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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
Ca2+ controls _________, which controls tropomyosin, which controls myosin binding site on actin
Troponin
26
The components and functions of the troponin complex
Troponin C - binds calcium Troponin T - binds troponin complex to tropomyosin Troponin I - binds tropomyosin and actin
27
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
Excitation-Contraction (E-C) Coupling
28
ER of skeletal muscle
Sarcoplasmic reticulum
29
The traverse tubules and SR surround the _________
myofibrils
30
Myofibril diameter (1-2 microns) is small enough for _________ to occur. This allows for efficient delivery and reuptake of Ca2+
diffusion
31
Ryanodine receptor is found in ___________ SR
junctional
32
SERCA is found in ___________ SR
longitudinal
33
How much force is formed after one AP
Twitch
34
To increase force, need to do more _________
Action potentials (AP short compared to twitch)
35
Only partial relaxation during twitches
Unfused tetanus
36
No relaxation of muscles, maximal tension
Fused tetanus
37
The speed of muscle shortening is related to the amount of ______
load
38
Tension equals the load | No shortening
Isometric contraction
39
Tension is greater than the load Shortening (tone is the same)
Isotonic contraction
40
Load exceeds tension | Sitting down, damages muscles, grows back stronger since you have to put in more myofibrils
Lengthening contraction
41
____________ of sarcomere affects tension capacity | If already short, or too long, won't be able to produce much tension/force
Geometry
42
Three sources of fuel for contraction
``` Creatine phosphate Anaerobic metabolism (glycolytic) Aerobic metabolism (oxidative) ```
43
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)
Creatine phosphate
44
Produces ATP and lactic acid during glycolysis Burns glucose and muscle glycogen (400 meter dash) Use after creating phosphate is gone
Anaerobic metabolism (glycolytic)
45
``` 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 ```
Anaerobic metabolism (glycolytic)
46
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)
Aerobic metabolism (oxidative)
47
The _________ state is protective so you can't exercise until all ATP of muscle is gone
fatigue state
48
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)
Fatigue state
49
Muscle fiber types differ in rates of _________ ratcheting activity and metabolism
myosin ATPase
50
____________ muscle fibers resist fatigue (muscles for posture) Lower tension, but lasts longer
Slow-oxidative
51
_____________ muscle fibers resist fatigue (muscles used in walking)
Fast-oxidative-glycolytic
52
_____________ muscle fibers are used for bursts of strong force (muscles used to jump) Good at relaxing
Fast-glycolytic
53
Most skeletal muscles include ______ types of muscle fibers, but then amount of each varies by individual (genetic component)
all three types are included which most skeletal muscles
54
Each motor unit has ____ type of muscle fiber.
one
55
Each fascicle contains more than one __________. | Can be composed of different types.
motor unit
56
___________ 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)
Slow-oxidative Fast-oxidative-glycolytic Fast-glycolytic
57
If you need more force, you need to recruit more ________ (more myofibrils)
motor neurons
58
``` Weight training induces _________ to generate more tension (force) Lengthening contractions (damages muscle, make effort into making more myofibrils, can lift more) ```
hypertrophy
59
Enlargement of cells (during weight training, muscles get bigger - not more muscle fibers, but the fibers get bigger - can generate more force)
Hypertrophy
60
Endurance training induces _____________ without dramatic hypertrophy
resistance to fatigue
61
Endurance doesn't increase myofibrils, but increases how they function such as:
increased blood flow, mitochondria, myoglobin
62
The balance between protein synthesis and breakdown determines _______
muscle size

MCT Exam 3 (9 decks)

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