CHAPTER 13

THE SENSES

RECEPTORS

• RECEIVE INFORMATION AND SEND IT TO THE BRAIN FOR PROCESSING

4 RECEPTOR TYPES

1. CHEMORECEPTORS- RESPOND TO CHEMICALS- SMELL, TASTE, BLOOD pH,

• PAIN RECEPTORS- SENSE CHEMICALS PRODUCED BY DAMAGED CELLS

2. MECHANORECEPTORS

• STIMULATED BY CHANGES IN PRESSURE OR MOVEMENT

• TOUCH, HEARING, POSITION OF BODY PARTS, BALANCE

3. THERMORECEPTORS

• COLD, WARMTH

• IN SKIN AND HYPOTHALAMUS (to regulate body temp.)

4. PHOTORECEPTORS

• RESPOND TO LIGHT

• CONES- Sense COLOR

• RODS- Sense only BLACK AND WHITE

• Rods work better than cones when it is fairly dark

SENSATION

• THE ARRIVAL OF ELECTRICAL IMPULSES AT THE BRAIN (CEREBRUM- the front part of brain)

• PERCEPTION- INTERPRETING THE MEANING OF THE SENSATION

ADAPTATION

• RESPONSE TO A REPEATED STIMULUS

• RECEPTORS STOP SENDING IMPULSES OR THE BRAIN FILTERS THEM OUT

• Farmers don’t notice manure smell anymore• People living beside railroads no longer get

awakened by trains at night

PROPRIOCEPTION

• SENSING THE POSITION OF BODY PARTS

• DEPENDS ON MUSCLE, TENDON AND LIGAMENT TENSION

RECEPTORS IN THE SKIN

2 LAYERS

• EPIDERMIS- PAIN

• DERMIS- TOUCH, COLD, HEAT, PAIN

REFERRED PAIN

• INTERNAL PAIN IS “FELT” SOMEWHERE ELSE ON THE BODY

• EX. HEART ATTACK “FELT” IN LEFT ARM

TASTE

• RECEPTORS ARE LOCATED IN PAPILLAE (BUMPS ON TONGUE)

• BITTER, SWEET, SALTY, SOUR

• TASTE = A COMBINATION OF THESE 4 SENSATIONS

SMELL

• OLFACTORY CELLS IN THE ROOF OF THE NASAL CAVITY

• 1,000 DIFFERENT RECEPTORS• ODORS STIMULATE DIFFERENT

COMBINATIONS OF RECEPTORS• NERVES CONNECT TO EMOTIONAL

CENTER OF THE BRAIN• TASTE BUDS ALSO STIMULATED

VISION

• SCLERA- TOUGH WHITE OUTER COVERING

• CORNEA- PUPIL COVER

• LENS- FOCUS LIGHT RAYS

• RETINA- BACK OF EYE WHERE IMAGE IS FOCUSED

• IRIS- REGULATES LIGHT

EYE

• FILLED WITH FLUID

• GIVES IT SHAPE

• FRONT SECTION- WATERY FLUID

GLAUCOMA- CAUSED WHEN DRAINS CLOG AND PRESSURE BUILDS

• REAR SECTION- JELLO LIKE FLUID

FOCUSING

• TINY MUSCLES CONTROL THE SHAPE OF THE LENS SO THAT LIGHT IS FOCUSED PROPERLY WHEN IT HITS THE RETINA

• CLOSE OBJECTS- MUSCLES CONTRACT, EYE STRAIN

• OLD AGE- BIFOCALS, CATARACTS

RETINA

• RODS, SENSE Black and White IN LOW LIGHT

• CONES SENSE Red,Green,Blue IN BRIGHT LIGHT

FOVEA- SMALL CENTRAL REGION OF RETINA FILLED WITH LOTS OF CONES

ABNORMALITIES

COLORBLINDNESS- LACK OF CONES

• CORRECTIVE LENSES- NEEDED FO MISSHAPEN EYEBALL OR LENS

NEARSIGHTED- EXTRA LONG EYEBALL

FARSIGHTED- EXTRA SHORT EYEBALL

ASTIGMATISM- UNEVEN LENS

HEARING

• OUTER EAR= PINNA AND AUDITORY CANAL

• MIDDLE EAR= TYMPANIC MEMBRANE + OSSICLES (bones)

Ossicles= MALLEUS (hammer), INCUS (anvil) AND STAPES (stirrup) HIT OVAL WINDOW of cochlea

EUSTACHIAN TUBE- EQUALIZES PRESSURE IN MIDDLE EAR- also called auditory tube

INNER EAR

• COCHLEA (HEARING) + VESTIBULE AND SEMICIRCULAR CANALS (BALANCE)

SENSING SOUND

• SOUND= AIR PRESSURE WAVES• EARDRUM VIBRATES• STAPES HITS OVAL WINDOW• PRESSURE WAVES OF FLUID IN

COCHLEA BENDS STEREOCILIA (HAIR CELLS) ALONG THE MEMBRANE

• Creates impulses which go to brain

BALANCE

• INNER EAR

• ACCELERATION- SEMICIRCULAR CANALS

• POSITION- VESTIBULE

ACCELERATION

• SEMICIRCULAR CANALS- ONE FOR EACH DIMENSION OF MOVEMENT

• MOVEMENT OF BODY CAUSES FLUID TO FLOW PAST CUPULA

POSITION

OTOLITHS- SMALL GRAINS OF CALCIUM CARBONATE WHICH REST ON SENSORY HAIRS

UTRICLE- DETECTS SIDE TO SIDE MOVEMENT

SACCULE- DETECTS UP AND DOWN MOVEMENT