Somatosensation Flashcards
characteristics of all somatosensory neurons
have cell bodies in dorsal root ganglion, all unipolar (only one neurite), all neuron project through dorsal root
proprioreceptors
skeletal muscle, “body sense,” thickest diameter, fastest APs
mechanoreceptors
skin, touch, second thickest diameter
nociceptors
myelinated: pain, temperature, second thinnest
non-myelinated: temperature, pain, itch, thinnest
what determines what a mechanoreceptor can detect?
type of specialized endings, location in the skin, rate of adaptation (rapid: good for things that are changing or slow: good for things that are constant), size of receptive field
how is mechanoreceptor information organized?
spinal segments: where neurons go into vertebra
dermatomes: area of skin innervated by the right or left dorsal root of a single spinal segment
how does mechanoreceptor information travel?
may stay in the spine (reflexes) OR project to the medulla (where decussation occurs) -> thalamus -> primary somatosensory cortex
how is mechanoreceptor information stored?
somatotopy (homunculus), columnar organization (parallel processing)
cortical plasticity
“use it or lose it,” representation of an area in the brain decreases if we don’t use the body part it controls, a neighboring region can increase its area as a result
how do nociceptors detect noxious stimuli?
mechanical, thermal (trp channels), and chemical stimuli can activate nociceptors
variations in pain intensity
alpha-beta fiber (mylinated) detects the first, sharp pain after the stimulus. C fiber (not mylinated so info travels slower) detects second, dull, longer-lasting pain
how does nociceptor information travel?
decussation occurs in the spinal cord after synapsing -> project to the medulla -> thalamus -> primary somatosensory cortex and diffuse projections
