1. Senses and Sensory Receptors

2. 5 major senses –Sight –Hearing –Taste –Smell –Touch Provide information from outside which stimulates the sensory nerves which carries the message to the brain for processing

3. Vision 2.5 cm in diameter 1/6 th is exposed Divided into 2 chambers separated by a lens Lens focuses light onto the RETINA at the back of the eye ball –Flattens when focusing on FAR objects –Thickens when focusing on NEAR objects Light enters thro’ opening in iris ( color)=PUPIL where it hits photoreceptors on the retina which conduct signals to the OPTIC NERVE OP carries signals to visual portion of the brain

4. Photoreceptors –Cones :- distinguish color, but need bright light –RODS :- need little light to function but cannot distinguish color Both produce signals (impulses) in sensory nerves Brain interprets impulses as image of object

5. Touch Skin main organ –Texture, temperature, pain –Sensory nerves not evenly distributed –Different receptors for each type –( Brain has no sensory receptors so surgery can be done on conscious patients)

6. Hearing/ Balance Ear –Contains a mechanoreceptor :- COCHLEA –Outer ear Catches the sound waves and sends to eardrum –Middle ear Air filled cavity Eustachian tube connects middle ear to throat 3 smallest bones in body –Hammer, anvil and stirrup  transmits sound to inner ear

7. Inner ear –Cochlea, looks like a snail shell –Filled with fluid –Covered I hair cells which transmits to AUDITORY Nerve, the pathway to the brain Semicircular canals –Mechanoreceptors for balance –At 90 0 angle to each other fluid filled –Brain interprets direction fluid moves  helps maintain balance

8. Taste/Smell Closely related Chemoreceptor—respond to specific chemicals Taste buds –50 chemoreceptors –Chemicals dissolved in liquid (saliva) Distinguish between salt, sweet, sour and bitter Different areas of tongue Smell receptors in the mucous membrane of the nose –These also have to be dissolved