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D1 Spring - Physiology Exam 2 > 2/22: Skeletal Muscle and Reflexes > Flashcards

2/22: Skeletal Muscle and Reflexes Flashcards

1
Q

Where do muscle fibers run?

A

Length of skeletal muscle

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2
Q

What is the dark band?

A

A band

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3
Q

What is the light band?

A

I band

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4
Q

What is the functional unit of cardiac and skeletal muscle?

A

Sarcomere

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5
Q

What components makes up skeletal muscle?

A

A. Whole muscle
B. Muscle fascicles
C. Muscle fibers (cells)
D. Myofibrils
E. Myofilaments (thick and thin) arranged in sarcomeres

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6
Q

What do alternating A bands and I bands create?

A

Striated appearance in skeletal and cardiac muscle

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7
Q

What is the composition of A band?

A

Entire length of thick filaments

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8
Q

What is the composition of I band?

A

Only thin filaments

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9
Q

What is the composition of H zone?

A

Only thick filaments

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10
Q

What is the composition of Z line?

A

Thin filaments anchored here

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11
Q

What is the composition of M-line?

A

Link the central regions of thick filaments

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12
Q

When do sarcomeres shorten?

A

During contraction

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13
Q

What does the muscle look like during contraction?

A
  • zone of overlap increases
  • I band decreases
  • H zone decreases
  • A band stays the same
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14
Q

What is the thin filament composed of?

A

Actin (with G-actin molecules), tropomyosin, and troponin

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15
Q

What is the active site which binds myosin?

A

G-actin molecules

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16
Q

What does troponin bind?

A

Actin, tropomyosin, and calcium

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17
Q

What makes up thick filaments?

A

Myosin

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18
Q

Describe the cross-bridges of the thick filament?

A

Multiple cross-bridges where the “heads” can bind to the G-actin molecule

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19
Q

What functions as an ATPase enzyme?

A

Myosin

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20
Q

What are the globular proteins of troponin?

A

T, C, and I

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21
Q

What does dystrophin protein connect?

A

Thin filaments to glycoproteins in sarcolemma

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22
Q

What does dystrophin-glycoprotein complex provide?

A

Scaffolding for sarcomeres

23
Q

What are muscular dystrophies?

A

A. Duchenne
B. Beckers
C. Myotonic
D. Oculopharyngeal
E. Limb girdle

24
Q

What does the alpha motor neuron release?

A

ACh

25
Q

What does the alpha motor neuron bind to?

A

A nicotinic ACh receptor on the muscle fiber

26
Q

What does botulinum toxin A inhibit?

A

The release of ACH at the neuromusclar junction

27
Q

What is botox used for in dentistry

A

Bruxism, sialorrhea, masseteric hypertrophy

28
Q

What are the 3 phases of a muscle twitch?

A

Latent, contraction, relaxation

29
Q

What must happen for contraction to occur?

A

The intracellular calcium in the muscle fiber must increase

30
Q

What does tropomyosin prevent in resting muscle?

A

A strong bond between the myosin head and G-actin molecules

31
Q

What happens when troponin binds to cytosolic Ca++?

A

Tropomyosin is pulled away from the myosin binding site, and allows for the power stroke

32
Q

What is released from the sarcoplasmic reticulum?

A

Calcium

33
Q

What is the sarcoplasmic reticulum?

A

Modified ER that sequesters Ca2+

34
Q

What is transverse (T)-tubules?

A

Invaginations of sarcolemma

35
Q

What is terminal cisternae?

A

Portion of SR that contact T-tubule

36
Q

Where does the AP travel?

A

Down T-tubules and activates voltage-sensitive dihydropyridine (DHP) receptors on the T-tubules

37
Q

What happens when the voltage-sensitive dihydropyridine receptors are activated?

A

The calcium channels (ryanodine receptors) open on the SR

38
Q

What happens when the calcium channels open?

A

Goes from SR to the sarcoplasm

39
Q

What does the intracellular structure of myocytes ensure?

A

The spread of action potential (and calcium) throughout the cell

40
Q

What is ATP necessary for?

A

Contraction

41
Q

What does ATP binding to the myosin head cause?

A

A break in the cross-bridge (connection between actin and myosin)

42
Q

What does energy release from ATP hydrolysis by the myosin head provide?

A

Energy for cocking the myosin head (myosin is now in the high energy form)

43
Q

What does release of inorganic phosphate from the myosin head provide energy for?

A

The power stroke

44
Q

What is the power stroke?

A

Myosin head pulling actin towards the center of the sarcomere

45
Q

What shortens the sarcomere?

A

The power stroke

46
Q

Muscle cells only have enough ATP for how many twitches?

A

~8

47
Q

What produces ATP for muscle fibers?

A

A. Aerobic and anaerobic metabolism
B. Phosphocreatine

48
Q

What does contribution of aerobic and anaerobic metabolism on each specific muscle depend on?

A

(1) the metabolic enzymes are present in the cell (ex. glycolytic
fibers versus oxidative fibers)
(2) the intensity of the exercise

49
Q

What are measurements of creatine kinase levels in the blood done to determine?

A

If damage to muscle tissues (skeletal and cardiac) has occurred (ex: heart attack or muscular dystrophy)

50
Q

What 3 things are associated with fatigued muscles?

A

1.have decreased tension generation,
2.take longer to contract
3.relax more slowly and may not completely
relax

51
Q

What are theories that lead to fatigue?

A

1.Change in membrane potential
2.Decreased ACH
3.Blockage of blood flow
4.Central Fatigue
5.Increased metabolic byproducts
6.Depleted glycogen

52
Q

What must be present for cross-bridge cycling?

A

both calcium AND ATP

53
Q

Describe the steps of the cross-bridge cycling (sliding filament theory)

A

A. Rigor State: myosin and actin are tightly bound
B. ATP binds myosin, decreases its affinity for
actin, and the two separate
C. Myosin head moves in the direction of the Z line,
ATP is hydrolyzed
D. Myosin binds the next actin (one closer to Z line)
and power stroke occurs (pulls actin toward the
M Line)
E. ADP is released and the actin and myosin
resume the brief rigor state

54
Q
A

D1 Spring - Physiology Exam 2 (7 decks)

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