Anatomy Practice Exam

What component do actin and myosin interact to enable?

1. Blood circulation

2. Nerve signal transmission

3. Muscle contraction

4. Bone growth

The correct answer is: Muscle contraction

Actin and myosin are two essential proteins that play a critical role in muscle contraction. They are found in muscle cells and are responsible for the sliding filament mechanism, which is the fundamental process that enables muscles to contract. When a muscle receives a signal to contract from the nervous system, these proteins interact with each other, resulting in the shortening of muscle fibers. During contraction, myosin heads attach to actin filaments, forming cross-bridges. They then pivot, pulling the actin filaments inward, which causes the entire muscle fiber to shorten and produce force. This interaction is regulated by calcium ions and ATP, highlighting the importance of actin and myosin in enabling movement. In contrast, blood circulation involves the heart and blood vessels, nerve signal transmission pertains to the action of neurons and neurotransmitters, and bone growth involves processes such as ossification and remodeling that do not directly involve the actin and myosin proteins. Therefore, muscle contraction is the precise interaction that actin and myosin facilitate.