Physiology: Somatosensory System Flashcards
how can you increase passive current speed in an axon?
decrease axonal resistance (increase diameter)
increase membrane resistance (myelin)
two types of synapse
- excitatory
2. inhibitory
excitatory synapse transmitter
glutamate- cation, ionotropic
inhibitory synapse transmitters
GABA
glycine
what type of vesicles are ACh, amino acids and amines released from?
synaptic vesicles
what type of vesicles are peptides released from?
secretory vesicles
define ionotropic
act directly
define metabotropic
act indirectly
what does the somatosensory system mediate?
fine touch proprioception temperature nociception pruriception
pathway of the somatosensory system
- 1st order neuron (primary sensory afferent) with cell body in dorsal root or cranial ganglia
- 2nd order neuron with cell body in dorsal horn of spinal cord or brainstem nuclei
- 3rd order neuron has cell body in thalamic nuclei
location of the somatosensory cortex
parietal lobe
how is the somatosensory cortex divided?
Brodman’s areas
if a territory is lost others expand into it and occupies more of the cortex > remapping is a continuous process
sensory receptors in the skin
- free nerve endings
- Meissner’s corpuscles
- Merkel’s discs
- Pacinian corpuscles
- Krause end bulbs
- hair-end organs
- Ruffini endings
where are meissner’s corpuscles located?
not in hairy skin
what do meissner’s corpuscles mediate?
touch
where are merkel’s discs present?
hairy skin
what do merkel’s discs mediate?
touch
what do pacinian corpuscles mediate?
pressure
where are Krause end bulbs found?
dry skin
mucous membranes
where are Ruffini endings found?
joint capsule
what inputs to the gracile nucleus of the DCLM pathway?
below T6
what inputs to the cuneate nucleus of the DCLM pathway?
above T6
