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

A: Troponin causes tropomyosin (which covers the binding site of actin) to be shifted away.

C: The origin is on the sternum and clavicle (sternocleido-), while the insertion (on the “moving bone”) is to the mastoid process of the temporal bone.

C: Ca must first enter the cytoplasm in order to bind with troponin. Once the binding site is exposed, the myosin head may engage the site. Prior to engagement, ATP must be hydrolysed to ADP.

D: “Sarco-” refers to flesh (muscle); “lemma-” refers to sheath (membrane) around the cell.

D: Femoris refers to location on the femur; quadriceps refers to four origins.

A: A myofibril extends the length of a muscle cell. A myofilament is shorter than a sarcomere, while myosin is a molecule in a thick myofilament.

A: Adduction is the action of bringing an abducted bone back towards the body’s midline.

A: Ca+ attaches to troponin causing a shape change which shifts the attached tropomyosin away from binding sites of actin.

A: 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.

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

B: They are two of the three “hamstring” muscles on the dorsal thigh, the other being the biceps femoris.

C: Actin is the major component of a thin filament. Tropomyosin covers the biding site, while troponin provides the mechanism for removing tropomyosin from the binding site.

D: Smooth muscle is not striated, and it is involuntary and has one nucleus.

D: The release of Ca+ from where it is stored (in the sarcoplasmic reticulum) is necessary before the active binding site of actin can be exposed.

C: A myofilament is a long line of sarcomeres joined end to end. So one section of a myofilament is a sarcomere.

C: Ligament is the “ligature” that joins articulating bones. A tendon (or an aponeurosis) attaches a muscle to a bone.

A: Sarcoma refers to a malignant tumour (a cancer) of connective or other non-epithelial tissue (bones, muscles, tendons, cartilage, nerves, fat and blood vessels).

B: A muscle cell is a bundle of myofibrils. Myofibrils contain many sarcomeres joined end to end. Within sarcomeres are found (the shorter) thick and thin myofilaments.

C: An agonist muscle performs the action, while the antagonist must relax (be stretched) while the action is being performed (and can reverse the action of the agonist).