Chapter 6

Section 4: Other Senses

Taste: Savory Sensations

• Taste occurs because chemicals stimulate thousands of receptors in the mouth, primarily on the tongue, but also in the throat, cheeks, & roof of mouth

• Papillae: Knoblike elevations on the tongue, containing the taste buds

• Actual receptors for taste are inside the taste buds–Cells send tiny fibers out through an

opening in the bud–Receptor cells are replaced by new

cells every ten days–After 40, total number of taste buds

declines

• Bitterness & sourness help us identify foods that are rancid or poisonous• Sweetness helps us identify foods

that are healthful or rich in calories• Salt is necessary for all bodily

functions

• Basic tastes can be perceived at any spot on the tongue–Center has no taste buds

• Taste differences are genetic, a matter of culture & learning• Attractiveness of a food can also be

affected by its color, temperature, texture, & odor

Smell: The Sense of Scents• Smell or olfaction

• Airborne chemical molecules enter the nose & circulate through the nasal cavity.–Vapors can also enter through the

mouth & pass into nasal cavity.

• Sniff out dangers by smelling smoke, food spoilage, & poisonous gases–Loss can be caused by

infection, disease, injury, or smoking

• Red bars show the people who could identify a substance dropped on the tongue when they were able to smell it

• Blue bars show the people who could identify the substance when they were not able to smell it

Senses of the Skin

• Protects our innards, helps identify objects, establish intimacy with others, gives us a sense of ourselves as a distinct from the environment• Basic senses- touch/pressure, warmth,

cold, & pain–Tickle, itch, & burning

The Mystery of Pain

• When the stimulus producing it is removed, the sensation may continue, sometimes for years• Chronic pain disrupts lives, puts

stress on the body, & causes depression, & despair

The Gate Control Theory of Pain

• Experience of pain depends (in part) on whether the pain impulse gets past neurological “gate” in the spinal cord & thus reaches the brain.

• Brain influences the gate–Thoughts & feelings can

influence our reactions to pain

Updating the Gate Control Theory

• Doesn’t explain phantom pain• Brain not only responds to incoming

signals from sensory nerves but is also capable of generating pain entirely on its own–A network of neurons in the brain

gives us a sense of our own bodies & body parts

Neuromatrix Theory of Pain

• Theory that the matrix of neurons in the brain is capable of generating pain (& other sensations) in the absence of signals from sensory nerves

The Environment Within

• Kinesthesis: The sense of body position and movement of body parts–Information provided by pain &

pressure receptors located in muscles, joints, & tendons

• Equilibrium: The sense of balance–Gives us information about our bodies as a

whole–Relies on three semicircular canals in the

inner ear• Tubes are filled with fluid that moves &

presses on hair like receptors whenever the head rotates

• Receptors intake messages that travel through a part of the auditory nerve not involved in hearing