Ana Phisio Lab Report.

AMOR, DIANA D. BS Biology 4-2

Animal Physiology SENSATION

09-05-11

Sensation  is the conscious or subconscious awareness of external or internal conditions of the body. For a sensation to occur, four conditions must be satisfied: 1. A stimulus, or change in the environment, capable of activating certain sensory neurons, must occur. 2. A sensory receptor  must convert the stimulus to nerve impulses. 3. The nerve impulses must be conducted along a neural pathway from the sensory receptor to the brain. 4. A region of the brain must receive and integrate the nerve impulses into a sensation. A stimulus that activates a sensory receptor may be in the form of light, heat, pressure, mechanical energy, or chemical energy.A sensory receptor responds to a stimulus by altering its membrane’s permeability permeability to small ions. In most types of sensory receptors, the resulting flow of ions across the membrane produces a depolarization called a generator  potential. When a generator potential is large enough to reach the threshold level, it triggers one or more nerve impulses that are conducted along the sensory neuron toward the CNS. Sensory receptors vary in their complexity. The simplest are free nerve endings  that have no visible structural specializations (for example, pain receptors). Receptors for other general sensations, such as touch, pressure, and vibration, have encapsulated nerve endings . Their dendrites are enclosed in a connective tissue capsule with a distinctive microscopic structure. Still other sensory receptors consist of specialized, separate cells that synapse with sensory neurons. Objectives: Objectives: at the end of the experiment, the student should. 1. Identify the different receptors receptors of of stimulus in the human body. body. 2. Enumerate the function of each receptor in in the human human body. body. 3. Explain the response of each receptor to some common stimulus from the environment. LABORATORY RESULTS: A. Cutaneous receptors Somatic sensations arise from stimulation of sensory receptors embedded in the skin or subcutaneous layer; in mucous membranes of the mouth, vagina, and anus; in muscles, tendons, and joints; and in the internal ear. The sensory receptors for somatic sensations are distributed unevenly. Some parts of the body surface are densely populated with receptors, whereas other parts contain only a few. The areas with the highest density of sensory receptors are the tip of the tongue, the lips, and the fingertips. Somatic sensations that result from stimulating the skin surface are called cutaneous sensations. 1. Tactile sensation

a. Back of the neck 60mm b. Fingertip 10mm c. Forearm (inner surface) 50 mm d. Tip of nose 20mm e. Palm 40mm f. Lips 10mm 2. Tactile localization localization a. Palm 40mm b. Fingertip 10mm c. Forearm (inner surface) 80mm d. Lips 30mm

AMOR, DIANA D. BS Biology 4-2

Animal Physiology SENSATION

09-05-11

The tactile sensations  are touch, pressure and vibration, and itch and tickle. Itch and tickle sensations are detected by free nerve endings. All other tactile sensations are detected by a variety of encapsulated mechanoreceptors. Tactile receptors in the skin or subcutaneous layer include corpuscles of touch, hair root plexuses, type I and II cutaneous mechanoreceptors, mechanoreceptors, lamellated corpuscles, and free nerve endings. B. Proprioception: keeping tract of our our body position 

Close your eyes and stretch your arms out to your sides. With eyes closed, bring your hands together and touch index fingers. Are you able to touch these small points without using eyes? NO

Standing in one foot with eyes open: 43.62 sec. Standing in one foot with eyes closed: closed: 23.31 secs  The subject had a hard time while the time becomes longer

Proprioceptive sensations  inform you, consciously and subconsciously, of the degree to which your muscles are contracted, the amount of tension present in your tendons, the positions of your joints, and the orientation of your head. The receptors for proprioception, called proprioceptors, adapt slowly and only slightly. Slow adaptation is advantageous because because your brain must be aware of the status of different parts of your body at all times so that adjustments can be made. Kinesthesia , - the perception of body movements, allows you to walk, type, or dress without using your eyes. Proprioceptive sensations also allow you to estimate the weight of objects and determine the amount of effort necessary to perform perform a task. Proprioceptors are located located in skeletal muscles, in in tendons, in and around synovial joints, and in the t he internal ear. C. Taste and Olfaction 

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Blindfold the subject and have them hold their nose closed. Alternately offer peeled and slices apple and potato. Can they tell which it is? correct, 1 incorrect.  9 correct, Next, have the subject release their nose and alternately offer apple while holding the potato under their nose (and vice versa). Can you trick the subject into believing they are eating the apple, when in fact they are eating potato? What does this experiment tell you about the interaction between taste and smell?  6 correct, 4 incorrect Perform the basic experiment described above, but using a variety of flavored jellybeans. Can the subject identify the flavor while holding their nose? NO. While eating the  jellybeans,  jellybeans, have them release release their nose. Now can they identify identify the flavor? YES

AMOR, DIANA D. BS Biology 4-2

Animal Physiology SENSATION

09-05-11

In the chemical senses, smell and taste sensations arise from the interaction of molecules with sensory receptors. The nose contains 10 million to 100 million receptors for the sense of smell, or olfaction . Because some nerve impulses for smell and taste propagate to the limbic system, certain odors and tastes can evoke strong emotional responses responses or a flood of memories. The other chemical sense, taste or gustation , is much simpler than olfaction because only four major classes of stimuli can be distinguished: sour, sweet, bitter, and salty. All other “tastes,” such as chocolate, pepper, and coffee, are combinations of these four, plus the accompanying olfactory sensations. Odors from food pass upward from the mouth into the nasal cavity, where they stimulate olfactory receptors. Because olfaction is much more sensitive than taste, foods may stimulate the olfactory system thousands of times more strongly than they stimulate the gustatory system. When persons with colds or allergies complain that they cannot taste their food, they are reporting blockage of olfaction, not of taste. D. Vision o

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Close both eyes for several seconds, then open them quickly CONSTRICT While the subject is looking at an object, shine a pocket flashlight beam in one eye while the other corresponding eye is shielded from the light DILATE

More than half the sensory receptors in the human body are located in the eyes. As a result, a large part of the cerebral cortex is devoted to processing visual information. In this section of the chapter, we examine the accessory structures of the eye, the eyeball, the formation of visual images, the physiology of vision, and the visual pathway. The study of the structure, function, and diseases of the eye is known as ophthalmology ). ). A physician who specializes in the diagnosis and treatment of eye disorders with drugs, surgery, and corrective lenses is known as an ophthalmologist. An optometrist  has a doctorate in optometry and is licensed to test the eyes and treat visual defects by prescribing corrective lenses. An optician  is a technician who fits, adjusts, and dispenses corrective lenses using the prescription supplied by an ophthalmologist or optometrist.

AMOR, DIANA D. BS Biology 4-2

Animal Physiology SENSATION

09-05-11

E. Adaptation of sensory neurons 1. Mechanoreceptors 

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Place a coin  on the inside of the subject’s forearm. Determine how long the sensation of pressure produced by the coin persists by having the subject announce when she can no longer perceive the coin’s presence 34.68 secs Repeat as above in a new location, but after sensory takes place, add two more coins on top of the first one. Note whether the pressure sensation returns, and if so for how long 2 mins and 18 secs

2. Photoreceptors Stimulation of Photoreceptors After an image is formed on the retina by refraction, accommodation, constriction of the pupil, and convergence, light rays must be converted into neural signals. The initial step in this process is the absorption of light rays by the rods and cones of the retina. To understand how absorption occurs, it is necessary to understand the role of photopigments. A photopigment  is a substance that can absorb light and undergo a change in structure. The photopigment in rods is called rhodopsin and rhodopsin and is composed of a protein called opsin and opsin  and a derivative of vitamin A called retinal. Rhodopsin is a highly unstable compound in the presence of even very small amounts of light. Any amount of light in a darkened room causes some rhodopsin molecules molecules to split into opsin and retinal and initiate a series of chemical changes in the rods. When the light level is dim, opsin and retinal recombine into rhodopsin so that production keeps pace with breakdown. Rods usually are nonfunctional in daylight, because rhodopsin is split apart faster than it can be re-formed. After going from bright sunlight into a dark room, it takes about 40 minutes before the rods function maximally. Cones function in bright light and provide color vision. As in rods, absorption of light rays causes breakdown of photopigment molecules. The photopigments in cones also contain retinal, but there are three different opsin proteins. One type of cone photopigment responds best to yellow-orange light, the second to green, and the third to blue. An individual cone photoreceptor contains just one type of cone photopigment. The cone photopigments re-form much more quickly than the rod photopigment. If there are only three types of color photopigments, why don’t we just see yellow orange, green, and blue ? Just as an artist can obtain almost any color by mixing them on a palette, the cones can code for different colors by differential stimulation. If all three types of cones are stimulated, an object is perceived as white in color; if none is stimulated, the object looks black. An individual with one type of cone missing from the retina cannot distinguish some colors from others and is said to be colorblind. In the most common type, red   – green colorblindness, one cone photopigment is missing. Color blindness is an inherited condition that affects males far more often than females.