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Kinesiology > Chapter 3 - Muscle > Flashcards

Chapter 3 - Muscle Flashcards

1
Q

fusiform muscle

A

fibers running parallel to each other and the central tendon

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2
Q

pennate muscle

A

approach central tendon obliquely

  • more muscle fibers
  • may be unipennate, bipennate, multipennate
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3
Q

muscle fiber

A

structural unit of muscle

  • individual cell with multiple nuclei
  • cell is surrounded by connective tissue(endomysium)
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4
Q

epimysium

A

surrounds muscle belly(bunches of fascicles)

- tightly woven collagen bundles highly resistive to stretch

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5
Q

perimysium

A

beneath the epimysium

  • surrounds fascicles = bunch of muscle fibers together
  • provides conduit for vessels and nerves
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6
Q

endomysium

A

surrounds individual muscle fibers

  • partly connected to perimysium
  • connections to muscle fibers allow for transmission of force to tendon
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7
Q

physiologic cross-sectional area

A

amount of contractile protein available to generate force

  • maximal force production is proportional to the sum of the cross-sectional area of all the fibers
  • increase area = increase max force
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8
Q

pennation angle

A

angle of orientation between fiber and tendon

  • if greater than zero, then less from the muscle is transmitted to tendon
  • can produce greater max force than fusiform muscles of similar size(fit more fibers)
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9
Q

elasticity

A

temporarily stores part of the energy used to create the stretch
- helps prevent injury during maximal elongation

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10
Q

viscosity

A

rate-dependent resistance encountered between surfaces of adjacent fluid-like tissues

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11
Q

muscle ideal resting length

A

length that allows the greatest number of crossbridges and therefore the greatest potential force
- as the sarcomere is lengthened or shortened from resting length, number of potential crossbridges decreases which yields less force production with max muscle activation

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12
Q

total length-tension curve

A

combines the active and passive length-tension curves

  • allows for a large range of muscle force over a wide range of muscle length
  • at shortened lengths, active force dominates
  • passive tension begins to contribute as muscle is stretched beyond resting length
  • passive tension dominates at end range of stretch
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13
Q

isometric state

A

there is no movement

  • internal torque = external torque
  • static state
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14
Q

max effort concentric activation

A

muscle force is inversely proportional to the velocity of muscle shortening

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15
Q

max effort eccentric activation

A

muscle force is directly proportional to the velocity of muscle lengthening

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16
Q

motor unit

A

the alpha motor neuron and all muscle fibers innervated by it

  • must first recruit the motor neuron then select rate of sequential activation
  • smaller motor neurons are recruited first, then bigger
17
Q

small motoneurons(SO)

A

twitch responses long in duration and low in amplitude

  • slow to respond to a stimuli
  • oxidative
  • show relatively little fatigue
18
Q

large motoneurons(FF or FG)

A

twitch responses brief in duration and high in amplitude

  • fast and fatigued
  • fast and glycolytic
19
Q

intermediate sized motoneurons(FOG)

A

between slow and fast

  • fast and fatigue resistant(FR)
  • combined oxidative and glycolytic
20
Q

rate coding

A

rate of excitation

  • muscle fiber twitch last longer than an action potential
  • subsequent action potentials can occur prior to the muscle twitch relaxing
  • muscle twitches summate and generate more peak force
  • motor units activated at high rates are capable of generating greater overall force than the same number of motor units activated at lower rates
21
Q

fused tetanus

A

the greatest force level that is possible for a muscle fiber

22
Q

muscle fatigue

A

force will decrease even though the rate of activation remains the same

  • nervous system compensates for fatigue by increasing rate of activation or recruiting more motoneurons
  • rest periods allow muscle to return to normal performance
  • type and intensity of contraction influences rest period needed
    - Rapidly fatigued = secs to minutes
    - slowly fatigued = hours
23
Q

central fatigue

A

affected by psychological factors such as sense of effort, physiological factors influencing descending pathways
- verbal encouragement may help temporarily

24
Q

peripheral fatigue

A

neurophysiological factors at level of motoneuron

- gradual reduction in acetylcholine release

25
Q

DOMS

A

delayed onset muscle soreness

  • more severe after repeated eccentric exercise
  • peaks 24-72 hours after exercise
  • caused by disruption of sarcomeres and damage to cytoskeleton within and around muscle fiber
26
Q

changes in muscle with strength training

A

neuromuscular system adapts

  • plasticity
  • muscle hypertrophy and increased strength(actin and myosin laid down)
  • eccentric activations produce greater force and more effective in promoting muscle hypertrophy
27
Q

muscle hypertrophy

A

results from increased protein synthesis within muscle fibers which leads to increased cross-sectional area of the whole muscle

  • primary cause of increased muscle mass
  • limited evidence of an increase in number of muscle fibers
  • greatest in fast twitch(type 2) fibers
28
Q

nervous system adaptation with strength gains

A

increased area of activity with cortex

  • increased motor neuron excitability
  • greater discharge frequency of motor units
  • decreased neural inhibition
  • increased muscle strength with imagery training
  • increased strength in contra-lateral, non-exercised side
  • strength gains due to more than just hypertrophy
29
Q

isometric exercise

A

a muscle contraction against a load which is immovable

  • muscle length remains constant
  • no joint movement
  • static or nonmoving contraction
  • zero speed, body segment does not move
30
Q

isotonic exercise

A

muscle contracts against a mechanical system which provides a constant load as the body segment moves against this constant load

  • the load remains the same, but the tension of the muscle changes
  • dynamic or moving contraction
  • constant resistance
  • can be varying speed
31
Q

isokinetic exercise

A

dynamic contraction

  • varying resistance
  • force exerted varies according to physiological and leverage factors(joint angle)
  • constant speed = speed is controlled so that the body segment moves at the same speed throughout the ROM

Kinesiology (8 decks)

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