Motor Unit Flashcards
Initial tension and length of the relaxed fibers, prior to their activation
Preload
The opposing force against which a muscle pulls when its activated
Afterload
Extrafusal fiber is innervated by____
a single alpha motor neuron
The particular group of fibers innervated by one particular alpha motor neuron
Motor unit
T/F each muscle fiber is innervated by one alpha motor neuron
True
T/F each alpha motor neuron innervates one muscle fiber
False- alpha motor neurons innervate many muscle fibers
Force generated by a muscle is dependent on what 2 variables
Strength of activation to each neuron fibers (frequency)
Number of fibers activated ( # of motor units)
T/F all motor units are all or none
True- a motor unit is active or not, there is no inbetween
Expresses how many fibers are innervated by one alpha motor neuron
Innervation ratio
Muscles that require precise adjustment in force (ration)
Small innervation ratio
Muscles that produce large sustained levels of force
large innervation ratio
Duration and peak force measured in a single twitch
response characteristic
long contraction time, less force production but fatigue resistant (muscle type)
slow-twitch muscle
Short contraction time, great force production but quick to fatigue
fast-twitch muscle
T/F Muscle contraction is all or none
False- depends on motor unit recruitment and level of activation of motor units
T/F Slow twitch fibers are activated first then Fast twitch
True
T/F All muscles are a mix of slow and fast twitch fibers
True
____ neurons supply slower, weaker motor neurons
Smaller neurons
____ neurons supply faster, stronger motor neurons
Larger neurons
The size of the EPSP is ____ proportional to the size of the neuron
inversely proportional
The external load determines how much _____ must be generated by the muscle
Counteracting force
What are the three parts to voluntary movement
perception
cognition
action
development of a “unified sensory representation” of the
external world and the individual within it
Perception
decision to initiate a course of action that incorporates the
current perception of the individuals place (location) within the external
world
cognition
development of a plan that models the intended action, followed by
execution of that plan
action
Execution of the motor plan involves both ______ and ______ signaling
feedforward and feedback signaling
Feedback runs through the ___ to make corrections of ongoing movements
Cerebellum
What reflexes help with feed back in motor planning
spinal level reflexes
Myotatic reflexes
inverse myotatic reflexes
located with the motor regions of the cortex (e.g. primary motor
cortex), and within the brainstem (e.g. vestibular nuclei, superior colliculus, reticular
formation)
upper motor neurons
alpha and gamma motor neurons within the ventral horns of the
spine, and the motor nuclei of the cranial nerves located within the brainstem
lower motor neurons
descending motor commands that direct fine and specific
movements originate from the______
primary motor cortex
The motor plan is developed in these two area
Premotor cortex and supplementary motor cortex
“movement planning” relayed to
the supplementary motor cortex via the thalamus
basal ganglia
“computation and feedback” relayed
to the primary motor and premotor areas via the
thalamus
Cerebellum
Rather than controlling just one particular muscle, signaling from
individual corticomotoneurons is often distributed to pools of lower
motor neurons to initiate____- muscular actions
coordinated
Specific movements require ___ of neurons to activate
Specific pools
