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PT411 Kinesiology & Biomechanics > Week 5 > Flashcards

Week 5 Flashcards

1
Q

What is spatial summation?

A

occurs as stimuli are applied simultaneously but in different areas

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2
Q

What is temporal summation?

A

when a high frequency of action potentials in the presynaptic neuron elicits postsynaptic potentials that summate with each other.

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3
Q

What does a differential amplifier do?

A

Differential amplifiers are used mainly to suppress noise

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4
Q

At what hz range do most motor units fire at?

A

5-2000Hz

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5
Q

What does a high pass filter do?

A

attenuates low frequencies below a certain cutoff frequency and allows frequencies above to pass.

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6
Q

What does a low pass filter do?

A

Low pass filters are used to filter noise from a circuit (wires)

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7
Q

What is the frequency of firing?

A

the number of spikes over an interval of preselected length is counted and then divided by the length of the interval

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8
Q

What is integration in EMG?

A

the mathematical integral of the absolute value of the raw EMG signal.

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9
Q

What is rectification in EMG?

A

processing step to identify the overall strength of the neural drive to the muscle and is correlated with the strength of muscle contraction and its output

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10
Q

What is the difference between half and full-wave rectification?

A
  • Full-wave rectification rectifies the negative component of the input voltage to a positive voltage, then converts it into DC (pulse current) utilizing a diode bridge configuration.
  • Half-wave rectification removes just the negative voltage component using a single diode before converting to DC
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11
Q

What is passive insufficiency?

A

When a multi-joint muscle is lengthened to its fullest extent at both joints, but also preventing the full range of motion of each joint it crosses.

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12
Q

What is active insufficiency?

A

When a multi-joint muscle shortens over BOTH joints simultaneously, and hence, creates so much slack, that muscle tension is almost completely lost.

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13
Q

What factors influence a muscle’s ability to produce movement?

A
  • Length of the muscle fibers
  • Speed of contraction
  • Muscle architecture
  • Size of the muscle’s moment arm
  • Number and type of motor units recruited
  • Reflex drive
  • Antagonist activity
  • GTO inhibition
  • Injury/immobilization
  • Age
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14
Q

What is the resting length of a sarcomere?

A

The length at which actin and myosin are optimally overlapped for cross-bridge formation.

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15
Q

Within multiarticulate muscles which type of insufficiency can occur?

A

Active insufficiency

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16
Q

When a muscle can’t develop force due to the actin-myosin overlap reducing the number of available sites for cross-bridge formation, what is this an example of?

A

Active Insufficiency

17
Q

As you stretch a muscle what happens to tension?

A

Tension progressively increases

18
Q

Based on the passive length-tension curve, as you increase tension and increase muscle length exponentially what might occur?

A

If tension and length become too great the tissues will fail or rupture.

19
Q

What is the utility of passive tension?

A
  • Stores a fraction of energy when stretched
  • Exhibits viscoelastic ← properties
    • this means that it has both viscous and elastic properties to resist shear force. Think of asphalt
  • Both are important for plyometrics
  • Elasticity can serve to protect structural components of the muscle and tendons by absorbing forces.
20
Q

Where does passive insufficiency occur?

A

Multiarticulate muscles

  • Wrist flexors and extensors
  • Hamstrings
  • etc…
21
Q

What is passive insufficiency?

A

In a lengthed muscle, the actin filaments are pulled away from the myosin heads so they cannot create as many crosses-bridges

22
Q

A muscle that can’t stretch enough to achieve full range of motion at all joints it crosses is an example of what?

A

Passive insufficiency

23
Q

What is the sensory receptor located within the muscle that is sensitive to stretch called?

A

Muscle spindle

24
Q

The sensory receptor within the tendon that is sensitive to tension and forces the muscle to relax in order to prevent injury is called what?

A

Golgi Tendon Organ

25
Q

A patient has had their elbow immobilized for an extended period of time in a fully flexed position, what are some of the effects on the muscle?

A
  • Slow-twitch fibers are subjected to more disuse compared to fast-twitch
  • Loss of strength is greatest in a shortened position
  • Decrease in number of sarcomeres
  • Increase in connective tissue
  • Muscle atrophy
26
Q

What are the phases for sit to stand?

A
  1. Flexion-momentum phase
  2. Momentum transfer phase
  3. Extension phase
  4. Stabilizaion phase
27
Q

In sit to stand which phase has the largest ground reaction force?

A

The second phase, Momentum transfer phase

PT411 Kinesiology & Biomechanics (9 decks)

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