Lecture 10: Control Of Motor Function Flashcards Preview

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Flashcards in Lecture 10: Control Of Motor Function Deck (41)
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1
Q

What fibers give rise to A(delta) fibers?

A
  • alpha motor neurons
2
Q

What is a single motor neuron of extramural fibers that act on specific muscle fibers?

A
  • motor unit
3
Q

What is the purpose of the motor neuron pool?

A
  • this group of motor neurons innervate fibers writhing the same muscle
4
Q

When multiple motor units are activated to increase the tension of muscle tension refers to what?

A
  • recruitment
5
Q

What is recruitment?

A
  • increasing the tension of muscle contractions by activating additional motor units
6
Q

What is the difference of how many fibers a small motor neuron and a large motor neuron innervate?

A
  • small= few fibers

- large= multiple fibers

7
Q

Small and large motor neurons have different thresholds. What is the difference?

A
  • small= lowest threshold

- large= highest threshold

8
Q

Large and small motor neurons differ in which fire. How do they differ?

A
  • the small neurons fire first, while the larger neurons fire last.
9
Q

How do small and large motor neurons differ in relation to force generated?

A
  • small neurons generate smallest forces while the largest generated much larger forces.
10
Q

What are Renshaw cells?

A
  • inhibitory cells of anterior horns of spinal cord, that receive collateral branches from alpha motor neurons
11
Q

What signals to Renshaw cells release?

A
  • release an inhibitory signal to other motor neurons.

- this results in lateral inhibition and enhances the fluidity of limb movement.

12
Q

What type of signaling and from what structure will recurrent inhibition be generated?

A
  • inhibitory signals are generated by the Renshaw cells, acting on the same motor neuron to produce recurrent inhibition
13
Q

Renshaw cells are able to transmit inhibitory signals to the same motor neuron, resulting in:_________

A
  • recurrent inhibition
14
Q

What are the different kinds of muscle sensors?

A
  • muscle spindle ( Ia, II afferent)
  • Golgi tendon organ (Ib afferent)
  • pacinian corpuscle (II afferent)
  • free nerve endings (III, IV afferent)
15
Q

The muscle spindle muscle sensors are arranged how, and produce what function?

A
  • parallel with the extramural fibers

- these detect both dynamic and static changes in muscle length

16
Q

The Golgi tendon muscle sensor is primarily responsible to what?

A
  • detects the muscle tension and therefore should be arranged in series with extrafusal fibers
17
Q

What do pacinian corpuscles most likely detect?

A
  • vibration
18
Q

Describe the components that form the muscle spindle.

A
  • innervation by small gamma motor neurons, that are encapsulated within a sheath. This sheath will then run parallel with muscular fibers
19
Q

Where are no contractile fibers contained that act as a sensory receptor for the muscle?

A
  • the muscle spindle
20
Q

How is the muscle spindle able to function as a sensory receptor?

A
  • the stretching of the central region of the intrafusal fibers generates a response.
  • therefore this structure (muscle spindle) functions to detect muscle length changes
21
Q

What type of function will consist of increased muscle spindle numbers?

A
  • finer movement require more spindles
22
Q

What are the types of intrafusal fibers?

A
  • nuclear bag fibers

- nuclear chain fibers

23
Q

What is the function of nuclear bag fibers?

A
  • detect the rate a muscle length changes
  • innervated by Ia afferent and dynamic gamma efferent
  • bag like configuration
24
Q

What do nuclear chain fibers do to function as an intrafusal fiber in the muscle spindle?

A
  • detect static changes in muscle length
  • group II (afferent) gamma (efferent) fibers
  • more numerous and contain multiple nuclei in a single row
25
Q

What happens when the sensory fibers from the central region of intrafusal fibers are stimulated?

A
  • stimulation occurs when the muscle lengthens and activates the alpha motor neurons, which will cause contraction and shortening of the muscle.
26
Q

What are spindle gamma motor neurons?

A
  • fibers that innervate intrafusal fibers and adjust the sensitivity of the muscle spindle.
  • these are coactivated with alpha motor neurons that are stimulated from a muscle being stretched.
27
Q

What are the different gamma motor neurons taht are stimulated?

A
  • gamma dynamic stimulate nuclear bag intrafusal fibers

- gamma static stimulate nuclear chain intrafusal fibers

28
Q

What is in control of the gamma motor neurons?

A
  • bulboreticular region of brain stem
  • cerebellum
  • basal nuclei
  • cerebral cortex
29
Q

What role does the muscle spindle play within dynamic stretch?

A
  • signals are transmitted to primary nerve endings, that are elicited by rapid stretch or unstretch
  • this will oppose sudden muscle length changes
30
Q

What is the function of static reflex of the muscle spindle?

A
  • this reflex is stimulated by primary and secondary endings that allow for degrees of contraction to remain constant
31
Q

The combination of dynamic stretch reflex, and static reflex of the muscle spindle provide what function?

A
  • provides damping which prevents jerkiness with body movements.
32
Q

What are the nerve fibers that play a significant role in the Golgi tendon organ?

A
  • Ib afferent synapse with an inhibitory interneuron, that synapse with an anterior motor neuron
33
Q

Why is a person unable to inhibit the knee-jerk reflex?

A
  • this consists of a Monosynaptic reflex, which prevents a inhibition from other neurons, that would occur in Polysynaptic reflexes.
34
Q

Understand the flexor and crossed extensor reflexes on figure 55-9

A

.

35
Q

What is after discharge?

A
  • the results of persistent neural activity in Polysynaptic circuits.
    Therefore it will prevent muscle from relaxing for some amount of time.
36
Q

What are the functions of the premotor and supplementary motor areas?

A
  • generate plan for movement
  • premotor cortex develops a “motor image” of the muscle movement that will be performed
  • supplementary cortex mentally rehearses a movement
37
Q

What does the supplementary motor cortex do?

A
  • provides sequence for complex motor sequences and is responsible for mental rehearsal of a movement
38
Q

What does the premotor cortex do?

A
  • develop a diagram of what the total movement will look like with respect to the muscle.
39
Q

Where will more complex patterns of movement be generated? More complex than what the primary motor cortex could form.

A

Premotor and supplementary motor areas.

40
Q

Where does the posterior motor cortex send its signal sequence?

A
  • primary motor cortex into the basal nuclei and thalamus and then into the primary motor cortex.
41
Q

What is an interneuron?

A
  • responsible to spinal cord integrative function that is small, highly excitable, and reacts spontaneously