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 pH, PAIN RECEPTORS- CHEMORECEPTORS 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

Reflex

RECEPTORS IN THE SKIN 2 LAYERS Upper= EPIDERMIS- PAIN Lower= DERMIS- TOUCH, COLD, HEAT, PAIN

Receptors in skin

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

Taste buds

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

Olfactory cells

VISION SCLERA- TOUGH WHITE OUTER COVERING CORNEA- PUPIL COVER LENS- FOCUS LIGHT RAYS RETINA- BACK OF EYE WHERE IMAGE IS FOCUSED IRIS- REGULATES LIGHT

Structure of eye

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

Focusing by lens

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

Retina

ABNORMALITIES COLORBLINDNESS- LACK OF CONES CORRECTIVE LENSES- NEEDED FO MISSHAPEN EYEBALL OR LENS NEARSIGHTED- EXTRA LONG EYEBALL FARSIGHTED- EXTRA SHORT EYEBALL ASTIGMATISM- UNEVEN LENS

Nearsightedness

Farsightedness

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

Anatomy of ear

INNER EAR COCHLEA (HEARING) + VESTIBULE AND SEMICIRCULAR CANALS (BALANCE)

Inner ear

SENSING SOUND 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

Receptors in cochlea

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

Receptors in semicircular canals

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

Position receptors