Receptor Physiology 4. Define receptive field. 5. Explain how the two-point discrimination test illustrates how the density of touch receptors in a receptive field varies in different areas of the body. How well did your results correspond to your predictions? 6. Explain how the error of localization correlates to the size of the receptive field as demonstrated by the tactile localization experiment. 7. Several questions regarding general sensation are posed below. Answer each by placing your response in the appropriately numbered blanks below. 1. Which cutaneous receptors are the most numerous? 2-3. Which two body areas tested were most sensitive to touch? 4-5. Which two body areas tested were least sensitive to touch? 6-8. Where would referred pain appear if the following organs were receiving painful stimuli: (6) gallbladder, (7) kidneys, and (8) appendix? (Use your textbook if necessary.) 9. Where was referred pain felt when the elbow was immersed in ice water during the laboratory experiment? 10. What region of the cerebrum interprets the kind and intensity of stimuli that cause cutaneous sensations? 1. 2-3. 4-5. 6.
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Which cutaneous receptors are the most numerous? The most numerous cutaneous receptors are the Merkel cells. They are found mainly on the surface of the skin. Show more…
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Receptor Physiology 4. Define receptive field. 5. Explain how the two-point discrimination test illustrates how the density of touch receptors in a receptive field varies in different areas of the body. How well did your results correspond to your predictions? 6. Explain how the error of localization correlates to the size of the receptive field as demonstrated by the tactile localization experiment. 7. Several questions regarding general sensation are posed below. Answer each by placing your response in the appropriately numbered blanks below. 1. Which cutaneous receptors are the most numerous? 2-3. Which two body areas tested were most sensitive to touch? 4-5. Which two body areas tested were least sensitive to touch? 6-8. Where would referred pain appear if the following organs were receiving painful stimuli: (6) gallbladder, (7) kidneys, and (8) appendix? (Use your textbook if necessary.) 9. Where was referred pain felt when the elbow was immersed in ice water during the laboratory experiment? 10. What region of the cerebrum interprets the kind and intensity of stimuli that cause cutaneous sensations?
Adi S.
Answer the following questions about sensory physiology: 1. A person who suddenly smells an extremely strong, offensive odor is able to perceive it as strong because of the A) suddenness with which the stimulus was perceived. B) offensiveness of the odor. C) strength of each action potential. D) brain location to which the stimulus goes. E) frequency of action potentials reaching the brain. 2. Sneezing normally occurs when irritation in the nasal cavity sends a signal through the ophthalmic branch of the trigeminal nerve to the brainstem. When a person sneezes in bright sunlight, what is most likely happening in the person’s sensory system? A) Stimulation of sensory receptors in the eye sends impulses to the visual cortex. B) Stimulation of the optic nerve triggers action potentials in the nearby trigeminal nerve, which sends impulses to the brainstem. C) Stimulation of sensory receptors in the nasal cavity sends impulses to the visual cortex. D) Stimulation of sensory receptors in the nasal cavity sends impulses to the trigeminal nerve and brainstem. E) Stimulation of sensory receptors in the eye sends impulses to the trigeminal nerve and brainstem. 3. In the mammalian eye, 1-2 percent of ganglion cells are photosensitive. If these cells were not photosensitive, which function would mammals be unable to carry out? A) Distinguishing between areas of contrast B) Production of images C) Responding appropriately to day-night cycles D) Detection of color E) Detection of light 4. A dog confronts another dog, seeing and smelling him at the same time. The dog’s eyes transduce light into action potentials, and his nose transduces scent chemicals into action potentials. How does his brain distinguish between them, so that he perceives both stimuli correctly? A) Action potentials from the eyes and nose are combined in the brain. B) The receptors respond differently to light and scent. C) The frequency of the light stimulus is greater than that of the scent stimulus. D) Action potentials from the eyes and nose arrive at different places in the brain. E) The light stimulus is stronger than the scent stimulus.
Investigating Somatic Senses Below are two investigations designed to help you understand the distribution of cutaneous receptors and cutaneous receptor adaptation. For the two-point discrimination test you need either two sharp pencils or two sharp round toothpicks or two similarly sharp-pointed tools and a calibrated rule (ruler). To complete the adaptation test you need between 6 to 8 nickel (preferred) or quarter coins and a timing device which measures in second intervals. To do both investigations you need a willing person (the subject) to test. The person you select does not need to understand the testing process, but the person will need to be patient and willing to respond to your questions. Completing both activities will require between 30 and 60 minutes. A. Investigate Two-Point Discrimination Test The density of touch (tactile) receptors varies in different areas of the body. Using your two-point testing tool, you will test the ability of the subject to tell the difference between two distinct sensations when the skin is touched simultaneously at two points. Try to be sure that each sharp point is applied at the same time and with the same force. When doing this test, the subject should not be looking at the test area. Eyes closed are fine, but some subjects may need to be blindfolded! At each test site begin with the two sharp points very close together. Touch the subject. Remove the tool and slightly increase the distance between the two sharp points and retest the subject's skin. Continue slightly increasing the distance between the two sharp points until the subject reports that two points of contact can be felt. Measure this distance. This measurement, the smallest distance at which two points of contact can be felt, is the two-point threshold. Test a single subject's two-point threshold for the face, back of hand, palm of hand, fingertips, back of neck, upper back, and ventral forearm. Results to report: 1. For each site tested, record the two-point threshold on a data sheet. 2. Which area had the smallest two-point threshold? 3. How do your results relate to the sensory homunculus which maps the location in the postcentral gyrus where sensations from each part of the body is processed. 4. What did you learn by completing this activity?
Sri K.
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