chapter 15 part 1 Flashcards
what are the three parts of the somatosensory system
cutaneous sense: perception of touch and pain from stimulation of the skin
proprioception: ability to sense position of the body and limbs
kinesthesis: ability to sense movement of the body and limbs
what is the heaviest organ in the body
skin
function of skin
protects the organism by keeping damaging agents from penetrating the body, prevents body fluids from escaping, and provides information about the various stimuli that contact it
epidermis vs dermis
epidermis: outer layer of the skin, made up of dead skin cells
dermis: below the epidermis and contains mechanoreceptors that respond to stimuli such as pressure, stretching, and vibration
slowly adapting (SA1) fiber vs rapidly adapting (RA1) fiber
nerve fibers associated with merkel receptors are called slowly adapting fibers because they fire continuously, as long as the stimulus is on
nerve fibers associated with the meissner corpuscle are called rapidly adapting fibers because they fire only when the stimulus is first applied and when it is removed
what are the two types of mechanoreceptors close to the surface of the skin, near the epidermis?
merkel receptors: fire continuously while stimulus is present and responsible for sensing fine details
meissner corpuscle: fires only when a stimulus is first applied and when it is removed and responsible for controlling hand grip
because these receptors are located close to the skin they have small receptive fields
what are the two types of mechanoreceptors located deeper in the skin?
ruffini cylinder: fires continuously to stimulation and associated with perceiving stretching of the skin - slowly adapting fiber
pacinian corpuscle fires only when a stimulus is first applied and when it is removed. Associated with sensing rapid vibrations and fine texture - rapidly adapting fiber
what are the two major pathways in the spinal cord from skin to cortex?
medial lemniscal pathway: large fibers that carry proprioceptive (sensing position of limbs) and touch information - high speed, large fibers
spinothalamic pathway: smaller fibers that carry temperature and pain information
these cross over to the opposite side of the body and synapse in the thalamus
how do we measure tactile acuity?
two point threshold: minimum separation needed between two points to perceive them as two units - most common
grating acuity: placing a grooved stimulus on the skin and asking the participant to indicate the orientation of the grating
raised pattern identification: using such patterns to determine the smallest size that can be identified
what causes high tactile acuity in the fingers/ receptor mechanisms for tactile acuity
high density of merkel receptors in the fingertipes
densely packed, similar to cones in the fovea
two point thresholds and grating acuity both show these results
cortical mechanisms for tactile acuity
body areas with high acuity have larger areas of cortical tissue devoted to them
secondary somatosensory cortex
both the primary (S1) and secondary (S2) somatosensory cortex receive signals from the thalamus
S2 processes neural signals related to touch, temperature, and pain
