Motor Systems Flashcards
the final output of the motor system to muscles; the final integration of multiple components of the motor system
motoneurons in the brainstem and spinal cord
the site of reflex and some stereotyped motor program circuitry (locomotion)
spinal cord
the sites of more rudimentary motor control for activities like posture and movement of the trunk, head, and neck
brainstem nuclei
the site of translation of sensory info and volition into a motor plan and execution
motor cortex
the site of fine motor control and for conscious aspects of motor learning
motor cortex
the control center for coordination and motor learning
cerebellum
the site where planned movements are compared to executed movements
cerebellum
the control center where overall level of motor activity is set
basal ganglia
lesions here result in too much or too little movement
basal ganglia
where are the cell bodies (which interpret info)
gray matter
lower motor neurons aka
alpha motor neurons
where are the motoneurons for a muscle usually located?
in a column within the VENTRAL horn of the spinal cord over several spinal levels
muscle unit consists of
just extrafusal fibers
motor unit consists of
nerve AND fibers (motoneurons AND muscle unit)
in Rexed’s lamina IX: proximal motorneuron pools are more ( ) than the distal muscls
medial
in Rexed’s lamina IX: flexor motoneuron pools are usually more ( ) to extensor motoneuron pools
dorsal
the number of muscle fibers innervated by one motoneuron depends on what?
1) the motoneuron’s properties
2) the muscle in question
large limb muscles can have motor units with more than ( ) muscle fibers; extraocular muscles can have motor units with less than ( ) muscle fibers
1000; 10
gamma motoneurons innervate ( ) muscle fibers; aplha motoneurons innervate ( ) muscle fibers
intrafusal; extrafusal
what motor units have slow contraction times?
type s
what motor units have fast contraction times?
type FR and type FF
motor unit: fatigue resistant and produce little force
type s
motor unit: fatigue resistant and make more force
type FR
motor unit: fatigable and produce most force
type FF
properties of muscle units such as force are correlated with the motor unit “types” and are largely due to differences in
numbers of muscle fibers in different types of motor units
the end product of motor unit activation is a combo of what?
1) muscle BIOCHEMICAL properties
2) NUMBER of muscle units
3) FREQUENCY of muscle activation
small motoneurons innervated with how many muscle fibers o make type S motor units?
relatively few
Ohm’s law for small motoneurons
- lower conductance (fewer ion channels to conduct current through)
- higher R
- greater depolarizaion (v) for a given current (I)
if synaptic ( ) is high enough, a motoneuron will depolarize sufficiently enough to fire an AP
current
Size Principle of motoneuron recruitment order
smaller motoneurons are recruited before larger motoneurons during a progressively more forceful contraction
What happens if you cut a nerve? can those muscle fibers contract?
No. Whether or not it’s S, FR, FF depends on junction (can change biochemical structure)
At approximately ( )X the synaptic current neccessary to cause its recruitment, a motoneuron will begin to fire repetitively
1.5X
motoneuron and motor unit firing rate
frequencies over which a motoneuron’s firing if found to vary corresponding to the frequencies over which its associated muscle unit’s force output is varied between its twitch force and its maximum or tetanic tension
do the number of motor and muscle units change?
No, the only thing that changes in the number of muscle fibers that contract when they need to and how big they are
the more precision control you need over a muscle, the ( ) number of muscle fibers per motor unit
smaller
what are used together to control muscle force?
motor unit recruitment and firing rate modulation
