Sliding Filament Theory Flashcards
What is a muscle fiber?
Muscle cell that are long, striated, and cylindrical with multiple nuclei in periphery
What is the orientation of striated muscle fibers?
Vertical
Which bands are light/isotropic?
I bands
Describe A bands
Dark/Anisotropic
Which structure in the fiber contains myofilaments and fills the majority of the sarcoplasm?
Myofibrils
List the 2 myofilaments
Actin and myosin
Which myofilament is thin?
Actin
The thick myofilament is _____________
Myosin
T/F: Myofilaments are interdigitated.
True
What are the limits of the sarcomere?
Z to Ζ line
What is the anchoring line for actin i the sarcomere?
Z line
What is in the center of the I band?
Z line
Which band contains both actin and myosin?
A band
What is the anchor site for myosin?
M band/line
What is within the A band that only contains myosin?
H zone
During muscle contraction, which filaments are pulled towards the center of the A band (M line)?
Actin filaments
What does the contraction do to the sarcomere?
Narrows the sarcomere
List 3 things that happen during a muscle contraction
- I band narrows
- Z lines move closer
- A band remains unaltered
How is the filament sliding achieved?
By the cross bridge cycle
Cross Bridges are part of _____________ proteins that extend from axis of thick filaments to form arms.
Myosin
What does cross bridges interact with that in turn leads to contraction?
Actin filaments
Which part of the myosin molecule is the actual cross bridge?
Globular head
What is the name of the globular heads of myosin in relation to their function?
Myosin ATPase
Define the function of Myosin ATPase
Enzyme that splits ATP to ADP to release energy
Describe the cross bridges in a resting fiber
Not attached to actin
What process activates the cross bridges?
Hydrolysis of ATP into ADP and Pi
What is Step 2 of the Cross Bridge cycle?
Activated Cross bridge binds to actin filament
What cause the conformational change in the myosin head and in turn leads to the power stroke?
The release of Pi
What is the power stroke?
When actin filaments are pulled towards the center of the A band
How does the cross bridge detach from actin at the end of a power stroke?
When fresh ATP binds and replaces ADP on the cross bridges
List the 4 steps of the Cross bridge cycle
- Cross bridge formation
- Power Stroke
- Cross Bridge Detachment
- Reactivation of myosin heads/cross bridges
What plays a critical role in energy source for the cross bridge steps and the pumping of Ca back into the SR for relaxation?
ATP
List the 3 way skeletal muscle generate ATP through
- Anaerobic respiration
- aerobic respiration
- phosphate groups donated by phosphocreatine
What is the “short cut way’’ to generate ATP during sustained muscle activity?
Phosphocreatinine
