Motor Neuron Flashcards
(33 cards)
What’s a neuron pool?
All motoneurons innervating the same muscle
How are lower motor neurons organized?
Spatially (based on what they innervate)
Cluster together, travel together
What type of neurons are alpha and gamma neurons?
Lower motor neurons
What’s a motor unit?
alpha motor neuron + innervated muscle fibers
What’s the innervation factor?
how many fibers controlled by a single alpha neuron
True or False? The fibers of a motor unit are clustered
False. They’re distributed
True or False? Size matters for motor unit force
True
small = precise, large = strong
What are the 3 types of alpha neurons?
Slow, intermediate and fast-fatigable
How does our brain grade muscle force?
By recruiting motor units according to size: S –> FR –> FF
True or False? We’re each born with set amounts of S, FR, FF motor units.
False. Depending on our needs, our bodies can adapt
True or False? Fused tetanus is a better activation frequency than unfused tetanus
False. Unhealthy and unnecessary
What’s muscle tone?
steady level of muscle tension (mediated by group II afferents)
True or False? The spindle always fires if alpha motor neurons are involved.
False. Without gamma neurons, they lose their shape after contraction.
True or False? GTOs are activated by both active and passive stretch.
False. Only active contractions.
How do GTOs counter fatigue and damage?
Inhibit agonist, excite antagonist through interneurons (relaying to alpha neurons)
True or False? Both spindles and GTOs have the same firing rates during active and passive stretch.
False.
During passive stretch, GTO is slow while spindle goes crazy. The opposite is true for active contraction.
What’s the flexion reflex?
painful stimuli –> excite ipsilateral flexor, inhibit ipsilateral extensor.
Opposite contralaterally.
Results in withdrawal of one leg and extension of the other
What are central pattern generators?
Local circuits in charge of rhythmic movements
Where are CPGs located?
In the spinal cord
What’s a key difference between reflexes and voluntary movement?
Voluntary movements don’t have a one to one mapping. (not necessarily the same output for the same input)
Name two examples of upper motor neurons
-Betz Pyramidal cells
-Non-Betz Pyramidal cells
How is M1 organized?
-Based on the body part
-Based on the mvt
What are some evidence suggesting movement organization in M1?
Small currents elicit excitation of several muscles
Movements elicited by far away stimulation sites
1 upper motoneuron –> many lower motoneurons
What’s an advantage of movement based organization in M1?
Easier to program (entire action rather than individual pieces)
