What is true for the events that occur during the generation of an action potential?
1. Potassium channels in the membrane open in response to depolarization
2. Sodium channels in the membrane open in response to neurotransmitter released from the adjacent membrane
3. The increase in sodium permeability in the membrane is an example of positive feedback
4. The movement of sodium into the neuron causes the cell to hyperpolarize

All the following statements with respect to the propagation of action potentials are correct except:
1. Saltatory conduction occurs in myelinated nerve fibers
2. During conduction of an action potential, current flows from the active area of the membrane to the adjacent inactive area, thereby decreasing the potential in the inactive area to the threshold
3. Action potential propagation is faster in myelinated fibers than in unmyelinated ones
4. Action potential propagation is faster for strong stimuli than for weaker stimuli

The change in membrane potential that returns it to a negative value just after an action potential has changed the membrane potential to a positive value is called as:

During the propagation of a nerve impulse, the action potential results from the movement of

1. Na⁺ ions from extracellular fluid to intracellular fluid.
2. K⁺ ions from extracellular fluid to intracellular fluid.
3. Na⁺ ions from intracellular fluid to extracellular fluid.
4. K⁺ ions from intracellular fluid to extracellular fluid.                         

All the following statements regarding nerve impulse conduction are correct except:
1. Myelinated neurons have a higher conduction velocity than unmyelinated neurons.
2. Nerve impulses occur in an all-or-none manner.
3. The neuron cannot be stimulated during the depolarization phase.
4. The strength of impulses carried along a single nerve fiber can vary with the strength of their stimulus.

Threshold stimuli are those that are strong enough to:
1. Hyperpolarize the neuron membrane
2. Cause a net flux of negatively charged ions from inside to outside the cell
3. Cause a net flux of positively charged ions from outside to inside the cell
4. Close calcium channels to retain them in the cell

The resting axonal membrane is impermeable/nearly impermeable to:
I. Sodium ions
II. Potassium ions
III. Negatively charged proteins