1. The Senses Ch. 18 Sect. 2

2. You and Your Environment
The sensory system is the part of your nervous system that detects or senses the environment.
Humans have 5 sense: hearing, sight, taste, touch, and smell.
Receptors- special features in the sensory system that detect stimuli.
Each of the 5 senses uses different receptors.

3. Vision (Sight)
Vision uses photoreceptors in the eye to detect light and create vision.
Eye Parts: Cornea – thin membrane in the eye that changes the direction of light rays. Iris- colored part of the eye that controls the amount of light that enters the eye. Pupil – opening in the iris. Lens – clear structure that focuses the light. Retina- back area of the eye with photoreceptors.
Retinas have rod (detects shapes & low levels of light) and cone (detect color and bright lights) cells.

5. How you see and Focusing Light
Light enters your eyes detected by the retina. The rods and cones (in retina) detect the colors and shapes from the light. The retina sends the information through the optic nerve in your brain. The brain creates a picture of what you are seeing.
Focusing Light:
Lens and cornea change the direction of the light that enters the eye. Both are curved. Changes the direction and focus it into the retina.

6. Hearing
Vibration of matter creates sound waves that travel through the air and other substances.
Auditory receptors in the ear detect the sound waves.
Waves are amplified within the ear and move hair cells.
Hair cells send information about the waves to the brain.
The brain processes the info about the loudness and tone of the sound.
3 parts of the ear: outer ear, middle ear, inner ear.
Inner ear helps maintain balance

8. Smell and Taste
Humans have over a hundred different receptors for detecting odors.
Chemoreceptors – receptors in your nose that detect odors.
Taste relies on chemoreceptors too.
Chemoreceptors on your tongue (taste buds) detect chemicals in foods and drinks.
Taste buds detect 5 different tastes: bitter, salty, sour, sweet, and umami

9. Touch & Senses and Homeostasis
Touch receptors in the skin can detect temperature, pain, and pressure.
Some areas have lots of receptors and some have very few.
The 5 senses collect information about the environment and send it to the nervous system.