal

incus

stapes

Auditory Tube (eustachian tube) - connects the middle

ear to the throat - helps maintain air pressureWhy do children get tubes put in their ears?Inner Ear

Labyrinth - communicating chambers and tubesInner Ear

Semicircular Canals - sense of equilibrium

Cochlea - sense or hearing

Organ of Corti - contains hearing receptors, hair cells

detect vibrationsWhy do we lose our hearing?

Inside the cochlea

are special neurons

called HAIR CELLS.

Loud noises damage

these fibers.

As you age, hair cells become damaged (loud music can speed this process

along). Older people usually can’t hear frequencies that younger people can

hear.stereocilia2. Eardrum Steps in Hearing

1. Sound waves enter external auditory canal

vibrates

3. Auditory ossicles (malleus, incus, stapes) amplify vibrations

4. Stapes hits oval window and transmits vibrations to cochlea

5. Organs of corti contain receptor cells (hair cells) that deform

from vibrations

6. Impulses sent to the vestibulocochlear nerve

7. Auditory cortex of the temporal impulses

lobe interprets sensory

8. Round window dissipates vibrations within the cochleaEXTERNAL MIDDLE INNERMalleus, Incus, Stapes

Vestibulocochlear

nerve

Tympanic

Cavity

Color the structures of the ear.Cochlear Implants A cochlear implant receives

sound from the outside

environment, processes it, and

sends small electric currents near

the auditory nerve.

The brain learns to recognize this

signal and the person

experiences this as "hearing".

8 month old reacts to cochlear implantSense of Equilibrium

Static Equilibrium - maintain

stability and posture

Dynamic Equilibrium -

balance during sudden

movement

Cerebellum - interprets

impulses from the

semicircular canals and

maintains overall balance

Walking on two legs is harder than you

think…

Robot FailsOTOSCOPE

Otolaryngology (pronounced oh/toe/lair/in/goll/oh/jee)

Otolaryngologists are physicians trained in the medical and surgical

management and treatment of patients with diseases and disorders of the

ear, nose, throat (ENT), and related structures of the head and neck. They

are commonly referred to as ENT physicians.Disorders of Sensory Systems

1. Synesthesia

2. Anosmia

3. Tinnitus

4. Anhidrosis (inability to sweat)

5. Congenital Analgesia (CIP)

Mutations in genes prevents nerve

impulses from pain receptors

(nociceptors) from sending signals

to the brain.Hereditary (Congenital) Deafness

Occurs in 1 of every 1000 to 2000 newborns

Syndromic

Pendred Syndrome

Usher Syndrome

A SYNDROME is a disease that has

more than one feature or symptom.

A person with Usher syndrome also

has vision problemsHereditary (Congenital) Deafness

Non-syndromic A specific mutation results in hearing

loss; can be recessive (80%) or

dominant (20%) .

Recessive inheritance, can you identify the

“carriers?”Deafness can also be caused by PRENATAL Infections from “ToRCH”

organisms

Toxoplasmosis Rubella

Cytomegalovirus (CMV) Herpes

Postnatal infections can also cause deafness

Meningitis Streptococcus

Listeria InfluenzaPresbycusis = age related hearing loss

-diminished hearing sensitivity

-poor speech comprehension in

noisy environments

-slowed central processing of

acoustic information

-high frequencies are more difficult

to hear

Fun Fact: Many vertebrates such as fish,

birds and amphibians do not suffer

presbycusis in old age as they are able to

regenerate their cochlear sensory cells,

whereas mammals including humans have

lost this regenerative ability.

It is estimated that 30-40% of people

over the age of 65 have presbycusisCareers Related to Hearing

Audiologist

Speech-Language Pathologist

Sign Language Interpreter

Teacher: Deaf & Hearing Impaired

Molly’s mother first noticed that she

problems with her vision when Molly

was a baby.

When Molly was breastfeeding, she

would often focus her gaze on lights

in the room.

Molly would also rub and press on

her eyes frequently. Case is based on HHMI’s Gene’s as Medicine

Guided Notes (Student Handout)

Molly was taken to the doctor where she

was given a battery of vision tests.

1. Response to light. An infant will blink in

response to a bright light.

Molly did not respond to a bright light.

The Snellen Eye

chart is used to

diagnose vision

acuity. Why might

this test be difficult

to administer to

Molly?

2. Pupil response.

The pupil is an opening that allows

light into the eye. Pupils will DILATE

in darkness and constrict in bright

light.

- Molly’s pupils were slow to

respond to a bright light shined on

them.

3. Ability to follow a target.

Infants will be able to follow a toy or other item

they are interested in. Molly could not track a toy.

4. Ability to navigate obstacles.

Molly would frequently bump into chairs and trip

over objects on the floor.

The doctor ordered additional tests, including a

genetic test to identify some types of hereditary

blindness.

What other methods

could be used to test a

baby’s vision?

Molly was diagnosed with Leber Congenital Amaurosis (LCE)

Molly inherited two defective copies of the RPE65 gene.

Each of her parents had one defective copy. (Recessive)

A a

A

What are the chances that

two parents who carried

the defective gene would

have a child with LCE?

a

The Structure of the Eye and Accessory Organs

EYELID - Covers and protects the

eye, thin skin

Skin will not protect you from intense

radiation, that’s why we use special

goggles in a tanning bed

EYELASHES - fine hairs that function to protect the eyes

from dust and debris.

Trichiasis - inversion of the eyelashes,

which can irritate the eye

CONJUNCTIVA is a covering around

the eye and under the eyelids.

PINK EYE - also known as

CONJUNCTIVITIS

(from bacteria, very contagious)

Extrinsic Eye Muscles - move the eye

1

3 4

6

2

5

LACRIMAL GLANDS produce

tears, which drain into the nasal

cavity via the LACRIMAL DUCT.

TEARS function is to moisten and

lubricate the eye surface, and it has

enzymes that kill bacteria. CANALICULI!

Outer Tunic of the Eye

Cornea - transparent dome that focuses

light

Cornea transplants can be done to replace damaged

or diseased corneas. Your corneas can be donated if

you have signed on to be an organ donor.

Keratoconus is an eye condition

in which the normally round

cornea thins, causing a

cone-like bulge to develop.

Source: NPR

http://n.pr/1a1oSx6

Outer Tunic of the Eye

Sclera – continuation of cornea, going

toward the back of the eye (white of the eye)

Unlike other primates, human beings have

eyes with a distinct color contrast between the

white sclera and the colored iris.

The cooperative eye hypothesis is

a proposed explanation for the

appearance of the human eye. It

suggests that the eye's distinctive

visible characteristics evolved to

make it easier for humans to follow

another's gaze while communicating.

Why do dogs have white sclera?

Outer Tunic of the Eye

Optic Disk

Optic Nerve – exits at optic disk and

transmits information from the eye to

of the brain.

occipital lobe During Prohibition,

methanol poisoning was

the main cause of

blindness. Wood

alcohol or “spirits”

contained a chemical

that would damage the

optic nerve.

Inflammation of the optic nerve can

cause optic neuritis, or sudden vision

loss. It is common in those with multiple

sclerosis.

Vision loss may not be permanent.

Middle Tunic of the Eye

Choroid – contains blood vessels

Ciliary Body – holds the lens in place

Lens – focusing

Iris – colored portion of the eye

Pupil – opening for light to enter

Aqueous humor – liquid surrounding

the lens

Eye Color

Melanin is a brownish pigment that adds color

to your hair, eyes, and skin.

Caucasian babies are born with very little

melanin in the eyes, so they appear blue.

When exposed to sunlight, melanin levels rise

and the eyes can change color.

Brown is the world’s most common eye color.

Heterochromia - one eye is a different

color than the other

Mila

Kunis

PUPILS - dilate or constrict to adjust light entering eye

Fun Fact: - When you are looking at someone you love,

your pupils dilate, and they do the same when you are

looking at someone you hate.

What causes red-eye?

The flash on a camera is bright

enough to cause a reflection off of the

retina -- what you see is the red color

from the blood vessels.

Many cameras have a "red eye

reduction" feature. In these cameras,

the flash goes off twice -- once right

before the picture is taken, and then

again to actually take the picture. The

first flash causes people's pupils to

contract, reducing "red eye"

Inner Tunic

Retina - visual receptor cells

Fovea Centralis - region of the sharpest vision, also called

the macula

Optic Disc – where nerve fibers leave the eye, creating the

blind spot

Vitreous Humor – supports internal parts, fluid eye

within the

BLIND SPOT (optic disk)

The region where the optic nerve and blood vessels goes in and out of

the eye has no photoreceptors = BLIND SPOT.

Hold your hands out at 45° and that’s the location of the blind spot.

You can still see your hands because the other eye sees it. Close your

right eye and look for your right hand and you’ll find the blind spot.

The Retina

- has

PHOTORECEPTORS,

which are sensors for light.

In LCA, the RPE65 protein is

expressed in the photoreceptor

cells. The mutated form of this

gene causes the cells to die,

resulting in blindness.

Rods = monochromatic (b&w)

Cones = color vision

RPE65 expressed in

epithelium

R.O.Y.G.B.I.V

Rainbows are seen after rain because light is

passing through water droplets. This separates

the white light into the individual colors of the

spectrum

Humans have three different color sensitive

cone cells (red, green, blue).

Dogs only have yellow and blue.

Stare at the 3 dots over her nose for 20

seconds. Then look at the wall or ceiling.

Aqueous Humor

Vitreous Humor

Fovea Centralis

(macula) = the center

of focus

How Does the Eye Work?

Accommodation = Lens changes

shape to facilitate focusing.

Images are then projected to the

back of the eye (focal points).

The lens reverses the image

(objects are seen upside-down)

Zonules of Zinn

- connect ciliary body to lens

- can change the shape of the lens

- also called suspensory ligaments

Information from retina passes through the optic nerve, crosses at the

chiasma, and is sent to the occipital lobe of the brain. The brain is

responsible for interpreting those images.

We have difficulty interpreting images that are upside down

Which one is the real mona lisa?

Problems with the Eyes

Cataracts - Clouding of the lens leads to a clinical

condition known as CATARACTS.

Treatment is to remove the lens and replace it with an artificial one,

(IOL)

called an intraocular lens

Problems with the IRIS and PUPIL

The function is to constrict or

dilate the pupil (opening) to allow

light in.

Therefore, it regulates the

amount of light passing to the

visual receptors of the eye.

ANIRIDIA = a condition

where a person is born

without an iris

Onchocerciasis, also known

as river blindness, is a

disease caused by infection

by a parasitic worm.

Symptoms include severe

itching, bumps under the

skin, and blindness.

Color Blindness

A genetic trait that affects boys more than girls. The location

of the gene is on the X chromosome.

FLOATERS occur when the

vitreous substance clumps

and casts shadows on the

retina.

Floaters don’t actually move,

the eye just tries to track

them.

Retinal Detachment

A retinal detachment occurs when the retina is pulled away

from its normal position. Blindness can occur if it is not

treated right away.

Symptoms

● flashing lights;

● new floaters;

● a shadow in the periphery of your field of vision;

● a gray curtain moving across your field of vision.

Glaucoma

-pressure from vitreous humor damages the optic nerve and can

lead to blindness. Can be managed with medication.

Hyperopia = farsightedness

You can see distant objects

fine, but close objects appear

blurry

Presbyopia is the loss of ability

to see close objects or small

print, age-related.

Myopia = nearsightedness

You can see near objects

fine, but distant objects

appear blurry

ASTIGMATISM is when the

cornea has an irregular

shape.

Part of the field of view is

out of focus.

Most vision problems are

treated with glasses or

contact lenses.

Both change the focal

point of the light entering

the eye.

Surgery is also an option

Gene Therapy may also be an option for some types of blindness. FDA approved gene therapy for Leber Amaurosis. Molly’s Story ~17 min

In 2010, the

R E T I N A L GENE T H E R A P Y

Retina Needle injects

replacement gene

Pigment layer rejuvenated

in t r e a t e d a r e a

L e n s Optic nerve Photoreceptor cells

SOURCE: Moorfields Eye Hospital

ciliary body

vitreous humor

fovea centralis

iris

pupil

aqueous humor

optic nerve

cornea

sclera

retina

optic disk

suspensory ligaments