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FHB exam one > Striated muscle physiology > Flashcards

Striated muscle physiology Flashcards

1
Q

Four major characteristics of muscle

A

Contractility, excitability, extensibility, and elasticity

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2
Q

Three functions of muscle

A

Motion, postural maintenance, and heat production

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3
Q

Fascicles

A

A group of muscle fibers

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4
Q

Myofiber

A

Muscle fiber = muscle cell

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5
Q

Myofibrils

A

Composed of many repeating sarcomeres

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6
Q

Myofilaments

A

Myosin and actin filaments

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7
Q

Endomysium

A

Surrounds individual fibers, contains capillaries

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8
Q

Perimysium

A

Surrounds each fascicle, contains blood vessels and nerves

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9
Q

Epimysium

A

Surrounds entire muscle

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10
Q

What do all the mysiums come together to create?

A

Tendons

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11
Q

Sarcomere

A

Basic contractile unit

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12
Q

Letters of the sarcomere

A

A-band: dark band (myosin)
H-zone: where only myosin fibers are
I-band: light band (actin only)
M-line: direct middle of the dark band that has proteins to anchor thick filaments together
Z-line: marks the end of the sarcomere; where the actin filaments attach

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13
Q

Thick filament structure

A

Polymer of ~200 myosin molecules

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14
Q

Structure of one myosin protein

A

Two heavy chains and four light chains; coil together to form a rod and two globular heads

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15
Q

Two functions of the globular head

A

Binds actin and has ATPase activity

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16
Q

Geometry of light chain heads

A

Each pair is oriented 120 degrees from the next pair so myosin interacts with the thin filament in 3D

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17
Q

F-actin structure

A

Double-stranded helix composed of many G-actin monomers (approximately 360)

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18
Q

Five interacting proteins involved in the thin filament

A 
F-acin
Tropomyosin
Troponin-T
Troponin-I
Troponin-C
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19
Q

Ratio of tropomyosin and troponin to actin

A

1 tropomyosin/troponin complex per 7 actin monomers

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20
Q

What does the troponin-tropomyosin complex do?

A

Typically blocks the myosin binding site on each G-actin while at rest

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21
Q

What happens to the T-T complex during muscle activation?

A

Moves into the “actin groove,” exposing the myosin binding site

22
Q

Transverse tubules

A

Invaginations of sarcolemma into the muscle fiber, conduct muscle action potential, and are closely apposed to the sarcoplasmic reticulum.

23
Q

Receptor on the T-tubule for voltage sensing

A

Dihydropyridine receptor

24
Q

Sarcoplasmic reticulum

A

Special type of smooth endoplasmic reticulum of muscle that stores a high concentration of Ca2+.

25
Q

Receptor on the sarcoplasmic reticulum for Ca2+ release

A

Ryanodine receptor

26
Q

Muscle triad

A

Association of one T-tubule with two adjacent “lateral sacs” of SR

27
Q

SERCA

A

Sarcoplasmic/endoplasmic reticulum Ca2+ ATPase

28
Q

What is the function of SERCA?

A

Pumps Ca2+ from the cytoplasm back into the SR lumen to restore the Ca2+ gradient

29
Q

The nervous system communicates with muscle through . . .

A

Neuromuscular junctions, which work very much like a synapse between neurons

30
Q

Neurotransmitter in the neuromuscular junction

A

Acetylcholine

31
Q

Nature of AChR in the NMJ

A

Nicotinic; opens as a cationic channel (mainly Na+)

32
Q

How many subunits does the AChR have?

A

Five: two alpha, one beta, one gamma, and one delta

33
Q

What is the link between excitation and contraction?

A

Calcium.

34
Q

Excitation-contraction coupling

A

A process whereby membrane depolarization is transformed into a chemical signal to initiate muscle contraction

35
Q

Six steps in muscle contraction

A
  1. Excitation-contraction coupling
  2. Ca2+ binds troponin
  3. Troponin/tropomyosin move to actin groove
  4. Myosin binds actin
  5. Crossbridge cycle/powerstroke
  6. Calcium sequestration -> relaxation
36
Q

Steric hindrance model

A

Myosin usually can’t bind because troponin is in the way

37
Q

Sliding filament model

A

Free energy cleavage of M*ATP induces a bend in the myosin head from 90 to 45 degrees, pulling the Z-lines inward and shortening the muscle fiber

38
Q

Twitch summation

A

Multiple action potentials can fire during a single muscle twitch, each causing a release of more calcium. This, in turn, will make more available thin filaments

39
Q

Which arrangement of sarcomeres produces more flexibility?

More force?

A

Series, parallel

40
Q

Force-velocity relationship of muscle contraction

A

There is maximum contractility with no load, and a negative hyperbolic relationship as the load gets heavier, eventually causing lengthening

41
Q

Power-stress curve

A

No power is created when there is no force, but there is also no power created when there is no movement. Curve with a peak, skewed right.

42
Q

Concentric contractions

A

Muscle is actively shortening

43
Q

Eccentric contractions

A

Muscle actively lengthening, which is physiologically common and associated with injury and soreness. Exercise with eccentric contractions increase muscle strength

44
Q

Isometric contraction

A

Muscle actively held at a fixed length

45
Q

Passive stretch

A

Muscle passively lengthening, likely resulting from a giant protein called “titin” within the muscle fiber

46
Q

Serum CK levels

A

Blood test revealing muscle injury

47
Q

Actomyosin ATPase accounts for ___% of all ATP consumed in contracting muscle

A

50-70

48
Q

Other ATP consuming processes in contracting muscle

A

SERCA: 20-30%

Na/K ATPase:

49
Q

Muscle fatigue

A

Lactate is produced as a by-product of anaerobic respiration, decreasing pH and inhibiting normal enzyme activity

50
Q

Neuromuscular fatigue

A

Myasthenia gravis, etc (not common in healthy people)

51
Q

Type of neuromuscular fibers

A

Slow twitch I
Fast twitch red IIA
Fast twitch white IIB

52
Q

Difference in E-C coupling between skeletal muscle and cardiac muscle

A

DHPR - physical coupling vs Ca2+ induced Ca2+ release

FHB exam one (23 decks)

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