Chapter 8, Neurons: Cellular and Network Properties
The all-or-none principle states that A) all stimuli will produce identical action potentials. B) all stimuli great enough to bring the membrane to threshold will produce action potentials of identical magnitude. C) the greater the magnitude of the stimuli, the greater the intensity of the action potential. D) only sensory stimuli can activate action potentials. E) only motor stimuli can activate action potentials.
B) all stimuli great enough to bring the membrane to threshold will produce action potentials of identical magnitude.
Exocrine glands, smooth muscles, and cardiac muscles are controlled by the A) central nervous system. B) autonomic nervous system. C) somatic motor division. D) peripheral nervous system. E) enteric nervous system.
B) autonomic nervous system.
Neurotransmitters are released from the A) dendrites. B) axon terminals. C) collaterals. D) axon hillock. E) synapse.
B) axon terminals.
Glial cells communicate primarily using A) electrical signals only. B) chemical signals only. C) neurotransmitters only. D) neuromodulators only. E) electrical signals and chemical signals.
B) chemical signals only.
The pattern of synaptic connectivity where a large number of presynaptic neurons provide input to a single postsynaptic neuron, is known as A) divergence. B) convergence. C) integration. D) saltatory conduction. E) potentiation.
B) convergence.
A home satellite dish receives signals from a satellite, allowing your television to display TV shows. Which part of a neuron is analogous to the satellite dish? A) cell body B) dendrites C) axon D) varicosities E) collaterals
B) dendrites
Microvilli are present on cells that, because of their function, benefit from an increased membrane surface area. Which structure(s) on a neuron provide a comparable benefit? A) cell body B) dendrites C) axon D) varicosities E) collaterals
B) dendrites
The enteric nervous system is a network of neurons that function in controlling A) reproduction. B) digestion. C) excretion, particularly urination. D) the skeletal system. E) the endocrine system.
B) digestion.
The neurotransmitter thought to be involved in learning and memory is A) norepinephrine. B) glutamate. C) acetylcholine. D) GABA. E) glycine.
B) glutamate.
Conduction occurs along an axon because A) outflow of K+ triggers the adjacent channels to open. B) inflow of Na+ triggers the adjacent channels to open. C) once Na+ enters the cell, the entire membrane depolarizes simultaneously. D) axonal transport "walks" voltage changes along the membrane
B) inflow of Na+ triggers the adjacent channels to open.
The inactivation gate A) quickly opens and closes after depolarization. B) is coupled to the movement of the activation gate, but is much slower. C) depends on a change of +100 mV from rest to be signaled to close. D) depends on a loss of Na+ permeability to be triggered. E) depends on a loss of K+ permeability to be triggered.
B) is coupled to the movement of the activation gate, but is much slower.
In order to signal a stronger stimulus, action potentials become A) higher in amplitude only. B) more frequent only. C) longer-lasting only. D) higher in amplitude and more frequent. E) higher in amplitude and longer-lasting.
B) more frequent only.
Spatial summation refers to A) electrical signals reaching neurons from outer space. B) multiple graded potentials arriving at one location simultaneously. C) repeated graded potentials reaching the trigger zone one after the other. D) suprathreshold potentials triggering action potentials that are extra large. E) All of the answers are correct.
B) multiple graded potentials arriving at one location simultaneously.
The inhibitory neurotransmitters of the CNS, GABA and glycine, act by opening ________ channels. A) only Na+ B) only Cl- C) only K+ D) only Ca2+ E) Na+ and K+
B) only Cl-
In the first phase of triggering an action potential in a neuron, Na+ ions flow in and A) only trigger a negative feedback loop. B) only trigger a positive feedback loop. C) only activate the sodium/potassium pump. D) trigger a negative feedback loop and activate the sodium/potassium pump. E) trigger a positive feedback loop and activate the sodium/potassium pump.
B) only trigger a positive feedback loop.
The portions of a neuron that extend off of the roughly spherical cell body are usually collectively called A) protrusions. B) processes. C) prostheses. D) projections.
B) processes.
Inhibitory postsynaptic potentials (IPSPs) A) result in local depolarizations. B) result in local hyperpolarizations. C) increase membrane permeability to sodium ions. D) prevent the escape of potassium ions. E) prevent the escape of calcium ions.
B) result in local hyperpolarizations.
Calcium is important in the synapse because it A) is necessary for acetylcholine synthesis. B) signals the exocytosis of the neurotransmitter. C) binds to receptors on the postsynaptic cell, opening ion channels, and triggering graded potentials. D) leaves the axon terminal, hyperpolarizing the cell.
B) signals the exocytosis of the neurotransmitter.
Autonomic motor neurons are subdivided into the A) visceral and somatic divisions. B) sympathetic and parasympathetic divisions. C) central and peripheral divisions. D) visceral and enteric divisions. E) somatic and enteric divisions.
B) sympathetic and parasympathetic divisions.
When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what occurs? A) spatial summation B) temporal summation C) inhibition of the impulse D) hyperpolarization E) decrease in speed of impulse transmission
B) temporal summation
What does the Goldman-Hodgkin-Katz equation take into account that the Nernst equation does NOT? A) the electrical charges of the ions B) the permeabilities of the ions C) the solubilities of the ions D) the sizes of the ions E) the temperature
B) the permeabilities of the ions
The cell body of neurons is generally A) 90% of the cell volume. B) 50% of the cell volume. C) 10% of the cell volume. D) found in the same position on every neuron.
C) 10% of the cell volume.
In general, the nervous system is composed of which two types of cells? 1. motor 2. neurons 3. sensory 4. glial 5. associative A) 1 and 2 B) 1 and 3 C) 2 and 4 D) 3 and 4 E) 3 and 5
C) 2 and 4
The falling phase of the action potential is due primarily to A) Na+ flow in the cell only. B) Na+ flow out of the cell only. C) K+ flow out of the cell only. D) K+ flow into the cell only. E) Na+ flow out of the cell and K+ flow into the cell.
C) K+ flow out of the cell only.
The major determinant of the resting potential of all cells is A) Ca2+ concentration in the blood and interstitial fluid. B) Na+ concentration in the blood and interstitial fluid. C) K+ gradient between the blood and interstitial fluid. D) K+ concentration inside cells. E) Na+ concentration inside cells.
C) K+ gradient between the blood and interstitial fluid.
When more action potentials arrive at the axon terminal, how is the postsynaptic cell affected? A) Neurotransmitter release increases, but does not change the graded potentials that follow. B) Neurotransmitter release does not change, thus the postsynaptic cell behaves the same way it always behaves. C) Neurotransmitter release increases, thereby increasing the frequency or magnitude of graded potentials in the postsynaptic cell. D) Neurotransmitter release does not change, but voltages applied to the postsynaptic cell increase.
C) Neurotransmitter release increases, thereby increasing the frequency or magnitude of graded potentials in the postsynaptic cell.
What stops the rising phase of the action potential? A) The K+ gate closes. B) The Na+ activation gate opens. C) The Na+ inactivation gate closes. D) The Na+ inactivation gate opens. E) The sodium activation gate closes.
C) The Na+ inactivation gate closes
Identify the FALSE statement. A) Under normal conditions, all action potentials in a given cell are identical. B) Between nodes of Ranvier, signal conduction is decremental. C) The amplitude of the action potential depends on the amplitude of the graded potential that precedes it. D) The voltage-gated sodium and potassium channels begin to open during the depolarization.
C) The amplitude of the action potential depends on the amplitude of the graded potential that precedes it.
Which is the correctly written Nernst equation? A) 61/z × log [ion]out / [ion]in B) 61/z × log [ion]in / [ion]out C) log 61/z × [ion]in / [ion]out D) log 61/z × [ion]out / [ion]in
A) 61/z × log [ion]out / [ion]in
In the membrane of a resting nerve cell, when chemically gated Cl- channels open, A) Cl- ions enter the cell. B) Cl- ions leave the cell. C) the cell becomes depolarized. D) Cl- ions enter the cell and the cell becomes depolarized. E) Cl- ions leave the cell and the cell becomes depolarized.
A) Cl- ions enter the cell.
How would the absolute refractory period be affected if voltage-gated sodium channels remained inactivated? A) It would be longer than normal. B) It would be shorter than normal. C) It would be the same whether the channels remained inactivated or not. D) None of the answers are correct.
A) It would be longer than normal.
When more action potentials arrive at the axon terminal, how are neurotransmitters affected? A) More molecules are released into the synapse. B) Different molecules are released into the synapse. C) Fewer molecules are released into the synapse. D) There is no effect—all signals are identical.
A) More molecules are released into the synapse.
Excitatory neurotransmitters of the CNS usually act by opening ________ channels. A) Na+ B) K+ C) Cl- D) H+ E) Ca2+
A) Na+
The rising phase of the action potential is due to A) Na+ flow into the cell only. B) Na+ flow out of the cell only. C) K+ flow out of the cell only. D) K+ flow into the cell only. E) Na+ flow out of the cell and K+ flow into the cell.
A) Na+ flow into the cell only.
The basis of neural integration is A) addition of postsynaptic potentials overlapping in time and space. B) command signals from central pattern generators. C) spontaneous activity in pacemaker neurons. D) the area under the curve of postsynaptic potentials overlapping in time and space.
A) addition of postsynaptic potentials overlapping in time and space.
The term hyperkalemia specifically indicates too much potassium in which fluid compartment? A) blood B) intracellular C) interstitial D) extracellular E) All of the answers are correct.
A) blood
A damaged neuron has a better chance of survival and repair if the ________ is/are undamaged. A) cell body B) axon C) dendrites D) Schwann cells E) axon and dendrites
A) cell body
The brain and spinal cord together compose the A) central nervous system. B) autonomic division system. C) somatic motor division of the nervous system. D) peripheral nervous system. E) visceral nervous system.
A) central nervous system.
Which type of synapse is most prevalent in the nervous system? A) chemical B) electrical C) mechanical D) processing E) radiative
A) chemical
Anterograde and retrograde axonal transport are forms of ________ transport. A) fast B) slow C) Neither of these.
A) fast
Which ion(s) is/are higher in concentration inside the cell compared to outside? A) potassium B) sodium C) chloride D) calcium E) More than one of the answers is correct.
A) potassium
All of the following must occur before a second action potential can begin, EXCEPT A) the Na+ and K+ ions that moved in/out of the cell must move back to their original compartments. B) the Na+ inactivation gate must open and the Na+ activation gate must close. C) the absolute refractory period must occur. D) the Na+ and K+ ions that moved in/out of the cell must move back to their original compartments; the Na+ inactivation gate must open; and the Na+ activation gate must close. E) None of the answers are correct.
A) the Na+ and K+ ions that moved in/out of the cell must move back to their original compartments.
A chemical synapse ALWAYS includes which of the following? 1. axon terminal 2. presynaptic cell 3. synaptic cleft 4. postsynaptic cell 5. dendrite A) 1, 2, 3, 4, 5 B) 1, 2, 3, 4 C) 2, 3, 4 D) 2, 3, 4, 5 E) 1, 3, 4
B) 1, 2, 3, 4
The following are steps involved in transmission at the cholinergic synapse: 1. Chemically regulated ion channels on the postsynaptic membrane are activated. 2. Calcium ions enter the axon terminal. 3. An action potential depolarizes the axon terminal at the presynaptic membrane. 4. Acetylcholine is released from storage vesicles by exocytosis. 5. Acetylcholine binds to receptors on the postsynaptic membrane. The correct sequence for these events is A) 4, 2, 1, 5, 3. B) 3, 2, 4, 5, 1. C) 2, 4, 1, 3, 5. D) 2, 5, 4, 1, 3.
B) 3, 2, 4, 5, 1.
Which of the following is the most common location where action potentials originate? A) dendrites B) cell body C) axon hillock D) synaptic cleft E) synaptic bouton
C) axon hillock
Action potentials are primarily associated with the membranes of A) dendrites only. B) cell bodies only. C) axons only. D) dendrites and axons. E) cell bodies and axons.
C) axons only.
The following are the main steps in the generation of an action potential: 1. sodium channels are inactivated 2. more voltage-regulated potassium channels open and potassium moves out of the cell, initiating repolarization 3. sodium channels regain their normal properties 4. a graded depolarization brings an area of an excitable membrane to threshold 5. a temporary hyperpolarization occurs 6. sodium channel activation occurs 7. sodium ions enter the cell and further depolarization occurs The proper sequence of these events is A) 4, 6, 7, 3, 2, 5, 1. B) 4, 6, 7, 1, 2, 5, 3. C) 6, 7, 4, 1, 2, 3, 5. D) 2, 4, 6, 7, 1, 3, 5. E) 4, 2, 5, 6, 7, 3, 1.
B) 4, 6, 7, 1, 2, 5, 3.
Arrange the following events in the proper sequence: 1. Efferent neuron reaches threshold and fires an action potential. 2. Afferent neuron reaches threshold and fires an action potential. 3. Effector organ responds by performing output. 4. Integrating center reaches decision about response. 5. Sensory organ detects change in the environment. A) 2, 3, 5, 1, 4 B) 5, 2, 4, 1, 3 C) 5, 1, 4, 2, 3 D) 5, 3, 4, 2, 1 E) 3, 1, 4, 2, 5
B) 5, 2, 4, 1, 3
Which of the following will best increase the conduction rate of action potentials? A) Increase the diameter of the axon, decrease the resistance of the axon membrane to ion leakage. B) Increase the diameter of the axon, increase the resistance of the axon membrane to ion leakage. C) Decrease the diameter of the axon, decrease the resistance of the axon membrane to ion leakage. D) Decrease the diameter of the axon, increase the resistance of the axon membrane to ion leakage.
B) Increase the diameter of the axon, increase the resistance of the axon membrane to ion leakage.
When voltage-gated K+ channels of a resting neuron open, A) K+ enters the neuron. B) K+ leaves the neuron. C) the neuron depolarizes. D) K+ enters the neuron and the neuron depolarizes. E) K+ leaves the neuron and the neuron depolarizes.
B) K+ leaves the neuron.
If a hyperpolarizing graded potential and a depolarizing graded potential of similar magnitudes arrive at the trigger zone at the same time, what is most likely to occur? A) An action potential is fired off more quickly than usual. B) Nothing. They will cancel each other out. C) The cell becomes hyperpolarized. D) The cell becomes easier to excite. E) The cell dies.
B) Nothing. They will cancel each other out.
Graded potentials can A) only act as signals over short distances. B) only act as signals over long distances. C) only cause or prevent an action potential. D) act as signals over short distances and cause or prevent an action potential. E) act as signals over long distances and cause or prevent an action potential
D) act as signals over short distances and cause or prevent an action potential.
Choose ALL of the items that are incorrectly matched. A) inactivation gate — closed at rest B) activation gate — open at rest C) inactivation gate — closed during repolarization D) activation gate — opens during depolarization E) All of the answers are incorrectly matched.
D) activation gate — opens during depolarization
Information coming into the central nervous system is transmitted along ________ neurons. A) afferent B) sensory C) efferent D) afferent and sensory E) sensory and efferent
D) afferent and sensory
The axon is connected to the cell body by the A) myelin sheath. B) axon terminal. C) collaterals. D) axon hillock. E) synapse.
D) axon hillock.
Presynaptic facilitation occurs when A) extracellular concentration of sodium increases. B) extracellular concentration of potassium increases. C) calcium channels in the presynaptic membrane are inhibited. D) calcium channels in the presynaptic membrane remain open longer. E) temporal summation occurs.
D) calcium channels in the presynaptic membrane remain open longer.
In terms of embryonic origin, neurons are most closely related to ________ cells. A) skeletal muscle B) cardiac muscle C) connective tissue D) epithelial
D) epithelial
Clusters of nerve cell bodies in the peripheral nervous system are called A) microglia. B) neuroglia. C) glia. D) ganglia. E) nodes.
D) ganglia.
When comparing action potentials to graded potentials, an/two important distinguishing characteristic/s is/are A) graded potentials can undergo summation. B) action potentials can undergo summation. C) that the rate of action potentials is limited by the refractory period. D) graded potentials can undergo summation and the rate of action potentials is limited by the refractory period. E) action potentials can undergo summation and the rate of action potentials is limited by the refractory period.
D) graded potentials can undergo summation and the rate of action potentials is limited by the refractory period.
Tom's father suffers a stroke that leaves him partially paralyzed on his right side. What type of glial cell would you expect to find in increased numbers in the damaged area of the brain that is affected by the stroke? A) astrocytes B) Schwann cells C) oligodendrocytes D) microglia
D) microglia
The point during an action potential when the inside of the cell has become more positive than the outside is known as the A) depolarization. B) rising phase. C) falling phase. D) overshoot. E) peak.
D) overshoot.
The afferent and efferent axons together form the A) central nervous system. B) autonomic division system. C) somatic motor division of the nervous system. D) peripheral nervous system. E) visceral nervous system.
D) peripheral nervous system.
When sodium channels open during an action potential, the opening is caused by A) binding of sodium ions. B) binding of potassium ions. C) presence of calcium. D) presence of positive charge.
D) presence of positive charge.
The Nernst equation predicts A) intracellular ion concentrations. B) extracellular ion concentrations. C) the membrane potential resulting from all permeable ions. D) the membrane potential resulting from permeability to a single ion.
D) the membrane potential resulting from permeability to a single ion.
The resting membrane potential results from A) uneven distribution of ions across the cell membrane only. B) differences in membrane permeability to Na+ and K+ only. C) activity of the sodium/potassium pump only. D) uneven distribution of ions across the cell membrane and differences in membrane permeability to Na+ and K+. E) None of the answers are correct.
D) uneven distribution of ions across the cell membrane and differences in membrane permeability to Na+ and K+.
If a stimulating electrode is placed in the middle of a resting axon and an above-threshold voltage is applied to the electrode action potentials A) will not occur. B) will start at that point and proceed only toward the axon terminal. C) will start at that point and proceed only toward the cell body. D) will start at that point and travel in both directions in the axon.
D) will start at that point and travel in both directions in the axon.
Glial cells A) only provide structural and metabolic support. B) only guide neurons during growth and repair. C) only help maintain homeostasis of the brain's extracellular fluid. D) provide structural and metabolic support and help maintain homeostasis of the brain's extracellular fluid. E) All of the answers are correct.
E) All of the answers are correct.
Graded potentials may A) initiate an action potential. B) depolarize the membrane to the threshold voltage. C) hyperpolarize the membrane. D) be called EPSPs or IPSPs. E) All of the statements are true.
E) All of the statements are true.
When two or more graded potentials arrive at the trigger zone, which of the following could happen? A) An excitatory and inhibitory signal can cancel each other out. B) Two excitatory stimuli may be additive, and summation could occur. C) Two inhibitory stimuli may be additive, resulting in lower excitability. D) An excitatory and inhibitory signal can cancel each other out and two excitatory stimuli may be additive, and summation could occur. E) An excitatory and inhibitory signal can cancel each other out; two excitatory stimuli may be additive, and summation could occur; and two inhibitory stimuli may be additive, resulting in lower excitability.
E) An excitatory and inhibitory signal can cancel each other out; two excitatory stimuli may be additive, and summation could occur; and two inhibitory stimuli may be additive, resulting in lower excitability.
During the relative refractory period, an initial threshold-level depolarization is usually not sufficient to trigger an action potential. Why? A) Only some Na+ channels have returned to their resting position. B) Only K+ channels are still open, so Na+ entry is offset by K+ loss. C) Only a few K+ channels have returned to their resting position. D) The statement is incorrect; a threshold-level depolarization always triggers an action potential. E) Some Na+ channels have returned to their resting position and K+ channels are still open, so Na+ entry is offset by K+ loss.
E) Some Na+ channels have returned to their resting position and K+ channels are still open, so Na+ entry is offset by K+ loss.
Neurotransmitter is stored and released from A) axon terminals only. B) axon varicosities only. C) dendritic spines only. D) cell bodies only. E) axon terminals and axon varicosities.
E) axon terminals and axon varicosities.
Some neurotoxins work essentially the same way as some local anesthetics, which is to A) inactivate the enzyme that destroys the neurotransmitter only. B) bind to Na+ channels and inactivate them only. C) prevent depolarization by blocking Na+ entry into the cell only. D) inactivate the enzyme that destroys the neurotransmitter and bind to Na+ channels and inactivate them. E) bind to Na+ channels and inactivate them and prevent depolarization by blocking Na+ entry into the cell.
E) bind to Na+ channels and inactivate them and prevent depolarization by blocking Na+ entry into the cell.
Which of the following is NOT a known drug effect on synaptic function? A) interfere with neurotransmitter synthesis B) alter the rate of neurotransmitter release C) prevent neurotransmitter inactivation D) prevent neurotransmitter binding to receptors E) change the type of neurotransmitter found in the synaptic vesicle
E) change the type of neurotransmitter found in the synaptic vesicle
The absolute refractory period of an action potential A) only ensures one-way travel down an axon. B) only allows a neuron to ignore a second signal sent that closely follows the first. C) only prevents summation of action potentials. D) ensures one-way travel down an axon and allows a neuron to ignore a second signal sent that closely follows the first. E) ensures one-way travel down an axon, allows a neuron to ignore a second signal sent that closely follows the first, and prevents summation of action potentials.
E) ensures one-way travel down an axon, allows a neuron to ignore a second signal sent that closely follows the first, and prevents summation of action potentials.
These CNS glial cells may be a source of treatment for neural degenerative disorders. A) Schwann cells B) astrocytes C) microglia D) oligodendrocytes E) ependymal cells
E) ependymal cells
Voltage-regulated channels are located A) within the cytosol only. B) in the membranes of dendrites only. C) in the membranes of axons only. D) on the neuron cell body only. E) in the membranes of dendrites, in the membranes of axons, and on the neuron cell body.
E) in the membranes of dendrites, in the membranes of axons, and on the neuron cell body.
Learning and memory are thought to be due to a synaptic phenomenon known as A) inhibition. B) excitation. C) modulation. D) facilitation. E) long-term potentiation.
E) long-term potentiation.
Presynaptic facilitation makes a pathway A) less likely to be in use, just through hyperpolarization of selected neurons. B) more likely to be in use, just through depolarization of selected neurons. C) capable of alteration, just through training and conditioning. D) less likely to be in use, just through hyperpolarization of selected neurons and capable of alteration, just through training and conditioning. E) more likely to be in use, just through depolarization of selected neurons and capable of alteration, just through training and conditioning
E) more likely to be in use, just through depolarization of selected neurons and capable of alteration, just through training and conditioning
Conduction speed is (or can be) enhanced by A) myelin. B) altering extracellular sodium concentration. C) increasing the temperature. D) altering extracellular potassium concentration. E) myelin and increasing the temperature.
E) myelin and increasing the temperature
The collection of axons that carries information between the central nervous system and the peripheral effectors is called the A) axon hillock. B) varicosity. C) axon. D) dendrite. E) nerve.
E) nerve.
During childhood, growth and development of the brain PRIMARILY occurs by increasing A) neuron numbers only. B) neuron size only. C) number of dendrites and synapses only. D) neuron numbers and neuron size. E) neuron size and number of dendrites and synapses.
E) neuron size and number of dendrites and synapses.
The primary problem in hyperkalemia is A) that neurons are harder to excite because their resting potential is hyperpolarized. B) that neurons are hyperexcitable because their resting potential is closer to threshold. C) that neurons respond too quickly to smaller graded potentials. D) neurons are harder to excite because their resting potential is hyperpolarized and neurons respond too quickly to smaller graded potentials. E) neurons are hyperexcitable because their resting potential is closer to threshold and neurons respond too quickly to smaller graded potentials.
E) neurons are hyperexcitable because their resting potential is closer to threshold and neurons respond too quickly to smaller graded potentials.
The ion necessary to initiate the release of acetylcholine into the synaptic cleft is A) sodium. B) potassium. C) calcium. D) chloride. E) zinc.
C) calcium.
Branches that sometimes occur along the length of an axon are called A) dendrites. B) axon terminals. C) collaterals. D) axon hillocks. E) synapses.
C) collaterals.
The multiple thin, branched structures on a neuron whose main function is to receive incoming signals are the A) cell bodies. B) axons. C) dendrites. D) somata. E) None of the answers are correct.
C) dendrites.
An excitatory postsynaptic potential (EPSP) A) depolarizes a neuron, decreasing the likelihood of an action potential. B) hyperpolarizes a neuron, decreasing the likelihood of an action potential. C) depolarizes a neuron, increasing the likelihood of an action potential. D) hyperpolarizes a neuron, increasing the likelihood of an action potential.
C) depolarizes a neuron, increasing the likelihood of an action potential.
The tip of an embryonic nerve cell's axon is called a A) kissing cone. B) stem tip. C) growth cone. D) growth tip. E) None of the answers are correct
C) growth cone.
If the resting axon's membrane becomes more permeable to potassium ions, A) the inside of the membrane will become more positively charged. B) the membrane will depolarize more rapidly. C) it will take a stimulus of larger magnitude to initiate an action potential. D) the hyperpolarization at the end of the action potential will not occur.
C) it will take a stimulus of larger magnitude to initiate an action potential.
These glial cells act as scavengers. A) Schwann cells B) astrocytes C) microglia D) oligodendrocytes E) ependymal cells
C) microglia
These glial cells may contribute to Lou Gehrig's disease. A) Schwann cells B) astrocytes C) microglia D) oligodendrocytes E) ependymal cells
C) microglia
Interneurons are found A) only in the brain. B) only in the spinal cord. C) only in the CNS. D) throughout the nervous system. E) only in spinal nerves.
C) only in the CNS.
The rearrangement of connections at synapses, which occurs throughout life, is termed A) elasticity. B) intelligence. C) plasticity. D) senility. E) synchronicity
C) plasticity.
When multiple, possibly even conflicting signals reach a neuron, the neuron evaluates the signals and may respond or not. This property is called A) temporal summation. B) spatial summation. C) postsynaptic integration. D) graded potentials. E) EPSPs.
C) postsynaptic integration.
Inhibition of neural activity can result from A) presynaptic events only. B) postsynaptic events only. C) presynaptic events and postsynaptic events
C) presynaptic events and postsynaptic events
To increase the amount of neurotransmitter released onto a postsynaptic cell, the presynaptic cell would have to A) send action potentials with higher voltage (higher amplitude). B) send action potentials with longer durations. C) send action potentials with higher frequency. D) do nothing; no change is possible since the all-or-none law is in effect.
C) send action potentials with higher frequency.
The region where the axon terminal meets its target cell is called the A) collateral. B) hillock. C) synapse. D) nerve. E) dendrites.
C) synapse.
Caffeine, nicotine, and alcohol all have effects on A) action potential conduction. B) long-term potentiation. C) synaptic activity. D) neurotransmitter degradation. E) neurotransmitter reuptake.
C) synaptic activity.
The total amount of neurotransmitter released at the axon terminal is directly related to A) the amplitude of the action potential. B) the length of the axon. C) the total number of action potentials. D) the amplitude of the graded potential.
C) the total number of action potentials.
The site of information integration in the nervous system is the A) chemical synapse. B) electrical synapse. C) trigger zone. D) dendritic membrane. E) axon terminal.
C) trigger zone.
The term axonal transport refers to A) the release of neurotransmitter molecules from the axon. B) the transport of microtubules to the axon for structural support. C) vesicle transport of proteins and organelles down the axon. D) the movement of the axon terminal to synapse with a new postsynaptic cell. E) None of the answers are correct.
C) vesicle transport of proteins and organelles down the axon.
If the sodium-potassium pumps in the cell membrane of a neuron fail to function, over time A) the extracellular concentration of potassium ion will increase. B) the intracellular concentration of sodium ion will increase. C) the membrane resting potential will become more positive than normal. D) All of the answers are correct.
D) All of the answers are correct.
Once the action potential reaches the axon terminal, what happens next? A) exocytosis of a neurocrine B) release of the neurotransmitter into the synaptic cleft C) release of a neurohormone into the blood D) Any of the above could happen next.
D) Any of the above could happen next.
Once the stimulus alters the receptor on the cell's membrane, what happens next? A) Ion channels open, allowing ions to enter or exit. B) The membrane permeability is altered. C) A second messenger is activated on the inside of the cell. D) Any of these actions could happen next.
D) Any of these actions could happen next.
Which is/are the most common inhibitory neurotransmitter(s) of the CNS? A) GABA only B) glycine only C) glutamate only D) GABA and glycine E) All of the answers are correct.
D) GABA and glycine
When voltage-gated Na+ channels of a resting neuron open, A) Na+ enters the neuron. B) Na+ leaves the neuron. C) the neuron depolarizes. D) Na+ enters the neuron and the neuron depolarizes. E) Na+ leaves the neuron and the neuron depolarizes.
D) Na+ enters the neuron and the neuron depolarizes.
Myelin is formed by A) axons only. B) Schwann cells only. C) oligodendrocytes only. D) Schwann cells and oligodendrocytes.
D) Schwann cells and oligodendrocytes.
Repair of damaged neurons can be assisted by certain neurotrophic factors secreted by the A) cell body only. B) axon only. C) dendrites only. D) Schwann cells only. E) axon and dendrites.
D) Schwann cells only.
When the neuron is at rest, which statement is true? A) The activation gate is closed. B) The inactivation gate is open. C) No Na+ crosses the membrane is the only observation. D) The activation gate is closed and the inactivation gate is open. E) The activation gate is closed and no Na+ crosses the membrane.
D) The activation gate is closed and the inactivation gate is open.
How would blocking retrograde transport in an axon affect the activity of a neuron? A) The neuron would not be able to produce neurotransmitters. B) The neuron would not be able to produce action potentials. C) The cell body would not be able to export products to the axon terminals. D) The cell body would not be able to respond to changes in the distal end of the axon. E) The neuron would be unable to depolarize when stimulated.
D) The cell body would not be able to respond to changes in the distal end of the axon.
Tetrodotoxin is a toxin that blocks voltage-gated sodium channels. What effect does this substance have on the function of neurons? A) Neurons depolarize more rapidly. B) Action potentials lack a repolarization phase. C) The absolute refractory period is shorter than normal. D) The neuron is not able to propagate action potentials. E) The toxin does not interfere with neuron function because the voltage-regulated sodium channels would still function.
D) The neuron is not able to propagate action potentials.
Ion concentrations are first significantly affected after ________ action potential(s). A) one B) a few dozen C) a few hundred D) a few thousand E) a few million
D) a few thousand
In response to binding a neurotransmitter, a postsynaptic cell can A) only open chemically gated ion channels, causing graded potentials known as fast synaptic potentials. B) only close ion channels via G proteins and second messenger systems, producing slow responses. C) only regulate protein synthesis and affect the metabolic activities of the postsynaptic cell. D) open chemically gated ion channels, causing graded potentials known as fast synaptic potentials and regulate protein synthesis and affect the metabolic activities of the postsynaptic cell. E) open chemically gated ion channels, causing graded potentials known as fast synaptic potentials, close ion channels via G proteins and second messenger systems, producing slow responses, and regulate protein synthesis and affect the metabolic activities of the postsynaptic cell.
E) open chemically gated ion channels, causing graded potentials known as fast synaptic potentials, close ion channels via G proteins and second messenger systems, producing slow responses, and regulate protein synthesis and affect the metabolic activities of the postsynaptic cell.
The sodium-potassium exchange pump A) must re-establish ion concentrations after each action potential. B) transports sodium ions into the cell during depolarization. C) transports potassium ions out of the cell during repolarization. D) moves sodium and potassium in the direction of their chemical gradients. E) requires ATP to function.
E) requires ATP to function.
The channelopathy known as QT syndrome is a result of mutation in ________ channels. A) sodium B) potassium C) calcium D) chloride E) sodium, potassium, or calcium
E) sodium, potassium, or calcium
Which of the following does NOT influence the time necessary for a nerve impulse to be conveyed by a particular neuron? A) length of the axon B) presence or absence of a myelin sheath C) diameter of the axon D) presence or absence of nodes of Ranvier E) whether axon is sensory or motor
E) whether axon is sensory or motor
