lecture 9 - muscle tension/contraction Flashcards
What are the key components of the myofilament?
Actin and myosin
What is actin in a myofibril?
A thin filament that runs along the myofilament and forms a structural scaffold.
What is myosin in the myofibril?
Myosin is a thick filament that acts as a motor molecule, when attaching to actin, generating a force.
What are the relative positions of Actin and Myosin and rest?
They are not in contact.
What must be supplied to the myofilament for contraction to occur?
Calcium ions (Ca2+)
What is a cross-bridge?
A bond between actin and myosin that allows the sarcomere to contract and shorten towards its centre.
What are the 5 states of the cross bridge cycle?
Attached, Released, Cocked, Cross-bridge, Power-stroke.
What is the attached state of the cross-bridge cycle?
Myofilament has just finished a power stroke (ADP and P has been released from myosin head), and the actin-myosin cross bridges are still present.
What is the released state of the cross-bridge cycle?
A molecule of ATP binds to myosin, causing its head to detach from actin, removing the cross-bridge.
What is the cocked state of the cross-bridge cycle?
The Myosin head burns ATP to make energy and a phosphate group binds to it. Energy is stored by changing the shape of Myosin, preparing it to attach to actin again.
What is the cross-bridge state of the cross-bridge cycle?
If calcium is present, the myosin head binds to the actin myofilament forming a cross bridge.
What is the power-stroke state?
The energised myosin head uses its stored energy to change conformation, releasing P and creating a power stroke that causes filaments to slide past each other to contract the sarcomere.
What are the two factors that muscle tension is dependent on?
The number of muscle fibres recruited and the rate at which the muscle is stimulated.
If a small number of neutrons are active, muscle force will be…?
Low
What is the name of the process of activating more muscle fibres to generate more force?
Recruitment