Psych 3312 1st Edition Exam #6 Study Guide Chapters: 14-15Chapter 14-151. Describe how Ian Waterman’s experiences illustrate the importance of touch.a. Destruction of his nerves from his muscles, tendons & joints after an illness eliminated his ability to sense the position of his arms, legs, & body. b. Ian learned to use his sense of vision to constantly monitor the positions of his limbs & body. c. We recognize that perception we experience thru our skin is crucial for everyday activities, protecting ourselves from injury & motivating sexual activity.d. Crucial to survival of our species.e. Perceptions felt through the skin & enable us to sense positions & movements of our limbs more important for survival than those provided by vision & hearing. 2. Name and define the three parts of the somatosensory system.a. Cutaneous senses=responsible for perceptions such as touch & pain that are usually caused by stimulation of the skin. b. Proprioception=ability to sense the position of the body & limbs. c. Kinesthesis=ability to sense the movement of the body & limbs.3. Identify the functions of the skin.a. Warning functions of pain or injury.b. Prevents body fluids from escaping & at same time protects us by keeping bacteria, chemical agents, & dirt from penetrating our bodies. c. Provides us w/information about various stimuli that contact it.4. Name and describe the four types of mechanoreceptors.a. Slowly adapting (SA) receptors=mechanoreceptors located in the epidermis & the dermis that respond w/prolonged firing to continued pressure. b. Merkel receptor (SA1) & Messiner corpuscle (RA1)=2 mechanoreceptors located close to the surface of the skin, near the epidermis. Because they are located close to the surface ofthe skin, the receptors have small receptive fields: cutaneous receptive field is the area of skin when stimulated, influences firing of the neuron.c. Ruffini cylinder (SA2) & Pacinian corpuscle (RA2 or PC)=mechanoreceptors that are locateddeeper in the skin so they have larger receptive fields. Ruffini cylinder responds continuously to stimulation, & Pacinian corpuscle responds when stimulus is applied & removed. Ruffini cylinder associated w/perceiving stretching of the skin, Pacinian corpuscle with sensing rapid vibrations & fine texture.5. Describe the pathways from the skin to the cortex.a. Medial leminscal pathway=pathway in the spinal cord that transmits signals from the skin towards the thalamus. b. Spinothalamic pathway=one of the nerve pathways in the spinal cord that conducts nerve impulses from the skin to the somatosensory area of the thalamus.6. Describe research by Penfield which led to the mapping of the sensory homunculus.a. Existence of a map of the body on S1 determined in series of classic investigations that neurosurgeon Wilder Penfield carried out while operating on awake patients who were having brain surgery to relieve symptoms of epilepsy.b. Penfield asked patients to perceive what they perceived when he stimulated points on S1. Patients reported sensations of tingling & touch on various parts of their body. c. Penfield found that stimulating the ventral part of S1 (lower on the parietal lobe) caused patients to have sensations on the lips & face, while stimulating higher on S1 caused sensations in the hands & fingers, & stimulating the dorsal S1 caused sensations in the legs & feet.7. Apply the previously-learned terms of cortical magnification, plasticity, and receptive fields to the somatosensory system.a. Plasticity of somatosensory systemi. Cortical representation of a particular function can become larger if that function is used often. ii. Effect of plasticity determined by measuring how special training affects the brain.iii. Plasticity has created more cortical area for parts of the body that are used more. iv. What the plasticity means is that while we can specify the general area of the cortex that represents a particular part of the body, the exact size of the area representing each part of the body is not totally fixed. v. Receptors in the skin make it possible for us to sense diff qualities such as small details, vibration, textures of surfaces, the shapes of three-dimensional objects, & potentially damaging stimuli. vi. Receptors are one of the things that determine what we experience when the skin is stimulated.b. Magnification i. Magnification of the representation on the brain of parts of the body such as the fingertips parallels the magnification factor in vision. Map of the body on the brain is enlarged to provide the extra neural processing that enables us to accurately sense fine details w/our fingers & parts of our body.8. Describe methods used to measure tactile acuity, and discuss receptor mechanisms and cortical mechanisms responsible for tactile acuity.a. Comparing two-point thresholds measured on diff parts of the body to how diff parts of the body are represented in the brain. Regions of high acuity like fingers & lips, represented by larger areas on the cortex. “Magnification” of the representation on the brain of parts of the body such as the fingertips parallels the magnification factor in vision.Map of body on the brain enlarged to provide the extra neural processing that enables us to accurately sense fine details with our fingers & other parts of the body.b. Determine the receptive fields of neurons in different parts of the cortical homunucleus. Small receptive fields of neurons receiving signals from the fingers translates into more separation on the cortex, which enhances ability to feel two close-together points on the skin as 2 separate points.9. Explain how vibrations are perceived.a. Mechanoreceptor primarily responsible for sensing vibrations is the Pacinian corpuscle. Recording from fibers associated w/ the corpuscle shows that these fibers respond poorly to slow or constant pushing, but respond well to high rates of vibration. b. Presence of the corpuscle surrounding the nerve fiber determines which pressure stimuli actually reach the fiber. The corpuscle, which has a series of layers, with fluid in between each layer, transmits rapidly applied pressure, like vibration, to the nerve fiber but does not transmit continuous pressure. Corpuscle causes the fiber to receive rapid changes in pressure, but not to receive continuous pressure.c. Properties of the corpuscle cause the fiber to respond poorly to continuous stimulation,