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 period of time during which a second action potential cannot be initiated, no matter how large the applied stimulus is the absolute refractory period. Which statement is true for this period?

1. Potassium channels are open and the membrane is hyperpolarized
2. It immediately follows the relative refractory period
3. It allows an action potential to proceed in two directions along the length of an axon
4. It occurs when the sodium channels are open

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

An Inhibitory Post-Synaptic Potential:
1. causes depolarization
2. is caused by an increase in the permeability of the postsynaptic membrane to potassium or chloride ions
3. causes repolarization
4. is caused by an increase in the permeability of the postsynaptic membrane to sodium ions

Common inhibitory neurotrnasmitters in brain and spinal cord are:

1. Glutamate
2. GABA (gamma-amino-butyric aci4.
3. Glutamate and glycine
4. GABA (gamma-amino-butyric acid and glycine

The blood–brain barrier (BBB) separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS) and:

1. Functions to control the exchange of substances between blood and the extracellular fluid in the CNS

2. Is comprised of the cells that line the largest blood vessels in the brain

3. Is comprised of the cells that line the ventricles of the brain

4. Prevents diffusion of lipid soluble molecules from the blood to the brain

In the peripheral nervous system, the cells that are capable of forming a regeneration tube through which a severed peripheral axon can regrow are the:

1. Schwann cells
2. astrocytes
3. oligodendrocytes
4. microglia

The relatively static membrane potential of quiescent cells is called the:

All the following statements regarding the action potential are true except:
1. Only a relatively small number of ${\mathrm{Na}}^{+}$ and ${\mathrm{K}}^{+}$ ions actually diffuse across the membrane.
2. This event includes both positive and negative feedback loops.
3. The ${\mathrm{Na}}^{+}$/${\mathrm{K}}^{+}$ pumps are directly involved in creating the action potential.
4. During an action potential, the ${\mathrm{Na}}^{+}$ and ${\mathrm{K}}^{+}$ total concentration are not significantly changed.

A local anesthetic is a medication that causes reversible absence of pain sensation. They:
1. block the closure of voltage regulated potassium ion channels
2. stimulate the opening of voltage regulated potassium ion channels
3. block the opening of the voltage regulated sodium ion channels
4. stimulate the opening of voltage regulated sodium ion channels