Lecture 11 Notes F09

Lecture 11 Notes F09 - PSYCH 301 LECTURE 11 Somatosensory...

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PSYCH 301 LECTURE 11 Somatosensory Perception I. Somatosensory   Perception :     bodily   sensations   not   specific   to   a  particular sensory organ. A. There are 3 main types of somatosensory perceptions: 1. Exteroceptive :  skin sensations:  touch, heat, cold, pain. 2. Proprioceptive :  body position determined from receptors in  muscles and joints (we’ll discuss this in the movement lecture), and also the  organs of balance. 3. Interoceptive :   information about the internal, particularly  chemical,   condition   of   the   body   -   temperature,   blood   pressure,   salt   levels,  glucose levels, etc. B. Somatosensory receptive cells : A variety of receptive cells have  been identified in the skin based on cellular morphology.  These cells differ in  depth under the skin, the stimuli which tend to cause them to fire, the size of their  receptive fields and rate of  adaptation .  Some cells adapt quickly, and thus stop  firing on continuous stimulation.  Some receptors adapt slowly and can respond  to continued stimulation. 1. Free nerve endings :   superficial, respond to temperature  change and pain. 2. Pacinian corpuscles :  deep, adapt rapidly, respond to high- frequency vibrations; and   Meissner   corpuscles :   superficial, respond to low  frequency vibrations. 3. Merkel’s  Disks   and   Ruffini endings :     superficial,  adapt  slowly, respond to pressure and stretching of skin.
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4. Ruffini corpuscles :  respond to broad field stimulation 5. In hairy skin (as opposed to glabrous) there are no Meissner  corpuscles, but instead there are  hair receptors . C. Skin perceptions :  sensitivity to particular sensations varies over  the body depending on the concentration of particular receptors. 1. Mechanical  (touch):  use A β  fibers, 2 general types. a. slowly adapting :   Merkel receptor, small receptive  field, and Ruffini corpuscle, large receptive field. b. quickly adapting :  Meissner and Pacinian corpuscles 2. Thermal  (temperature):  Separate hot and cold sensation in  the skin; receptors are generally free nerve endings. a.
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Lecture 11 Notes F09 - PSYCH 301 LECTURE 11 Somatosensory...

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