Contraction and Relaxation of Skeletal Muscle Fibres Flashcards
What is the Sliding Filament Mechanism?
This is a model describing:
Skeletal muscle shortens during contraction because Thick and Thin filaments Slide past one another.
During muscle contraction where do the Thin Filaments move?
They move toward the M-Line of each Sarcomere.
What leads to shortening of the entire muscle fibre?
Shortening of the Sarcomeres when the Z discs are pulled closer together.
When Sarcomeres in the muscle fibre are shortening what will be the end result?
The Entire muscle itself will shorten.
During the Contraction cycle what happens after the (SR) releases Calcium ions into the Sarcoplasm?
They bind to Troponin.
What are the steps to the Contraction Cycle?
ATP Hydrolysis, Attachment of Myosin to Actin, Power Stroke, Detachment of Myosin from Actin.
What is step 1 to the contraction cycle?
ATP Hydrolysis:
A myosin head includes an ATP binding site that functions as a ATPase. An enzyme that Hydrolyses ATP into ADP and a phosphate group.
The energy created is stored in the Myosin head for later.
What is step 2 to the contraction cycle?
Attachment of Myosin to Actin:
The energized Myosin head attaches to the myosin binding site on the Actin.
Releases the phosphate group.
A cross bridge is formed after the attachment.
What is step 3 to the contraction cycle?
Power Stroke:
After the cross bridge is formed the myosin head pivots.
As the myosin pivots it pulls the Thin Filament past the Thick Filament.
The energy needed for this is the energy derived form the Hydrolysis of ATP.
What is step 4 to the contraction cycle?
Detachment of Myosin from Actin:
At the end of the power stroke the cross bridge remains firmly attached until it binds to another ATP molecule.
As ATP binds to the binding site the myosin head detaches from the actin.
How many of the Myosin Heads attach at a time out of the 2 during the contraction cycle?
Only one of the two.
How many of the Myosin Heads attach at a time out of the 2 during the contraction cycle?
Only one of the two.
What is the power stroke during the Contraction Cycle?
This is when the Myosin head is changing to its new position
Where does the energy of the power stroke come from?
It is the stored energy in the Myosin Head from the ATP Hydrolysis.
What happens at the end of the Power stroke?
ADP is released from the Myosin head.
What is Excitation-Contraction Coupling?
This is the sequence of events that links excitation to contraction.
What is the Length Tension Relationship?
This indicates how the Forcefulness of muscle contraction depends on the Length of the Sarcomeres within a Muscle before contraction begins.
What is the position of the Sarcomere for max Tension?
This is when the Zone of Overlap is between a Thick and Thin filament that extends from the edge of the H zone to one end of a thick filament.
What are the Steps to the Contraction Cycle?
1: ATP Hydrolosis
2: Attachement of Myosin to Actin
3: Power Stroke
4: Detachment of Myosin from Actin
What is step one to the Contraction cycle?
ATP Hydrolysis:
A myosin head includes an ATP binding site that functions as a ATPase. An enzyme that Hydrolyses ATP into ADP and a phosphate group.
The energy created is stored in the Myosin head for later.
What is step two to the contraction cycle?
Attachment of Myosin Head to Actin:
The energized Myosin head attaches to the myosin binding site on the Actin.
Releases the phosphate group.
A cross bridge is formed after the attachment.
What is step three to the contraction cycle?
Power Stroke:
After the cross bridge is formed the myosin head pivots.
As the myosin pivots it pulls the Thin Filament past the Thick Filament.
The energy needed for this is the energy derived form the Hydrolysis of ATP.
What is step four to the contraction cycle?
Detachment of Myosin Head from Actin:
At the end of the power stroke the cross bridge remains firmly attached until it binds to another ATP molecule.
As ATP binds to the binding site the myosin head detaches from the actin.
What is a cross bridge?
This is when a Myosin head attaches to actin during the contraction cycle.
What stage of the contraction cycle is the Cross bridge formed?
This occurs in the “Attachment of Myosin head” stage of the Cycle.
What happens to ATP in the Myosin head after the Power stroke occurs?
The ATP is released from the head.
At what point does the Myosin head detach from the Actin?
After the power stroke when another ATP molecule is binding to the ATP binding site.
The Myosin head will detach from the current Actin.
