Neuromuscular Junction

One neuron and all the skeletal muscles it stimulates is known as a ________.

• sarcoplasmic reticulum

• motor unit

• synaptic cleft

• neuromuscular junction

What is the unstoppable electrical current that travels down the length of the entire surface of a sarcolemma?

• neurotransmitter

• graded response

• acetylcholine

• action potential

What is released by axon terminals into the synaptic cleft to stimulate a muscle to contract?

• potassium ions

• sodium ions

• acetylcholine

• actin

Why are calcium ions necessary for skeletal muscle contraction?

• Calcium ions increase the speed of the action potential transmitted along the sarcolemma.

• Calcium ions release the inhibition on Z discs.

• Calcium ions trigger the binding of myosin heads to actin filaments.

• Calcium ions cause ATP binding to actin.

What is acetylcholine?

• an ion pump on the postsynaptic membrane

• a source of energy for muscle contraction

• a component of thick myofilaments

• a neurotransmitter that stimulates skeletal muscle to contract

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

• motor unit

• synaptic cleft

• cross bridge

• sarcomere

What must rush into a muscle cell to promote its depolarization?

• potassium ions

• calcium ions

• acetylcholine

• sodium ions

What enzyme breaks down acetylcholine into acetic acid and choline to prevent continued contraction of the muscle fiber?

• potassium ions

• calcium ions

• cross bridges

• acetylcholinesterase

Neurotransmitters are released upon stimulation from a nerve impulse from the ________.

• axon terminals of the motor neuron

• myofibrils

• sarcolemma of the muscle cell

• sarcoplasmic reticulum

Which of these events must occur first to trigger the skeletal muscle to generate an action potential and contract?

• Potassium ions diffuse out of the muscle cell.

• Acetylcholine (ACh) binds to receptors on the sarcolemma and allows passage of sodium ions into the cell.

• The sodium-potassium pump restores sodium and potassium back to their initial positions.

• Acetylcholinesterase (AchE) breaks down acetylcholine (ACh).