Chapter 48: The Nervous System

A neuron's nucleus is located in its _____. cell body axon myelin sheath dendrite synaptic terminals

A nerve impulse moves toward a neuron's cell body along _____. dendrites synaptic terminals oligodendrocytes axons nodes of Ranvier

A nerve impulse moves away from a neuron's cell body along _____. dendrites Nissl bodies synapses axon glia

An impulse relayed along a myelinated axon "jumps" from _____ to _____. oligodendrocyte ... Schwann cell node of Ranvier ... Schwann cell node of Ranvier ... node of Ranvier Schwann cell ... Schwann cell Schwann cell ... node of Ranvier

Axons insulated by a(n) _____ are able to conduct impulses faster than those not so insulated. node of Ranvier synaptic terminal myelin sheath layer of asbestos astrocytes

What type of cell makes up the myelin sheath of a motor neuron? astrocytes microglial cells Ranvier cells ependymal cells Schwann cells

What part of a neuron relays signals from one neuron to another neuron or to an effector? dendrite axon hillock synaptic terminal axon node of Ranvier

The "information receiving" section of a neuron is its _____. Schwann cells dendrites glia axon terminal

Which term describes the difference in electrical charge across a membrane? Membrane potential. Resting potential. Electrical current. Electrical potential.

Resting neurons are most permeable to which of the following ions? Cl-. K+. O-. Na+.

True or false? The potential energy of a membrane potential comes solely from the difference in electrical charge across the membrane. True False

Which channel is mainly responsible for the resting potential of a neuron? Potassium leak channel. Voltage-gated sodium channel. Voltage-gated potassium channel. Chloride leak channel.

Which term describes an electrical signal generated by neurons? Membrane potential. Resting potential. Action potential. Equilibrium potential.

Which channel maintains the concentration gradients of ions across a neuronal membrane? The sodium leak channel allowing Na+ ions out. The potassium leak channel allowing K+ ions out. The sodium-potassium pump moving Na+ ions in and K+ ions out. The sodium-potassium pump moving Na+ ions out and K+ ions in.

What behavior is observed if the voltage across a neuronal membrane is set to -20 mV? The sodium channel opens, and Na+ ions flow in. The sodium channel opens, and Na+ ions flow out. The voltage-gated sodium and potassium channels both remain closed. The potassium channel opens, and K+ ions flow in.

Choose the set that includes the most charged compounds that are more abundant inside neurons, in the cytosol, than outside the neurons, in the extracellular fluid. potassium ions and proteins sodium and potassium ions chloride ions and proteins proteins and sodium ions sodium and chloride ions

A neuron has a resting potential of about _____ millivolts. +50 +35 -55 -70 -80

An action potential moves along a(n) _____. myelin sheath axon dendrite synapse cell body

At rest, which of these plays a role in establishing the charge differential across a neuron's plasma membrane? the sodium-potassium pump moving sodium ions into the neuron and potassium ions out of the neuron the diffusion of sodium ions out of the neuron the diffusion of potassium ions into the neuron the sodium-potassium pump moving sodium ions out of the neuron and potassium ions into the neuron the diffusion of sodium ions into the neuron

The transmission first triggers the _____. action of the sodium-potassium pump opening of voltage-gated sodium channels and the diffusion of sodium ions into the neuron opening of voltage-gated sodium channels and the diffusion of sodium ions out of the neuron opening of voltage-gated potassium channels and the diffusion of potassium ions out of the neuron opening of voltage-gated potassium channels and the diffusion of potassium ions into the neuron

A stimulus has opened the voltage-gated sodium channels in an area of a neuron's plasma membrane. As a result, _____ rushes into the neuron and diffuses to adjacent areas; this in turn results in the _____ in the adjacent areas. potassium ... opening of voltage-gated potassium channels sodium ... opening of voltage-gated potassium channels sodium ... opening of voltage-gated sodium channels sodium ... closing of voltage-gated sodium channels potassium ... opening of voltage-gated sodium channels

The simultaneous arrival of graded depolarization and a graded hyperpolarization of equal but opposite magnitude at a particular location on the dendritic membrane is likely to _____. cause depolarization, because graded depolarizations are more important to neuron function cause hyperpolarization, because graded hyperpolarizations are more important to neuron function cancel each other out, making it appear as if there was no change in membrane potential cause the apoptosis of the neuron allow only the entry of sodium ions into the neuron, and prevent potassium ions from exiting the neuron

Select the choice that describes neurons with the fastest conduction velocity for action potentials. thick, myelinated neurons thin, nonmyelinated neurons thick, nonmyelinated neurons thin, myelinated neurons All of these choices conduct action potentials at the same velocity.

Which structure is not part of a neuron? Cell body. Axons. Dendrite. Myelin sheath.

Which of the following statements about action potentials in a given neuron is false? They occur after the threshold potential is reached. They are identical in duration. They are propagated down the length of the dendrite. They are identical in magnitude.

True or false? Action potentials travel in only one direction down an axon because potassium channels in the neuron are refractory and cannot be activated for a short time after they open and close. True False

Which event triggers the creation of an action potential? Voltage-gated potassium channels open, and K+ ions diffuse out of the neuron. There is an undershoot of the resting potential. The membrane depolarizes above a certain threshold potential. The sodium—potassium pump shuttles ions across the membrane.

Which of the following terms describes how a neuronal membrane's potential is altered in the presence of inhibitory signals? Depolarization. Repolarization. Hyperpolarization. Polarization.

Where in the neuron do action potentials begin? Dendrite. Cell body. Synapse. Axon hillock.

How is an action potential propagated down an axon after voltage-gated sodium channels open in a region of the neuron's membrane? Potassium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated potassium channels farther down the axon. Sodium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated potassium channels farther down the axon. Potassium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated sodium channels farther down the axon. Sodium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated sodium channels farther down the axon.

Which of these causes the release of neurotransmitter molecules? the receipt of a signal from the postsynaptic neuron the opening of voltage-regulated calcium channels and the diffusion of calcium ions out of the neuron an action potential reaching the end of the cell body an action potential reaching the end of the axon an action potential reaching the end of the dendrite

The space between an axon of one neuron and the dendrite of another neuron is called a(n) _____. synaptic cleft node of Ranvier internodes synapse synaptic terminal

Neurons store neurotransmitter molecules in vesicles located within _____. the cell body myelin the synaptic cleft dendrites synaptic terminals

A nerve poison that blocks acetylcholine receptors on dendrites would _____. reduce the binding of acetylcholine to its receptors on the postsynpatic membrane inhibit the regeneration of acetylcholine for use by the presynaptic terminals inactivate acetylcholinesterase, allowing acetylcholine to persist in the synapse cause continued stimulation of the postsynaptic membrane cause an immediate and enduring depolarization

acetylcholine is an excitatory stimulus to the muscle binding of acetylcholine to its receptor triggers release of a second messenger, e.g., cAMP, inside the muscle these receptors have a corequisite binding of magnesium ions in order to function binding of acetylcholine to the receptor protein converts the protein to an open ion channel the receptors ionize as a result of binding acetylcholine, and this directly alters membrane potentials

What happens when a resting neuron's membrane depolarizes? There is a net diffusion of Na+ out of the cell. The neuron is less likely to generate an action potential. The cell's inside is more negative than the outside. The equilibrium potential for K+ (E K) becomes more positive. The neuron's membrane voltage becomes more positive.

A common feature of action potentials is that they move at the same speed along all axons. require the diffusion of Na+ and K+ through ligand-gated channels to propagate. cause the membrane to hyperpolarize and then depolarize. are triggered by a depolarization that reaches the threshold. can undergo temporal and spatial summation.

Where are neurotransmitter receptors located? the nodes of Ranvier the postsynaptic membrane the myelin sheath the nuclear membrane synaptic vesicle membranes

Temporal summation always involves inputs that are not simultaneous. electrical synapses. multiple inputs at a single synapse. synapses at more than one site. both inhibitory and excitatory inputs.

Why are action potentials usually conducted in one direction? The nodes of Ranvier conduct potentials in one direction. Voltage-gated channels for both Na+ and K+ open in only one direction. Ions can flow along the axon in only one direction. The brief refractory period prevents reopening of voltage-gated Na+ channels. The axon hillock has a higher membrane potential than the terminals of the axon.

Which of the following is a direct result of depolarizing the presynaptic membrane of an axon terminal? Synaptic vesicles fuse with the membrane. Voltage-gated calcium channels in the membrane open. The postsynaptic cell produces an action potential. Ligand-gated channels open, allowing neurotransmitters to enter the synaptic cleft. An EPSP or IPSP is generated in the postsynaptic cell.

If the membrane potential of a neuron decreases, the membrane potential _____. becomes less negative. remains unchanged. becomes more negative.

The plasma membrane of a neuron has voltage-gated sodium and potassium channels. What is the effect of membrane depolarization on these channels? Membrane depolarization opens sodium channels but closes potassium channels. Membrane depolarization first opens sodium channels and then opens potassium channels. Membrane depolarization opens sodium and potassium channels at the same time.