The Senses (3)The Senses (3)

Anatomy and PhysiologyAnatomy and Physiology

The SensesThe Senses

The body contains millions of neurons that The body contains millions of neurons that react directly to stimuli from the react directly to stimuli from the environment, including light, sounds, environment, including light, sounds, motion, chemicals, pressure, and changes motion, chemicals, pressure, and changes in temperature. in temperature.

These neurons are called These neurons are called sensory sensory neuronsneurons, which react to specific neurons , which react to specific neurons and eventually to the CNS. The sensory and eventually to the CNS. The sensory receptors are located throughout the body receptors are located throughout the body and are concentrated in the sense organs. and are concentrated in the sense organs. (eyes, ears, mouth, nose, and skin)(eyes, ears, mouth, nose, and skin)

The SensesThe Senses

There are 5 categories of sensory There are 5 categories of sensory receptors:receptors:– Pain receptorsPain receptors (respond to chemicals released (respond to chemicals released

by damaged cells)by damaged cells)– ThermoreceptorsThermoreceptors (detect variation in body (detect variation in body

temperature)temperature)– MechanoreceptorsMechanoreceptors (sensitive to touch, (sensitive to touch,

pressure, stretching of muscles, sound and pressure, stretching of muscles, sound and motion)motion)

– ChemoreceptorsChemoreceptors (sensitive to chemicals in the (sensitive to chemicals in the external environment)external environment)

– PhotoreceptorsPhotoreceptors (sensitive to light) (sensitive to light)

VisionVision

Eyes are a sense organ used to sense lightEyes are a sense organ used to sense light Light enters the eye through the Light enters the eye through the corneacornea , ,

which helps focus the lightwhich helps focus the light The impulses created by the light leave The impulses created by the light leave

each eye by the optic nerveeach eye by the optic nerve The optic nerve then carries the impulses The optic nerve then carries the impulses

to the appropriate parts of the brainto the appropriate parts of the brain The brain interprets the impulses as visual The brain interprets the impulses as visual

images and provides info about the images and provides info about the external worldexternal world

Structures of the EyeStructures of the Eye

CorneaCornea tough transparent layer of cells tough transparent layer of cells that helps focus lightthat helps focus light

Aqueous HumorAqueous Humor chamber filled with chamber filled with fluid that is located behind the corneafluid that is located behind the cornea

IrisIris a disk-like structured that is the a disk-like structured that is the colored eye colored eye

Pupil Pupil small opening that is adjusted by small opening that is adjusted by tiny muscles which regulate the amount of tiny muscles which regulate the amount of light that enters the eyelight that enters the eye

Structures of the EyeStructures of the Eye LensLens has small muscles attached to it has small muscles attached to it

and allow it to change its shape to help and allow it to change its shape to help you adjust your eye’s focus to see near or you adjust your eye’s focus to see near or distant objectsdistant objects

RetinaRetina photoreceptors are arranged in a photoreceptors are arranged in a layer and convert light energy into nerve layer and convert light energy into nerve impulses that get sent to the CNSimpulses that get sent to the CNS

FoveaFovea site of the sharpest vision site of the sharpest vision Optic NerveOptic Nerve passes through the back passes through the back

of the eye and there is no photoreceptors of the eye and there is no photoreceptors (blind spot)(blind spot)

2 Types of Photoreceptors2 Types of Photoreceptors

RodsRods extremely sensitive to light extremely sensitive to light but do not distinguish colorsbut do not distinguish colors

ConesCones less sensitive and respond less sensitive and respond to light of different colors producing to light of different colors producing color vision (concentrated in the color vision (concentrated in the fovea)fovea)

Hearing and BalanceHearing and Balance

Sound is nothing more than Sound is nothing more than vibrations in the air around us. vibrations in the air around us.

The ear is the sensory organ that can The ear is the sensory organ that can distinguish both the pitch and distinguish both the pitch and loudness of those vibrationsloudness of those vibrations

Vibrations enter the auditory canalVibrations enter the auditory canal

Structures of the EarStructures of the Ear

TympanumTympanum (eardrum) vibrations (eardrum) vibrations from the external environment cause from the external environment cause vibrations in the tympanumvibrations in the tympanum

Hammer, anvil, and stirrupHammer, anvil, and stirrup tiny tiny bones that pick up vibrations from bones that pick up vibrations from the tympanum.the tympanum.

Oval WindowOval Window picks up vibrations picks up vibrations from the stirrup and causes pressure from the stirrup and causes pressure waves in the fluid of the cochleawaves in the fluid of the cochlea

Structures of the EarStructures of the Ear

CochleaCochlea fluid filled and found in fluid filled and found in the inner ear. It is lined with tiny hair the inner ear. It is lined with tiny hair cells that are pushed back and for cells that are pushed back and for the by pressure waves. The hair cells the by pressure waves. The hair cells then produce nerve impulses that then produce nerve impulses that are sent to the brain throught he are sent to the brain throught he cochlear nerve.cochlear nerve.

BalanceBalance

Within the inner-ear just above the Within the inner-ear just above the cochlea are three canals at right cochlea are three canals at right angles to one another called angles to one another called semicircular canalssemicircular canals. .

The canals and 2 tiny sacs located The canals and 2 tiny sacs located behind them monitor the position of behind them monitor the position of your body, especially your head in your body, especially your head in relation to gravity. relation to gravity.

BalanceBalance

The canals and sacs are filled with a The canals and sacs are filled with a fluid and lined with hair cells. As the fluid and lined with hair cells. As the head changes position. The fluid also head changes position. The fluid also changes position, which causes the changes position, which causes the hair on the hair cells to bend. This hair on the hair cells to bend. This action sends impulses to the brain action sends impulses to the brain that enable it to determine body that enable it to determine body motion and position.motion and position.

SmellSmell

Your sense of smell is actually a Your sense of smell is actually a ability to detect chemicals. ability to detect chemicals. Chemoreceptors in the lining of the Chemoreceptors in the lining of the nasal passageway respond to nasal passageway respond to specific chemicals and send impulses specific chemicals and send impulses to the brain through sensory nerves.to the brain through sensory nerves.

The “taste” of food and drink is The “taste” of food and drink is actually smellactually smell

TasteTaste

The sense of taste is a chemical The sense of taste is a chemical sense. sense.

The sense organs that detect taste The sense organs that detect taste are the are the taste budstaste buds, most of which , most of which are located on the tongue, but a few are located on the tongue, but a few are in other locations of the mouth. are in other locations of the mouth.

Tastes are: salty, bitter, sweet, and Tastes are: salty, bitter, sweet, and sour.sour.

For Your Information:For Your Information:

Be ready for stations next class, Be ready for stations next class, where we will be discovering the where we will be discovering the effects of drugs on the nervous effects of drugs on the nervous system. system.

You need to be familiar with lectures: You need to be familiar with lectures: 1, 2, and 3 in order to be successful. 1, 2, and 3 in order to be successful. Tonight complete the review Tonight complete the review paper for homework.paper for homework.