Assignment 11 (chapter 11)

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

Continuous conduction

In which area of the neuron is an action potential initially generated? Dendrites Axon Terminals Axon Hillock Axon

Dendrites

At which point of the illustrated graph are the action potential are the most gated Na+ channels open? Resting state Depolarization Repolarization Hyperpolarization

Depolarization

Signals generated at a chemical synapse are said to move only in the direction of the presynaptic cell to the postsynaptic cell. Which of the following statements regarding the mechanisms determining this one way transmission is incorrect? Neurotransmitter receptors are found in the postsynaptic membranes, not in the presynaptic membranes. The contents of synaptic vesicles are released from presynaptic membranes, not from postsynaptic membranes. Ions diffusing out of the presynaptic cell can enter the postsynaptic cell, but cannot reenter the presynaptic cell. All the above statements are incorrect.

Ions diffusing out of the presynaptic cell can enter the postsynaptic cell, but cannot reenter the presynaptic cell.

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

K+; Na+

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

Leak channels

Which of the following is not true of association neurons? Most association neurons are confined within the PNS. Association neurons make up over 99% of the neurons in the body. Association neurons are also known as interneurons. Almost all association neurons are multipolar.

Most association neurons are confined within the PNS.

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

Myelinated axons with the largest diameter

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

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

Na+-K+ ATPase

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? Threshold potential Positive membrane potential Resting membrane potential (RMP) Action potential

Resting membrane potential (RMP)

Which neuroglial cell are found in the PNS? oligodendrocyte astrocyte microglial cell ependymal cell Schwann cell Satellite cells

Satellite cells

What characterizes depolarization, the first phase of the action potential? The membrane potential changes from a negative value to a positive value. The membrane potential changes to a much more negative value. The membrane potential reaches a threshold value and returns to the resting state. Voltage gated sodium channels close. .

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

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? glutamate acetylcholine

acetylcholine

Which of the following is true? An EPSP can summate with an IPSP. all the above are true. An IPSP can summate with other IPSPs. An EPSP can summate with other EPSPs.

all the above are true.

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

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

Which of the following statements most accurately describes the effects caused by binding a neurotransmitter to the specific receptors on the postsynaptic membrane? The membrane potential of the presynaptic membrane changes. The ligand is transported into the postsynaptic neuron. The membrane potential of the postsynaptic membrane changes. all the above

The membrane potential of the postsynaptic membrane changes.

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

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

Why does an increasing level of stimulation lead to increased frequency of action potentials? The neuron is able to reach threshold faster following the previous action potential. The neuron is able to return to the resting membrane potential more rapidly after each action potential. The neuron is able to reach the peak voltage of approx. +30mV more rapidly during each action potential.

The neuron is able to reach threshold faster following the previous action potential.

Which of the following does not factor into the rate of impulse propagation? The number of axon collaterals extending from a truncated axon. Diameter of the axon. The speed at which neural impulses are transmitted. Degree of myelination of the axon.

The number of axon collaterals extending from a truncated axon.

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

Which of the following allows us to consciously control our skeletal muscles? The sympathetic division of the autonomic nervous system The involuntary nervous system The parasympathetic division of the autonomic nervous system The somatic nervous system

The somatic nervous system

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+. The Na+-K+ pumps transport more K+ into cells than Na+ out of cells. There are many more K+ leak channels than Na+ leak channels in the plasma membrane. 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.

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

Voltage-gated Na+ channels

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

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

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. 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 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? Nodes of Ranvier Axon terminal Cell body Initial segment

Initial segment

Which neuroglial cell is the most abundant in the CNS? oligodendrocyte astrocyte microglial cell ependymal cell Schwann cell

astrocyte

What part of the nervous system performs information processing and integration? parasympathetic nervous system central nervous system somatic nervous system sympathetic nervous system

central nervous system

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

chemically gated; postsynaptic

Which of the following mechanisms is most significant in returning the membrane potential back to the resting state from hyperpolization? closure of the voltage-gated K+ channels the closing of leakage channels in the axon membrane the opening of voltage gated Na+ channels the opening of voltage gated K+ channels

closure of the voltage-gated K+ channels

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 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 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 major ion currents occur at the point along the action potential phase Hyperpolarization? diffusion of both Na+ and K+ across the membrane in the direction of their respective electrochemical gradients diffusion of K+ into the axon through gated ion channels diffusion of Na+ out of the axon through gated ion channels diffusion of Na+ into the axon through gated ion channels diffusion of K+ out of the axon through gated ion channels

diffusion of K+ out of the axon through gated ion channels

The cell body of the sensory neuron is located within the dorsal root ganglion. receptor to which it is associated. ventral horn of the spinal cord. dorsal horn of the spinal cord.

dorsal root ganglion.

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

either depolarize or hyperpolarize

Which neuroglial cell control the flow of cerebrospinal fluid within the CNS? oligodendrocyte astrocyte microglial cell ependymal cell

ependymal cell

Which of the following types of neurons carries impulses away from the CNS? association sensory motor afferent

motor

What is the 2nd event in the information transfer across a chemical synapses? movement of Na+ into the interior of the axonal terminus through chemically gated channels movement of neurotransmitters into the interior of the axonal terminus through chemically gated channels movement of Ca2+ into the interior of the axonal terminus through voltage gated channels movement of the action potential into the interior of the axonal terminus through voltage gated channels

movement of Ca2+ into the interior of the axon terminus through voltage gated channels

Destruction of which type of neuroglial cell leads to the disease multiple sclerosis (MS)? oligodendrocyte astrocyte microglial cell ependymal cell Schwann cell

oligodendrocyte

Which neuroglial cell form myelin sheaths within the CNS? oligodendrocyte astrocyte ependymal cell Schwann cell

oligodendrocyte

Which of the following is expected to occur first if the membrane potential increases to reach the threshold value indicated at -55 mV? opening of chemically gated Na+ channels opening of chemically gated K+ channels opening of voltage-gated K+ channels opening of voltage gated Na+ channels the simultaneous opening of voltage-gated Na+ and K+ channels

opening of voltage gated Na+ channels

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

presynaptic neuron

Which of the following most accurately describes the involvement of synaptic vesicles in synaptic signaling? release of Ca2+ into the synaptic cleft by exocytosis release of Na+ and/or K+ ions into the synaptic cleft by facilitated diffusion release of neurotransmitter into the synaptic cleft by active transport release of neurotransmitter into the synaptic cleft by exocytosis

release of neurotransmitter into the synaptic cleft by exocytosis

Step 6 in the information transfer across a chemical synapses has three mechanisms by which the effects of a neurotransmitter may be terminated. Which of the following mechanisms is not included in the figure? reuptake of the neurotransmitter by transport into the postsynaptic cell diffusion of the neurotransmitter out of the synaptic cleft breakdown of the neurotransmitter within the synaptic cleft reuptake of the neurotransmitter by transport into the presynaptic cell

reuptake of the neurotransmitter by transport into the postsynaptic cell

Which of the following neurons is typically unipolar? motor sensory interneron all the above

sensory

Increasing the number of action potentials in a presynaptic axon in a given period of time would cause __________________________ summation axoaxonic axodendritic spatial temporal

temporal

Multiple EPSPs can cause a postsynaptic neuron to generate an AP because the depolarization produced is great enough to reach the resting membrane potential. the hyperpolarization produced is great enough to reach threshold. the hyperpolarization produced is great enough to reach the resting membrane potential. the depolarization produced is great enough to reach threshold.

the depolarization produced is great enough to reach threshold.

An inhibitory post synaptic potential (IPSP) results in the hyperpolarization of the post-synaptic cell. the repolarization of the post-synaptic cell. the generation of an action potential in the post-synaptic cell. the depolarizationof the post-synaptic cell.

the hyperpolarization of the post-synaptic cell.

What structural classification describes the neuron associated with the neuroglia Schwann cell? bipolar nonpolar unipolar multipolar

unipolar

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

voltage-gated Ca2+ channels

Why can't another action potential be generated during the absolute refractory period? voltage-gated sodium channels are opening. voltage-gated potassiumchannels become inactivated. voltage-gated sodium channels become inactivated.

voltage-gated sodium channels become inactivated.

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

-70 mV

Which of the following membrane regions would have significant numbers of voltage gated ion channels? Dendrites only Axon Hillock and Axon Dendrites and Nucleus Axon only

Axon Hillock and Axon

Which area of a motor neuron would contain an abundance of vesicles containing neurotransmitter? Dendrites Axon Terminals Axon Hillock Axon

Axon Terminals

Which of the following is true regarding a response to an excitatory event which might occur soon after the initial stimulus? No action potential can be induced in the neuron by an excitatory event if it occurs during the response observed in the graph. An excitatory event will be more likely to generate an action potential if it occurs during the response to the stimulus observed in the graph. An excitatory event may result in an action potential, but this will be less likely if the excitatory stimulus occurs during the response to the stimulus observed in the graph.

An excitatory event may result in an action potential, but this will be less likely if the excitatory stimulus occurs during the response to the stimulus observed in the graph.

At which of the points along the illustrated action potential graph can a second action potential be produced, but only with a stimulus significantly greater than that which produced the first? Resting state Depolarization Repolarization Hyperpolarization

Hyperpolarization Note: Despite the hyperpolarized (D) state of the membrane, a significantly strong stimulus may create enough depolarization to return the membrane to threshold. Point D would be considered within the relative refractory period. An important consequence of this design is that greater stimulus intensity will result in an increase in nerve impulse frequency.

Which of the following are gaps found along a myelin sheath? Axon collaterals Nodes of Ranvier Axonal termini Neurilemma Nissl bodies

Nodes of Ranvier

What characterizes repolarization, the second phase of the action potential? 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. Before the membrane has a chance to reach a positive voltage, it repolarizes to its negative resting value of approximately -70 mV.

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

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 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 activation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just depolarized.

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 is much more negatively charged than the outside surface. The inside surface of the plasma is much more positively charged than the inside surface. There is no electrical potential difference between the inside and the outside surfaces of the plasma membrane. The outside surface of the plasma is much more negatively charged than the inside surface.

The inside surface of the plasma is much more negatively charged than the outside surface.

Which of the following can be described as a graded potential? action potential EPSP IPSP both EPSP and IPSP

both EPSP and IPSP

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

both the electrical and chemical gradients