Muscles

The upper arm at the shoulder is the location of the deltoid. It is the gluteus medius (rather than the gluteus maximus) that is used for IM injections to avoid the sciatic nerve.

The hydrolysis of ATP energises the cross-bridge (myosin molecules do not get shorter; calcium binds to troponin, not tropomyosin; calcium returns to the SR after contraction).

An agonist muscle causes a movement to occur (by contracting), while an antagonist muscle cooperates in the movement by relaxing (allowing itself to lengthen).

Choice A lasts for a few seconds only. Choice B can provide energy for a couple of minutes. Choice C can provide energy for vigorous activity lasting about 15 s.

While there are thick and thin myofibrils within a sarcomere, choice C is the better answer.

While the erector spinae and infraspinatus are on the dorsal side, their partners are not. Choice A muscles are on the ventral surface.

A skeletal muscle cell is a “syncytium” being derived from many cells and so retains their many nuclei.

Both types of muscle cells are striated. Choices B, C and D are characteristics of cardiac muscle cells only.

Myosin is a molecule that makes up a thick myofilament. Many thick and thin myofilaments make up a sarcomere. Many sarcomeres joined end to end form a myofibril.

Aerobic respiration produces 36 ATP molecules, while anaerobic respiration produces just 2 molecules of ATP.