1. The Senses of the Nervous System
There are five general categories of sensory receptors: pain receptors, thermoreceptors, mechanoreceptors, chemoreceptors, and photoreceptors.

2. The Eye
Pupil - small opening in the middle of the iris through which light enters the eye
Lens - transparent object behind the iris that changes shape to help adjust the eye’s focus to see near or distant objects
Retina - innermost layer of the eye
Cornea – tough, clear covering that protects the eye and allows light to pass through
Humor – fluids that maintain the shape of the eye
Iris – colored part of the eye that controls how much light enters
Rod - photoreceptor in eye that is extremely sensitive to light
Cones - in the retina of the eye, a photoreceptor that responds to light of different colors, producing color vision

3. Eye

4. The Ear (Hearing and Balance)
Auditory Canal – ear canal, where sound enters
Tympanum – Ear Drum, vibrates as sound wave hit it
Cochlea - fluid-filled part of the inner ear; sends nerve impulses to the brain through the cochlear nerve
Ear bones
Hammer
Anvil
Stirrup
Eustachian tube – equalizes pressure between environment and inner ear
Oval window – sends waves of pressure to cochlea
Balance
semicircular canal - one of three structures within the inner ear that help an organism maintain balance (oriented perpendicular to each other)

5. Ear

6. Semicircular Canals

7. Smell and Taste
Chemoreceptors – receptors which sense different Chemicals
Taste and smell are linked closely together
“Hold your Nose”
taste bud - sense organ that detects the flavor of a substance

8. Touch Related Senses Touch – Mechanoreceptors
Temperature – Thermoreceptors
Pain – Pain Receptors

9. Questions
Name the five types of sensory receptors and list where they are found in the body.
Identify the parts of the eye and the function of each part.
What parts of the ear are responsible for hearing? For balance?
Explain why you can’t “taste” food when you have a bad cold.
Why do you feel dizzy after spinning around? How can a dancer or ice skater do lengthy spins?