During skeletal muscle contraction, myosin cross bridges attach to active sites of:

• actin filaments

• the H zone

• Z discs

• myosin filaments

• thick filaments

Muscle tissue that has involuntary regulation of contraction is:

• skeletal muscle only

• cardiac muscle and skeletal muscle

• smooth muscle only

• cardiac muscle only

• cardiac muscle and smooth muscle

The striations that give skeletal muscle its characteristic striped appearance are produced, for the most part, by:

• a difference in the thickness of the sarcolemma

• the arrangement of myofilaments

• the "cocked" positions of the heads of the thick filaments

• the T tubules

• the sarcoplasmic reticulum

Creatine phosphate (CP) functions within the muscle cells by:

• inducing a conformational change in the myofilaments

• storing energy that will be transferred to ADP to resynthesize ATP as needed

• forming a chemical compound with actin

• storing energy that will be transferred to ATP to resynthesize ADP as needed

• forming a temporary chemical compound with myosin

The condition of skeletal muscle fatigue can be best explained by:

• inadequate numbers of mitochondria

• the inability to generate sufficient quantities of ATP due to feedback regulation of synthesis

• the all-or-none law

• insufficient intracellular quantities of ATP due to excessive consumption

• a total lack of ATP

The axon terminals of a nerve cell and the sarcolemma of a skeletal muscle cell join at the:

• neuromuscular junction

• myofibril

• action potential

• motor unit

• synaptic cleft

The mechanical force of contraction is generated by:

• the temporary disappearance of thin filaments

• shortening of the thick filaments

• shortening of the thin filaments

• the "accordian-like" folding of thin and thick filaments

• a sliding of thin filaments past thick ones

Acetylcholine is:

• an oxygen-binding protein

• a source of energy for muscle contraction

• a neurotransmitter that stimulates skeletal muscle

• an ion pump on the postsynaptic membrane

• a component of thick myofilaments

The gap between the axon terminal of a motor neuron and the sarcolemma of a skeletal muscle cell is called the:

• sarcomere

• cross bridge

• neuromuscular junction

• synaptic cleft

• motor unit

Neurotransmitters are released upon stimulation from a nerve impulse by the:

• motor unit

• thick filaments

• myofibrils

• sarcolemma of the muscle cell

• axon terminals of the motor neuron