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Suzanne D'Anna1 Somatic and Special Senses. Suzanne D'Anna2 Senses n constantly provide us with information about our surroundings n Grouped into two

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  • Suzanne D'Anna1 Somatic and Special Senses
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  • Suzanne D'Anna2 Senses n constantly provide us with information about our surroundings n Grouped into two major categories: - general senses - special senses
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  • Suzanne D'Anna3 Sensory Pathway n Includes: - receptors - sensory neurons - sensory tracts - sensory area
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  • Suzanne D'Anna4 Receptors n detect stimuli n specific with respect to changes to which they respond Sensory Neurons n transmit impulses from receptors to central nervous system n found in both spinal and cranial nerves (each carries only one type of receptor)
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  • Suzanne D'Anna5 Sensory Tracts n white matter in spinal cord or brain n transmit impulses to a specific part of brain Sensory Areas n most are in cerebral cortex n feel and interpret sensations n learning to interpret sensations begins in infancy without awareness and continues throughout life
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  • Suzanne D'Anna6 General Senses n Somatic: - tactile - touch, pressure, vibration, itch, etc. - thermal - hot and cold - pain - acute and chronic - proprioceptive - muscle, tendon, joint n Visceral - distension of viscera - internal organs - chemical composition of extracellular fluid
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  • Suzanne D'Anna7 Special Senses n Somatic: - visual - sight - auditory - hearing - equilibrium - static and dynamic equilibrium n Visceral: - olfactory - smell - gustatory - taste
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  • Suzanne D'Anna8 Skin Receptors
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  • Suzanne D'Anna9 Tactile Sensations n Touch receptors: - root hair plexuses - tactile discs - type II cutaneous mechanoreceptors - corpuscles of touch - (Meissners corpuscles)
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  • Suzanne D'Anna10 Root Hair Plexuses n dendrites arranged around hair follicles n receptors that rapidly adapt to detect movements when hair is disturbed
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  • Suzanne D'Anna11 Tactile Discs n expanded (flattened) nerve endings n slowly adapting touch receptors for discriminative touch
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  • Suzanne D'Anna12 Type II Cutaneous Mechanorecptors n also called end organ for Ruffini n expanded nerve endings n embedded in dermis n receptors that adapt slowly to heavy and continuous touch
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  • Suzanne D'Anna13 Corpuscles of Touch (Meissners Corpuscles) n small, oval, encapsulated nerve endings n rapidly adapting touch receptors n recognize exactly what point to which body is touched n abundant in hairless portions of skin
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  • Suzanne D'Anna14 Corpuscles of Touch (cont.) n rapidly adapting receptors that respond to low frequency vibrations n also respond to pressure and touch stimuli
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  • Suzanne D'Anna15 Tactile Sensations n Pressure and vibration receptors: - corpuscles of touch (Meissners) - lamellated corpuscles (Pacinian)
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  • Suzanne D'Anna16 Lamellated Corpuscles (Pacinian) n oval structures n composed of connective tissue n layered like an onion n enclose a dendrite n rapidly adaptive receptors that respond to pressure and high frequency vibrations
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  • Suzanne D'Anna17 Tactile Sensations (itch and tickle receptors) n free nerve endings are receptors for both tickle and itch sensations
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  • Suzanne D'Anna18 Thermal Sensations (thermoreceptors) n heat receptors most sensitive to temperatures above 25 o C (77 o F) and become unresponsive at temperatures above 45 o C (113 o F) n cold receptors most sensitive to temperatures between 10 o C (50 o F) and 20 o C (68 o F)
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  • Suzanne D'Anna19 Thermal Sensations (cont.) n intermediate temperature sensory input from combination of cold and heat receptors n both heat and cold receptors rapidly adapt to continuous stimulation
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  • Suzanne D'Anna20 Pain Sensations (Nociceptors) n free, naked nerve endings n located between cells of epidermis n respond to all types of stimuli
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  • Suzanne D'Anna21 Referred Pain n pain that feels as if it originated from a part other than site being stimulated n Example: - pain from heart attack (myocardial infarction) may be felt in left shoulder or inside of left arm - pain from gallstones may be felt in right shoulder

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