Muscle Contraction

Question 1

Describe the basic process of muscle contraction

Answer 1

Sarcomere is shortened
Size of actin and myosin filaments is unchanged
Actin and Myosin filaments slide past each other
Overlap has increased

Question 2

Describe the composition of an Actin Filament

Answer 2

Composed mostly of actin molecules. Each actin molecule contains a myosin binding site. Actin molecules also contain troponin and tropomyosin. While relaxed tropomyosin blocks access to the myosin binding sites. Tropomyosin is supported by the Troponin.

Question 3

Describe the cross bridge cycle involving actin and myosin filaments?

Answer 3

• Muscle is stimulated via motor neurone
• Calcium Ions are released from the sarcoplasmic reticulum
• calcium ions diffuse into muscle filaments and bind onto troponin
• troponin changes shape, shifting the tropomyosin that blocks the myosin receptors
• myosin heads now bind to myosin receptors on actin filaments
• myosin heads rotate and muscle contracts
• ATP now binds to myosin heads allowing them to detach and then reattach to next actin myosin binding site in the chain
• process repeats while calcium is available