suzanne d'anna1 somatic and special senses. suzanne d'anna2 senses n constantly provide us...
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Suzanne D'Anna 2
Senses constantly provide us with information
about our surroundings Grouped into two major categories:
- general senses
- special senses
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Sensory Pathway Includes:
- receptors
- sensory neurons
- sensory tracts
- sensory area
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Receptors detect stimuli specific with respect to changes to which
they respond
Sensory Neurons transmit impulses from receptors to central
nervous system found in both spinal and cranial nerves
(each carries only one type of receptor)
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Sensory Tracts white matter in spinal cord or brain transmit impulses to a specific part of brain
Sensory Areas most are in cerebral cortex feel and interpret sensations learning to interpret sensations begins in infancy
without awareness and continues throughout life
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General Senses Somatic:
- tactile - touch, pressure, vibration, itch, etc.
- thermal - hot and cold
- pain - acute and chronic
- proprioceptive - muscle, tendon, joint Visceral
- distension of viscera - internal organs
- chemical composition of extracellular fluid
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Special Senses Somatic:
- visual - sight
- auditory - hearing
- equilibrium - static and dynamic equilibrium Visceral:
- olfactory - smell
- gustatory - taste
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Tactile Sensations Touch receptors:
- root hair plexuses
- tactile discs
- type II cutaneous mechanoreceptors
- corpuscles of touch - (Meissner’s corpuscles)
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Root Hair Plexuses dendrites arranged around hair follicles receptors that rapidly adapt to detect
movements when hair is disturbed
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Tactile Discs expanded (flattened) nerve endings slowly adapting touch receptors for
discriminative touch
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Type II Cutaneous Mechanorecptors also called end organ for Ruffini expanded nerve endings embedded in dermis receptors that adapt slowly to heavy
and continuous touch
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Corpuscles of Touch (Meissner’s Corpuscles)
small, oval, encapsulated nerve endings rapidly adapting touch receptors recognize exactly what point to which
body is touched abundant in hairless portions of skin
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Corpuscles of Touch (cont.)
rapidly adapting receptors that respond to low frequency vibrations
also respond to pressure and touch stimuli
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Tactile Sensations Pressure and vibration receptors:
- corpuscles of touch (Meissner’s)
- lamellated corpuscles (Pacinian)
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Lamellated Corpuscles(Pacinian)
oval structures composed of connective tissue layered like an onion enclose a dendrite rapidly adaptive receptors that respond
to pressure and high frequency vibrations
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Tactile Sensations(itch and tickle receptors)
free nerve endings are receptors for both tickle and itch sensations
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Thermal Sensations(thermoreceptors)
heat receptors most sensitive to temperatures above 25oC (77oF) and become unresponsive at temperatures above 45oC (113oF)
cold receptors most sensitive to temperatures between 10oC (50oF) and 20oC (68oF)
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Thermal Sensations (cont.)
intermediate temperature sensory input from combination of cold and heat receptors
both heat and cold receptors rapidly adapt to continuous stimulation
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Pain Sensations(Nociceptors)
free, naked nerve endings located between cells of epidermis respond to all types of stimuli
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