somesthesis (14) Flashcards
what are the two categories that tactile receptors can be divided into?
- slowly adapting mechanoreceptors
- rapidly adapting mechanoreceptors
does this statement describe slowly or rapidly adapting mechanoreceptors?
“ big initial burst then maintaining the stimulus over time”
slowly adapting
are meissner’s corpuscles rapidly or slowing adapting?
rapidly
where are meissner’s corpuscles located
in the superficial layers of the skin
tend to be in areas of high sensitivity (finger tips, lips)
are merkel receptors rapidly or slowing adapting?
slow adapting
what are merkel receptors?
a number of diff individual receptors innervated by the same axon
where are merkel’s receptors?
tend to areas of high sensitivity (lips, finger tips)
where are ruffini’s end organs?
tend to be in deeper tissues
also in deep layers of the skin
describe ruffini’s end organs
receptors that are multibranched, encapsulated nerve endings that adapt very little
are pacinian corpuscles rapidly or slowing adapting?
rapidly adapting
where are pacinian corpuscles found?
found in deep tissue & immediately below the skin
what is one function that pacinian corpuscles are important for?
imp for vibration
define a receptive field
portion of the skin directly innervated by the receptor terminals and the area of adjacent tissue through which a stimulus can be conducted to the receptor
describe the relationship between receptor density and receptor field size
inverse relationship
what are the two major parallel systems that carry somatosensory info tot he cerebral cortex?
- dorsal column lemniscal system
2. anterolateral system
what is the dorsal column lemniscal system important for?
carrying high tactile info and spatial discrimination
what is the anterolateral system important for?
Carries info chiefly about pain & temp
where does the first segregation of sensory information begin?
at the end of the spinal cord
describe the path of nerve fibers entering the dorsal column
Nerve fibers entering the dorsal columns pass up these columns on the ipsilateral side to the caudal medulla where they synapse in the dorsal column nuclei (the cuneate & gracile nuclei)
where do fibers of the medial lemnicus synapse?
they synapse on the ventral posterior nucleus of the thalamus
what two categories can the ventral posterior nucleus be divided into
- medial view
- lateral view
medial view of the ventral posterior nucleus of the thalamus:
describe what type of information and where it projects that information to
information from head/neck/face
projects info most laterally in the postcentral gyrus
lateral view of the ventral posterior nucleus of the thalamus:
describe what type of information and where it projects that information to
information from trunk & limbs
projects info most medially in the postcenral gyrus
what are the 4 areas that S1 can be divided into
brodman’s area 3a, 3b, 1 and 2
where do most of the thalamic fibers terminate in?
areas 3a and 3b
where do cells in 3a and 3b project to?
areas 1 and 2
what does area 3a mainly respond to?
deep tissue input
what does area 3b primarily respond to?
to the activation of rapidly or slowing adapting cutaenous receptors
what does area 2 primarily respond to?
to deep pressure
what does area 1 primarily respond to?
activation of rapidly adapting cutaneous receptors
where are most direction sensitive neurons found
found in area 1 and more notably in area 2 (NOT found in 3a or 3b)
what does it mean if a neuron is direction sensitive?
the cell will only respond when a stimulus moves across the skin in a particular direction
