anatomy test 3

Each muscle cell (fiber) is surrounded by this tissue:

• perimysium

• endomysium

• epimysium

• sarcolemma

Troponin binds to this:

• G actin

• calcium ions

• tropomyosin

• all of these

• a and c only

During muscle contraction, this region shortens:

• A band

• I band

• H zone

• both a and b

• both b and c

These statements about myosin myofilaments are all true except:

• are thicker than actin

• make up the H zone

• attached to the Z disc

• attached to filaments that form the M line

Depolarization must reach this value in a cell to trigger an action potential:

• 0 mv

• +20 mv

• -85 mv

• threshold

Energy is needed to make muscles contract and relax.

• True

• False

These events occur during contraction except:

• exposure of active sites on actin

• active transport of Ca+ back into sarcoplasmic reticulum

• cross-bridges are formed and released

• power stroke

List the events occurring at a neuromuscular junction in order.

1. ACh binds to receptors on postsynaptic membrane

2. acetylcholinesterase breaks down ACh

3. choline is reabsorbed by presynaptic membrane

4. depolarization of sarcolemma

5. ligand-gated Na+ ion channels open

• 1, 5, 4, 2, 3

• 5, 3, 2, 1, 4

• 1, 4, 2, 3, 5

• 1, 5, 2, 3, 4

This kind of contraction results in an increase of tension, but the length of the muscle does not change:

• isometric

• isotonic

• concentric

• eccentric

Incomplete tetanus occurs when action potentials are produced so rapidly that the muscle completely contracts without any relaxation.

• True

• False