Spinal Cord Motor Circuits Flashcards
Somatosensory receptor process
Stimulus interacts with receptor…moves down axon into trigger zone and causes AP if high enoguh threshold
Frequency of AP generated depends on
Intensity and duration
If higher intensity - more
If longer - more
In somatosensory, first order neuron is always
Excitatory
If stimulus applied to center of receptive field
Greater response initiated than it in peripheral region
Higher order somatosensory neurons
Can be excititory or inhibitory
Have central excitatory field with a surrounding inhibitory region
Lateral inhibition
If touch in the center, excitatory repsonse in the middle while inhibitory from the peripheral
Helps define 2 point touch
3 types of central motor system movements
Voluntary
Rhythmic
Reflex
Muscle spindles and golgi tendons
Spindle - positive feedback that induces contraction when stretched
Golgi - reduces force of contraction to compensate the load
Extra vs intrafusal innervation
Extra - alpha, fast
Intra - gamma, sloweer
Static and dynamic muscle spindle sensory
Static - 1a, fast acting and sense change
Dynamic - 2…duration and tension
Passive stretching
Increases firing of 1a afferent which activates alpha motor neurons to increase tnesion
Golgi tendon
Sensitive to contraction
1b afarents ysnapse on inhibitory interneurons that innervate alpha neurons and inhibited alpha neuron contraction
CPG
Rhythmic activity capable in absence of phasic sensory input from peripheral receptors
Bilateral half inhibt opposing muscle groups within ipsilateral and 180 out of phase with contralateral half center
Walking - lesion spinal cord or mesencephalic locomotion region
Spianl - can walk but not weight bear
MLR - stimulation responsible for initiating walking
Important descending pathways in CPG
R/F, RN, VN
