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NRSC 434 > week 7 motor control > Flashcards

week 7 motor control Flashcards

1
Q

Organization of neural structures involved in the control of movement

A
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2
Q

Organization of control of movement

A
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3
Q

Motor neuron cell bodies are located and arranged how?

A
  • located in ventral horn of spinal cord
  • Arranged logically along body axis.
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4
Q

within the ventral horn of the spinal cord

A

there is a medial-to-lateral topographical map of body muscles

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5
Q

In addition to sensory input and motor outputs, there are many _______________ in the spinal cord that create networks to control simple motor behaviors (ex: reflexes, balance, coordination)

A

interneurons

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6
Q

define a motor unit

A
  • an a-motor neuron and all of the muscles it innervates
  • two kinds:
    • small (few fibers)
    • large (many fibers)
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7
Q

a muscle fiber is only innervated by one a-motor neuron BUT

A

it takes many a-motor neurons to innervate all the fibers in a complete muscle

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8
Q

How does the brain encode a command for force?

A

rate coding; the rate of AP coming from the brain

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9
Q

what are the three different types of motor neurons? what is different about them?

A
  • fast fatigable
  • fast fatigue resistant
  • slow
  • training can change the amount/proportion of these (ex: long distance runners would build more fast fatigue resistant)
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10
Q

With increased motor unit size, a-motor neurons exhibit:

A
  • increase in:
    • cell body size
    • dendridic complexity
    • short term EPSP potentiaton with repeated activation
    • axonal diameter (faster conduction)
    • # of axonal branches (more muscle fibers innervated)
  • decrease in:
    • input resistance
    • excitability
    • Ia EPSP amplitude
    • PSP decay constant
    • duration of after-hyperpolarization
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11
Q

a-motor neurons vary in:

A
  • cell size
  • excitability
  • axon branches
  • dendrites
  • synapses received
  • input resistance
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12
Q

what types of summation do motor neurons perform and what does this look like?

A
  • temporal summation
  • spatial summation (NOT mutually exclusive)
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13
Q

what is the size principle? why?

A

smaller motor units depolarize sooner than big motor units
- this is bc smaller cell bodies have higher input resistance, which makes it easier to reach AP threshold with few EPSPs
- input resistance refers to the amount of resistance a neuron puts on the flow of electrical current (higher = current cant leave = bigger change in neuron membrane potential)

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14
Q

smaller motor units excite _______ muscle fibers, meaning there is ____ ______.

A

smaller motor units excite FEWER muscle fibers, meaning there is LESS FORCE.

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15
Q

Small and large units can be innervated by the same ____________ ________ __________ and as firing rate ___________ , _________ motor units are recruited

A

Small and large units can be innervated by the same DESCENDING MOTOR PATHWAYS and as firing rate INCREASES , LARGER motor units are recruited

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16
Q

Motor neuron recruitment in the cat medial gastrocnemius muscle under different behavioral conditions

A
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17
Q

Effect of stimulation rate on muscle tension

A
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18
Q

The number of active motor units and their rate of firing both increase with voluntary force

A

(this is an entire motor neuron pool)

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19
Q

a-motor neurons cause __________________

A

MUSCLE BODIES TO CONTRACT

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20
Q

what do y-motor neurons do?

A

ADJUST LENGTH OF MUSCLE SPINDLES

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21
Q

what do Ia and II afferents do?

A

carry feedback about stretch from muscle spindle to the spinal cord a-motor neurons

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21
Q

Stretch reflex circuitry : How spinal circuits modulate motor unit activity.

A
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22
Q

what is the role of γ-motor and a-motor neurons in regulating muscles

A
  • During normal movements, your brain
    sends commands to both α-motor
    neurons and γ-motor neurons to
    coordinate them.
  • This ensures muscles spindles stay
    sensitive and stretch reflexes don’t
    interfere with intended movements.
  • y-motor neurons stop firing when a-motor neurons are stimulated and they are not, but when both stimulated they fire nonstop
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23
Q

Golgi tendon organ makeup

A
  • made up of the capsule (outside)
  • and collagen fibrils (inside)
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24
Q

Golgi tendon organs (GTO) and their role in the negative feedback regulation of muscle tension

A
  • Golgi tendon organs (GTO) relay force info back to spinal cord.
  • Here the GTO is also exciting an excitatory interneuron (purple) to activate antagonist muscle group.
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25
Q
  • _________ ________ ___ _______ _________ can prevent muscle from self-injury.
A

negative feedback via inhibitory interneurons

26
Q

spindle organs and tendon organs respond __________ to passive stretch and active force, but together…

A

differently; they provide sufficient information to smoothly coordinate the amount of stretch and force exerted by the muscle

27
Q

muscle spindles fire _______ when the muscle is stretched, while golgi tendon organs fire more when the muscle is __________.

A

MORE ; CONTRACTED

28
Q

myotatic and inverse myotatic reflexes

A
29
Q

_________ ________ are simple networks controlling simple behaviors

A

spinal reflexes

30
Q

_________ _________ are created by connecting sensory inputs, inhibitory and excitatory interneurons and motor output neurons together to produce desired behaviors

A

Neural Networks

31
Q

Spinal cord circuitry for the flexion–crossed extension reflex

A
32
Q

define Central Pattern Generators

A
  • simple neural networks that control rhythmic motor patterns, often involving the alternating activation of antagonistic muscle groups.
  • Ex: locomotion (swimming, walking), breathing, or even chewing gum.
33
Q

CPGs often include…

A

Pacemaker Neurons, which fire bursts of action potentials spontaneously (without synaptic inputs) and rhythmically.

34
Q

Pacemaker cells (neurons or cardiac muscle) function like other neurons except

A
  • that a leak current slowly and repeatedly depolarizes them to threshold
  • size of this leak channel (# of ion channels) determines how frequently cell fires an AP
  • neurotransmitters and hormones can increase or decrease the leak current, activating or altering the frequency of action potentials
35
Q

what affects the pacemaker cells leak channels

A
  • neurotransmitters and hormones can increase or decrease the leak current, activating or altering the frequency of action potentials
36
Q

Pyloric circuit of crustacean stomatogastric ganglion.

A
37
Q

Breathing requires a CPG that…

A

alternately activates inspiratory or expiratory muscles.

38
Q

Inhibitory interneurons (blue) ensure that…

A

the pacemaker neurons fire out of sync with each other

39
Q

Spontaneously firing (Pacemaker) neurons in medulla that project to motor neurons controlling breathing.

A
40
Q

Locomotion in the Leech and the Lamprey

A

CPGs don’t have to be limited to antagonistic muscle pairs: they can control sequences, such as during leech swimming.

41
Q

The mammalian cycle of locomotion is organized by central pattern generators in the spinal cord

A
  • Highly conserved locomotor pattern in tetrapods controlled by spinal CPGs
  • Spinal cord injury prevents volitional activation of walking, but does not eliminate spontaneous CPG activation by sensory feedback (proprioceptive feedback in legs).
42
Q

Conceptual framework for mammalian CPGs controlling locomotion.

A
43
Q

Organization of neural structures involved in the control of locomotion

A
44
Q

Overview of descending motor control

A
45
Q
  • there are ____________ ______ of the body in the spinal cord
A

topographical maps

46
Q

fill in the blanks

A
47
Q

Motor Representation on the Cerebral Cortex

A

the numbers refer to Brodmann’s areas

48
Q

fMRI Images of Human Primary Motor Cortex

A
49
Q

in what layer of the primary motor cortex are Betz cells found

A

5

50
Q

Cytoarchitectonic appearance of the primary motor cortex in the human brain

A
51
Q

Corticobulbar tracts project from…

A

cortex to midbrain central pattern generator areas that coordinate major muscle groups for things like walking.

52
Q

Corticospinal pathways project from…

A

cortex directly to spinal motor neurons that control specific muscles and motor units, thereby supporting more complex learned behaviors.

53
Q

Direct pathways that activate hand movements also engage… that ensure maintenance of posture and balance

A

indirect pathways through brainstem

54
Q

???

A
55
Q

The influence of single cortical upper motor neurons on muscle activity

A
56
Q

What is the “receptive field” for an M1 neuron?

A
57
Q

Early models described M1 as ___________ ________ _____but couldn’t explain ___________ __________

A

topographical (somatotopic) map ; functional organization

58
Q

Functional connectivity patterns make it difficult to envision ….

A

how the system works as a whole

59
Q

How are coordinated movements encoded by motor cortex?

A

Neurons in motor cortex show activity related to specific movement directions:
Yellow indicates increased firing rates just before and during moving.
Blue indicates shows suppressed activity for opposite directions.

60
Q

Population Vectors:

A

groups of cortical motor neurons show coordinated activity that drives movements in a particular direction (vector).

61
Q

Mirror Neurons:

A
  • are active during execution of a task, but are similarly activated by watching someone else perform the same task.
  • Remains unclear what the function of these premotor neurons do, but hypothesized that they are important for learning new tasks from observation.
62
Q

Minds and Machines : the challenges to create Brain-Machine Interfaces (BMI)

A

NRSC 434 (16 decks)

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