MODULE 4- Touch + Proprioception Flashcards
how are mechanical forces on the skin conveys to the CNS
via an array of somatosensory affect neurons
what is reflected by the wide variety of mechanical forces that can impinge on the skin
the comparably diverse array of mechanoreceptors embedded in the skin
2 types of skin
-glabrous
-hairy
**glabrous skin
-found on the soles of heads, feet, lips
-capable of highly discriminative touch
**hairy skin
-covers 90% of the body
-capable of both discriminative + non-discriminative touch
somatosensory afferent neurons (2)
-mechanoreceptors
-dorsal root ganglion
**mechanoreceptors
-detect innocuous (harmless) mechanical stimuli impinging on the skin
-transduce mechanical forces into neural signals
-serve as the path by which signals reach the CNS
**dorsal root ganglion
pseudo-unipolar neurons soma with a bifurcating axon with one branch from the PNS + the other to the CNS
trigeminal ganglia/nerve
sensory receptors for the face
**dermatome
the territory innervated by each spinal nerve
-aka each fiber of the cell is from a single dorsal root ganglion
do dermatological maps vary?
yes, they vary among individuals
how do dermatomes maintain sensation
they overlap significantly for touch, pressure, + vibration so that injury to one set of dorsal root doesn’t result in a complete loss of sensation
what are the sensations where dermatomes do not overlap
pain + temperature
how do somatosensory afferent neurons vary
vary widely in
-size
-conduction
-velocity
-types of stimuli to which they respond
-response properties
which afferent sensory neurons have the smallest diameter + slowest velocity
pain + temperature
which afferent sensory neurons have medium diameter + medium velocity
cutaneous mechanoreceptors
which afferent sensory neurons have the largest diameter + fastest velocity
muscle spindles
where else are muscle spindles used
balance
**receptive fields
the area of the skin surface that results in the firing of APs when touched/activated
**how is size of receptive field determined
by the amount of branching of the afferent axons
**what test determines size of receptive field
2-point discrimination test
**2-point discrimination test
-uses calipers to measure
-distinguishing closer together is harder than far apart
**somatic acuity
how sensitive each region is
-region-specific
-some body parts are more sensitive than others
why are some body parts more sensitive than others
due to overlapping receptive fields in the former