Lecture 10: Spinal Cord, Brainstem, & Cortex Control of Motor Function Flashcards Preview

Human Physiology 2 - Unit 2 - Zach H. > Lecture 10: Spinal Cord, Brainstem, & Cortex Control of Motor Function > Flashcards

Flashcards in Lecture 10: Spinal Cord, Brainstem, & Cortex Control of Motor Function Deck (61)
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1

What are the 3 groups of neurons in the spinal cord?

  • Sensory (afferent)
  • Anterior motor neurons (efferent)
  • Interneurons

2

What is a motor unit composed of?

  • Composed of a single motor neurons and the muscle fibers it innervates.
  • Composed of extrafusal fibers.

3

What is a motor neuron pool?

Group of motor neurons that innervate fibers within the same muscle.

4

When talking about motor units, what does the term recruitment refer to?

Refers to the increase in tension of muscle contractions by the activation motor units (size principle).

5

What are the characteristics of small motor neurons?

  • innervate a few muscle fibers
  • lowest thresholds
  • fire first
  • generate smallest force

6

What are the characteristics of large motor neurons?

  • innervate many muscle fibers
  • highest thresholds
  • fire last
  • generate largest force

7

Do small or large motor neurons fire first?

Small motor units fire first.

8

What are Renshaw cells?

Inhibitory cells in anterior horns of the spainal cord.

9

From what cell type do Renshaw cells receive collateral branches from?

Receive collateral braches from alpha motor neurons.

10

What is the function of Renshaw cells?

  • Transmit inhibitory signals to surrounding motor neurons.
    • results in lateral inhibition
    • enhance fluidity of limb movement
  • Transmit inhibitory signals to same motor neuron.
    • results in recurrent inhibition

11

What action of Renshaw cells enhance fluidity of limb movement?

Transmission of inhibitory signals to surrounding motor neurons.

12

List the functions of interneurons?

  • 30x as numerous as anterior motor neurons
  • small and highly excitable
  • capable of spontaneous activity
  • responsible for most of spinal cord integrative function

13

Are interneurons capable of spontaneous activity?

Yes

14

Which cells are responsible for most of the spinal cord integrative functions?

Interneurons

15

Which fiber type does alpha motor neurons give rise to?

A-alpha fibers

16

List the different muscle sensors?

  • Muscle spindle (group Ia and II afferents)
  • Golgi tendon organ (group Ib afferents)
  • Pacinian corpuscles (group II afferents)
  • Free nerve endings (groups III and IV afferents)

17

Which muscle sensor detects noxious stimuli?

Free nerve endings (groups III and IV afferents)

18

Which muscle sensor detects vibration?

Pacinian corpuscles (group II afferents)

19

Which muscle sensor is arranged in parallel with extrafusal fibers?

Muscle spindle (group Ia and II afferents)

20

Which muscle sensor is arranged in series with extrafusal fibers?

Golgi tendon organ (group Ib afferents)

21

Which muscle fiber detects BOTH dynamic and static changes in muscle length?

Muscle spindle (groups Ia and II afferents)

22

Which muscle sensor detects muscle tension?

Golgi tendon organ (group Ib afferents)

23

Which nerve fiber types are myelinated and which are not?

  • Groups I, II, and III -> myelinated
  • Group IV -> non-myelinated

24

What type of neurons are muscle spindles innervated by?

small gamma motor neurons (group II afferents)

25

Describe the central region of a muscle spindle?

  • Central region of spindle has no contractile fibers; functions as a sensory receptor.
    • sensory fibers originate from central region
    • stretching of central region of intrafusal fiber stimulates sensory fibers

26

You know that muscle spindles consist of 3-12 intrafusal fibers. What are the characteristics of these intrafusal fibers?

  • innervated by small gamma motor neurons (group II afferents)
  • encapsulated within a sheath to form muscle spindle
  • run parallel to extrafusal fibers

27

True or False:

Extrafusal fibers make up the "muscle fibers", which are innervated by alpha motor neurons.

True

28

What are the two types of intrafusal fibers?

  • Nuclear bag fibers
  • Nuclear chain fibers

29

What do nuclear bag fibers, a type of intrafusal fiber, detect?

Detect rate of change in muscle length.

30

What do nuclear chain fibers, a type of intrafusal fiber, detect?

Detect static change in muscle length.