Neuroscience Test 2 Practice Questions

A good definition of a nerve impulse is a. a transient change in the charge on the membrane of the cell which moves along the length of the neurite. b. a sudden influx of sodium ions. c. a sudden influx of potassium ions. d. a change in membrane potential with a definite time course.

A

A nonspiking neuron a. continually releases transmitter substance in a graded fashion. b. does not generate action potentials because it uses only electrical synaptic transmission. c. is an inhibitory type of neuron that reacts by hyperpolarizing when it is stimulated. d. does not generate action potentials because it totally lacks Na+ channels.

A

A placebo may act to reduce pain by inducing the brain to a. increase endorphin levels. b. increase substance P levels. c. selectively block some neuromuscular transmission. d. increase blood glucose levels.

A

A voltage sensitive ion channel is a channel a. whose conductance to an ion changes as the membrane potential changes. b. that allows different ions to pass through when the membrane potential is near zero than when it does when the membrane potential is near resting level. c. that desensitizes when the neuron depolarizes. d. that becomes non-functional when the membrane becomes inside positive.

A

Acetylcholine is known to be a transmitter substance at a. the vertebrate neuromuscular junction. b. the arthropod neuromuscular junction. c. synapses in the substantia nigra. d. synapses involved in transmission of pain.

A

Halving the external sodium concentration around a neuron would do what to an action potential? a. Reduce its amplitude. b. Increase its amplitude. c. Eliminate it. d. Leave it unchanged.

A

In a given neuron, action potentials are always the same size under normal conditions. This statement a. is true because the concentrations of the inward and outward flowing ions don't change appreciably over time in normal cells. b. must be false because it is known that AP's change size during facilitation. c. is true because action potentials are never recorded the same size twice extracellularly. d. must be false because the flow of ions during one AP changes the concentration gradients enough to the affect the size of the next AP.

A

Most of the neurons whose cell bodies are in the Substantia nigra use ______ as a transmitter substance. a. dopamine b. serotonin c. norepinephrine d. Substance P

A

Neurons in the Raphe nuclei seem to use which transmitter substance? a. Serotonin. b. Dopamine. c. Octopamine. d. Epinephrine.

A

Patch clamping refers to a technique a. for manipulating the voltage across a restricted patch of membrane so that the ion flow through single channels can be studied. b. for grasping a patch of membrane tightly, to make it possible to penetrate small, hard-to-record-from cells in the CNS. c. used by Hodgkin & Huxley to determine resting potentials in squid giant axons. d. used by Hodgkin & Huxley to determine which ions carry the action potential in squid giant axons.

A

Suppose you apply electrodes to the middle of a squid giant axon and apply a supra-threshold stimulus. The result will be a. two action potentials, one traveling toward the cell soma, one traveling toward the end of the axon. b. no action potential, since supra-threshold stimuli must be applied on a dendrite to be effective. c. a single action potential traveling toward the cell soma, away from the end of the axon. d. a single action potential traveling away from the cell soma, toward the end of the axon.

A

The conductance of an ion depends on a. the density of open channels for that ion in the membrane. b. the concentration and electrical gradients of the ion. c. the total number of all channels for that ion in the membrane. d. all of the above.

A

The enzyme MAO acts in the a. degradation of serotonin. b. degradation of acetylcholine. c. synthesis of dopamine. d. synthesis of acetylcholine.

A

The process of conduction of an action potential involves the following steps a. depolarization --> increase Na+ conductance --> increased K+ conductance and Na+ inactivation --> decreased K+ conductance. b. increased Na+ conductance --> depolarization --> increased K+ conductance and Na+ inactivation --> decreased K+ conductance. c. depolarization --> decreased K+ conductance --> increased Na+ conductance --> increased K+ conductance and Na+ inactivation. d. increased Na+ conductance --> decreased K+ conductance --> increased K+ conductance and Na+ inactivation --> depolarization.

A

The protein that has been shown to form a cage-like barrier around clear synaptic vesicles is known as a. synapsin I. b. kinesin. c. tubulin. d. kinysin I.

A

The repolarization of the membrane during an action potential is due largely to a. an increase in K+ conductance. b. the passive influx of Cl- ions inside the neuron. c. the opening of Na+ channels. d. action of the ATP-dependent Na-K pump, which recreates the ion gradients.

A

The theoretical limit to the peak of the action potential is a. ENa+ b. EK+ c. ENa+ - EK+ d. EK+ - ENa+

A

Which of the following substances is NOT considered a realistic candidate for a transmitter substance? a. Vitamin C. b. Glycine. c. Acetylcholine. d. Serotonin.

A

The all-or-none principle of nerve action states that a. the entire length of the nerve conducts an action potential or no part does. b. an action potential always reaches its maximum strength or it doesn't appear at all. c. all available ions contribute to the rise and fall of the action potential or none do. d. all synapses on a neuron must be active in order for them to excite it.

B

A typical intracellularly recorded resting potential for a neuron is a. about +54 mV b. about -60 mV c. indeterminate, because you cannot determine the resting potential from the Nernst equation, which would apply to the intracellular recording situation. d. nothing, because you cannot record a resting potential by using intracellular recording.

B

Acetylcholine seems unusual among non-peptide transmitter substances in that it a. can cause an action potential directly in the synaptic membrane. b. is inactivated entirely by extracellular enzymatic breakdown. c. is usually found together with a neuromodulatory co-transmitter. d. can act directly on axonal membrane to cause the opening of voltage-sensitive sodium channels.

B

As a rule, saltatory conduction is faster than non-saltatory conduction because a. myelinated neurons have a lower internal resistance than do non-myelinated ones, thereby leading to faster conduction. b. the insulation provided by myelin forces the depolarizing current farther down the axon, thereby allowing the AP to skip parts of the membrane. c. myelinated axons are bigger than non-myelinated ones, and larger diameter axons conduct faster. d. the concentration of sodium channels at the nodes generates much larger than normal Na+ currents, which generate faster conduction.

B

At chemical synapses, the ion thought to be necessary inside the presynaptic cell to facilitate the release of transmitter is a. Na+. b. Ca2+. c. K+. d. Cl-.

B

Destruction of the Raphe nuclei or injection of certain drugs in cats causes insomnia. Injection of 5-HTP relieves this insomnia, suggesting that a. 5-HTP can be used to induce sleep. b. serotonin may be the transmitter in brain pathways that control sleep. c. cats have neuron centers for both sleeping and wakefulness. d. dopamine may be the transmitter in brain pathways that control sleep.

B

Dopamine is a(n) a. amino acid. b. catecholamine. c. monoamine, but not a catecholamine. d. peptide.

B

During chemical synaptic transmission, which of the following sequences of events occurs in a presynaptic neuron? a. Depolarization of the terminal --> Ca2+ entry --> AP in axon --> vesicle fusion --> transmitter release. b. AP in axon --> depolarization of the terminal --> Ca2+ entry --> vesicle fusion --> transmitter release. c. Ca2+ entry --> AP in axon --> depolarization of the terminal --> vesicle fusion --> transmitter release. d. AP in axon --> Ca2+ entry --> depolarization of the terminal --> vesicle fusion --> transmitter release.

B

During the action potential the nerve cell can be considered a sodium battery because a. there is movement of sodium across the membrane. b. the membrane potential at the peak of the action potential is mainly determined by the external concentration of Na+. c. sodium must be pumped out again later. d. more sodium rushes in than potassium rushes out.

B

In neurons, a voltage clamp device is used to measure a. the resting membrane potential. b. current flow under certain experimental conditions. c. the currents flowing at the peak of the action potential. d. the potential at the peak of the action potential.

B

Quantal release of neurotransmitter refers to the fact that a. Only one molecule is released at a time. b. Transmitter is released in packets (units). c. Only one axon releases transmitter at a given instant. d. Only one packet of transmitter is released at a time.

B

Raising substantially the internal concentration of sodium in an axon would do what to an action potential? a. Increase its amplitude. b. Reduce its amplitude. c. Prevent its development by blocking ion channels from the inside. d. Leave it unchanged.

B

Re-uptake is the process of entry of transmitter a. precursor molecules into a neuron after synaptic transmission. b. molecules into a neuron after synaptic transmission. c. molecules through post-synaptic binding sites. d. precursor molecules into a neuron before synaptic transmission.

B

Some of the peptide neurotransmitter substances seem to be especially involved in a. hunger. b. pain. c. thirst. d. neuromuscular control.

B

The histofluorescence technique involves the a. production of fluorescent histones in the tissue to be studied. b. interaction of chemicals in the tissue under study with formaldehyde to form a fluorescent material. c. histological study of the distribution of naturally occurring fluorescent materials. d. measurement of the amount of fluorescent antibodies in tissue after appropriate chemical treatment.

B

The immediate energy required for an action potential is a. stored in the form of ATP. b. the potential energy of the ion imbalances across the membrane. c. the energy contained in the structure of the cell membrane. d. none of the above.

B

Tryptophan is a precursor of a. MAO. b. serotonin. c. norepinephrin. d. COMT.

B

Which of the following statements is true for most dendritic membrane AND for axonal membrane just after an action potential has passed (i.e., during the refractive period) a. There are receptor sites available to bind with transmitter substance. b. There are no voltage-sensitive sodium channels in an operational state. c. There are no voltage-sensitive potassium channels in an operational state. d. The membrane has high permeability to calcium ions.

B

Action potentials travel relatively slowly along unmyelinated axons that have small diameters because a. the Na+/K+ exchange pump cannot pump out Na+ fast enough to restore the membrane potential quickly. b. there are relatively few ion channels per mm2 in the axonal membrane. c. the internal resistance of the axoplasm is higher, retarding the spread of electrical charges along the axon. d. the electrical resistance of the axonal membrane is higher, slowing down the rate at which the membrane can depolarize.

C

Compared to other regions of the vertebrate brain, brainstem nuclei seem especially rich in a. acetylcholine. b. substance P. c. 5-hydroxytryptamine. d. octopamine.

C

During the absolute refractory period of a neuron, the threshold of the neuron is extremely high because a. it can not be depolarized, due to a temporary increase in Cl- conductance. b. an action potential has just passed by. c. sodium inactivation has closed the sodium channels temporarily so they do not open in response to reductions in membrane potential. d. all the external sodium has entered the neuron and must be pumped out before the nerve can fire again.

C

During the rising phase of an action potential the current flow is dominated by a. an inward K+ current. b. an outward K+ current. c. an inward Na+ current. d. an outward Na+ current.

C

Hodgkin and Huxley a. demonstrated the quantal nature of neuromuscular transmission. b. described the physiological properties of synaptic transmission. c. revealed the quantitative movements of ions across the membrane that lead to an action potential. d. studied the quantitative relation between ion movements and the post synaptic potential in a squid.

C

In chemical synaptic transmission, the Ca2+ that is necessary for release of the transmitter substance a. is already present in the presynaptic cell as free Ca2+. b. is released by the AP from internal stores of bound Ca2+. c. enters the presynaptic cell from the extracellular fluid. d. comes from the synaptic vesicles themselves.

C

In the patch clamp method, a. a spring-loaded pair of electrodes are used, which "clamp" a nerve to obtain better recordings of small action potentials. b. a micropipette is used to iontophoretically adjust ion concentrations to "clamp" membrane potentials. c. a micropipette is applied by suction to a small area of cell membrane for study of the properties of individual ion channels. d. a tiny clamp is applied to a small area of cell membrane to stabilize it for detailed molecular analysis.

C

In the treatment of Parkinson's disease, L-DOPA is used as medication because a. it is necessary to avoid bringing on the symptoms of schizophrenia. b. dopamine is present in neurons of the Raphe nuclei that seem to cause the disease. c. the neural deficit seems to be in neurons that use DA as a transmitter. d. L-DOPA can readily be converted to 5-HT, the substance that actually has the therapeutic effect.

C

In the vesicular hypothesis of synaptic transmission, the ______ in discrete particles called vesicles. a. electrical charges associated with the action potential are thought to be packaged b. electrical charges associated with the post-synaptic potential are thought to be packaged c. transmitter substance is thought to be packaged d. calcium ions are thought to enter the pre-synaptic cell

C

In two axons of the same diameter, a myelinated axon will conduct impulses faster than an unmyelinated one because a. the channels through which ions flow are larger in the myelinated axon, allowing more rapid depolarization. b. there are more sodium channels per mm2 of membrane in the myelinated axon. c. currents due to the presence of the action potential spread farther along the length of the myelinated axon before they cause generation of a new action potential. d. myelinated axons have a lower internal resistance to the flow of ionic currents.

C

Measurement of the net current flowing across the membrane of a neuron can be made with a. an intracellular microelectrode. b. an extracellular electrode. c. a voltage clamp device. d. none of the above.

C

Miniature end plate potentials (mepps) are a. the small changes in the presynaptic membrane potential generated each time a Ca2+ ion enters the cell. b. the random opening of ion channels in the postsynaptic muscle cell membrane in the absence of any electrical or chemical stimulus. c. small depolarizations of muscle cell membrane due to the random release of packets of transmitter substance, in the absence of any stimulation. d. the small "reference" spike in the end plate that occurs before facilitation takes place.

C

Miniature end plate potentials are thought to represent a. leakage of molecular transmitter. b. the effect of calcium leakage into the presynaptic neuron. c. leakage of quantal packets of transmitter substance. d. the prelude to an action potential.

C

Most dendritic membrane cannot carry an action potential because a. the currents generated by the action potential in the pre-synaptic terminal are carried away in the extracellular fluid and thus do not cross the post-synaptic dendritic membrane. b. dendrites are usually too short. c. it lacks voltage-sensitive sodium channels. d. the internal resistance of dendrites is too great to allow current to spread far.

C

Octopamine is a(n) a. amino acid. b. catecholamine. c. monoamine, but not a catecholamine. d. peptide.

C

Saltatory conduction describes a. the transmission of action potentials in a chain of excitatory synapses. b. the fact that the electrical charges generated on dendrites have to jump to the axon hillock to trigger an action potential. c. the appearance of action potentials at discrete places along a myelinated axon. d. the jumping of ions from one side of the membrane to the other during an action potential.

C

Saltatory conduction is the jumping of a. the membrane potential during the action potential. b. the membrane potential during an EPSP. c. an action potential from node to node of a myelinated nerve. d. ions across the membrane during the action potential.

C

Serotonin is a(n) a. amino acid. b. catecholamine. c. monoamine, but not a catecholamine. d. peptide.

C

Suppose you insert a single electrode into the middle of a squid giant axon and apply a supra-threshold stimulus. The result will be a. a single action potential traveling toward the cell soma, away from the end of the axon. b. a single action potential traveling away from the cell soma, toward the end of the axon. c. two action potentials traveling in opposite directions along the axon. d. no action potential, since supra-threshold stimuli must be applied at the soma to be effective.

C

Synapsin-I is a protein that a. is involved in anterograde axoplasmic transport of synaptic vesicles. b. is involved in retrograde axoplasmic transport of synaptic vesicles. c. is involved in binding synaptic vesicles to the presynaptic cytoskeleton. d. is part of the postsynaptic membrane responsible for stabilizing the synapse.

C

Synaptic transmission from nonspiking neurons is referred to as graded because a. the amount of transmitter released is proportional to the membrane potential. b. transmitter is not released in discrete packets. c. the amount of transmitter released depends on the graded size of the EPSP. d. larger neurons release more transmitter substance than do smaller ones.

C

The individuals largely responsible for demonstrating that transmitter release could be quantal were a. Hodgkin and Huxley. b. Hodgkin and Katz. c. Katz and Miledi. d. Eccles and Miledi.

C

The medical importance of knowing the synthetic pathway for a specific transmitter in humans is demonstrated by the present treatment for a. schizophrenia. b. alcoholism. c. Parkinson's disease. d. extreme pain in terminally ill individuals.

C

The movements of sodium and potassium ions during the action potential do not cancel each other out because a. the ions are moving in opposite directions. b. the ions are moving in the same direction. c. potassium conductance changes more slowly than does sodium conductance as membrane potential changes. d. sodium conductance changes more slowly than does potassium conductance as membrane potential changes.

C

The phrase "quantal transmission" refers to a. the all or none characteristic of an action potential. b. the transmission of discrete packets of transmitter (quanta) along axons by axoplasmic transport. c. the release of transmitter substance in discrete packets (quanta) at a synapse. d. the communication of one spiking neuron with another in units (quanta) represented by action potentials.

C

The rapid depolarization of an axonal membrane during the rising phase of the action potential is due to a. an increase in sodium resistance. b. an increase in sodium connectance. c. an increase in sodium conductance. d. an increase in the sodium equilibrium potential.

C

The synthetic pathway for norepinephrine is a. tyrosine --> DA --> DOPA --> NE. b. tyrosine --> DOPA --> DA --> adrenaline --> NE. c. tyrosine --> DOPA --> DA --> NE. d. tyrosine --> adrenaline --> DA --> DOPA --> NE.

C

Tyrosine is a precursor of a. MAO. b. serotonin. c. norepinephrine. d. COMT.

C

Voltage clamp devices work by a. controlling the flow of ions across the cell membrane. b. stimulating the cell until it responds. c. generating current to oppose that which flows through the cell's open ion channels. d. shutting down certain ion channels so no current can flow through them.

C

"Sodium inactivation" refers to a. the inability of sodium to move across the membrane. b. the expulsion of sodium from the neuron by the sodium pump. c. the movement of sodium during presynaptic inhibition. d. the closing of the sodium channels a short time after they have opened, independent of the membrane potential.

D

A method for locating some specific transmitter pathways in the brain is a. the Golgi silver stain. b. iontophoresis. c. intracellular staining. d. the histofluorescence method.

D

A reduction in the size (peak potential) of an action potential can be brought about by a. increasing the external K+ concentration. b. increasing the external Na+ concentration. c. decreasing the external K+ concentration. d. decreasing the external Na+ concentration.

D

Dopamine is not effective as a treatment for Parkinson's disease because a. the deficit causing the disease is a deficiency of serotonin, not dopamine. b. injections of dopamine cause an immunological reaction that render it ineffective. c. the deficit causing the disease is a deficiency of norepinephrine, not dopamine. d. dopamine cannot cross the blood-brain barrier.

D

Endogenous (internal) levels of endorphin in humans are LOWERED by a. giving birth. b. taking a placebo against pain. c. acupuncture. d. addiction to opium.

D

Hodgkin and Huxley came back from a visit to Gully's to do a demonstration of their voltage clamp experiment. Unfortunately, they accidentally clamped the squid axon at -80 mV instead of 0 mV, in normal saline. The result was an initial a. net outward current produced by the cell due to the efflux of both K+ and Na+ ions. b. net outward current produced by the cell due to the efflux of Na+ ions and some influx of K+ ions. c. net inward current produced by the cell due to the influx of Na+ ions and some efflux of K+ ions. d. net inward current produced by the cell due to the influx of both K+ and Na+ ions.

D

In a voltage clamp device, the variable that is measured is a. the current flowing into the cell only. b. the current flowing out of the cell only. c. the K+ current only. d. the net current flowing across the membrane in either direction.

D

In a voltage clamp experiment, the quantity that the experimenter wants to determine is a. the total resistance of the membrane due to passive ion channels. b. the capacitance of the membrane due to the lipid bilayer. c. the voltage across the membrane due to ion concentration differences.

D

Most dendritic membrane cannot carry an action potential because a. it is not myelinated. b. most dendrites are stimulated by chemical transmission rather than electrical currents, and since an action potential is electrical, dendrites can not carry one. c. it lacks a spike initiation zone. d. it lacks voltage-sensitive (sodium) channels.

D

Nearly all amino acid and amine transmitter substances appear to be inactivated mainly by the process of a. enzymatic breakdown. b. chemical sequestration. c. diffusion. d. re-uptake.

D

One important role of calcium ions at a chemical synapse is to a. act as a transmitter substance. b. facilitate the binding of the transmitter substance with receptor molecules in the post-synaptic membrane. c. aid in the inactivation of the transmitter. d. facilitate the release of transmitter from the pre-synaptic terminal.

D

One reason that action potentials are all-or-none is that a. they are always the same size in a given neuron. b. axonal membranes do not allow partial electrical responses to electrical stimuli. c. they must travel long distances without decrement. d. once the membrane potential is past threshold, the influx of Na+ keeps driving it more positive until the maximum number of Na+ channels is open.

D

Ouabain is a drug that inhibits the Na+-K+ pump in a nerve cell. Applying the drug to a squid giant axon would within 10 minutes destroy the cell's ability to generate an action potential because a. Ouabain blocks the voltage-sensitive Na+ channels needed to generate action potentials. b. Ouabain blocks the voltage-sensitive K+ channels needed to recover from action potentials. c. Stopping the pump quickly allows the inward leak of Na+ and the outward leak of K+ to depolarize the cell to 0 mV so no action potential can be generated. d. ... the premise is wrong. The cell's ability to generate an action potential will not be affected in the first 10 minutes.

D

Proctolin is a(n) a. amino acid. b. catecholamine. c. monoamine, but not a catecholamine. d. peptide.

D

Re-uptake is a. the pumping of K+ into the cell after the passage of an AP. b. retrograde transport that prevents too much pressure in the axonal ending. c. the normalization of the levels of endorphin after a patient is cured of morphine addiction. d. absorption of transmitter into a neuron.

D

Subjecting a neuron to a metabolic poison will over the short term not affect the ability of the neuron to conduct an action potential. This shows that a. the Na+/K+ pump is not required for an action potential to be generated. b. no metabolic energy is required to drive the movement of ions during the action potential. c. the energy of the action potential comes from stored (potential) energy. d. statements a, b, and c above are all true.

D

The ionic basis for an action potential is usually the opening of a. Na+ channels alone. b. K+ or Cl- channels alone. c. Na+ and K+ channels simultaneously. d. Na+ channels first, followed by K+ channels.

D

The main ionic carrier of inward current flow during the rising phase of the action potential is a. K+. b. Ca2+. c. Cl-. d. Na+.

D

The vesicular hypothesis of synaptic transmission states that a. the presence of vesicles in an electron micrograph of nerve cells defines the presence of a synapse. b. vesicles are manufactured in the soma and transported to synapses by axoplasmic transport. c. vesicles are the site of synthesis of transmitter substance. d. transmitter is packaged in the vesicles and released quantally from them into the synaptic cleft.

D

Which of the following is NOT an important factor in the generation of and recovery from an action potential in a squid giant axon? a. The increase in sodium conductance. b. The efflux of potassium. c. Depolarization of the membrane to a potential above threshold. d. The influx of calcium.

D

_____ is found in high concentration in the dorsal root ganglia and the spinal cord of vertebrates. a. Acetylcholine b. Serotonin c. Endorphins d. Substance P

D