1. Human Senses

2. What you will do today . . .
Name five kinds of sense receptors and explain their functions
Explain how a sensation arises
Identify the locations of the receptors of the special senses
Describe the accessory structures of each of the special senses

3. Specialized Sensory Neurons

4. Sensory Regions of the Brain

5. The Sensations in the Skin
The skin is full of receptors that allow us to detect touch, pain, and pressure
1. Touch receptors are concentrated in the fingertips, face, and tongue
2. Body hair also helps to detect touch; the base of the hair follicles are loaded with receptors

6. The Sensations in the Skin

7. The Sensations in the Skin
B. Thermoreceptors monitor temperature change

8. The Sensations in the Skin
Pain receptors are sensory receptors that are found throughout the epidermis and interior of the body. They can be stimulated by four types of energy . . .
1. Mechanical
2. Thermal
3. Chemical
4. Electrical

9. The Sensations in the Skin
5. Pain receptors are most abundant in the hands and mouth
6. Pain receptors generally follow the reflex arc

10. The Chemical Senses: Taste and Smell
Taste buds are the sensory receptor organ for taste; most are on the tongue itself
1. Five general taste groupings
a. Sweet
b. Sour
c. Salty
d. Bitter
e. Umami

11. A Map of the Tongue

12. The Chemical Senses: Taste and Smell
2. Different tastes have a purpose
3. Chemicals must be dissolved in saliva to be tasted
4. Three cranial (connected directly to the brain) nerves are involved in the process of gustation
a. Facial
b. Glossopharyngeal
c. Vagus

13. The Chemical Senses: Taste and Smell
5. Taste triggers digestion
6. Taste is 80% smell

14. The Chemical Senses: Taste and Smell

15. The Chemical Senses: Taste and Smell
The olfactory epithelium, located in the nasal cavity, allow us to smell odors
1. The trigeminal nerves and olfactory nerves send signals to the olfactory bulbs, which lie in the limbic system of the brain
2. Smell signals also travel to the amygdala, which trigger emotions, memories, and eating behaviors
3. Chemicals must be in a gaseous (volatile) state to be smelled

16. The Eye and Vision
70% of all sensory receptors are located in the eye

17. The Eye and Vision Accessory Structures 1. Eyebrows
a. Shade eyes from sunlight
b. Keep perspiration out of eye
2. Eyelids
a. Closed by orbicularis oculi
b. Protect the eye and keeps it from drying out
3. Conjunctiva
a. Thin, outer layer of eyeball
b. Produces mucus to lubricate eye
c. Infection is called Pink Eye

18. The Eye and Vision Accessory Structures 4. Lacrimal Glands
a. Release tears
b. Cleans eye with lysozyme, an antibacterial enzyme
5. Eye Muscles

19. The Eye

20. The Eye and Vision Parts of the Eye
1. Sclera: the white part that shapes the eyeball
2. Cornea: clear structure on surface of eye that bends light
3. Choroid layer: blood vessels that provide nutrients to the eye
4. Ciliary body: alters the shape of the lens in response to light

21. The Eye and Vision Parts of the Eye
5. Iris: colored part of eye that regulates the amount of light that enters the eye
6. Pupil: center of eye where light enters
7. Rods: peripheral vision, dark conditions
8. Cones: operate in bright light and allow color vision

22. The Eye and Vision Parts of the Eye
9. Retina: light-sensitive inner layer of the eye
10. Optic nerves: pathway from eye to brain

23. The Ear, Hearing, and Balance

24. The Ear, Hearing, and Balance
Sound is transmitted as vibrations, usually of air
The external air is connected to the tympanic membrane (eardrum) by the auditory canal
Air pressure in the ear can be regulated by the eustachian tube, which is an opening into the throat
Vibrations of the tympanic membrane are sent to the hammer, anvil, and stirrup

25. The Ear, Hearing, and Balance
These three bones send vibrations to the cochlea, a coiled tube
1. Cochlea contains the Organ of Corti, the organ of hearing
2. Organ of Corti contains sensory receptors called hair cells which send sound to the brain via the auditory nerve
F. Semicircular canals of the inner ear contain fluid that regulate balance

26. References