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Physio-BLOCK 2 (muscle, cardio, resp, renal) > muscles > Flashcards

muscles Flashcards

1
Q

What muscle type is limited by its ability to diffuse O2 and nutrients?

A

Skeletal muscle (big!)

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2
Q

What is the covalent action of ATP in skeletal muscle?

A

Hydrolysis of ATP by myosin energizes the cross-bridges, providing the energy for force generation

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3
Q

What is the allosteric action of ATP in the skeletal muscle?

A

Binding of ATP to myosin dissociates cross bridges bound to actin, allowing the bridges to repeat their cycle of activity.

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4
Q

Where does the calcium for cross bridge formation come from?

A

Intra-organelle (SR) calcium!

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5
Q

How does Ca get back into the sarcoplasmic reticulum?

A

ATP is require to provide the energy for the calcium pump in the SR

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6
Q

The body uses which form of contraction to create movement?

A

Unfused tetany

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7
Q

What causes a muscle to fail to sustain tension/fatigue?

A
  1. depletion of metabolic substrates
  2. depletion of neuromuscular transmitter
  3. psychological inability to drive nerve impulse
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8
Q

What metabolic substrate becomes less available to the muscles over periods of prolonged exercise?

A

muscle glycogen

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9
Q

what is the functional unit of muscular contraction?

A

motor unit

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10
Q

what is the definition of the motor unit?

A

the motor neuron and all the muscle fibers that it innervates

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11
Q

what are the contractile properties of muscle fibers?

A

speed
strength
endurance

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12
Q

what does the speed of contraction depend on?

A

the form of myosin ATPase (fast or slow)

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13
Q

what does the strength of contraction depend on?

A

the number and SIZE of muscle fibers innervated

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14
Q

what does endurance of contraction depend on?

A

the metabolic enzymes present (oxidative or glycolytic)

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15
Q

what is summation?

A

the increase in muscle tension from successive action potentials occurring during the phase of mechanical activity

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16
Q

what is a maintained contraction in response to repetitive stimuli?

A

tetanus

17
Q

what is unfused tetanus?

A

low stimulation frequencies–tension oscillates as the muscle fiber partially relaxes between stimuli

18
Q

what is produced at higher stimulation frequencies?

A

fused tetany

19
Q

what are 3 ways a muscle fiber can form ATP?

A
  1. phosphorylation of ADP by creatine phosphate
  2. oxidative phosphorylation of ADP in the mitochondria
  3. phosphorylation of ADP by the glycolytic pathway in the cytosol
20
Q

what are 3 types of skeletal muscle fiber?

A
  1. slow-oxidative fibers (SO)
  2. fast-oxidative-glycolytic fibers (FOG)
  3. fast-glycolytic fibers (FG)
21
Q

how do type I or slow oxidative fibers work?

A

by combining LOW myosin-ATPase activity with high oxidative capacity

22
Q

how do type IIa or fast oxidative glycolytic fibers work?

A

by combining HIGH myosin-ATPase activity with high oxidative capacity and intermediate glycolytic capacity

23
Q

how do type IIb or fast glycolytic fibers work?

A

by combining HIGH myosin-ATPase activity with high glycolytic activity

24
Q

what is the order of motor unit activation?

A

SO–>FOG–>FG

always start by activating fibers LEAST susceptible to fatigue, and those MOST fatigable for LAST

25
Q

what are 3 characteristics of cardiac muscle?

A
  1. moderate SR with T-tubules
  2. dispersed mitochondria
  3. centrally located nuclei
26
Q

which type of fiber gets its calcium from SR and EC?

A

cardiac muscle!

27
Q

true or false: cardiac muscle has fused and unfused tetany?

A

FALSE - no tetany!

28
Q

true or false: skeletal muscle has NO calcium channels in its plasma membrane?

A

TRUE

29
Q

what type of Ca channels are in the plasma membrane of a cardiac muscle cell?

A

L-type

30
Q

cardiac muscle has a LONG or SHORT refractory period?

A

LONG

31
Q

skeletal muscle has a LONG or SHORT refractory period?

A

SHORT

32
Q

true or false: smooth muscle lacks troponin

A

TRUE - which means tropomysin never covers actin binding sites (its not the regulatory step like striated muscle)

Physio-BLOCK 2 (muscle, cardio, resp, renal) (3 decks)

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