11.2

What is bone X and muscle Y in the diagram of the elbow joint?

• Bone X: radius Muscle Y: biceps

• Bone X: radius Muscle Y: triceps

• Bone X:ulna Muscle Y: biceps

• Bone X: ulna Muscle Y: triceps

What is a function of synovial fluid in the elbow joint?

• Joins the humerus to the radius and ulna

• Grows red blood cells

• Protects the biceps

• Allows easy movement

What is the role of calcium in muscle contraction?

• To release tropomyosin from myosin

• To bind to troponin so myosin-binding sites on actin are exposed

• To bind to tropomyosin so ATP can bind to actin

• To release ATP from actin so myosin can bind to troponin

Which process is part of the mechanism that controls muscle contraction?

• Troponin enables actin heads to attach to ATP and slide along myosin.

• Myosin heads attach to troponin and tropomyosin pulls on actin filaments.

• Tropomyosin attaches to calcium and breaks the bond between actin and myosin.

• Calcium frees actin filaments for myosin heads to attach.

What is the role of the joint capsule in an elbow joint?

• It seals the joint to retain the synovial fluid.

• It provides a point of attachment for muscles.

• It produces cartilage to reduce friction during movement.

• It directs the formation of bone tissue during growth and development.

What structure is indicated by the arrows?

• One muscle fibre

• One sarcomere

• One myofibril

• One Z line

A skeletal muscle contains bundles of elongated muscle fibre cells. What is the longest structure within each fibre?

• A myosin filament

• The sarcomere

• A myofibril

• The Z line

Which processes require calcium?

I. Muscle contraction

II. Movement of an action potential along an axon

III. Production of the skeleton of hard corals

• I and II only

• I and III only

• II and III only

• I, II and III

Which of the following is the function of myosin and actin in muscle contraction?

• formation of cross-bridges bind to actin

• sliding of actin and myosin filaments

• contraction ceases when myosin head detaches from actin

• all of the above

Which part of the myofibril releases calcium ions?

• Sarcolemma

• T tubules

• Sarcoplasmic reticulum

• Actin and myosin