Answer:
a. Myosin heads attach to and pull on a series of actin-binding sites.
Explanation:
Muscle contraction is a phenomenon whereby the muscles in the body responds to electrical activity also known as stimulus when an action potential travels or moves through the nerve fibres of the muscles.
Muscle contraction is explained by a mechanism known as the Sliding filament mechanism.
Muscle contraction occurs when the protein in the muscles known as Actin and Myosin slide over each other and this is due to the presence sufficient calcium ions which are released by protein filaments also known as sacromeres in the body when they are stimulated.
The calcium ions that are released causes the tropomyosin to detach itself from the binding sites on the actin filaments, allowing myosin heads to bind to the actin which results in the formation of a cross bridge.
The sacromeres then contract and become shorter and this leads to the contraction of the muscles.
