7.1 How the Sacromere shortens Flashcards
What two other protein molecules are associated with Actin?
Tropomyosin and Troponin
In a contraction what brings about movement in action
Change in orientation of the myosin heads
Where does the nerve impulse arrive? Where does this impulse come from?
A neuromusclar junction which is positioned on the surface of the sacromella. The impulse originates from the motor neurone.
How does the nerve impulse spread from the whole muscle fiber?
Through transverse tubles
Where are the Calcium ions released from?
The sacroplasmic reticulum and doffuse into the sacroplasm.
What attaches to the troponin molecule?
Calcium ion attaches to the troponin molecule, causing it to move.
When the tropomyosin in the actin filament shifts postition what happens?
The myosin binding sites are exposed.
What binds to the myosin binding sites?
Myosin heads
What happens after the myosin head binds to the binding site?
ADP and Pi are released
After the ADP and Pi are released the myosin head changes shape. What is the consequence of this?
The myosin head moves forward causing relative movement of the filament and the attached actin moves over the myosin.
What binds to the myosin head after it nods forward? What does this cause?
An ATP molecule. It causes the myosin head to detach.
What hydrolyses the ATP?
ATPase on the myosin head forming ADP and Pi
What does the hydrolysis cause a change in?
The shape of the myosin head causing the myosin head to detach.
Therefore how is muscle contraction achieved?
Through the shortening of the sacromeres where many myosin heads combine to move the actin filaments relative to the myosin filament.
When a muscle relaxes what is it no longer stimulated by?
Nerve impulses
