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MCT Exam 3 > Skeletal Muscle Contraction > Flashcards

Skeletal Muscle Contraction Flashcards

1
Q

Large, multinucleate cells
Nuclei on periphery of cell
Part of somatic nervous system
Huge cells

A

Striated, skeletal muscle

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2
Q

Small, contain 1-2 nuclei
Connected by specialized junctions
Part of autonomic nervous system

A

Striated, cardiac muscle

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3
Q

Small, single nucleated cells
Nucleus located in the center of the cell
No striations, less ordered
Part of autonomic nervous system

A

Smooth muscle

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4
Q

The ____________ mechanism, in which myosin filaments bind to and move actin filaments, is the basis for shortening of stimulated muscle.

A

sliding filament mechanism

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5
Q

Myosin and actin interactions are regulated by _________ ions

A

calcium

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6
Q

Changes in the membrane potential lead to contraction, called:

A

E-C Coupling (excitation-contraction coupling)

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7
Q

A muscle _________ typically contains many muscle fibers

A

fascicle

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8
Q

Muscle fiber is the same as muscle ______

A

cell

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9
Q

Muscle is several bundles of __________

A

fascicles

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10
Q

A muscle fiber has many _________, whose number determines the force generating capability of the fiber

A

myofibrils

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11
Q

Each myofibril has many _____________ in series, the contractile units

A

sarcomeres

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12
Q

Each __________ has many actin (thin) and myosin (thick) filaments (myofilaments)
Two sets of actin with myosin spanning the length in between
Myosin = dark stripes
Only actin = light stripes

A

sarcomere

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13
Q

Band of sarcomere where there is myosin

A

A band

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14
Q

Band of sarcomere where there is only actin

A

I band

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15
Q

Band of sarcomere where there is only myosin

A

H band

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16
Q

Region of sarcomere that the actin filaments are attached to, marks the ends of sarcomere

A

Z line

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17
Q

In a sarcomere, the middle of the myosin where the myosin filaments are held together

A

M line

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18
Q

Myosin moves actin towards the Z line during contraction (myosin ratchets along actin), so the _____ band gets shorter

A

I band

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19
Q

During the sliding filament model of contraction, shortening occurs when the thick (A band) and thin filaments (I band) slide past one another pulling the __________ closer and together and reducing the width of the I-bands

A

Z-lines

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20
Q

During contraction ____________ lengths have not changed. The I band is reduced in contraction but not the A band

A

myofilament

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21
Q

Steps of ____________:
Rigor state (no ATP)
ATP bound - myosin lets go of actin
ATP hydrolysis - myosin head ratchet forward
Release of Pi causes power stroke
Release of ADP returns the myosin to the rigor state

A

Cross bridge cycling

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22
Q

Cross bridge cycling requires ATP to break a bridge and ______ to unmask actin

A

Ca2+

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23
Q

Important accessory proteins for muscle contraction

A

Titin
Tropmodulin
Nebulin

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24
Q

Long filamentous molecules along actin that bind where myosin would bind if accessible
Also binds troponin

A

Tropomyosin

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25
Q

Ca2+ controls _________, which controls tropomyosin, which controls myosin binding site on actin

A

Troponin

26
Q

The components and functions of the troponin complex

A

Troponin C - binds calcium
Troponin T - binds troponin complex to tropomyosin
Troponin I - binds tropomyosin and actin

27
Q

Steps of _________:

  1. AP passes down transverse tubule (T tubule) and opens the dihydropyridine receptor (DHP) (L-type Ca2+ channel, voltage sensor, slow channel)
  2. SR ryanodine receptor opens (in response to DHP) releasing Ca2+ into the cytosol
  3. Ca2+ binds to troponin exposing the actin to the myosin heads. Cross bridges form.
  4. SR Ca2+-ATPase (SERCA) pumps Ca2+ back into SR
A

Excitation-Contraction (E-C) Coupling

28
Q

ER of skeletal muscle

A

Sarcoplasmic reticulum

29
Q

The traverse tubules and SR surround the _________

A

myofibrils

30
Q

Myofibril diameter (1-2 microns) is small enough for _________ to occur. This allows for efficient delivery and reuptake of Ca2+

A

diffusion

31
Q

Ryanodine receptor is found in ___________ SR

A

junctional

32
Q

SERCA is found in ___________ SR

A

longitudinal

33
Q

How much force is formed after one AP

A

Twitch

34
Q

To increase force, need to do more _________

A

Action potentials (AP short compared to twitch)

35
Q

Only partial relaxation during twitches

A

Unfused tetanus

36
Q

No relaxation of muscles, maximal tension

A

Fused tetanus

37
Q

The speed of muscle shortening is related to the amount of ______

A

load

38
Q

Tension equals the load

No shortening

A

Isometric contraction

39
Q

Tension is greater than the load
Shortening
(tone is the same)

A

Isotonic contraction

40
Q

Load exceeds tension

Sitting down, damages muscles, grows back stronger since you have to put in more myofibrils

A

Lengthening contraction

41
Q

____________ of sarcomere affects tension capacity

If already short, or too long, won’t be able to produce much tension/force

A

Geometry

42
Q

Three sources of fuel for contraction

A 
Creatine phosphate
Anaerobic metabolism (glycolytic) 
Aerobic metabolism (oxidative)
43
Q

Donates P to convert ADP to ATP in the first seconds of muscle activity (100 meter dash)
Only requires a single enzymatic reaction, quick (but also run out quickly)

A

Creatine phosphate

44
Q

Produces ATP and lactic acid during glycolysis
Burns glucose and muscle glycogen
(400 meter dash)
Use after creating phosphate is gone

A

Anaerobic metabolism (glycolytic)

45
Q 
Produces ATP and lactic acid during glycolysis
Burns glucose and muscle glycogen 
(400 meter dash) 
Use after creating phosphate is gone
Build up a lot of metabolites
A

Anaerobic metabolism (glycolytic)

46
Q

Produces ATP, CO2, and water using oxidative phosphorylation
Burns glucose and fatty acids
(marathon)
Most efficient
Unlimited as long as there is enough material
Endurance
Complicated process (slower)

A

Aerobic metabolism (oxidative)

47
Q

The _________ state is protective so you can’t exercise until all ATP of muscle is gone

A

fatigue state

48
Q

Contributing factors of __________ include:
1. Build up of ECF [K+] = persistent depolarization of fiber
So many AP in skeletal muscle, effected equilibrium potential - so much K+ has leaked out - increases Keq (less of a gradient) - easier to get to threshold
Don’t get down to rest to reset your channels, less responsive to stimulation (channels still inactive)
2. Build up of metabolites which impair SR Ca2+ ATPase and troponin-tropomyosin
3. Buildup of Pi in ICF inhibits cross bridge detachment and slows cross bridge cycling
4. Decrease in feel stores (glycogen, fatty acids, glucose)

A

Fatigue state

49
Q

Muscle fiber types differ in rates of _________ ratcheting activity and metabolism

A

myosin ATPase

50
Q

____________ muscle fibers resist fatigue (muscles for posture)
Lower tension, but lasts longer

A

Slow-oxidative

51
Q

_____________ muscle fibers resist fatigue (muscles used in walking)

A

Fast-oxidative-glycolytic

52
Q

_____________ muscle fibers are used for bursts of strong force (muscles used to jump)
Good at relaxing

A

Fast-glycolytic

53
Q

Most skeletal muscles include ______ types of muscle fibers, but then amount of each varies by individual (genetic component)

A

all three types are included which most skeletal muscles

54
Q

Each motor unit has ____ type of muscle fiber.

A

one

55
Q

Each fascicle contains more than one __________.

Can be composed of different types.

A

motor unit

56
Q

___________ fibers are small and get to threshold first. If not enough force is produced, then __________ fibers will reach threshold then _______.
(order of motor unit recruitment)

A

Slow-oxidative
Fast-oxidative-glycolytic
Fast-glycolytic

57
Q

If you need more force, you need to recruit more ________ (more myofibrils)

A

motor neurons

58
Q 
Weight training induces \_\_\_\_\_\_\_\_\_ to generate more tension (force) 
Lengthening contractions (damages muscle, make effort into making more myofibrils, can lift more)
A

hypertrophy

59
Q

Enlargement of cells (during weight training, muscles get bigger - not more muscle fibers, but the fibers get bigger - can generate more force)

A

Hypertrophy

60
Q

Endurance training induces _____________ without dramatic hypertrophy

A

resistance to fatigue

61
Q

Endurance doesn’t increase myofibrils, but increases how they function such as:

A

increased blood flow, mitochondria, myoglobin

62
Q

The balance between protein synthesis and breakdown determines _______

A

muscle size

MCT Exam 3 (9 decks)

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