9A.4 Flashcards

1
Q

Twitch=

A

contractile response of a single muscle fiber to a muscle fiber to a muscle impulse

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2
Q

Threshold stimulus

A

minimal strength required to cause contraction

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3
Q

Latent period

A

brief delay between time of stimulation and the beginning of contraction (2 msec)

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4
Q

Period of contraction

A

muscle contracts reaction time is 40 msec

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5
Q

Period of relaxation

A

muscle relaxes reaction time is 50 msec

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6
Q

Refractory period

A

period of lost excitability (time in which you cant make another action potential) reaction time is 5 msec

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7
Q

Myogram=

A

recording of a twitch contraction

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8
Q

All or none principle

A
  • whole muscle fiber contracts or not (no halfsies)
  • each muscle fiber generates same force in a contraction
    -whole muscles though, have varying size of contractions
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9
Q

Strength of Contraction (reasons why some muscles are stronger than others)

A
  • Frequency of stimulation of individual fiber
  • Number of muscle fibers making up whole muscle
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10
Q

Summation

A
  • application of a series of stimuli of increasing frequency
  • complete relaxation cannot occur combining individual twitches
  • contraction becomes sustained
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11
Q

Tetanic contraction

A
  • frequency of stimulation occurs often enough that partial relaxation cannot even take place
  • most common and used for usual body movements
  • also accounts for muscle tone
    • small, sustained contractions not causing body movements
    • Mostly helps to maintain posture
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12
Q

What are the different types of contractions

A
  • Isotonic
  • Eccentric
  • Isometric
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13
Q

Isotonic (def)

A

muscle contracts and changes length

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14
Q

Isotonic

A
  • Most common type moving bones
  • Muscle tension is constant and muscle shortens
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15
Q

Eccentric (def)

A

“lengthening” contraction

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16
Q

Eccentric

A
  • type of isotonic
  • cross bridges are not generating enough force to shorten the muscle (resistance is stronger)
  • tension is not constant
17
Q

Isometric (def)

A

muscle contracts but does not change length

18
Q

Isometric

A
  • no body movement, just stabilizing positions
  • pushing on a wall
  • tension is constant
19
Q

Cramps

A

= painful spasmodic contraction
- caused by prolonged physical activity or prolonged cold
- insufficient amount of ATP/ lactic acid build up
- Ca^2+ does not return properly to the sarcoplasmic reticulum prevents muscle from relaxing

20
Q

Muscle strain/ Pull/ Tear

A
  • overstretched of muscle fibers causing tearing
  • can also tear fascia
  • severity is determined by tear and amount of lost usage
21
Q

Atrophy

A

= muscle fibers decrease in size
- due to extreme inactivity
- can decrease muscle strength by 5% each day
- eventually is replaced by fibrous connective tissue
and cannot be rehabilitated -> muscle cannot divide
- takes about 2 years immobilization

22
Q

Rigor Mortis

A

= few hours after death
- loss of ATP (because u ded) and excessive leakage of Ca^2+ -> SR no longer controlling flow
- cross bridges do not let go of actin causing stiffening
- can continue for 72 hours until tissue starts to decompose