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Lecture 12

Week:Lecture 12- Sensory, Motor and Integrative Systems.pdf

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BIOL 171

Sensory, Motor, and Integrative Systems sensory: how info gets from receptors to brain through spinal cord motor: how info gets down from brain (motor cortex) to effectors Sensation vs. Perception Sensation: conscious or unconscious awareness of any stimulus Perception: conscious awareness of the meaning of a sensation Sensory Modalities modalities: ways each individual stimulus can be interpreted must change stimuli into neural energy (action potential) through receptors each receptor responds to only one kind of stimulus senses classified as general or special general: receptors widely distributed throughout body structures and skin touch, vibration, temperature, pain, etc. proprioceptors in muscles and joints special: receptors in specialized organs in head that respond to specific stimuli taste, smell, vision, hearing, equilibrium Structural Classification of Receptors free nerve endings bare dendrites pain, temperature, tickle, itch, light touch encapsulated nerve endings dendrites enclosed in connective tissue capsule regulates action potential generated pressure, vibration, deep touch separate sensory cells includes 2 individual specialized cells that respond to stimuli vision, taste, hearing, balance Classification of Receptors by Location exteroreceptors: receive external stimuli near surface of body hearing, vision, smell, taste, touch, pressure, pain, vibration, temperature interoreceptors: monitor internal environment not conscious of info transfer except pain and pressure *proprioceptors: sense body position and movements in muscle, tendons, joints, inner ear Classification of Receptors by Nature of Stimulus Detected mechanoreceptors: pressure or stretch touch, pressure, vibration, hearing, proprioception, equilibrium, blood pressure thermoreceptors: temperature nociceptors: tissue damage photoreceptors: light (vision) chemoreceptors: specific molecules detect taste, smell, changes in body fluids (pH, Na+, etc) Sensory Adaptation adaptation of receptors decreased sensitivity to sustained stimulation ex: odours disappear, water temperature feels less extreme ability to adapt varies... smell, pressure, touch receptors are fast don't feel your clothes/shoes if not moving pain, body position receptors are slow cut on your hand hurts for a couple of days; urgent Somatic Tactile Sensations Somatic: body Tactile: touch Touch crude touch perception something has touched the skin discriminative touch provides location, texture of source Pressure sustained sensation over a large area Vibration rapid, repetitive sensory signals Itch chemical irritation of free nerve endings Tickle stimulation of free nerve endings Skin receptors (dermis) Merkel disc discriminative touch located at surface of skin: light pressure and fast information Meissner corpuscle vibration, discriminative touch Ruffini corpuscle pressure sustained touch: aware of holding hands, etc Pacinian corpuscle pressure, high frequency vibration requires high pressure Hair root plexus feels movement of hair (something close to you) Nociceptor pain receptor close (but not too close) to surface for fast information Pressure: sustained sensation over a large area Vibration: rapid, repetitive sensory signals Itch: chemical irritation of free nerve endings (bradykinin) Tickle: stimulation of free nerve endings (can't tickle self b/c of motor signals) Thermal Sensations cold receptors respond to 10-40°C warm receptors respond to 32-48°C adapt rapidly, but continue to generate impulses at a low frequency <10 or >48°C—> pain receptors Nociceptors (Pain Receptors) free nerve endings in all tissues except brain could be b/c brain would be over-stimulated stimulated by excessive distension, muscle spasm, inadequate blood flow little adaptation occurs Types of Pain Fast (acute) pain sharp, rapid onset (0.1 sec) pain ex: needle puncture, cut) felt in superficial tissues only Slow (chronic) pain slower onset (>1sec) aching or throbbing pain that increases in intensity felt in superficial and deep tissues Localization of Pain superficial somatic pain from skin deep somatic pain from muscles, joints, tendons, fascia visceral pain from visceral organs (stomach, gallbladder) Referred Pain visceral pain felt just deep to skin over affected organ or in skin area served by the same spinal cord segment ex: heart attack—>pain in left arm, chest, jaw (innervated by spinal cord segments T1-T5) Proprioceptive/Kinesthetic Sense sensory information sent from muscles, tendons, joint capsules, receptors in ear, to cerebellum, cerebral cortex increases proprioception and kinaesthetic sense
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