Chapter 2: Structure and Functions of Cells of the Nervous System 2.1 Multiple Choice 1) The major symptom experienced by Katharyn D. in the chapter prologue was A) manic symptoms while at her job. B) taking a long time to get to sleep at night. C) excessive tiredness. D) seizure-like activity just prior to a meal. E) the recurrence of thoughts of dread and doom. Answer: C Rationale: The major symptom experienced by Katharyn D. in the chapter prologue was excessive tiredness. 2) ________ neurons gather information from the environment related to light, odors, and bodily contact with objects. A) Sensory B) Motor C) Golgi D) Relay inter- E) Efferent Answer: A 3) ________ neurons function to contract muscles. A) Sensory B) Motor C) Golgi D) Afferent E) Local inter- Answer: B 4) Which of the following is correct regarding neurons? A) Interneurons are located outside the brain and spinal cord. B) Motor neurons gather information from the environment. C) The number of neurons in the human nervous system is estimated at more than 100 billion. D) Neurons are found only inside the brain and spinal cord. E) The number of neurons in the human nervous system is estimated at less than 10 billion. Answer: C 5) The ________ is comprised of the brain and spinal cord. A) peripheral nervous system B) central nervous system C) enteric nervous system D) brainstem E) antebrain Answer: B Rationale: The central nervous system is comprise of the brain and spinal cord. 6) ________ are located entirely within the central nervous system. A) Sensory neurons B) Motor neurons C) Relay interneurons D) Efferent interneurons E) Multipolar neurons. Answer: C 7) The ________ system is comprised of the nervous system outside of the brain and spinal cord. A) peripheral nervous B) central nervous C) enteric nervous D) corticospinal E) corticospinal nervous Answer: A 8) The neuron region that resembles a tree is the A) soma. B) axon. C) dendrites. D) terminal buttons. E) cell body. Answer: C Rationale: The neuron region that resembles a tree is the dendrites. 9) The ________ contain(s) the nerve cell nucleus and functions to ______. A) soma; provide for the life processes of the cell B) axon; conduct action potentials C) axon terminals; form the membrane of the nerve cell D) dendrites; provide for the life processes of the cell E) mitochondria; conduct action potentials Answer: A 10) The _____ carries information from the cell body out to the terminal buttons. A) soma. B) axon. C) dendrites. D) terminal buttons. E) glia Answer: B Rationale: The axon carries information from the cell body out to the terminal buttons. 11) The portion of a neuron that carries a signal toward the cell body is the A) soma. B) axon terminal. C) presynaptic membrane. D) dendrite. E) glial membrane. Answer: D 12) The physical gap between two nerve cells across which messages are transmitted is the A) glial junction. B) axonal contact. C) synapse. D) dendritic apposition. E) neural gap. Answer: C 13) The membranes that most commonly form synapses are the ________ and the ________. A) axon terminals; dendrites B) dendrites; soma C) soma; glial D) axon terminals; soma E) glial cells; soma Answer: A Rationale: The membranes that most commonly form synapses are the axon terminals and the dendrites. 14) Which of the following is true regarding the action potential (AP)? A) The AP is carried along the glial membrane. B) The AP is always of the same amplitude and duration in a given cell. C) The AP is a graded signal. D) The AP is a long-lasting electrical signal. E) The AP is due to chloride currents. Answer: B Rationale: The action potential is always of the same amplitude and duration in a given cell. 15) The ________ neuron is the most common nerve cell type in the central nervous system. A) apolar B) multiglial C) unipolar D) bipolar E) multipolar Answer: E 16) The _____ neuron has dendrite-like branches and transmits sensory information to the brain. A) bipolar B) multipolar C) unipolar D) apolar E) tripolar Answer: C Rationale: The unipolar neuron has dendrite-like branches and transmits sensory information to the brain. 17) An impaired ability to sense temperature and touch might be expected after damage to which type of nerve cell? A) glial cells B) multipolar neurons C) unipolar neurons D) Schwann cells E) microglial cells Answer: C Rationale: An impaired ability to sense temperature and touch might be expected after damage to unipolar neurons. 18) Neurotransmitter molecules are secreted from a(n) ________ in response to the arrival of an action potential. A) glial cell B) dendrite C) axon terminal D) mitochondrion E) soma Answer: C 19) The membrane of a nerve cell is comprised of A) protein molecules. B) vesicle remnants. C) a double layer of lipid molecules. D) cytoplasm. E) a double layer of protein molecules. Answer: C 20) A key function of specialized lipid molecules located in a nerve cell is to A) detect the presence of chemicals inside the cell. B) form the matrix that gives a neuron its shape.. C) form channels to carry ions into and out of the cell. D) transport hormones into blood stream. E) induce DNA synthesis. Answer: C 21) Match up the correct pairing of each cell structure with its function. A) mitochondria; production of cytoplasm B) cytoskeleton; production of DNA C) lipid bi-layer; formation of the cell membrane D) synapse; production of ribosomes E) microtubules; production of cytoplasm Answer: C Rationale: The lipid bi-layer of a cell forms the cell membrane. 22) The recipes for generating individual proteins are contained within the A) mitochondria. B) cytoskeleton. C) genes. D) terminal buttons. E) dendrites. Answer: C Rationale: The recipes for generating individual proteins are contained within the genes. 23) Enzymes A) are formed from lipids. B) are molecules that control chemical reactions. C) control the aborption of glucose into cells.. D) provide energy to the cell. E) form the boundary of a nerve cell.. Answer: B 24) Match the correct function with the appropriate neuronal organelle. A) mitochondria; extraction of energy from nutrients B) mitochondria; formation of vesicles C) microtubules; breakdown of proteins D) microtubules; transport of chemicals across the synapse E) cytoskeleton; extraction of energy from nutrients Answer: A Rationale: Mitochondria act to extract energy from nutrients. 25) Which of the following is correct regarding axoplasmic transport? A) Anterograde transport involves moving substances from the dendrites to the soma. B) Retrograde transport involves moving substances from the soma to the axon terminals. C) Vesicles are the major factor involved in retrograde transport. D) Retrograde transport is half as fast as anterograde transport. E) Vesicles are the major factor involved in anterograde transport. Answer: D Rationale: Retrograde transport is half as fast as anterograde transport. 26) ________ is made up of thirteen filaments arranged around a hollow core and is involved in axoplasmic transport. A) The myelin sheath B) The terminal button C) A neurofilament D) A nanotubule E) A microtubule Answer: E 27) Match the correct function with the appropriate neuronal organelle. A) cell membrane; production of fat-like molecules B) mitochondria; formation of vesicles C) DNA; breakdown of proteins D) microtubules; transport of molecules between the soma and the axon terminals E) cytoskeleton; extraction of energy for cell use Answer: D 28) The ________ cells are the most important support cells of the central nervous system. A) Schwann B) glial C) Golgi D) platelet E) microtubule Answer: B 29) A key function of glial cells is to A) provide nutrition to the brain. B) remove physical debris from the blood. C) secrete cerebrospinal fluid.. D) insulate a nerve cell from other nerve cells. E) slow down conduction of action potentials. Answer: D Rationale: A key function of glial cells is to insulate a nerve cell from other nerve cells. 30) Which of the following is true of neurons? A) Neurons have a high metabolic rate and require a continuous source of fuel. B) The dendrites store nutrients and oxygen for later use by the soma of the neuron. C) Dead neurons are consumed by other neurons. D) Neurons make up 89 percent of the volume of the brain. E) Dead glial cells are replaced by newly formed neurons. Answer: A Rationale: Neurons have a high metabolic rate and require a continuous source of fuel. 31) Oligodendrocytes perform which of the following functions? A) physical support of nerve cells B) provision of nourishment to neurons C) clean up debris within the brain D) regulation of the chemical environment in the fluid surrounding neurons E) enhance conduction velocity along an axon. Answer: E 32) Which of the following glial cells are important for the supply of energy for neurons? A) Schwann cells. B) phagocytes C) dendrocytes D) astrocytes E) nanotubules Answer: D 33) The process of phagocytosis involves A) the removal of neuronal debris. B) the transfer of lactate from a glial cell to a neuron. C) the wrapping of layers of fatty material around an axon membrane. D) structural support of a nerve cell. E) the conversion of glycogen to glucose. Answer: A 34) Which of the following cells are important for the removal of nerve cell debris? A) Schwann cells B) phagocytes C) dendrocytes D) microglia E) nanotubules Answer: D 35) Which of the following cells are important for the immune system reaction to brain damage? A) Schwann cells B) phagocytes C) dendrocytes D) astrocytes E) microglia Answer: E 36) The ________ are important for the process of myelination of nerve axon membranes in brain. A) oligodendrocytes B) microglia C) astrocytes D) neurocytes E) Schwann cells Answer: A 37) Which of the following is true of Schwann cells? A) Schwann cells are found within the brain. B) Schwann cells provide myelin for central nerve cells. C) A single Schwann cell wraps a single segment of a peripheral nerve cell. D) A single Schwann cell myelinates up to 3 segments of axon membrane. E) Schwann cells slow down conduction of action potentials along the axon. Answer: C Rationale: A single Schwann cell wraps a single segment of a peripheral nerve cell. 38) The presence of a barrier between the blood stream and the brain is suggested by the observation that A) all cells of the body are stained by a dye injected into the bloodstream. B) injection of dye into the bloodstream stains all cells but those of the brain and spinal cord. C) the gut is stained by a dye injected into the brain ventricles. D) injection of dye into the ventricles stains all cells of the body. E) most chemicals rapidly reach the brain after oral ingestion.. Answer: B Rationale: The presence of a barrier between the blood stream and the brain is suggested by the observation that injection of dye into the bloodstream stains all cells but those of the brain and spinal cord. 39) Activation of cells within the area postrema would be predicted to produce A) stimulation of locomotion. B) the experience of a visual hallucination. C) consumption of a palatable food. D) feelings of nausea and vomiting. E) auditory hallucinations. Answer: D Rationale: Activation of cells within the area postrema would be predicted to produce feelings of nausea and vomiting. 40) Which of the following is true of the blood-brain barrier? A) The barrier is uniform throughout the brain. B) The barrier is selectively permeable. C) The barrier functions to regulate the chemical composition of the cerebrospinal fluid. D) The barrier is formed by Schwann cells that line the capillaries of the brain. E)The barrier is formed by astrocytes. Answer: B Rationale: The blood-brain barrier is selectively permeable. 41) Toxic substances in the blood are detected at the ______ which in turn triggers vomiting. A) cerebellum B) blood-brain barrier C) hypothamus D) amygdala E) area postrema Answer: E 42) Which of the following represents the normal order of activation in neuronal transmission? A) axon → dendrite → cell body → axon terminals B) axon terminals → cell body → axon → dendrite C) dendrite → cell body → axon → terminal button D) cell body → axon → dendrite → axon terminal E) dendrite → axon terminal → cell body → axon Answer: C 43) The simplest version of a withdrawal reflex involves a A) pain receptor synapsing onto a motor neuron in the spinal cord. B) pain receptor that projects to the thalamus, which then projects to motor cortex and then down to the spinal cord. C) motor neuron within the spinal cord that is spontaneously active. D) sensory neuron in visual cortex that synapses onto a motor neuron in the spinal cord. E) muscle fiber connecting onto an interneuron. Answer: A Rationale: The simplest version of a withdrawal reflex involves a pain receptor synapsing onto a motor neuron in the spinal cord. 44) The giant squid axon is specialized for which of the following? A) integration of sensory messages regarding the environment B) planning of feeding-related movements C) rapid contraction of the squid mantle which propels the squid away from danger D) coordination of general sensory-motor function E) contraction of the mouth of the squid to produce chewing movements Answer: C Rationale: The giant squid axon is specialized for rapid contraction of the squid mantle which propels the squid away from danger. 45) Which of the following is inserted into an axon to record electrical potentials? A) a single reference wire. B) a microelectrode inserted into the axon interior C) an oscilloscope D) a voltmeter terminal E) A thin metal cannula Answer: B 46) The interior of a neuron at rest A) is positively charged relative to the outside. B) is at the same voltage potential as the outside. C) has the same ionic concentrations as the outside. D) is negatively charged relative to the outside. E) contains high levels of sodium ions.. Answer: D Rationale: The interior of a neuron at rest is negatively charged relative to the outside. 47) The ________ is defined as the difference in electrical charge between the inside and the outside of the axon membrane. A) membrane B) local C) glial D) action E) axon Answer: A 48) Movement of the axon membrane potential from -70 mV to -90 mV would be termed a(n) A) action potential. B) threshold potential. C) depolarization. D) hyperpolarization. E) excitatory local potential. Answer: D Rationale: Movement of the axon membrane potential from -70 mV to -90 mV would be termed a(n) hyperpolarization. 49) Movement of the axon membrane potential from -90 mV to -80 mV would be termed a(n) A) depolarization. B) threshold potential. C) action potential. D) hyperpolarization. E) inhibitory local potential. Answer: A Rationale: Movement of the axon membrane potential from -90 mV to -80 mV would be termed a(n) depolarization. 50) An electrical charge applied to an axon that moves the membrane potential from -70 mV to -45 mV will result in a(n) A) action potential. B) local potential. C) downward shift of the threshold of excitation. D) upward shift of the membrane threshold. E) long-term change in the membrane potential. Answer: A 51) The membrane voltage level at which an action potential is triggered is termed the A) refractory period. B) hyperpolarization event. C) threshold of excitation. D) rate level. E) equilibrium point. Answer: C 52) The process by which molecules are evenly distributed throughout a medium is A) retrograde transport. B) diffusion. C) anterograde transport. D) electrostatic pressure. E) carrier-mediated transport. Answer: B 53) ________ are substances that form charged particles when dissolved in water. A) Ions B) Molecules C) Electrolytes D) Cations E) Anions Answer: C 54) ________ are charged particles formed when certain molecules dissolves in water. A) Ions B) Solvents C) Electrolytes D) Electrons E) Proteins Answer: A 55) ________ are positively charged particles. A) Transmitters B) Solvents C) Electrolytes D) Cations E) Anions Answer: D 56) Cation is to anion as A) transport is to diffusion. B) positive is to negative. C) diffusion is to transport. D) negative is to positive. E) intracellular is to extracellular. Answer: B Rationale: Cation is to anion as positive is to negative. 57) ________ are negatively charged particles. A) Transmitters B) Solvents C) Electrolytes D) Cations E) Anions Answer: E 58) The process by which similarly charged particles repel each other and are thus distributed throughout a medium is termed A) diffusion. B) carrier-mediated transport. C) refraction. D) electrostatic pressure. E) diffraction. Answer: D 59) Which of the following is true of ion distribution across the axon membrane? A) Sodium ions are concentrated outside the axon membrane. B) Potassium ions are concentrated outside the axon membrane. C) The action potential is the balance point between diffusion and electrostatic pressure. D) Chloride ions are concentrated inside the axon membrane. E) Sodium ions are concentrated inside the axon membrane. Answer: A 60) The force of diffusion would tend to move ________ ions ________ the axon. A) chloride; out of B) sodium; into C) potassium; into D) organic; into E) sodium; out of Answer: B 61) The force of ________ moves sodium ions ________ the axon A) diffusion; into B) retrograde transport; out of C) diffusion; out of D) electrostatic pressure; out of E) sodium-potassium pump; into Answer: A 62) Which of the following is a consequence of the activity of the sodium-potassium transporters? A) Extracellular sodium concentrations are kept low. B) Intracellular sodium concentrations are kept very high. C) Extracellular potassium concentrations are kept very high. D) Intracellular sodium concentrations are kept low. E) Little energy is required to maintain ionic differences across the membrane. Answer: D Rationale: As a consequence of the activity of the sodium-potassium transporters, intracellular sodium concentrations are kept low. 63) In a resting nerve cell, which of the forces listed below will act to push sodium ions into the cell? A) diffusion B) osmotic pressure C) sodium-potassium pump D) ion channel inactivation E) electrostatic pressure resulting from positive charge inside the axon Answer: A Rationale: In a resting nerve cell, diffusion acts to push sodium ions into the cell. 64) The specialized pores located in the axon membrane that open or close are termed A) receptors. B) voltage transporters. C) autoreceptors. D) ion channels. E) sodium-potassium transporters. Answer: D 65) Which of the following is true of an action potential? A) The sodium channels are opened at a lower voltage than are potassium channels. B) An action potential requires 5 msec for completion. C) During an action potential, the interior becomes even more negative. D) The potassium channels are opened at a lower voltage than are sodium channels. E) The overshoot is due to a prolonged change in sodium conductance. Answer: A Rationale: During an action potential, the sodium channels are opened at a lower voltage than are potassium channels. 66) Which of the following events restores the membrane potential from the peak of the action potential back to the resting level? A) Sodium ions move into the cell. B) Potassium ions move out of the cell. C) Potassium ions move into the cell. D) Chloride ions move into the cell. E) Chloride ions are extruded from the cell. Answer: B Rationale: Movement of potassium ions out of the cell restores the membrane potential to baseline from the peak of the action potential. 67) The "all-or-none law" refers to the observation that an action potential A) will diminish to near zero when transmitted down a long axon. B) fires at the same rate regardless of the inputs to the neuron. C) is conducted more rapidly down the axon as it reaches the axon terminal. D) is produced whenever the membrane potential reaches threshold. E) travels only in one direction. Answer: D 68) Sensory stimuli that vary in intensity are coded by variations in the ________ of a neuron. A) firing rate B) resting membrane potential C) speed of conduction of action potentials D) total amplitude of the action potential E) repolarization rate Answer: A Rationale: Sensory stimuli that vary in intensity are coded by variations in the firing rate of a neuron. 69) Subthreshold depolarizations of the axon membrane A) are not conducted along the membrane. B) remain the same size at each point along the membrane. C) are just smaller versions of the action potential. D) decrease in amplitude as they sweep along the membrane. E) involve the closing of ion channels. Answer: D Rationale: Subthreshold depolarizations of the axon membrane decrease in amplitude as they sweep along the membrane. 70) Ions enter and leave the membrane of a myelinated axon at the A) terminal buttons. B) axon hillock. C) nodes of Ranvier. D) segment of membrane under the Schwann cell wrapping. E) release zone. Answer: C Rationale: Ions enter and leave the membrane of a myelinated axon at the nodes of Ranvier. 71) A key advantage of saltatory conduction is that A) more sodium ions have to be pumped out of the cell after an action potential. B) myelin allows the nerve cell to recycle neurotransmitter molecules. C) less transmitter is required to send a message across the next synapse. D) myelin speeds up the velocity at which an axon can conduct an action potential. E) myelin requires that nerve cell axons be larger in order to rapidly conduct a signal. Answer: D Rationale: A key advantage of saltatory conduction is that myelin speeds up the velocity at which an axon can conduct an action potential. 72) Saltatory conduction is rapid because A) the action potential does not have to depolarize every segment of the axon membrane. B) myelinated cells have more leakage through the membrane. C) myelinated axons are larger in diameter. D) myelinated cells have more ion channels per unit area than do non-myelinated cells. E) myelinated fibers have a lower threshold of activation. Answer: A Rationale: Saltatory conduction is rapid because the action potential does not have to depolarize every segment of the axon membrane. 73) Neuronal signals are carried across the synapse by A) direct electrical connections between the two cells. B) the secretion of transmitter molecules into the synapse. C) the transfer of ions from one cell to another. D) an inhibitory effect of a transmitter molecule on the postsynaptic membrane. E) an influx of potassium ions into the axon terminal. Answer: B Rationale: Neuronal signals are carried across the synapse by the secretion of transmitter molecules into the synapse. 74) Which of the following is true of synapses? A) Action potentials open chloride channels to release neurotransmitters. B) Presynaptic voltage changes past threshold triggers the release of neurotransmitters. C) The interior of the nerve cell becomes more negative during the action potential. D) The exterior of the nerve cell becomes more positive during the action potential. E) Glia are shown to slow down the release of transmitter substances from the axon. Answer: B Rationale: Presynaptic voltage changes past threshold triggers the release of neurotransmitters into the synapse. 75) A common form of a synapse can involve a junction between an axon terminal and a(n) ________. A) dendrite B) blood vessel C) axon hillock D) glial cell E) Node of Ranvier. Answer: A 76) The term ________ means "little bladder." A) vesicle B) neurite C) cisternae D) mitochondria E) storage pool Answer: A 77) In which portion of a neuron would you expect to find the largest number of vesicles? A) the dendritic spines B) the soma C) near the nuclear membrane D) the release zone E) the axon hillock Answer: D Rationale: You would expect to find the largest number of vesicles in the release zone. 78) A key event for the release of neurotransmitter from the presynaptic membrane is the A) hyperpolarization of the axon membrane. B) arrival of an action potential at the axon terminal. C) influx of potassium ions into the axon terminal. D) activation of the sodium-potassium pumps. E) opening of ion channels within the microtubules. Answer: B 79) Which of the following is true of neurotransmitter function? A) Neurotransmitters diffuse widely across the brain to exert changes in metabolism. B) Neurotransmitters directly alter ion channels using a second-messenger chemical. C) Neurotransmitters are released into the synapse from the cistaerna. D) Neurotransmitters open ion channels in the postsynaptic membrane. E) Neurotransmitters alter ion channel activity for minutes. Answer: D Rationale: Neurotransmitters open ion channels in the postsynaptic membrane. 80) Match up the receptor type with its action. A) metabotropic; direct opening of an ion channel B) ionotropic; more time required to open an ion channel C) metabotropic; G-protein activation leads to activation of a second messenger D) metabotropic; second messenger effects are specific to opening ion channels E) metabotropic; rapid and short-lived effects on ion channels Answer: C Rationale: In metabotropic receptors, G-protein activation leads to activation of a second messenger. 81) Match up the correct pairing of a receptor type with its action. A) ionotropic; direct opening of an ion channel B) ionotropic; more time required to open an ion channel C) ionotropic; G-protein activation leads to activation of a second messenger D) metabotropic; second messenger effects that are specific to neuronal communication E) metabotropic; rapid and short-lived effects on ion channels Answer: A Rationale: Activation of ionotropic receptor results in the direct opening of an ion channel. 82) Match the correct PSP effect with each ion channel action. A) entry of a negative ion; hyperpolarization B) entry of a positive ion; hyperpolarization C) exit of a positive ion; depolarization D) exit of a negative ion; hyperpolarization E) B and D are correct. Answer: A 83) Which of the following ion channel events will produce an EPSP? A) opening a sodium channel B) closing a sodium channel C) opening a potassium channel D) opening a manganese channel E) closing a calcium channel Answer: A 84) Which of the following will "neutralize" the effect of an EPSP? A) further opening a sodium channel B) allowing intracellular anions to leave the cell C) closing a potassium channel D) opening a chloride channel E) B and D are correct. Answer: D Rationale: The opening of a chloride channel will “neutralize” the effect of the EPSP. 85) Which of the following ion channel events will reliably produce an IPSP regardless of the current level of the membrane potential? A) opening a sodium channel B) losing a potassium channel C) opening a potassium channel D) opening a chloride channel E) opening a channel to admit calcium ions into the axon Answer: C Rationale: The opening of a potassium channel will reliably produce an IPSP regardless of the current level of the membrane potential. 86) The process which terminates the postsynaptic potentials induced by most neurotransmitters is A) disruption of the postsynaptic receptor. B) enzymatic degradation of the transmitter molecule. C) inhibition of transmitter synthesis. D) facilitation of transmitter release. E) reuptake of the molecule into the axon terminal. Answer: E Rationale: The process which terminates the postsynaptic potentials induced by most neurotransmitters reuptake of the molecule into the axon terminal. 87) The process which terminates the postsynaptic potentials induced by acetylcholine is A) disruption of the postsynaptic receptor. B) enzymatic degradation via AChE. C) inhibition of ACh synthesis. D) facilitation of ACh release. E) reuptake. Answer: B 88) A drug that inactivates AChE would be expected to A) prolong the effects of ACh in the synapse. B) terminate the effects of ACh in the synapse. C) speed up the synthesis of ACh. D) impair the synthesis of ACh. E) activate the presynaptic autoreceptor for ACh. Answer: A Rationale: A drug that inactivates AChE would be expected to prolong the effects of Ach in the synapse. 89) An auto receptor is located on the ________ and is sensitive to ________. A) presynaptic membrane; the transmitter released by that neuron B) presynaptic membrane; a different transmitter released by another neuron C) presynaptic membrane; calcium ions located in the synapse D) postsynaptic membrane; calcium ions located in the synapse E) presynaptic membrane; the amount of second messenger activity in the postsynaptic cell Answer: A Rationale: Auto receptors are metabotropic in nature. 90) Auto receptors A) are sensitive to the presence of neuropeptides in the synapse. B) control the release of calcium ions from the axon terminal. C) mostly facilitate neuron function. D) are metabotropic in nature. E) control the formation of new dendritic spines. Answer: D 91) Neuromodulators A) have a lipid structure. B) directly elicit postsynaptic potentials. C) are usually found in small dense-core vesicles in terminal buttons. D) diffuse widely to effect many neurons. E) have only a local action at a few synapses. Answer: D 92) Neuromodulators A) are rarely of a peptide form. B) are secreted from a neuron and only affect an adjacent neuron. C) are inevitably inhibitory. D) are secreted from neurons, but dispersed widely in brain. E) are typically secreted in very small amounts compared to neurotransmitters. Answer: D 93) Most ________ are secreted into the extracellular fluid from endocrine glands or tissues. A) neurotransmitters B) neuropeptides C) modulators D) hormones E) pheromones Answer: D 94) The key symptom of myasthenia gravis is A) fatigability. B) mania and excitation. C) depression and sleep disturbance. D) inability to make coordinated movements. E) impaired auto receptor function. Answer: A 2.2 True-False 1) Motor neurons gather information from the environment. Answer: False 2) The cell membrane is formed by a single layer of lipid molecules. Answer: False 3) The myelin sheath around an axon in the brain is formed by oligodendrocytes. Answer: True 4) The blood-brain barrier is formed by astrocytes. Answer: False 5) In a neuron at rest, the inside of the cell is more negative than the cell exterior. Answer: True 6) A hyperpolarizing stimulus makes the interior of the neuron even more negatively charged. Answer: True 7) Both electrostatic and diffusion forces affect the concentration of ions in the extracellular and intracellular fluids. Answer: True 8) An anion is positively charged ion. Answer: False 9) The sodium-potassium transporter keeps the intracellular concentration of sodium ions low by pushing them out of the axon. Answer: True 10) Chloride ions are found in high concentration outside neurons. Answer: False 11) An action potential decreases in size as it moves along the axon toward the terminal buttons. Answer: False 12) A thick myelinated axon fiber will conduct an action potential more rapidly than will a thin unmyelinated fiber. Answer: True 13) Saltatory conduction speeds up conduction velocity in non-myelinated neurons. Answer: False 14) Transmitter substances are secreted from the terminal buttons of a neuron. Answer: True 15) The most important source of EPSPs is the neurotransmitter-dependent sodium channel. Answer: True 16) Opening a chloride channel will neutralize an EPSP. Answer: True 17) Enzymatic inactivation allows for the rapid reuse of a transmitter molecule. Answer: False 18) The transmitter acetylcholine is primarily inactivated by reuptake of the molecule into the axon terminal. Answer: False 19) Auto receptors are metabotropic receptors. Answer: True 2.3 Short-Answer Essay 1) Contrast the various forms of neurons in brain by their connections and functions. Answer: Sensory neurons carry information toward the brain while motor neurons carry signals to the muscles and glands of the periphery. 2) Name and discuss the general functions of the three glial cell types in the brain. Answer: Oligodendrocytes form CNS myelin. Astroglia provide support and nutrition for neurons. Microglia are involved in brain immune function. 3) Explain how the area postrema may play a role in minimizing poison toxicity. Answer: Because the blood-brain barrier is weak near this structure, toxins in blood can stimulate this brain region to cause emesis, which would void the stomach and in turn may reduce the total amount of toxicity to the organism. 4) What would be the effect of opening potassium channels in the axon membrane? Answer: Potassium ions would leave the cell, making the interior even more negative. This in turn would limit the excitability of the nerve cell. 5) What would you expect the impact to be on an organism treated with a drug that blocks neuronal sodium channels? Answer: Rapid death owing to the cessation of action potentials. 6).Contrast local potentials versus action potentials. Answer: Local potentials are graded in size, degrade with distance and can summate to produce an action potential. Action potentials are fixed in size, do not degrade and cannot summate. 7) Explain why saltatory conduction speeds up the velocity of action potentials. Answer: In saltatory conduction, the action potential does not have to depolarize every segment of membrane, only those at the widely separated nodes of Ranvier. 8) What would you expect to happen if the enzyme AChE were to be disabled in your body? Answer: My ACh activity would greatly increase, because AChE normally serves to degrade ACh. Later, this would lead to overstimulation of cholinergic receptors. 9) What is the general function of autoreceptors? Answer: To modulate the internal biochemical activity of the presynaptic cell. 2.4 Essay 1) Discuss the general support functions of glial cells for the nervous system. Answer: Glial cells: provide physical or structural support for individual neurons; provide energy to neurons; take away waste products; buffer the environment of a nerve cell; provide insulation in the form of myelin; digest dead or dying nerve cells; are involved in immune function. 2) Explain how ion channels alter the electrical properties of a nerve cell membrane. Answer: Ions are charged particles that are unequally distributed across the cell membrane. When ion channels open, diffusion and electrostatic pressure push sodium ions into the cell or potassium ions out of the cell. These movements result in changes in voltage across the membrane. 3). Provide an overview of the ionic events that produce the action potential. Answer: Movements of the membrane potential past threshold, open sodium channels, which moves the membrane potential from -60 to roughly +40 mV. The sodium channels then close, and the potential is restored to resting by an opening of the potassium channels. 4) Explain why the reuptake process has become a critical target for therapeutic drugs. Answer: The postsynaptic action of many neurotransmitters is terminated via reuptake of the molecule through the membrane transporter. A drug that blocks such a transporter would be expected to raise the synaptic levels of that neurotransmitter. For a disease or disorder that is thought to result from a low synaptic activity of that transmitter, blockade of the reuptake process would generate a beneficial effect. 5) Explain how the nerve cell membrane acts as an integrator of incoming inputs. Answer: Neurotransmitter-gated receptors can open separate ion channels. Opening a sodium channel would result in an EPSP, while opening a potassium channel would result in an IPSP. The critical event which produces an action potential is reaching the threshold value for the membrane. EPSPs move the potential closer to that value; IPSPs move it further away. The PSPs can add together spatially and temporally, because of the residual nature of these potentials. Test Bank for Foundations of Behavioral Neuroscience Neil R. Carlson 9780205968091, 9780134639796, 9780205947997
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