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BS357: Introduction to Neuroscience I > Chapter 13: Spinal Control of Movement > Flashcards

Chapter 13: Spinal Control of Movement Flashcards

1
Q

Muscles and neurons that control muscles

A

motor system

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2
Q

role of motor system:

A

generation of coordinated movements

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3
Q

Parts of motor control (2 types of motor programs)

A
  1. spinal cord - control of coordinated muscle contraction
  2. brain - modulates control of motor programs in spinal cord
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4
Q

types of muscle

A

smooth, striated

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5
Q

Each muscle has hundreds of (), the fused skeletal muscle cells (multiple nuclei). And each fiber is innervated by a single axon branch from the CNS

A

muscle fibers

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6
Q

Inner movement of arms: (1) -> Promoted by (2) muscles

A
  1. flexion
  2. flexor
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7
Q

outward movement of arms: (1) -> Promoted by (2) muscles

A
  1. extension
  2. extensor
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8
Q

Groups of Somatic Musculature and Distribution of Lower Motor Neurons

A

Axial muscles: trunk movement/ maintaining posture

Proximal muscles: shoulder, elbow, pelvis, knee movement/locomotion

Distal muscles: hands, feet, digits (fingers and toes) movement/manipulation of objects

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9
Q

(): neurons in the brain that supply input to the spinal cord;

A

Upper motor neurons

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10
Q

Somatic muscles are majorly innervated by (1), whose somas are found in (2)

A
  1. lower motor neurons
  2. ventral horn of spinal cord
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11
Q

Motor neurons innervating proximal and distal muscles are found mainly in the (1) segments of the spinal cord, whereas those innervating axial muscles are found (2).

A
  1. cervical and lumbar-sacral
  2. at all levels
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12
Q

Motor neurons controlling flexors lie (dorsal/ventral) to extensors.

A

dorsal

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13
Q

Motor neurons controlling axial muscles lie (lateral/medial) to those controlling distal muscles.

A

medial

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14
Q

() motor neurons directly trigger the generation of force by muscle

A

Alpha

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15
Q

(): motor neuron and all the muscle fibers it innervates

A

Motor unit

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16
Q

(): all the alpha motor neurons that innervate a single muscle

A

Motor neuron pool

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17
Q

The () is one important way the CNS grades muscle contraction

A

rate of firing of the motor unit

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18
Q

Recruiting additional synergistic motor units -> muscles with a large number of small motor units can be ().

A

more finely controlled by the CNS

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19
Q

Inputs to Alpha Motor Neurons (3)

A
  1. sensory input from muscle spindles
  2. upper motor neurons in brain
  3. spinal interneurons
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20
Q

Sensory input from muscle spindles: via (1); provide feedback about (2)

A
  1. stretch receptors
  2. muscle length
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21
Q

Upper motor neurons in the brain: ()

A

initiation and control of voluntary movement and will

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22
Q

Spinal interneurons can be ()

A

excitatory or inhibitory

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23
Q

types of motor units

A

fast and slow motor units

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24
Q

types of fast motor units (fibers)

A

fatigue-resistant (FR)
fatigable (FF)

25
Q

(): large number of mitochondria and enzymes for oxidative energy metabolism, slow to contract, can sustain contraction

A

Red muscle fibers (slow motor unit)

26
Q

(): fewer mitochondria, anaerobic metabolism (no need for O2), contract and fatigue rapidly-escape reflex

A

Fast motor units (White muscle fibers)

27
Q

(): white fibers with moderate strength and fast contractions

A

Fatigue-resistant (FR) fast fibers

28
Q

(): fastest, strongest white fibers, but rapidly fatiguing

A

Fast fatigable (FF) fibers

29
Q

rank strength of contraction of types of motor units

A

FF > FFR > S

30
Q

() are important for transporting AP towards SR to induce significant Ca2+ release

A

T-tubules

31
Q

(): division of myofibril into segments (sarcomeres) by disks

A

Z lines

32
Q

(): two Z lines and myofibril; basic unit of muscle fiber

A

Sarcomere

33
Q

(): series of bristles anchored to Z lines

A

Thin filaments

34
Q

(): between and among thin filaments

A

Thick filaments

35
Q

Muscle contraction occurs when the thin filaments slide along the thick filaments, bringing adjacent Z lines toward one another.

A

Sliding-Filament Model of Muscle Contraction

36
Q

() allows myosin heads (thick filaments) to bind to actin (thin filament)—myosin heads then pivot, causing filaments to slide.

A

Ca+ binding to troponin

37
Q

Sensory feedback from muscle spindles—()

A

stretch receptor (proprioceptors)

38
Q

stretch receptors are specialized for body sense () : how our body is positioned and moving in the space

A

proprioception

39
Q

() axons -> thickest myelinated axons in the boy -> conduct AP very rapidly

A

Group I

40
Q

Stretch reflex: muscle pulled results in () as a result

A

strong and rapid tendency to pull back

41
Q

feedback loop involved in stretch reflex:

A

Bet. G IA axons and alpha motor neurons

42
Q

Discharge rate of sensory axons of Group 1a: related to ()

A

muscle length

43
Q

Innervate intrafusal fibers inside muscle spindle (both ends) -> Like a “sensory organ” of muscle

A

Gamma Motor Neurons

44
Q

Keeps spindle “on air” – sensitive, able to activate Ia axons; Changes set point of the stretch feedback loop

A

Gamma loop

45
Q

() activation -> decrease Ia activity

A

Alpha

46
Q

() activation -> increase Ia activity

A

Gamma

47
Q

Alpha motor neurons can inhibit (1) and stimulate (2) based on sensory input from muscle spindle

A
  1. further muscle stretching
  2. contraction
48
Q

During (), muscle spindle is short and “loosened” -> Ia sensory axons cannot be activated -> no AP transmitted

A

off-air

49
Q
  • Gamma motor neurons work on ends of muscle spindle to keep it ()
A

long and “tight”

50
Q

Additional proprioceptive input—acts like strain gauge— monitors muscle tension.

A

Golgi Tendon Organs

51
Q

Golgi Tendon Organs exist inside (1), among (2)

A
  1. tendons
  2. collagen fibers
52
Q

Golgi Tendon Organs are innervated by () -> deliver signals spinal cord if tendons are stretched

A

Ib axons

53
Q

Tendons are stretched when muscles are ()

A

contracted

54
Q

2 types of sensing in the muscle

A

Spindles in parallel with fibers— sense muscle length
Golgi tendon organs in series with fibers – sense muscle tension

55
Q

function of golgi tendon organs is to: regulate () -> Important for the proper execution of fine motor acts

A

muscle tension within optimal range

56
Q

Golgi tendon organs sense tension in muscle -> fire AP via Ib axons -> stimulate () -> inhibits alpha motor neurons to suppress muscle contraction

A

inhibitory interneurons

57
Q

Most input to alpha motor neurons mediated by ()

A

spinal interneurons

58
Q

Variety of synaptic inputs to spinal interneurons; modulate overall activity of motor neurons

A

Primary sensory axons (e.g. muscle spindles, Golgi tendon organs, etc)
Descending axons from brain
Collaterals of lower motor neuron axons
Other interneurons

59
Q

(): contraction of one muscle set accompanied by relaxation of antagonist muscle

A

Reciprocal inhibition

BS357: Introduction to Neuroscience I (13 decks)

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