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Neuroscience > Ch. 10: The Motor System > Flashcards

Ch. 10: The Motor System Flashcards

1
Q
  1. What is a Lower Motor Neuron (LMN)?
  2. What does it connect?
  3. Is it located Superior or Inferior?
A
  1. “Peripheral” motor neurons
  2. Spinal cord to muscle
  3. Inferior
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2
Q
  1. What is an Upper Motor Neuron (UMN)?
  2. What does it connect?
  3. Is it located Superior or Inferior?
A
  1. “Central” motor neurons - “descending tracts”
  2. Head to spinal cord
  3. Superior
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3
Q

What is the neurotransmitter of muscle contraction?

A

ACh

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4
Q

What is the ion of muscle movement?

A

Calcium

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5
Q

Which contractile protein moves over the other: Actin or Myosin?

A
  • Actin mvoes on myosin
  • Myosin stays still
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6
Q

What is the M line?

A

Anchors Myosin

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7
Q

What is the Z line?

A

Anchors Actin

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8
Q

What is Titin and what is its function?

A
  • Rubber band like sarcomere
  • Stabilize muscle aginst stretch or overstretch
  • Does NOT cause muscle contraction
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9
Q

What is Active Stiffness?

A
  • Contraction of muscles
    • Conscious/intentional = normal
    • Unconscious/unintentional = pathological
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10
Q

What is Reflex Activity?

A
  • Type of active stiffness
  • Branches of sensory neurons can activate lower motor neurons
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11
Q

What is Intrinsic Stiffness?

A
  • Weak attachments of actin and myosin (velcro)
  • happens when you do not move - easily broken apart
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12
Q

What is Passive Stiffness?

A

Limits of stretching out Titin

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13
Q

What sarcomere length produces maximal force?

A

Mid length

(starting patient here is easiest for them)

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14
Q

What is a contracture?

A

Loss of muscle fibers shortens muscle

(can result from shortened immobilization)

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15
Q

What is Serial Casting or Chronic Stretching?

A

stretching the promotes the addition of sarcomeres

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16
Q

What is co-contraction or joint stiffness?

What are the 2 types?

A

Partial or full contraction of muscles on both sides of a joint or “around” a “body segment”.

  1. Static (stiffly lock a joint) - tightening on both sides
  2. Dynamic (control movement of a joint) - one side shortens, one lengthens
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17
Q

LMN’s:

What are the two types?

A
  1. Alpha motor neurons (A-alpha).
    • Innervate extrafusal muscle fibers = contract muscle
  2. Gamma motor neurons (A-gamma).
    • Innervate intrafusal muscle fibers = keep spindle sensitive during movement
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18
Q

What is a motor unit?

A

1 peripheral axon and the muscle FIBERS it innervates

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19
Q

What is the order of recruitment (Henneman’s size principle)?

A

Usually slow twitch first, then fast

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20
Q

For gross motor control, how many muscle fibers per axon?

A

Many

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21
Q

For fine motor control, how many muscle fibers per axon?

A

Few

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22
Q

What is Alpha-Gamma co-activation?

A
  • Simultaneous activity in A-alpha and -gamma motor neurons - intra and extrafusal muscle fibers contract at the same time
    • Occurs during all voluntary movement.
    • Functional significance: Activity in alpha and gamma at the same time - muscle spindle sensitive to stretch during voluntary movements
    • Mechanism: Every UMN, xerox message and send copy to alpha and gammas
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23
Q

What happens in the convergence of info on alpha motorneurons?

A
  1. Messages from brain coming down
  2. Messages from sensory receptors coming in
  3. Both converge on peripheral motor neurons
24
Q

What do axons from a motor neuron pool project to?

A

a single muscle

25
Q

How many spinal levels are included in a single pool?

A

could be several

But, only 1 muscle

26
Q

How many dermatomes are included in a single pool?

A

could be several

But, only 1 muscle

27
Q

What is the horizontal organization of the motor neuron pools in the spinal cord?

A

All in ventral horn

  • Medial pools = axial (core) and proximal muscles
  • Lateral pools = distal muscles
  • Anterior pool = more extensors
  • Posterior pool = more flexors
28
Q

What is reciprocal inhibition?

A

Both sides of joint: muscle of interest contracted, muscle on other side is inhibited

  • Connections from upper motor neurons to alpha motoneurons.
    • think to move, inhibition is automatic
  • Connections from muscle spindle afferents to alpha motoneurons.
    • when reflexes affect your muscles, inhibition is automatic
29
Q

What are muscle synergies created by?

A

Any or all of the following:

  • Activation of multiple upper motor neurons
    • multiple messages to move comes from brain
  • Branching of upper motor neurons
    • branches to several different motor neurons
  • Interneurons networks
    • small connecting neurons between other connections
30
Q

What is a “normal” muscle synergy?

A

group of muscle work together under conscious control in any pattern for functional outcome.

31
Q

What is a “abnormal” muscle synergy?

A

group of muscle work together NOT under conscious control in LIMITED pattern AND DON’T ACHIEVE a functional outcome.

32
Q

What is the role of Golgi Tendon Organs in movement?

A
  • Tension in a tendon or muscle
    • Adjusts muscle activity based on tension in context of desired functional activity
33
Q

What are stepping pattern generators?

A

Wiring within spinal cord between spinal cord and brain that supports automatic walking

34
Q

What is a Phasic Stretch Reflex?

A
  • Stimulus = stretch of MUSCLE SPINDLE primary endings
  • Monosynaptic connection
  • Response = brief facilitation or activation of alpha motorneurons in same muscle
35
Q

What is a Withdrawal Reflex?

A
  • Stimulus = activation of nociceptor –> A-delta fiber.
  • Multisynaptic (vertical branching)
  • Response = automatic withdrawal of limb with pain.
36
Q

What is the relationship between reflexes and voluntary movement?

A
  • Sensory input (reflexes) can modify voluntary movements.
  • Voluntary activation of upper motor neurons can modify the effects of reflexes.
37
Q

What motor neurons are considered the “director” tracts?

A

Upper Motor Neurons (UMN)

38
Q

hat motor neurons are considered the “helper” tracts?

A

Lower Motor Neurons (LMN)

39
Q

Where do UMN’s “director” tracts usually start and end?

A
  • Start: cell bodies above the brainstem (in the precentral gyrus)
    • high level of conscious control
  • End: in ventral horn of spinal cord
40
Q

Where does the MEDIAL division of the UMN “director” tracts project?

A

to LMN’s of PROXIMAL arms & legs

“move any way I want”

41
Q

Where does the LATERAL division of the UMN “director” tracts project?

A

to LMN’s of DISTAL arms & legs

“move any way I want”

42
Q

Where do UMN “helper” tracts usually start and end?

A
  • start: have cell bodies in the brainstem
    • heavy lifters - limited concious control
  • end: in ventral horn
43
Q

Where does the MEDIAL division of the UMN “helper” tracts project?

A
  • to LMN’s of prox arm & leg
  • to LMN’s of flexors
    • “Help pick stuff up against gravity”
44
Q

Where does the LATERAL division of the UMN “helper” tracts project?

A
  • to LMN’s of distal arm & leg
  • to LMN’s of extensors
    • “Hold me up and balance me against gravity”
45
Q

Which of the UMN’s have the highest level of conscious control?

A

UMN “director” tracts

46
Q

Which of the UMN’s have the highest level of voluntary control?

A

UMN “director tracts”

47
Q

What are the 2 lateral activation systems that cover both distal extremities?

A
  1. Lateral corticospinal tract - director
  2. Rubrospinal tract - helper
48
Q

What is the Lateral Corticospinal Tract and what does it do?

A
  • biggest director - highest level of control
  • Produces fractionation of movement
    • fine motor control
  • Majority of finers from “primary motor cortex”
    • Crosses midline at bottom of medulla
49
Q

What is the Rubrospinal Tract and what does it do?

A
  • Helper - lower level of control
    • lateral division - more to extensors
  • 100% crosses midline
50
Q

What are the 4 descneding motor tracts (UMN’s) of the medial activation system?

A
  • Medial Corticospinal Tract
    • Director - medial division
  • Reticulospinal Tract
    • Helper - medial division - more to flexors
  • Medial Vestibulospinal Tract
    • Helper - medial division - more to extensors
  • Lateral Vestibulospinal Tract
    • Helper - medial division - more to extensors
51
Q

What is the Reticulospinal Tract and what does it do?

A
  • Helper - medial division - more to flexors
    • Mian helper for “pick stuff up” (esp arms)
    • Projects bilaterally
    • Medial division helper (core & prox muscles)
    • Flexor muscles
52
Q

What is the Medial Corticospinal Tract and what does it do?

A
  • Director - medial division
    • ONLY director of medial core and proximal musclescore & proximal
    • cortico = high level of contral
    • Bliateral projects
53
Q

What is the Medial Vestibulospinal Tract and what does it do?

A
  • Helper - medial division - more to extensors
    • “Keep you upright against gravity”
    • Bilateral projections
    • starts in vestibular nucleus
54
Q

What is the Lateral Vestibulospinal Tract and what does it do?

A
  • Helper - medial division - more to extensors
    • Extend legs to keep you upringt against gravity
    • Unilateral - projects to same side of body
    • Starts in vestibular nucleus
    • Lateral BUT part of core & prox muscle division
55
Q

In the descending Motor Tracts (UMN’s) what are the 2 Nonspecific Activation Ststems?

What do they do?

A
  1. Ceruleospinal Tract
  2. Raphespinal Tract

Connect emotional and autonomic system (back to spinal cord) to motor neurons → inc activity of all other motor neurons/tracts

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