Which one of the following statements is true concerning fluid compartments in the body.
A. The body is 80% water. No, the body is approximately 60% water.
B. Total body water is equally divided among all the fluid compartments. No, approximately two-thirds of TBW is intracellular, the remainder is extracellular.
C. Intracellular fluid is approximately two-thirds of the total body water. Correct.
D. Extracellular fluid has the same ionic composition as intracellular fluid. No, these fluid spaces have very different ionic compositions.
E. Plasma is intracellular fluid. No, plasma is part of the extracellular fluid.

All of the following can be components of a cell membrane except:
A. deoxyribonucleic acid. No, most DNA is found in the aqueous phase within the nucleus.
B. phospholipids. Correct.
C. protein. Correct.
D. glycoprotein. Correct.
E. cholesterol. Correct.

One function of a cell membrane and its components is to:
A. synthesize long-chain carbohydrates. No, this usually occurs in the cytosol.
B. regulate the transport of substances to and from the intracellular fluid compartment. Correct.
C. synthesize DNA and RNA. No, this primarily occurs in the nucleus.
D. allow the free movement of substance to and from the plasma fluid compartment. No, the transport is regulated.
E. prevent cells from exchanging substances with their environment. No, cells require a regulated transport of substances to and from the intracellular fluid compartment.

Membrane junctional proteins can provide
A. energy to cells. No, energy is provided by intracellular metabolism.
B. fluid exchange between the intracellular and extracellular environment. No. However, they may allow exchange from one cell to another (gap junctions).
C. exchange of lipids between cells. No, this is not a process that normally occurs.
D. ion exchange between the intracellular and extracellular environment. No. However, they may allow exchange from one cell to another (gap junctions).
E. a physical linkage between cells. Correct.

Primary active transport mechanisms:
A. do not require energy. No. Energy is an absolute requirement.
B. can move a substance up its concentration gradient. Correct.
C. indirectly couple the transport of one molecule with that of another. No. Substances are directly transported.
D. indirectly usesconcentration gradients to move substances. No. A concentration gradient is not required.
E. are unaffected by metabolic poisons. No. Energy is required.

Facilitated transport (facilitated diffusion) will:
A. move a substance up its concentration gradient. No. A "downhill" gradient is required.
B. require the direct expenditure of energy. No. It is a passive process.
C. require a concentration gradient. Correct. It is a passive process.
D. create a concentration gradient. No. It is a passive process.
E. result in zero net-flux of the transported substance. No. The substance moves down its concentration gradient.

An isotonic solution
A. results in the net movement of water out of a cell. No.
B. results in the net movement of water into a cell. No.
C. creates a concentration gradient for impermeant substances. No.
D. can be hyperosmolar. Correct.
E. is always isoosmotic. No.

If potassium has a concentration of 12 mM outside a cell and 120 mM inside a cell, its equilibrium potential at body temperature is (hint, a calculator is not necessary):
A. -60 mV. Correct. The log10 of 12/120 is 1, times -60 mV.
B. 60 mV. No.
C. 120 mV. No.
D. -120 mV. No.
E. 30 mV. No.

If calcium ions (z=+2) have a higher concentration outside the cell than inside, the equilibrium potential for calcium will be:
A. negative. No. A positive potential would be required to maintain the concentration difference.
B. positive. Correct.
C. zero. No.
D. opposite to the sodium equilibrium potential. No.
E. equal to the sodium equilibrium potential. Not necessarily. The ions are independent of one another.

The resting membrane potential is often near the potassium equilibrium potential because:
A. the sodium permeability is high. No.
B. sodium and potassium have similar permeabilities. No.
C.intracellular protein excludes sodium. No.
D. the membrane permeability to potassium is high relative to the sodium permeability. Correct.
E.the membrane permeability to all ions except for potassium is high. No.

A graded potential:
A. is determined by the sodium equilibrium potential. No. Other ions can also cause a graded potential.
B. decrements in time and distance. Correct.
C. will always produce an action potential. No. Only if it is above threshold.
D. decrements in time but not distance. No. A graded potential will decrement in both time and distance.
E. is always depolarizing. No. Graded potentials can also be hyperpolarizing.

Two graded potentials:
A. can summate when they occur near to each other in time but not distance. No. They must occur near one another in both time and distance.
B. can summate when two action potentials occur at the same time. No. Action potentials do not summate.
C. can summate to cancel one another. Correct, if one is depolarizing and the other hyperpolarizing.
D. cannot summate during the relative refractory period. No. Refractoriness does not affect graded potentials.
E. cannot summate during the absolute refractory period. No. Refractoriness does not affect graded potentials.

The sodium permeability of an electrically excitable cell membrane is highest:
A. near the peak positive value of an action potential. Correct
B. before an action potential begins. No. Sodium permeability is low at this point.
C. during the absolute refractory period. No. Sodium channels are inactive.
D. at the same time that potassium permeability is greatest. No. Sodium permeability decreases as potassium permeability increases.
E. during hyperpolarization following an action potential. No. Potassium permeability is high at this point, so membrane potential is near the potassium equilibrium potential.

Some local anesthetics, such as lidocaine, work on nerves by:
A. blocking potassium channels. No.
B. causing potassium channels to open. No.
C. causing sodium channels to become hypersensitive. No.
D. blocking chloride channels. No.
E. blocking sodium channels. Correct.

For an action potential to propagate in a nerve, the nerve membrane nearby an area that is firing an action potential must:
A. be hyperpolarized. No. This would decrease the probability of an action potential in the nearby membrane.
B. be brought above threshold. Correct. This occurs through local circuit currents.
C. be absolutely refractory. No. This would decrease the probability of an action potential in the nearby membrane.
D. be relatively refractory. No. This would decrease the probability of an action potential in the nearby membrane.
E. be without sodium channels. No. The sodium channels are essential for action potentials in nerves

Myelinated have a greater conduction velocity than unmyelinated fibers because:
A. they are smaller. No. Smaller fibers usually have a slower velocity of conduction.
B. they have a smaller space constant. No. The space constant is larger because the membrane resistance is greater.
C. the Nodes of Ranvier are unequally spaced. No. Unmyelinated fibers do not have nodes.
D. they have a larger space constant. Correct.
E. they are larger. No. Myelination is not a determinant of fiber diameter, though larger fibers (myelinated or unmyelinated) generally have a greater conduction velocity than unmyelinated fibers.


Which one of the following factors would increase the velocity of nerve conduction?
A. Reduction in nerve fiber diameter. No.
B. Hyperpolarization by 10 mV. No.
C. Demyelinating disease (loss of myelin). No.
D. Decreased extracellular sodium concentration. No.
E. Increase in nerve fiber diameter. Correct.

The myelin sheaths from Schwann cells:
A. increases membrane resistance between Nodes of Ranvier. Correct.
B. increases membrane resistance at the Nodes of Ranvier. No. They increase membrane resistance between the nodes and thus increase the space constant.
C. decreases the space constant. No. They increase the space constant by increaseing membrane resistance.
D. increases the magnitude of the action potential. No. Action potentials have a relatively fixed magnitude (approaching the equilibrium potential for sodium).
E. decreases the magnitude of the action potential. No. Action potentials have a relatively fixed magnitude (approaching the equilibrium potential for sodium).

Inhibitory post-synaptic potentials (IPSPs):
A. increase the probability of a threshold depolarization. No.
B. decrease the probability of a threshold depolarization. Correct.
C. are caused by an increase in sodium permeability. No. Potassium permeability increases.
D. are cause by a decrease in potassium permeability. No. Potassium permeability increases.
E. cannot occur unless accompanied by an EPSP. No. They are independent.

A post-synaptic potential is:
A. excitatory if it hyperpolarizes the post-synaptic membrane. No.
B. inhibitory if it depolarizes the post-synaptic membrane. No.
C. excitatory if it depolarizes the post-synaptic membrane. Correct.
D. inhibitory if it depolarizes the pre-synaptic membrane. No.
E. excitatory if it hyperpolarizes the pre-synaptic membrane. No.

Which one of the following does NOT occur during chemical synaptic transmission:
A. diffusion of the neurotransmitter across the synaptic cleft. This DOES occur.
B. binding of the neurotransmitter to its receptor. This DOES occur.
C. influx of calcium into the pre-synaptic neuron. This DOES occur.
D. removal of neurotransmitter from the synaptic cleft. This DOES occur.
E. fusion of synaptic vesicles with the post-synaptic membrane. This does NOT occur.

Monoamine oxidase (MAO) degrades the biogenic amine neurotransmitters. Inhibitors of this enzyme are often given as antidepressants. These inhibitors would have the effect of:
A. increasing the concentration of the neurotransmitter in synaptic clefts. Correct.
B. decreasing the concentration of the neurotransmitter in synaptic clefts. No. Concentration would increase.
C. decreasing the reuptake of the neurotransmitter by the neurons. No. Uptake would not be affected.
D. increasing the amount of calcium that enters the pre-synaptic terminal. No. Calcium entry would not be affected.
E. increasing the number of receptors on the post-synaptic membrane. No. Receptor number would not be affected.