somatic sensory system Flashcards
give some examples of encapsulated nerve endings
meissner corpuscle
pacinian corpuscle
ruffini corpuscles
give some unencapsulated nerve endings
merkal discs
free nerve endings
hair follicles ??????
give features of meissner corpuscles
encapsulated
on dermal papillae of skin
light, touch, temperature
rapidly adapting
give features of pacinian corpuscle
encapsulated
dermis, joint capsules, viscera
deep pressure, stretch, tickle, vibration
rapidly apadting
give features of ruffini corpuscle
encapsulated
dermis, subcutaneous tissue, joint capsules
heavy touch, pressure, stretch, joint movements
slowly adapting
give features of merkal discs
superficial skin(epidermis)
slowly adapting
light touch, texture, edges and shapes
give features of free nerve endings
wide spread in epithelia and connective tissue
pain heat cold
are hair follicles rapidly or slowly adapting?
rapid and slowly adapting subtypes
compare rapid adapting with slowly adapting nerve endings
rapidly adapting (phasic) which gives information about changes in a stimulus slowly adapting (tonic) which continues to respond as long a stimilus is present (persistant)
how are primary afferent axons classified?
according to conduction velocity (reflects diameter)(faster= larger diameter)
how are skin afferent axons classified?
A—–>C fastest—–>slowest
A group - alpha - beta …. (alpha is fastest)
how are muscle afferent axons classified
numbers I—–>VI fastest—-> slowest
what is a proprioceptor?
sensory receptor that especially responds to position + movement
how are sensory neurons organised?
cell bodies of sensory neurons grouped in dorsal root ganglia + their projections are organised into layers of dorsal horn.
how do info from sensory subtypes get to brain?
via.. medial lemniscal tract (mechanoreceptive and proprioreceptive signals to thalamus) spinothalamic tract (pain and temp signals to thalamus)
what neurons does sensory info travel through to reach higher centres?
first- order neurons (stimulus–>spinal cord)
second-order neurons (signal to thalamus)
third-order neurons (thalamus —> cortex)
how are axons organised in medial lemniscal system?
topographically
what pathway do first order neurons take?
1st order from upper body follow lateral pathway + synapse on 2nd order neurons in CUNEATE NUCLEUS
1st order neurons from lower body follow medial pathway and synpase on neurons in GRACILE NUCLEUS
what do 2nd order neurons do?
croos midline and ascend in medial lemniscus
what doe each DRG innervates?
dermatones
what is discrimination in small and large receptive fields?
large receptive field - low discrimination
small receptive field - high discrimination
