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 WAVES1. EARDRUM VIBRATES2. STAPES HITS OVAL WINDOW3. 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