Sliding Filament Theory

Question 1

What is a muscle fiber?

Answer 1

Muscle cell that are long, striated, and cylindrical with multiple nuclei in periphery

Question 2

What is the orientation of striated muscle fibers?

Answer 2

Vertical

Question 3

Which bands are light/isotropic?

Answer 3

I bands

Question 4

Describe A bands

Answer 4

Dark/Anisotropic

Question 5

Which structure in the fiber contains myofilaments and fills the majority of the sarcoplasm?

Answer 5

Myofibrils

Question 6

List the 2 myofilaments

Answer 6

Actin and myosin

Question 7

Which myofilament is thin?

Answer 7

Actin

Question 8

The thick myofilament is _____________

Answer 8

Myosin

Question 9

T/F: Myofilaments are interdigitated.

Answer 9

True

Question 10

What are the limits of the sarcomere?

Answer 10

Z to Ζ line

Question 11

What is the anchoring line for actin i the sarcomere?

Answer 11

Z line

Question 12

What is in the center of the I band?

Answer 12

Z line

Question 13

Which band contains both actin and myosin?

Answer 13

A band

Question 14

What is the anchor site for myosin?

Answer 14

M band/line

Question 15

What is within the A band that only contains myosin?

Answer 15

H zone

Question 16

During muscle contraction, which filaments are pulled towards the center of the A band (M line)?

Answer 16

Actin filaments

Question 17

What does the contraction do to the sarcomere?

Answer 17

Narrows the sarcomere

Question 18

List 3 things that happen during a muscle contraction

Answer 18

• I band narrows
• Z lines move closer
• A band remains unaltered

Question 19

How is the filament sliding achieved?

Answer 19

By the cross bridge cycle

Question 20

Cross Bridges are part of _____________ proteins that extend from axis of thick filaments to form arms.

Answer 20

Myosin

Question 21

What does cross bridges interact with that in turn leads to contraction?

Answer 21

Actin filaments

Question 22

Which part of the myosin molecule is the actual cross bridge?

Answer 22

Globular head

Question 23

What is the name of the globular heads of myosin in relation to their function?

Answer 23

Myosin ATPase

Question 24

Define the function of Myosin ATPase

Answer 24

Enzyme that splits ATP to ADP to release energy

Question 25

Describe the cross bridges in a resting fiber

Answer 25

Not attached to actin

Question 26

What process activates the cross bridges?

Answer 26

Hydrolysis of ATP into ADP and Pi

Question 27

What is Step 2 of the Cross Bridge cycle?

Answer 27

Activated Cross bridge binds to actin filament

Question 28

What cause the conformational change in the myosin head and in turn leads to the power stroke?

Answer 28

The release of Pi

Question 29

What is the power stroke?

Answer 29

When actin filaments are pulled towards the center of the A band

Question 30

How does the cross bridge detach from actin at the end of a power stroke?

Answer 30

When fresh ATP binds and replaces ADP on the cross bridges

Question 31

List the 4 steps of the Cross bridge cycle

Answer 31

1. Cross bridge formation
2. Power Stroke
3. Cross Bridge Detachment
4. Reactivation of myosin heads/cross bridges

Question 32

What plays a critical role in energy source for the cross bridge steps and the pumping of Ca back into the SR for relaxation?

Answer 32

ATP

Question 33

List the 3 way skeletal muscle generate ATP through

Answer 33

• Anaerobic respiration
• aerobic respiration
• phosphate groups donated by phosphocreatine

Question 34

What is the “short cut way’’ to generate ATP during sustained muscle activity?

Answer 34

Phosphocreatinine