Motor Systems

Question 1

the final output of the motor system to muscles; the final integration of multiple components of the motor system

Answer 1

motoneurons in the brainstem and spinal cord

Question 2

the site of reflex and some stereotyped motor program circuitry (locomotion)

Answer 2

spinal cord

Question 3

the sites of more rudimentary motor control for activities like posture and movement of the trunk, head, and neck

Answer 3

brainstem nuclei

Question 4

the site of translation of sensory info and volition into a motor plan and execution

Answer 4

motor cortex

Question 5

the site of fine motor control and for conscious aspects of motor learning

Answer 5

motor cortex

Question 6

the control center for coordination and motor learning

Answer 6

cerebellum

Question 7

the site where planned movements are compared to executed movements

Answer 7

cerebellum

Question 8

the control center where overall level of motor activity is set

Answer 8

basal ganglia

Question 9

lesions here result in too much or too little movement

Answer 9

basal ganglia

Question 10

where are the cell bodies (which interpret info)

Answer 10

gray matter

Question 11

lower motor neurons aka

Answer 11

alpha motor neurons

Question 12

where are the motoneurons for a muscle usually located?

Answer 12

in a column within the VENTRAL horn of the spinal cord over several spinal levels

Question 13

muscle unit consists of

Answer 13

just extrafusal fibers

Question 14

motor unit consists of

Answer 14

nerve AND fibers (motoneurons AND muscle unit)

Question 15

in Rexed’s lamina IX: proximal motorneuron pools are more ( ) than the distal muscls

Answer 15

medial

Question 16

in Rexed’s lamina IX: flexor motoneuron pools are usually more ( ) to extensor motoneuron pools

Answer 16

dorsal

Question 17

the number of muscle fibers innervated by one motoneuron depends on what?

Answer 17

1) the motoneuron’s properties

2) the muscle in question

Question 18

large limb muscles can have motor units with more than ( ) muscle fibers; extraocular muscles can have motor units with less than ( ) muscle fibers

Answer 18

1000; 10

Question 19

gamma motoneurons innervate ( ) muscle fibers; aplha motoneurons innervate ( ) muscle fibers

Answer 19

intrafusal; extrafusal

Question 20

what motor units have slow contraction times?

Answer 20

type s

Question 21

what motor units have fast contraction times?

Answer 21

type FR and type FF

Question 22

motor unit: fatigue resistant and produce little force

Answer 22

type s

Question 23

motor unit: fatigue resistant and make more force

Answer 23

type FR

Question 24

motor unit: fatigable and produce most force

Answer 24

type FF

Question 25

properties of muscle units such as force are correlated with the motor unit “types” and are largely due to differences in

Answer 25

numbers of muscle fibers in different types of motor units

Question 26

the end product of motor unit activation is a combo of what?

Answer 26

1) muscle BIOCHEMICAL properties
2) NUMBER of muscle units
3) FREQUENCY of muscle activation

Question 27

small motoneurons innervated with how many muscle fibers o make type S motor units?

Answer 27

relatively few

Question 28

Ohm’s law for small motoneurons

Answer 28

• lower conductance (fewer ion channels to conduct current through)
• higher R
• greater depolarizaion (v) for a given current (I)

Question 29

if synaptic ( ) is high enough, a motoneuron will depolarize sufficiently enough to fire an AP

Answer 29

current

Question 30

Size Principle of motoneuron recruitment order

Answer 30

smaller motoneurons are recruited before larger motoneurons during a progressively more forceful contraction

Question 31

What happens if you cut a nerve? can those muscle fibers contract?

Answer 31

No. Whether or not it’s S, FR, FF depends on junction (can change biochemical structure)

Question 32

At approximately ( )X the synaptic current neccessary to cause its recruitment, a motoneuron will begin to fire repetitively

Answer 32

1.5X

Question 33

motoneuron and motor unit firing rate

Answer 33

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

Question 34

do the number of motor and muscle units change?

Answer 34

No, the only thing that changes in the number of muscle fibers that contract when they need to and how big they are

Question 35

the more precision control you need over a muscle, the ( ) number of muscle fibers per motor unit

Answer 35

smaller

Question 36

what are used together to control muscle force?

Answer 36

motor unit recruitment and firing rate modulation