PHGY 209 CNS lecture IV

PHGY 209 CNS lecture IV - PHGY 209 CNS lecture IV-somatic...

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PHGY 209 CNS lecture IV-somatic sensation November 1. 2008 Mechanoreceptors Neurons (nerve endings) are all the same. Is the tissues that surround them, it give them different properties. Shallow layers Meissner’s corpuscle- big receptors close to the glabrous skin (hairless). Fluid filled structures that enclose the nerve terminal. They are rapidly adapting (very sensitive to temporal changes) light stroking and fluttering. They are easily activated due to their proximity to the surface hence sensitive to light touch. Merkel disk- small epithelial cells around the nerve terminal. Slow adapting, good at detecting pressure and texture. Deeper layers Pacinian corpuscle – like an onion. Nerve endings wrapped in layers of connective tissue. Rapidly adapting and activated by strong vibrations. (Deep – only sensitive to strong, rapid adapting = only sensitive to vibrations but not pressure) Ruffini endings-nerve endings wind around a spindle like structure. Slowly adapting- stretch and bend. (able to tell you the shape of the object) Proprioception -Receptors that tell you the position of your limbs. Located within the muscles. Activation of mechanoreceptors -from physical deformation. Ion channels are all linked up with cytoskeleton strands. Mechanical deformation pull/loosen the cytoskeleton strands and open up the ion channels and the nerve endings depolarizes. This change of mechanical stimulus to electrical signal/response is called transduction. Activations of rapidly adapting receptors give rise to sensations of touch, movement, and vibrations. Activations of slowly adapting receptors give rise to sensations of pressure. Thermoreceptors Different from mechanoreceptors in the sense that they are free nerve endings. The nerve endings have channels that are sensitive to temperatures. There are two classes –
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PHGY 209 CNS lecture IV - PHGY 209 CNS lecture IV-somatic...

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