Muscles

The contraction of a myofibril is due to the shortening of its component sarcomeres.

All somatic motor neurons release ACh at their synapses with skeletal muscle fibres, that is, at the neuromuscular junction.

The release of Ca from where it is stored (in the SR) is necessary before the active binding site of actin can be exposed.

A muscle fascicle is a bundle of muscle fibres (cells). Choice A and B are smaller than a cell.

Vigorous exercise may require more oxygen than can be supplied by the circulation. In this case ATP must be produced anaerobically which is less efficient than when sufficient oxygen is present. Hence choices C and D are wrong.

Thin myofilaments contain these three proteins. Choices C and D are wrong as myosin has a cross-bridge rather than a binding site.

Creatinine phosphate is used to “recharge” the ADP that forms from ATP when the cross-bridge is energised.

Smooth muscle occurs in the walls of tubes, whereas skeletal muscle does not.

The syllable “mys-” refers to muscle. The other choices refer to the heart, abdomen and bone, respectively.

There are three (not four) muscles in the hamstrings. The rectus femoris and vastus lateralis are in the quadriceps, not the hamstrings.