The Other Senses

1. The Other Senses

2. Taste: Gustatory System • Physical stimuli→ chemical substances that are soluble • Receptors→ taste cells found in the taste buds that line the trenches around tiny bumps on the tongue • Also have receptors in the back and roof of the mouth • Absorb chemicals dissolved in saliva and trigger neural impulses • Short life, constantly replaced • Primary tastes→ sweet, sour, bitter and salty, some add umami • Supertasters→ four times as many taste buds per square cm as nontasters • Much more sensitive to certain sweet and bitter substances

3. Taste: Gustatory System • Taste receptors replace themselves every week or two • As you grow older, the number of taste buds decrease, as does taste sensitivity • Smoking and alcohol use accelerate this decline • Sensory interaction- principle that one sense may influence another, as when the smell of food influences its taste

4. Smell: Olfactory System • Physical stimuli→ chemical substances- volatile ones that can evaporate and be carries in the air • Dissolved in fluid (mucus in the nose) • Receptors→ olfactory cilia, hairlike structures located in the upper portion of the nasal passages • Short life, constantly replaced • Receptors have axons that synapse with cells in the olfactory bulb and then are routed directly to various areas in the cortex

5. Touch • Physical stimuli→ mechanical, thermal, and chemical energy that impinge on the skin • Produce perceptions of tactile stimulation (pressure of touch against skin), warmth, cold and pain • Only pressure has identifiable receptors • At least six different types of receptors • Specialized to some degree, however, distinctions are not always clear

6. Touch • Pain is a property not only of the senses but of the brain as well • Phantom limb sensation- amputees may fell pain or movement in their nonexistent limbs • Gate control theory- theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain • “gate” is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by information coming from the brain

7. Kinesthetic System • Monitors the positions of various parts of the body (Ex.- helps you know where your limbs are) • Receptors reside in joints (indicating how much they are bending) and muscles (registering tautness, or extension) • Transmitted to brain along same paths as tactile senses

8. Vestibular System • Provides the sense of balance, or equilibrium, compensating for changes in the body’s position • Responds to gravity and keeps people informed of their body’s location in space • Primarily located in the semi-circular canals of the inner ear

9. Vestibular System • Inside the semi-circular canals and vestibular sacs (connects canals with cochlea) are substances that move when the head rotates or tilts. This movement stimulates hair like receptors in these organs of the inner ear. • These receptors send messages to the cerebellum enabling us to sense our body position and maintain balance.

10. Ear