Exam 3 Worksheet

Arrange the following in the order in which they occur at the postsynaptic side of a neuromuscular junction: 1. An action potential is propagated over the muscle cell membrane 2. Depolarization of the postsynaptic membrane 3. Sodium ions move into muscle cell

3, 2, 1

The absolute refractory period causes which of the following?

Action potential propagation to occur in one direction

Acetylcholine is actively transported from the presynaptic membrane to the postsynaptic membrane.

False

Action potentials travel in both directions on the axon.

False

Receptors that bind the neurotransmitter at the postsynaptic cell membrane are voltage-gated.

False

The sodium-potassium pump uses bulk transport to move the sodium and potassium ions.

False

At its peak, an action potential does which of the following?

It causes the inside of the neuron cell membrane to become positively charged in reference to the outside.

Upon arriving at the node of a myelinated neuron, the excitatory postsynaptic potential (EPSP) does which of the following?

It causes the neurons inner cell membrane to become more positively charged.

Acetylcholine has which effect on the postsynaptic neuron?

Ligand gated sodium ion channels open and sodium diffuses in.

Why does depolarization occur?

More Na+ diffuse into the cell than K+ diffuse out of it.

During depolarization, which of the following statements about voltage-gated ion channels is true?

Na+ gates open before K+ gates.

Why does repolarization occur?

Potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close.

What happens as a result of ion flow at a presynaptic terminal?

Synaptic vesicles migrate to the plasma membrane and release acetylcholine.

Which of the following statements about the resting membrane potential is true?

The exterior of the cell has a net positive charge and the interior has a net negative charge.

Why does hyperpolarization occur?

The increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level.

Which of the following is an immediate result of partial depolarization?

The sodium channels open and sodium ions pour into the intracellular fluid.

After the passage of the action potential, the sodium-potassium pump re-establishes the resting membrane potential.

True

During the transmission of an action potential along the neurilemma of a myelinated neuron, as one node is repolarizing, the next node is depolarizing.

True

If the postsynaptic membrane potential reaches threshold level, an action potential will be produced.

True

The area between the presynaptic nerve cell and the postsynaptic muscle cell is termed the synaptic cleft.

True

The inflow of sodium ions into the intracellular fluid causes depolarization of the neuron's inner cell membrane.

True

The nerve impulse is an electrical current that travels along dendrites or axons.

True

The sodium-potassium pump is involved in establishing the resting membrane potential.

True

Threshold is the minimum current required for the cell membrane to generate an action potential.

True

An action potential arriving at the presynaptic terminal causes what to occur?

Voltage-gated calcium ion channels open, and calcium ions diffuse into the cell.

The primary neurotransmitter at the neuromuscular junction is __________.

acetylcholine

An action potential generates local currents that tend to __________ the membrane immediately adjacent to the action potential.

depolarize