CHAPTER 14 THE SENSES RECEPTORS RECEIVE INFORMATION AND

CHAPTER 14 THE SENSES

RECEPTORS • RECEIVE INFORMATION AND SEND IT TO THE BRAIN FOR PROCESSING

4 RECEPTOR TYPES 1. CHEMORECEPTORS- RESPOND TO CHEMICALS- SMELL, TASTE, BLOOD p. H, • PAIN RECEPTORSCHEMORECEPTORS WHICH 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 • Upper= EPIDERMIS- PAIN • Lower= 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) • 4 types= 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= AIR PRESSURE WAVES 1. EARDRUM VIBRATES 2. STAPES HITS OVAL WINDOW 3. PRESSURE WAVES OF FLUID IN COCHLEA BENDS STEREOCILIA (HAIR CELLS) ALONG THE MEMBRANE 4. Creates impulses which go to brain

BALANCE • INNER EAR ACCELERATION- SENSED BY SEMICIRCULAR CANALS POSITION- SENSED BY VESTIBULE

ACCELERATION • 3 SEMICIRCULAR CANALS per ear. ONE FOR EACH DIMENSION OF MOVEMENT • MOVEMENT OF BODY CAUSES FLUID TO FLOW PAST CUPULA • As the Cupula bends, a signal is sent to the brain

POSITION OTOLITHS- SMALL GRAINS OF CALCIUM CARBONATE WHICH REST ON SENSORY HAIRS - These will sag from side to side as the head is tilted UTRICLE- DETECTS SIDE TO SIDE MOVEMENT SACCULE- DETECTS UP AND DOWN MOVEMENT