CHAPTER 14 SECTION 14.1 SENSORY INFORMATION

Sensory receptors Sensory receptors –are highly modified dendrites of a sensory neuron that are activated by an environmental (internal or external) stimulus. A stimulus is a form of energy. Sensory receptors convert one source of energy into another. Taste receptors in your tongue convert chemical energy (dissolving food) into electrical energy (action potential).

SENSORY RECEPTORS CONT’D Light receptors in your eye converts light energy into electrical energy. Balance receptors convert gravitational potential energy and mechanical energy into electrical energy. Sensory receptors are usually specialized based on their sensory organ (eye,ear, etc.)

The Body’s Sensory Receptors Receptor Type Stimulus Information Provided Taste Chemical energy Presence of specific chemicals (identified by taste buds) Smell Presence of specific chemicals (identified by olfactory cells) Pressure Mechanical energy Movement of skin or changes in body surface Proprioceptor Movement of the limbs Balance Body movements Audio Sound Sounds waves Visual Light energy Changes in light intensity, movement and colour Thermoreceptor Temperature changes Flow of heat

Sensory adaptation Sensory adaptation – occurs once you have adjusted to a change in the environment; sensory receptors become less sensitive when stimulated repeatedly. Ex. When you climb into a hot shower, immediately the water feels very hot, however after 30s to 60s your body adjusts to the temperature and the water does not feel as hot, even though the temperature has not changed. Ex. If a strong smell persists in a classroom (formaldehyde) by the end of the class you will become accustomed to it.

taste Taste receptors allow you to differentiate between things that are edible and things that are inedible. Taste receptors are found in different locations in different species. (Humans – tongue vs. Octopus – tentacles) In humans, taste receptors are concentrated on our tongue and detect chemicals in food. They detect only chemicals that have been dissolved by saliva.

TASTE CONT’D We have 4 main types of taste: - sweet - sour - salty - bitter Different sections of our tongue are responsible for detecting the different types of taste.

Taste areas on tongue

smell Smell receptors are responsible for detecting airborne chemicals. Our smell receptors are concentrated in olfactory cells lining our nasal passageways.

Taste and smell working together Taste and smell work together. Clogged nasal passageways reduce the effectiveness of olfactory cells. If mucus in your nasal passages becomes too thick, air and odor molecules can’t reach your olfactory receptor cells. Thus, your brain receives no signal identifying the odor, and everything you eat tastes much the same. You can feel the texture and temperature of the food, but no messengers can tell your brain, “This cool, milky substance is chocolate ice cream.” The odor molecules remain trapped in your mouth. The pathway has been blocked off to those powerful perceivers of smell--the olfactory bulbs.