Looks like no one added any tags here yet for you.
long distance circuit neuron
NS cell located in medial ventral horn, which controls axial muscles bilaterally, body position, and location
local circuit neuron
NS cell in lateral ventral horn, which controls limbs ipsilaterally, mediates fine control of distal muscles
γ motor neuron
small diameter NS cell that innervates muscle spindles in intrafusal capsules, sends sensory info about muscle length and its speed of change to 1a and 2a; adjusts tension level in intrafusal muscle fibers
α motor neuron
large diameter NS cell that innervates extrafusal muscle fibers and sends motor info, such as generating force for movement in striated muscles
innervation ratio
how many fibers innervated by a single α motor neuron, low is good for fine muscle control, high good for lots of force, forms motor unit w/ muscle fibers
motor unit
α motor neuron & its fibers
slow
red, rich in myoglobin and mitochondria, fatigue resistant, muscle unit responsible for sustained muscle activation (tonically active); low activation threshold
intermediate
muscles in between S and FF, used for tasks such as walking
fast fatiguable
easily tired, pale, low mt, motor units needed for high force in rapid movements
motor unit plasticity
ability to acquire new motor skills depending on upper MNs in motor units
extrafusal
motor muscle fiber outside spindle; large diameter for produce force via α motor neurons
intrafusal
sensory muscle fiber inside spindle; regulates muscle length via γ motor neurons (dynamic or static), w/ 2 stretch receptors: group Ia and II sensory afferents
group Ia sensory afferent
spiraled bag and chain fibers responding phasically to small stretches, forming excitatory connections on α MNs, which innervate synergistic muscles
reciprocal innovation
contraction of the streched synergistic muscle and relaxation of the antagonist muscle
group II sensory afferent
neuron on chain fibers which fire tonically proportionally to stretch, mediates muscle tone
muscle tone
steady tension level in a muscle
stretch reflex
muscles provide resistance and maintain muscle length as objects get heavier
Golgi tendon organ
reflex regulator located at junction of muscle and tendon, made of collagen 😡, which is innervated by 1b sensory axons, signal slowly during passive muscle stretch, rapidly during contraction; monitor and maintain force
stance
extending muscle, limb stays in contract w/ ground
swing
muscle is flexed, off ground
vestibular nucleus
motor control center responsible for vestibulospinal tract
reticular formation
motor control center responsible for colliculospinal tract
red nucleus
motor control center responsible for rubrospinal tract
medial IZ
region of spinal cord w/ local circuit neurons that synapse w/ medial lower motor neurons
lateral IZ
region of spinal cord where neurons synapse w/ the lateral ventral horn
lateral white matter
spinal cord region responsible for voluntary movement from the cortex
medial white matter
spinal cord region whose axons come from brainstem and control postural muscles
primary motor cortex
where upper MNs mediate planning and initiation of movements in precentral gyrus receiving input from basal ganglia and cerebellum via thalamus
Betz cell
pyramidal cell, w/ largest soma in CNS responsible for distal muscle control found in primary motor cortex
non Betz pyramidal cell
pyramidal cell found in both motor and premotor cortex (all divisions)
Montreal procedure
Dr. Penfield stimulated different brain regions while patients were awake and described reactions, mapped site of precentral gyrus
corticobular tract
pathway from brainstem to local circuit neurons that controls head, neck, and face muscles
lateral corticospinal tract
direct pathway terminating in lateral ventral horn and IZs w/ most axons synapsing on local circuit neurons
ventral corticospinal tract
pathway from medial and dorsal regions of the motor cortex going to the spinal cord
spike triggered avaeraging
method to correlate the activity of an individual neuron w/ muscle activity
premotor cortex
brain region that exerts both indirect (reciprocal projections to primary motor cortex) and direct (axons to corticobular and spinal tracts) control on behavior
closed loop movement
movement encoded by lateral premotor cortex, where external cue is needed to move
open loop movement
movement encoded by medial premotor cortex triggered by internal cues
feedforward adjustment
movement to stabilize posture during movement, where compensatory movements precede primary one, w/ both intiated by cortical upper MNs