Chapter 12 A+P

How do action potential propagation speeds in myelinated and unmyelinated axons compare? Propagation is faster in unmyelinated axons. Propagation speeds are similar in both axon types. Propagation in myelinated axons is faster over short distances, but slower over long distances. Propagation is faster in myelinated axons.

Propagation is faster in myelinated axons.

Branches that may occur along an axon are called telodendria. hillocks. synaptic terminals. collaterals. synapses.

collaterals

What mechanism releases neurotransmitter from presynaptic neurons? endocytosis phagocytosis exocytosis pinocytosis

exocytosis

________ neurons are the most common structural class in the CNS. Bipolar Anaxonic Unipolar Sensory Multipolar

multipolar

In a typical neuron, what is the equilibrium potential for sodium? +30 mV -70 mV +66 mV -90 mV

+66 mV

Around what transmembrane potential does threshold commonly occur? +60 mV -60 V -60 mV -70 mV

-60 mV

What is the value for the resting membrane potential for most neurons? +30 mV -70 mV -90 mV

-70 mV

In a typical neuron, what is the equilibrium potential for potassium? -70 mV -90 mV 0 mV +66 mV

-90 mV

The equilibrium potential for potassium ion occurs at approximately +66 mV. +30 mV. -90 mV. 0 mV. -70 mV.

-90 mV

Approximately how fast do action potentials propagate in unmyelinated axons in humans? 1 meter per second 120 meters per second 12 meters per second 0.1 meters per second

1 meter per second

What is the magnitude (amplitude) of an action potential? 70 mV 30 mV 100 mV

100 mv

What is the typical duration of a nerve action potential? 20 ms 200 ms 2 ms 0.2 ms

2 ms

At the normal resting potential of a typical neuron, its sodium-potassium exchange pump transports

3 intracellular sodium ions for 2 extracellular potassium ions.

Type ________ fibers have the largest diameter axons. F C A S B

A

What is the primary role of the enzyme acetylcholinesterase (AChE) at a cholinergic synapse? AChE binds to ACh receptors, causing them to open. AChE degrades acetylcholine in the synaptic cleft. AChE releases acetylcholine into the synaptic cleft. AChE depolarizes the postsynaptic cell.

AChE degrades acetylcholine in the synaptic cleft

Active neurons need ATP to support which of the following? the movement of materials from the soma by axoplasmic transport the synthesis of neurotransmitter molecules the movement of materials to the soma by axoplasmic transport the recovery from action potentials All of the answers are correct.

All of the answers are correct

Which of the following is a recognized class of opioid neuromodulators? dynorphins enkephalins endomorphins endorphins All of the answers are correct.

All of the answers are correct

The effect that a neurotransmitter has on the postsynaptic membrane depends on the characteristics of the receptors. nature of the neurotransmitter. frequency of neurotransmitter release. quantity of neurotransmitters released. All of the answers are correct.

All of the answers are correct.

Ions can move across the plasma membrane in which of the following ways? through chemically gated channels as in neuromuscular transmission through voltage-gated channels as in the action potential through passive or leak channels by ATP-dependent ion pumps like the sodium-potassium exchange pump All of the answers are correct.

All of the answers are correct.

How is an action potential propagated along an axon? Stimuli from the graded (local) potentials from the soma and dendrites depolarize the entire axon. An influx of sodium ions from the current action potential depolarizes the adjacent area. An efflux of potassium from the current action potential depolarizes the adjacent area.

An influx of sodium ions from the current action potential depolarizes the adjacent area.

Which of the following best describes the role of calcium in synaptic activity? Calcium influx into the synaptic terminal causes vesicle fusion with the plasma membrane and the release of neurotransmitter. Calcium breaks down acetylcholine. Calcium diffuses across the synaptic cleft and binds to chemically gated channels on the postsynaptic cell. Calcium influx into the axon causes an action potential to propagate into the synaptic terminal.

Calcium influx into the synaptic terminal causes vesicle fusion with the plasma membrane and the release of neurotransmitter.

________ open or close in response to binding specific molecules. Leak channels Voltage-gated and chemically gated channels Voltage-gated channels Activated channels Chemically gated channels

Chemically gated channels

What type of conduction takes place in unmyelinated axons? Continuous conduction Electrical conduction Saltatory conduction Synaptic transmission

Continuous conduction

Which of the following is not true regarding the establishment of a neuron's resting potential? Resting membrane permeability to Na+ is very low. •Chemical and electrical forces both favor sodium ions entering the cell. •The chemical gradient for potassium ions tends to drive them out of the cell. •Electrical forces push sodium ions into the cell. •Ion pumps in the plasma membrane eject sodium ions as fast as they cross the membrane.

Electrical forces push sodium ions into the cell.

________ line the brain ventricles and spinal canal. Astrocytes Ependymal cells Oligodendrocytes Satellite cells Microglia

Ependymal cells

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization? Activation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open. Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open. Inactivation gates of voltage-gated Na+‎ channels close, while inactivation gates of voltage-gated K+‎ channels open. Activation gates of voltage-gated Na+‎ channels close, while inactivation gates of voltage-gated K+‎ channels open.

Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

Where do most action potentials originate? Axon terminal Initial segment Nodes of Ranvier Cell body

Initial segment

Where on the neuron is the action potential initiated? Choose the best answer. Initial segment Dendrite Cell body Axon

Initial segment

Which of the following is true about threshold for an action potential? Threshold for a typical neuron is approximately -30 mV. It is more positive than the resting potential. Voltage-gated potassium channels begin to close. Voltage-gated potassium channels begin to open. The membrane begins to hyperpolarize.

It is more positive than the resting potential.

How would the absolute refractory period be affected if voltage-regulated sodium channels failed to inactivate? It would last indefinitely. It would be much briefer. It would be basically unaffected.

It would last indefinitely.

What ion causes repolarization of the neuron during an action potential? Mg2+ (magnesium) Ca2+ (calcium) K+ (potassium) Na+ (sodium)

K+ (potassium)

The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____. Na+; Cl- Na+; K+ K+; Na+ K+; Cl-

K+; Na+

________ channels open or close in response to physical distortion of the membrane surface. Leak Mechanically gated Chemically gated Active Voltage-gated

Mechanically gated

In which type of axon will velocity of action potential conduction be the fastest? Unmyelinated axons of the shortest length Myelinated axons with the largest diameter Myelinated axons with the smallest diameters Unmyelinated axons with the largest diameter

Myelinated axons with the largest diameter

What ion is responsible for the depolarization of the neuron during an action potential? Na+ (sodium) Ca2+ (calcium) K+ (potassium) Cl- (chloride)

Na+ (sodium)

The concentrations of which two ions are highest outside the cell. Na+ and Cl- Na+ and A- (negatively charged proteins) K+ and Cl- K+ and A- (negatively charged proteins)

Na+ and Cl-

The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped? Both Na+ and K+ are pumped out of the cell. K+ is pumped out of the cell and Na+ is pumped into the cell. Na+ is pumped out of the cell and K+ is pumped into the cell. Both Na+ and K+ are pumped into the cell.

Na+ is pumped out of the cell and K+ is pumped into the cell.

What prevents the Na+ and K+ gradients from dissipating? Na+-K+ ATPase H+-K+ ATPase Na+ and K+ leaks Na+ cotransporter

Na+-K+ ATPase

What is the role of neurotransmitter at a chemical synapse? Neurotransmitter binds to receptors on the postsynaptic cell membrane. Neurotransmitter causes calcium to enter the presynaptic cell. Neurotransmitter causes vesicles to fuse with the presynaptic membrane. Neurotransmitter causes an action potential in the presynaptic cell.

Neurotransmitter binds to receptors on the postsynaptic cell membrane.

What characterizes repolarization, the second phase of the action potential? Before the membrane has a chance to reach a positive voltage, it repolarizes to its negative resting value of approximately -70 mV. As the membrane repolarizes to a negative value, it goes beyond the resting state to a value of -80 mV. Once the membrane depolarizes to a threshold value of approximately -55 mV, it repolarizes to its resting value of -70 mV. Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.

Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference? Action potential Threshold potential Resting membrane potential (RMP) Positive membrane potential

Resting membrane potential (RMP)

Certain details about Mr. Roosevelt's case call into question whether he really suffered from polio. The pathological features that Mr. Roosevelt experienced were much more characteristic of Guillain-Barré syndrome, an autoimmune disease that involves the demyelination of peripheral nerves. Which neuroglia cells form the myelin sheath of motor nerves? Schwann cells astrocytes satellite cells ependymal cells

Schwann cells

The sodium-potassium exchange pump transports potassium and sodium ions in which direction(s)? Sodium ions are transported into the cell. Potassium ions are transported out of the cell. Sodium and potassium ions are both transported into the cell. Sodium ions are transported out of the cell. Potassium ions are transported into the cell. Sodium and potassium ions are both transported out of the cell.

Sodium ions are transported out of the cell. Potassium ions are transported into the cell.

Why does the action potential only move away from the cell body? The flow of the sodium ions only goes in one direction—away from the cell body The areas that have had the action potential are refractory to a new action potential.

The areas that have had the action potential are refractory to a new action potential.

Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons? Action potentials would lack a repolarization phase. Neurons would depolarize more rapidly. The absolute refractory period would be shorter than normal. The axon would be unable to generate action potentials. None, because the chemically gated sodium channels would still function

The axon would be unable to generate action potentials.

Why does regeneration of the action potential occur in one direction, rather than in two directions? The activation gates of voltage-gated K+‎ channels open in the node, or segment, that has just depolarized. The activation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just depolarized. The inactivation gates of voltage-gated K+‎ channels close in the node, or segment, that has just fired an action potential. The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential.

The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential.

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you? The inside surface of the plasma membrane is much more negatively charged than the outside surface. The inside surface of the plasma membrane is much more positively charged than the inside surface. The outside surface of the plasma membrane is much more negatively charged than the inside surface. There is no electrical potential difference between the inside and the outside surfaces of the plasma membrane.

The inside surface of the plasma membrane is much more positively charged than the inside surface.

Josh and a bunch of friends decided to see how many people they could squeeze into a small car for a charity event. Once inside, Josh felt it get hot, smelly, and like the air was getting squished out of his lungs. He also noticed aches and pains in his joints. Which of the following statements best describes the type of sensory neurons involved? His interoceptors were monitoring his respiratory system. His exteroceptors were bringing in information from the outside world. The proprioceptors were monitoring the position of his skeletal muscles and joints. The interoceptors, exteroceptors, and proprioceptors were all monitoring his condition.

The interoceptors, exteroceptors, and proprioceptors were all monitoring his condition.

At rest, why is the transmembrane potential of a neuron (-70 mV) closer to the potassium equilibrium potential (-90 mV) than it is to the sodium equilibrium potential (+66 mV)? The concentration of potassium ions inside the cell is greater than the concentration of sodium ions outside the cell. The membrane is much more permeable to potassium ions than to sodium ions. For each ATP hydrolyzed, the sodium-potassium exchange pump transports more sodium ions out of the cell (three) than it transports potassium ions into the cell (two). There are more negatively charged proteins inside the cell than outside the cell.

The membrane is much more permeable to potassium ions than to sodium ions.

What characterizes depolarization, the first phase of the action potential? The membrane potential changes to a much more negative value. The membrane potential changes from a negative value to a positive value. The membrane potential reaches a threshold value and returns to the resting state. The membrane potential changes to a less negative (but not a positive) value.

The membrane potential changes from a negative value to a positive value.

What event triggers the generation of an action potential? The membrane potential must return to its resting value of -70 mV from the hyperpolarized value of -80 mV. The membrane potential must hyperpolarize from the resting voltage of -70 mV to the more negative value of -80 mV. The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV. The membrane potential must depolarize from the resting voltage of -70 mV to its peak value of +30 mV.

The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

What is the function of the myelin sheath? The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals. The myelin sheath decreases the speed of action potential conduction from the initial segment to the axon terminals. The myelin sheath decreases the resistance of the axonal membrane to the flow of charge. The myelin sheath increases the insulation along the entire length of the axon.

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors. The presence of concentration gradients and leak channels The presence of concentration gradients and Na+-K+ pumps The presence of concentration gradients and voltage-gated channels The presence of a resting membrane potential and leak channels

The presence of concentration gradients and leak channels

In an unmyelinated axon, why doesn't the action potential suddenly "double back" and start propagating in the opposite direction? The extracellular sodium concentration is too low around the previous axonal segment for an action potential to be (re)generated. New action potential generation near the soma repels previously generated action potentials. Positive charges only move in one direction. The previous axonal segment is refractory.

The previous axonal segment is refractory.

Which answer best describes the relative refractory period in the neuron? Choose the correct answer. The neuron's membrane potential is -70 mV. The neuron cannot generate another action potential under extreme stimulation. The resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state. Potassium ions are entering the neuron through open membrane channels

The resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

The plasma membrane is much more permeable to K+ than to Na+. Why? Ligand-gated cation channels favor a greater influx of Na+ than K+. There are many more K+ leak channels than Na+ leak channels in the plasma membrane. The Na+-K+ pumps transport more K+ into cells than Na+ out of cells. There are many more voltage-gated K+ channels than voltage-gated Na+ channels.

There are many more K+ leak channels than Na+ leak channels in the plasma membrane.

Sensory information from skeletal muscles travels over ________ fibers. type A type B type C type D type E

Type A

What opens first in response to a threshold stimulus? Ligand-gated cation channels Voltage-gated Na+ channels Ligand-gated Cl- channels Voltage-gated K+ channels

Voltage-gated Na+ channels

What is the first change to occur in response to a threshold stimulus? Voltage-gated Na+ channels change shape, and their inactivation gates close. Voltage-gated Ca2+ channels change shape, and their activation gates open. Voltage-gated K+ channels change shape, and their activation gates open. Voltage-gated Na+ channels change shape, and their activation gates open.

Voltage-gated Na+ channels change shape, and their activation gates open.

Which of the following channels is most directly responsible for the properties of the axon that lead to action potential generation? Choose the best answer. Ligand-gated potassium channels Ligand-gated sodium channels Leak potassium channels Voltage-gated sodium channels Leak sodium channels Voltage-gated potassium channels

Voltage-gated sodium channels

During an action potential, after the membrane potential reaches +30 mV, which event(s) primarily affect(s) the membrane potential? Voltage-gated sodium channels begin to inactivate (close) and the sodium-potassium exchange pump begins removing the excess sodium ions from the inside of the cell. Voltage-gated sodium channels begin to inactivate (close). Voltage-gated potassium channels begin to open and the sodium-potassium exchange pump begins removing the excess Na+ ions from the inside of the cell. Voltage-gated sodium channels begin to inactivate (close) and voltage-gated potassium channels begin to open.

Voltage-gated sodium channels begin to inactivate (close) and voltage-gated potassium channels begin to open.

Multiple sclerosis (MS) is a disease that stops action potential propagation by destroying the myelin around (normally) myelinated axons. Which of the following best describes how MS stops action potential propagation? Without myelin, the internode membrane resistance decreases, preventing local currents from reaching adjacent nodes. Without myelin, the node membrane more easily becomes refractory. Without myelin, the internode membrane is depolarized more easily. Without myelin, the internode membrane resistance increases, preventing local currents from reaching adjacent nodes.

Without myelin, the internode membrane resistance decreases, preventing local currents from reaching adjacent nodes.

The electrochemical gradient for potassium ions when the transmembrane potential is at the resting potential (-70 mV) is caused by what? a chemical gradient going into the cell and an electrical gradient going out of the cell chemical and electrical gradients both going into the cell a chemical gradient going out of the cell and an electrical gradient going into the cell chemical and electrical gradients both going out of the cell

a chemical gradient going out of the cell and an electrical gradient going into the cell

What type of channel in the postsynaptic membrane binds neurotransmitter? a mechanically gated channel a leakage channel a chemically gated channel a voltage-gated channel

a chemically gated channel

Poliomyelitis is caused by a virus that spreads easily in human populations. Most people with polio infections show no symptoms of disease. However, in a small percentage of victims, the virus enters the central nervous system and attacks the motor neurons of the spinal cord. Motor neurons are an example of what type or class of neuron? an anaxonic neuron that has processes that are all dendrites a multipolar neuron that has two or more dendrites and a single axon a bipolar neuron that has two processes separated by the cell body a unipolar neuron that has a single elongated process, with the cell body located off to the side

a multipolar neuron that has two or more dendrites and a single axon

Which of the following is an example of a presynaptic cell? a muscle cell a secretory cell a Schwann cell a neuron

a neuron

The velocity of the action potential is fastest in which of the following axons? a small myelinated axon a large unmyelinated axon a small unmyelinated axon

a small myelinated axon

If the axolemma becomes more permeable to potassium ion, the membrane will depolarize to threshold. sodium ions will enter the cell to replace the lost potassium ions. the membrane will depolarize to +30 mV. the inside of the membrane will have a positive charge. a stronger stimulus will be required to cause an action potential.

a stronger stimulus will be required to cause an action potential.

Both poliomyelitis and Guillain-Barré syndrome can involve paralysis where control over skeletal muscle function is lost. What is the neurotransmitter that a motor neuron uses to communicate with a skeletal muscle? dopamine acetylcholine gamma aminobutyric acid (GABA) norepinephrine

acetylcholine

Cholinergic synapses release the neurotransmitter GABA. norepinephrine. serotonin. acetylcholine. adrenalin.

acetylcholine

The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned? acetylcholine glutamate

acetylcholine

The ________ division of the peripheral nervous system brings sensory information to the central nervous system. somatic autonomic peripheral parasympathetic afferent

afferent

________ carry sensory information to the CNS. Motor neurons Interneurons Efferent neurons Multipolar neurons Afferent neurons

afferent neurons

The function of the astrocytes in the CNS includes which of the following? adjusting the composition of the interstitial fluid maintaining the blood-brain barrier repairing damaged neural tissue guiding neuron development All of the answers are correct.

all correct

The all-or-none principle states that only motor stimuli can activate action potentials. the greater the magnitude of the stimuli, the greater the magnitude of the action potential. all stimuli great enough to bring the membrane to threshold will produce identical action potentials. all stimuli will produce identical action potentials. only sensory stimuli can activate action potentials.

all stimuli great enough to bring the membrane to threshold will produce identical action potentials.

IPSPs (inhibitory postsynaptic potentials) block the efflux of calcium ions. are local depolarizations. are local hyperpolarizations. increase membrane permeability to sodium ions. block the efflux of potassium ions.

are local hyperpolarizations.

The largest and most numerous of the glial cells in the central nervous system are the microglia. satellite cells. oligodendrocytes. astrocytes. ependymal cells.

astrocytes

The neuroglial cells that participate in maintaining the blood-brain barrier are the Schwann cells. ependymal cells. oligodendrocytes. astrocytes. microglia.

astrocytes

Where are action potentials regenerated as they propagate along an unmyelinated axon? at every segment of the axon at the nodes at the internodes at myelin

at every segment of the axon

Where are action potentials regenerated as they propagate along a myelinated axon? at every segment of the axon at the internodes at myelin at the nodes

at the nodes

The plasma membrane of an axon is called the neurilemma. sarcolemma. myelin sheath. axon terminal. axolemma.

axolemma

The simplest level of information processing takes place at the __________. soma axon hillock axon terminals dendrites

axon hillock

Where in the neuron is an action potential initially generated? anywhere on the axon axon hillock soma and dendrites

axon hillock

The site in the neuron where EPSPs and IPSPs are integrated is the dendritic membrane. synaptic terminal. axon hillock. electrical synapse. chemical synapse.

axon hillock.

Raising the potassium ion concentration in the extracellular fluid surrounding a nerve cell will have what effect? increase the magnitude of the potassium equilibrium potential hyperpolarize it depolarize it decrease the magnitude of the potassium equilibrium potential both hyperpolarize it and decrease the magnitude of the potassium equilibrium potential

both hyperpolarize it and decrease the magnitude of the potassium equilibrium potential

During depolarization, which gradient(s) move(s) Na+ into the cell? Na+ does not move into the cell. Na+ moves out of the cell. only the electrical gradient only the chemical gradient both the electrical and chemical gradients

both the electrical and chemical gradients

Events that occur at a cholinergic synapse are listed here, but they are arranged in an incorrect order. Choose the correct order of these events below. (a) Calcium influx triggers exocytosis of ACh. (b) An action potential depolarizes the synaptic terminal. (c) ACh is removed by AChE. (d) ACh binds to receptors on the postsynaptic membrane. b→ a→ d→ c c→ d→ b→ a a→ b→ d→ c b→ a→ c→ d

b→ a→ d→ c

The ion that triggers the release of acetylcholine into the synaptic cleft is magnesium. potassium. calcium. chloride. sodium.

calcium

Presynaptic facilitation by serotonin is caused by temporal summation. increased extracellular concentration of potassium ion. blockage of calcium channels in the presynaptic membrane. calcium channels in the presynaptic membrane remaining open longer. increased extracellular concentration of sodium ion.

calcium channels in the presynaptic membrane remaining open longer.

The ________ nervous system is composed of the brain and spinal cord. central autonomic afferent peripheral efferent

central

Which of these components is usually absent from a neuron? axons cell body dendrites centrioles

centrioles

Leak channels allow the movement of potassium and sodium ions by what type of membrane transport? facilitated diffusion simple diffusion channel-mediated diffusion active transport

channel-mediated diffusion

The electrochemical gradient for sodium ions in a neuron when the transmembrane potential is at the resting potential is caused by what? a chemical gradient going out of the cell and an electrical gradient going into the cell chemical and electrical gradients both going out of the cell a chemical gradient going into the cell and an electrical gradient going out of the cell chemical and electrical gradients both going into the cell

chemical and electrical gradients both going into the cell

Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane. voltage-gated; postsynaptic voltage-gated; presynaptic chemically gated; presynaptic chemically gated; postsynaptic

chemically gated; postsynaptic

If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind? voltage-regulated sodium channel chemically-regulated potassium channel chemically-regulated sodium channel mechanically-regulated channel voltage-regulated calcium channel

chemically-regulated potassium channel

Functions of astrocytes include all of the following except guiding neuron development. forming a three-dimensional framework for the CNS. conducting action potentials. responding to neural tissue damage. maintaining the blood-brain barrier.

conducting action potentials.

Integral membrane proteins that connect electrical synapses are called receptors. synapsins. sodium channels. connexons. desmosomes.

connexons

________ nerves are nerves that connect to the brain. Interneural Unmyelinated Cranial Spinal Myelinated

cranial

A movement of charges in response to a potential difference is called action potential. depolarization. current. hyperpolarization. electricity.

current.

Demyelination disorders such as Multiple Sclerosis and Guillain-Barre Syndrome are particularly dangerous because they __________. facilitate retrograde action potential transmission block sodium channels and thus interfere with action potential transmission decrease the speed of action potential transmission reduce the size of the axon diameter

decrease the speed of action potential transmission

The sensory loss and muscle weakness associated with multiple sclerosis are a consequence of demyelination. excessive myelin layers around the axonal fibers. a neuron without a neurilemma. a neuron not having a myelin sheath. too few nodes of Ranvier.

demyelination

A threshold stimulus is the resting potential. electrical current that crosses the synaptic cleft. depolarization necessary to cause an action potential. peak of an action potential. hyperpolarization of an axon.

depolarization necessary to cause an action potential.

Opening of sodium channels in the axon membrane causes hyperpolarization. depolarization. increased negative charge inside the membrane. repolarization. inhibition.

depolarization.

An action potential is self-regenerating because __________. repolarizing currents established by the efflux of Na+‎ flow down the axon and trigger an action potential at the next segment depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment depolarizing currents established by the influx of K+‎ flow down the axon and trigger an action potential at the next segment repolarizing currents established by the efflux of K+‎ flow down the axon and trigger an action potential at the next segment

depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment

What triggers the release of acetylcholine from a synaptic terminal? diffusion of sodium ions out of the synaptic terminal synaptic vesicles fuse to dendrites release of calcium ions from the synaptic vesicles graded potentials in the synaptic terminal diffusion of calcium ions into the synaptic terminal

diffusion of calcium ions into the synaptic terminal

Which of the following is not a function of the nervous system? control peripheral effectors direct long-term functions, such as growth sense the internal and external environments coordinate voluntary and involuntary activities integrate sensory information

direct long-term functions, such as growth

The ________ division of the nervous system carries motor commands to muscles and glands.

efferent

Binding of the neurotransmitter to its receptor causes the membrane to __________. hyperpolarize depolarize either depolarize or hyperpolarize

either depolarize or hyperpolarize

The sum of the electrical and chemical forces acting on an ion is known as its electrochemical gradient. thermodynamic difference. summation difference. permeability gradient. action potential.

electrochemical gradient.

Which of these substances is considered a neuromodulator? norepinephrine acetylcholine nitric oxide endorphins

endorphins

________ provide information about the external environment. Internoceptors Anaxonic neurons Spinal nerves Exteroceptors Proprioceptors

exteroceptors

EPSPs (excitatory postsynaptic potentials) occur when chloride ions enter a cell. hyperpolarizations occur. extra sodium ions enter a cell. more calcium ions than usual leak out of a cell. more potassium ions than usual leak out of a cell.

extra sodium ions enter a cell.

What type of membrane transport causes the depolarization phase of the action potential in neurons? filtration active transport simple diffusion facilitated diffusion

facilitated diffusion

Neuron cell bodies in the PNS are clustered together in masses called fibers. tracts. nerves. nuclei. ganglia.

ganglia

In contrast to the internodes of a myelinated axon, the nodes __________. are wrapped in myelin have higher membrane resistance to ion movement only occur at the beginning and end of the axon have lower membrane resistance to ion movement

have lower membrane resistance to ion movement

Voltage-gated channels are present along the perikaryon of neurons. at the motor end plate. on the surface of dendrites. in the membrane that covers axons. on the soma of neurons.

in the membrane that covers axons.

Compared to the electrical gradient for sodium at rest, the electrical gradient for potassium at rest is __________. in the opposite direction but of the same magnitude. in the same direction and of the same magnitude. in the same direction but of lesser magnitude. in the same direction but of greater magnitude.

in the same direction and of the same magnitude.

Voltage-gated sodium channels have both an activation gate and a(n) ________ gate. repolarization inactivation ion threshold swinging

inactivation

Action potential propagation begins (is first generated at) what region of a neuron? node dendrite initial segment myelin

initial segment

In what part of the neuron does the action potential typically initiate? soma (cell body) dendrites axon terminals initial segment of the axon

initial segment of the axon

The most common neuron of the nervous system is the bipolar neuron. externoceptor. unipolar neuron. interneuron. microglial cell.

interneuron

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron, ion channels in the plasma membrane of the receiving neuron open. the receiving neuron becomes more positive inside. vesicles in the synaptic terminal fuse to the plasma membrane of the sending neuron. ion channels in the plasma membrane of the sending neuron open. the receiving neuron becomes more negative inside.

ion channels in the plasma membrane of the receiving neuron open.

Rabies illustrates a negative consequence to otherwise healthy retrograde flow within axons. Which of the following components will not be involved in retrograde flow?

kinesin

Ion channels that are always open are called ________ channels.

leak

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel? Leak channels Voltage-gated channels Ligand-gated channels Sodium-potassium ATPases

leak channels

Extensive damage to oligodendrocytes in the CNS could result in a breakdown of the blood-brain barrier. loss of sensation and motor control. decreased production of cerebrospinal fluid. inability to produce scar tissue at the site of an injury. loss of the structural framework of the brain.

loss of sensation and motor control.

Graded potentials produce an effect that spreads actively across the membrane surface. may be either a depolarization or a hyperpolarization. are often all-or-none. produce an effect that increases with distance from the point of stimulation. cause repolarization.

may be either a depolarization or a hyperpolarization.

Which of the following is not a function of the neuroglia? secretion of cerebrospinal fluid phagocytosis memory maintenance of blood-brain barrier support

memory

The sodium-potassium ion exchange pump transports sodium ions into the cell during depolarization. transports potassium ions out of the cell during repolarization. depends on a hydrogen gradient for energy. moves sodium and potassium opposite to the direction of their electrochemical gradients. must reestablish ion concentrations after each action potential.

moves sodium and potassium opposite to the direction of their electrochemical gradients.

The most abundant class of neuron in the central nervous system is multipolar. unipolar. bipolar. pseudopolar. anaxonic.

multipolar

Saltatory propagation occurs in _________ axons, in which action potentials _________. Select the best answer. myelinated; move continuously along the axon toward the axon hillock myelinated; move from one node of Ranvier to another unmyelinated; move from one node of Ranvier to another unmyelinated; spread by depolarizing the adjacent region of the axon membrane

myelinated; move from one node of Ranvier to another

________ account for roughly half of the volume of the nervous system. Efferent fibers Axons Neuroglia Dendrites Synapses

neuroglia

The basic functional unit of the nervous system is the nerve. glial cell. receptor. neuron. axon.

neuron

Adrenergic synapses release the neurotransmitter acetylcholine. dopamine. norepinephrine. GABA. serotonin.

norepinephrine

A molecule that carries information across a synaptic cleft is a synapse. sending neuron. neurotransmitter. synaptic cleft. receiving neuron.

neurotransmitter

The same ________ can have different effects depending on the properties of the ________. propagation; neurotransmitter substrate; receptor hormone; neurotransmitter receptor; neurotransmitter neurotransmitter; receptor

neurotransmitter; receptor

The tiny gaps between adjacent Schwann cells are called terminals. nodes of Ranvier. neurillema. vesicles. axolemma.

nodes of ranvier

Demyelination results from issues associated with myelin producing cells. Which of the following is an example of a myelin producing cell in the central nervous system (CNS)? ependymal cells astrocytes schwann cells oligodendrocytes

oligodendrocytes

The myelin sheath that covers many CNS axons is formed by microglia. satellite cells. astrocytes. oligodendrocytes. ependymal cells.

oligodendrocytes

The cytoplasm that surrounds the nucleus of a neuron is called the sarcoplasm. nucleoplasm. perikaryon. neuroplasm. protoplasm.

perikaryon

What causes repolarization of the membrane potential during the action potential of a neuron? potassium efflux (leaving the cell) sodium efflux (leaving the cell) sodium influx (entering the cell) potassium influx (entering the cell)

potassium efflux (leaving the cell)

During repolarization of a neuron both sodium and potassium ions move into the cell. potassium ions move out of the cell. sodium ions move into the cell. sodium ions move out of the cell. potassium ions move into the cell.

potassium ions move out of the cell.

The separation of positive and negative charges across the membrane creates a ________ difference, or voltage. potential dialysis thermodynamic electrochemical permeability

potential

The neurotransmitter GABA blocks presynaptic voltage-gated calcium channels. Consequently, GABA produces __________. EPSPs IPSPs presynaptic facilitation presynaptic inhibition

presynaptic inhibition

In a synapse, neurotransmitters are stored in vesicles located in the __________. presynaptic neuron postsynaptic neuron synaptic cleft

presynaptic neuron

After acetylcholinesterase acts, the synaptic terminal reabsorbs the choline. pinches off and a new terminal grows. reabsorbs the acetate. reabsorbs the acetylcholine. reabsorbs axoplasm.

reabsorbs the choline.

Neuroglia perform all of these functions EXCEPT __________. release neurotransmitters secrete CSF provide supportive framework regulate extracellular fluid composition

release neurotransmitters

Myelin limits the movement of ions across the axon membrane, so the action potential "jumps" from node to node along the axon. This is an example of what type of propagation? hyperpolarization continuous saltatory graded

saltatory

The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________. saltatory propagation myelinated propagation continuous propagation local propagation

saltatory propagation

Rapid impulse conduction from "node" to "node" is called continuous propagation. divergent propagation. saltatory propagation. spatial propagation. synaptic transmission.

saltatory propagation.

Glial cells that surround the neurons in ganglia are ependymal cells. oligodendrocytes. satellite cells. microglia. astrocytes.

satellite cells

Which of the following activities or sensations is/are not monitored by interoceptors? urinary activities sight cardiovascular activities activities of the digestive system taste

sight

Hyperpolarization results from __________. fast closing of voltage-gated K+ channels slow closing of voltage-gated Na+ channels slow closing of voltage-gated K+ channels

slow closing of voltage-gated K+ channels

The movement of what ion is responsible for the local currents that depolarize other regions of the axon to threshold? calcium (Ca2+) voltage-gated sodium (Na+) channels sodium (Na+) Potassium (K+)

sodium (Na+)

When cholinergic receptors are stimulated, sodium ions enter the postsynaptic neuron. chloride ions leave the postsynaptic neuron. sodium ions leave the postsynaptic neuron. norepinephrine deactivates acetylcholine. chloride ions enter the postsynaptic neuron.

sodium ions enter the postsynaptic neuron.

The ________ nervous system controls the skeletal muscles. autonomic parasympathetic sympathetic afferent somatic

somatic

________ nerves are nerves that connect to the spinal cord. Cranial Spinal Autonomic Multipolar Afferent

spinal

Opioids relieve pain by blocking the release of substance P. substance Q. substance O. substance X. None of the answers is correct.

substance P.

The site of intercellular communication between a neuron and another cell is the collateral. synaptic terminals. telodendria. synapse. hillock.

synapse

What separates the presynaptic and postsynaptic cells at a chemical synapse? chemically gated ion channels calcium channels vesicles filled with neurotransmitter synaptic cleft

synaptic cleft

The small space between the sending neuron and the receiving neuron is the synaptic terminal. synaptic cleft. vesicle. neurotransmitter. calcium channel.

synaptic cleft.

The events shown here at a functioning cholinergic synapse cause __________.

synaptic delay

Axons terminate in a series of fine extensions known as dendrites. telodendria. terminals. synapses. collaterals.

telodendria

When potassium channels open and the ions diffuse through the membrane, the inside of the membrane will become more positive. there will be almost no effect on transmembrane potential. the membrane will depolarize to threshold. the inside of the membrane will become more negative. the membrane will become depolarized.

the inside of the membrane will become more negative.

If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except the intracellular concentration of sodium ions will increase. the membrane will slowly lose its capacity to generate action potentials. the inside of the membrane will have a resting potential that is more positive than normal. the intracellular concentration of potassium ions will increase. the neuron will slowly depolarize.

the intracellular concentration of potassium ions will increase.

What is the function associated with the indicated neural activity?

the moment-to-moment variation of the transmembrane potential in all living cells, resting membrane potential

If the axon terminal of a motor neuron suddenly became permeable to calcium ion, the neuron will become unable to stimulate the muscle cell. the neuron will fire an action potential. neurotransmitter release will be blocked. the motor end plate will be hyperpolarized. the motor end plate will be depolarized.

the motor end plate will be depolarized.

The repolarization phase of an action potential results from __________. the opening of voltage-gated Na+ channels the closing of voltage-gated Na+ channels the closing of voltage-gated K+ channels the opening of voltage-gated K+ channels

the opening of voltage-gated K+ channels

If a signal from a sending neuron makes the receiving neuron more negative inside, the sending neuron becomes more positive inside. the receiving neuron is less likely to generate an action potential. the receiving neuron is more likely to generate an action potential. the sending neuron becomes more negative inside. the receiving neuron immediately generates an action potential.

the receiving neuron is less likely to generate an action potential.

In a neuron, sodium and potassium concentrations are maintained by the sodium-potassium exchange pump such that __________. the sodium concentration is higher inside the cell than outside the cell and the potassium concentration is higher outside the cell than inside the cell. both sodium and potassium concentrations are higher outside the cell compared to inside. the sodium concentration is higher outside the cell than inside the cell and the potassium concentration is higher inside the cell than outside the cell. the concentration of sodium outside the cell is equal to the concentration of potassium inside the cell.

the sodium concentration is higher outside the cell than inside the cell and the potassium concentration is higher inside the cell than outside the cell.

What is the electrochemical gradient of an ion? the transmembrane potential at which the electrical and chemical gradients are equal in magnitude, but opposite in direction the sum of the electrical and chemical gradients for that ion the difference between the concentrations of an ion inside and outside the cell The electrochemical gradient is the direction an ion would diffuse (either outward or inward) when the neuron is at rest, regardless of the transmembrane potential.

the sum of the electrical and chemical gradients for that ion

During an action potential of a neuron, what directly causes the different channels to open and close? neurotransmitter binding to chemically gated channels the transmembrane potential (voltage) Sodium and potassium ions calcium ions

the transmembrane potential (voltage)

When calcium ions enter the synaptic terminal, they cause an action potential in the sending neuron. they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron. the inside of the receiving neuron becomes more positive. the inside of the receiving neuron becomes more negative. neurotransmitter molecules are quickly removed from the synaptic cleft.

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

The minimum stimulus required to trigger an action potential is known as the threshold. summation. potential. all-or-none response. incentive.

threshold

Tumors that originate within the central nervous system (CNS) are due to __________. a lack of centrioles within neuronal cell bodies uncontrolled divisions of neuroglia uncontrolled division of neurons in adults all of the above

uncontrolled divisions of neuroglia

Neurotransmitters ready for release are stored in synaptic neurosomes. terminals. mitochondria. vesicles. telodendria

vesicles

An action potential releases neurotransmitter from a neuron by opening which of the following channels? voltage-gated K+ channels chemically gated Ca2+ channels voltage-gated Ca2+ channels voltage-gated Na+ channels

voltage-gated Ca2+ channels

The depolarization phase of an action potential results from the opening of which channels? chemically gated K+ channels voltage-gated K+ channels chemically gated Na+ channels voltage-gated Na+ channels

voltage-gated Na+ channels

The generation of an action potential in a neuron requires the presence what type of membrane channels? Select the best answer. leakage channels voltage-gated channels chemically gated channels membrane channels are not required

voltage-gated channels

What is primarily responsible for the brief hyperpolarization near the end of the action potential? voltage-gated potassium channels taking some time to close in response to the negative membrane potential voltage-gated sodium channels taking some time to recover from inactivation voltage-gated potassium channels opening as the membrane potential becomes more negative (repolarized) the sodium/potassium exchange pump taking some time to restore the normal ion concentrations

voltage-gated potassium channels taking some time to close in response to the negative membrane potential