Unit 6: Sensation (cont.)

                                 TOUCH
Touch or tactile sense involves a mixture of at least 4 distinct skin senses--pressure, warmth, cold, and pain.  Only pressure has identifiable sense receptors.
COLD + PRESSURE = WETNESS
COLD + WARMTH = HOT

PAIN
Gate-Control-Theory: Theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass.  The gate is opened by stimulation of small nerve fibers and closed by stimulation of larger fiber or by information coming from the brain.

                                  TASTE
Taste is the Gustatory Sense. 
Taste is a CHEMICAL SENSE and consists of the four basic tastes of sweet, sour, bitter, & salty.  There may also be a 5th sense called "umami" or a meaty taste.

Each bump on the tongue contains over 200 taste buds.  Each bud contains a pore that captures food molecules.  The molecules cause hair-like neurons within the pores to fire.

Taste Buds reproduce themselves every 2-3 weeks.
Sensory Interaction: The principle that one sense may be influenced by another, as when the smell of food influences its taste.

                                  SMELL
Smell is the Olfactory Sense.
Smell is also a CHEMICAL SENSE.

Very little is known about the olfactory sense.  However, we are able to detect about 10,000 different odors.

Smells are processed in the temporal lobes of the brain and in the LIMBIC SYSTEM, which may explain why certain smells seem to have an emotional component and can trigger memories.

 Molecules in the air reach millions of receptor cells in each nasal cavity.  These cells send messages to the olfactory bulb  and the olfactory nerve which transmits the messages to the brain. 

             BODY POSITION & MOVEMENT
Kinesthesis: The system for sensing the position and movement of individual body parts.  The receptor cells for kinesthesis are found in our muscles, tendons, & joints.

Vestibular Sense: The system that monitors the head's (and thus the body's) position and movement.  It is our sense of equilibrium.
The semicircular canals and vestibular sacs  in the inner ear contain receptors that tell us about our head's position.


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