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Transcript
5 Types of Receptors • 1) Chemoreceptor – responsive to changes in chemical concentrations • 2) Pain Receptor – responsive to chemicals released during tissue damage • 3) Thermoreceptors – responsive to changes in temperature • 4) Mechanoreceptors – responsive to changes in pressure and fluid movement • 5) Photoreceptors – respond to light energy • Sensations – feeling that occurs when sensory impulses are interpreted by the brain. Different sensations depend on the region of the brain that interprets the impulse • Sensory Projection – The brain causes the feeling to come from the receptors being stimulated • Sensory Adaptation – receptors adapt by failing to send impulses under constant stimulation. Stimulus must increase in order for more impulses to be sent. Somatic Senses • Senses associated with the skin, muscles joints and visceral organs. • Touch and pressure employ 3 kinds of receptors • 1) Free nerve endings in between epithelial cells • 2) Meissner’s Corpuscles – most common in hairless portions of the skin. Most responsive to light touch. • 3) Pacinian’s Corpuscles – Found in the subcutaneous layers of the skin, tendons and ligaments. Responsive to pressure. Temperature Receptors • Free nerve endings. Are responsive to heat or cold. • Heat receptors are most responsive to temperatures between 77o F and 113o F. • Cold Receptors are most responsive to temperatures between 50o F and 68o F. • Above 113o F and below 50o F pain receptors cause a freezing or burning sensation. • Both heat and cold receptors adapt very rapidly. Pain Receptors • Free nerve endings. Found everywhere except the nerve tissue of the brain. • Stimulated by tissue damage • Pain receptors adapt very poorly. The send impulses under constant stimulation. • Pain receptors are the only receptors in visceral organs • Referred Pain – The brain makes you feel as though pains in the abdomen originate in another part of the body. Sense of Smell • Olfactory receptor cells are Chemoreceptors located on the roof of the nasal cavity • They are neurons with tiny knobs at their ends covered with cilia • Chemicals that stimulate these cells enter as gases. They must partially dissolve in the fluid surrounding the cells to be detected • Olfactory cells undergo adaptation rapidly for a particular odor Sense of Taste • The special organs of taste are chemoreceptors called Taste Buds • Taste buds occur in association with tiny elevations on the tongue called Papillae • Each taste bud consists of many taste cells (Gustatory Cells) • Each gustatory cell has hairs which are the sensitive parts of the cell • Taste receptors adapt rapidly for a particular taste • Chemicals are detected only when dissolved in Saliva. • There a 4 varieties of taste cells each most sensitive to a particular taste • 1) Sweet Receptors – most concentrated on the tip of the tongue • 2) Sour Receptors – most concentrated on the sides of the tongue • 3) Salty Receptors – also most concentrated on the tip of the tongue • 4) Bitter Receptors – most concentrated on the back of the tongue