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DAT > Biology - Chapter 11.5: Muscular System > Flashcards

Biology - Chapter 11.5: Muscular System Flashcards

1
Q

Smooth muscle

A
  • present in organs, airways, blood vessels
  • involuntary
  • 1 nucleus per cell
  • not striated
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2
Q

Cardiac muscle

A
  • present in heart
  • involuntary
  • 1 nucleus per cell
  • striated
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3
Q

Skeletal muscle

A
  • present around bone
  • voluntary
  • many nuclei per cell
  • striated
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4
Q

Striated

A
  • means muscle contains sarcomeres

- smooth muscle is not striated

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5
Q

Intercalated discs

A
  • found in cardiac muscle
  • contains desmosomes (hold cells together)
  • contains gap junctions (connect cytoplasms of cells)
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6
Q

Skeletal Muscle Organization

A

Muscle -> Muscle fascicles -> Muscle fibers (muscle cells) -> Myofibrils (contractile proteins)

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7
Q

Sarcolemma

A
  • Muscle fiber’s cellular membrane, protects each muscle fiber
  • contains T-tubules, invaginations that quicken action potential propagations
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8
Q

Sarcoplasm

A

Cytoplasm of the muscle fiber and holds the myofibrils

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9
Q

Sarcomeres

A
  • Inside of myofibrils

- functional unit of muscle fibers and shorten to cause muscle contraction

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10
Q

Myofilaments

A
  • Inside sarcomeres
  • thin actin filaments and thick myosin filaments
  • slide past each other to shorten sarcomeres
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11
Q

Stimulation of muscle contraction

A

1) Action potential reaches the end of motor neuron’s axon
2) Acetylcholine released at neuromuscular junction
3) Acetylcholine binds to ligand-gated sodium channels, allowing sodium to enter the cell, creating a graded potential on the muscle fibers
4) Graded potentials trigger opening of voltage-gated sodium channels, which can produce action potential

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12
Q

Sarcoplasmic reticulum

A
  • ER of muscle fibers
  • Releases stored calcium ions into the sarcoplasm through voltage-gated calcium channels when triggered by the depolarization of a muscle cell
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13
Q

Calcium ions binding to troponin…

A

… removes tropomyosin from the myosin-binding sites on actin, allowing myosin to interact with actin and cause sarcomere shortening, via sliding filaments

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14
Q

Cross bridge cycling

A

1) Initiation: calcium ions expose the myosin-binding sites on actin
2) A cocked back, high-energy myosin head (ADP+Pi) forms a cross bridge with the actin
3) The myosin head contracts and the POWER STROKE occurs, bringing the myosin head back to a low energy state and releasing ADP+Pi. The sarcomere shortens
4) New ATP molecule binds to myosin, causing detachment of the myosin head from the actin filament
5) Hydrolyzes ATP into ADP + P. Causes myosin head to re-enter a cocked back, high-energy state

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15
Q

Rigor mortis

A

Occurs because there is no ATP available to release myosin from actin

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16
Q

Z lines

A
  • ends of sarcomere

- thin actin filaments branch from the Z lines towards the middle of the sarcomere

17
Q

M lines

A
  • midpoint of sarcomere

- thick myosin filaments branch from M lines towards the end of the sarcomere

18
Q

I band

A

-Area of sarcomere where only actin is present

19
Q

A band

A

-Area of sarcomere where actin and myosin overlap

20
Q

H zone

A

-Area of sarcomere where only myosin is present

21
Q

Motor units

A

Make up muscles and a single motor unit refers to all the muscle fibers innervated by a single neuron

22
Q

Small motor units

A

Include only a few muscle fibers (precision movement)

23
Q

Large motor units

A

Include many muscle fibers that are innervated by a single neuron (powerful movements)

24
Q

Twitch contraction

A
  • contraction of a muscle fiber through motor unit stimulation
  • each twitch has same size and duration
  • all-or-none principle
25
Q

3 Phases of a Twitch

A

1) Latent: action potential spreads over sarcolemma and T-tubules, signaling sarocplasmic reticulum to release calcium
2) Contraction: formation of cross bridges as a result of calcium ions binding to troponin
3) calcium is pumped back into the SR, ending cross bridge cycling and decreasing muscle tension

26
Q

Summation

A

Process by which twitches add up to create larger overall contraction

27
Q

Wave summation (temporal summation)

A
  • Depolarizing a motor unit again during relaxation phase
  • Can cause tetanus (muscle fiber cannot be further stimulated due to a lack of relaxation)
  • Twitches blend together during tetany, eventually causing fatigue
28
Q

Motor unit summation

A
  • Different motor units are stimulated at different times to produce the intended amount of muscle contraction
  • Small motor units are stimulated first before larger motor units

DAT (16 decks)

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