Mastering: Nervous Systems

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

-70 This is the resting potential, the charge difference found across the plasma membrane of a "resting" neuron.

Which of the following choices correctly describes an action potential? An action potential is an all-or-none event moving in two directions. A stronger stimulus generates a faster frequency moving back and forth between the central nervous system and the sensory structure. An action potential is an all-or-none event moving in one direction. A stronger stimulus generates a faster frequency of action potentials moving to the central nervous system from the sensory structure. An action potential is a graded event moving in two directions. A stronger stimulus generates a stronger action potential moving back and forth between the central nervous system and the sensory structure. An action potential is a graded event moving in one direction. A stronger stimulus generates a stronger action potential moving to the central nervous system from the sensory structure.

An action potential is an all-or-none event moving in one direction. A stronger stimulus generates a faster frequency of action potentials moving to the central nervous system from the sensory structure. If you gently brush your knee against your desk or slam it against the desk, this does not alter the strength of the action potentials generated—there are just more of them in a more violent event. An action potential is an all-or-none event, moving only in one direction. A stronger stimulus generates a faster frequency of action potentials moving only from the sensory structure to the central nervous system.

Which of the following statements is FALSE? The myelin sheath limits the points where signals can be transmitted along the length of an axon. A neuron typically has many more dendrites than axons. Most of the nervous system consists of neurons. As a signal travels down a myelinated axon, the signal jumps from one node of Ranvier to the next node of Ranvier.

Most of the nervous system consists of neurons. This is the false statement. Most of the nervous system consists of supporting cells called glia. Glia may outnumber neurons by as much as 50 to 1.

Which of the following statements regarding the nervous system is true? The CNS and the brain are the same thing. The PNS is composed entirely of nerves. Sensory neurons convey signals from the CNS to sensory receptors. Motor neurons convey signals from the CNS to effector cells.

Motor neurons convey signals from the CNS to effector cells.

Which of the following statements about the transmission across a typical chemical synapse is true? Action potentials trigger chemical changes that make the neurotransmitter vesicles fuse with the plasma membrane of the receiving neuron. Neurotransmitter molecules bind to receptors in the receiving neuron's plasma membrane. Neurotransmitter molecules are stored in vesicles in the axon. Vesicles containing neurotransmitter molecules diffuse to the receiving neuron's plasma membrane.

Neurotransmitter molecules bind to receptors in the receiving neuron's plasma membrane. Neurotransmitter molecules move across the synaptic cleft and bind to receptors embedded in the membrane of the receiving neuron.

What role do neurotransmitters play in neuron communication? They regulate rhythmic muscle contractions, such as those that occur in the small intestine. They are accepted into the receiving cell, where they initiate more action potentials. They relay electrical signals from one axon to the next axon. Neurotransmitters are chemical signals that carry information across a gap called the synaptic cleft and may or may not generate an action potential in neighboring neurons.

Neurotransmitters are chemical signals that carry information across a gap called the synaptic cleft and may or may not generate an action potential in neighboring neurons. Neurotransmitters work by many different mechanisms, but this answer describes their general role.

Which of the following statements about chemical synapses is FALSE? Neurotransmitters that bind to receptors controlling excitatory membrane channels increase the tendency to develop action potentials. Neurotransmitters that bind to receptors controlling inhibitory membrane channels decrease the tendency to develop action potentials. Receiving neurons receive either inhibitory or excitatory signals, but not both. The closer the synapse is to the base of the receiving cell's axon, the stronger the effect.

Receiving neurons receive either inhibitory or excitatory signals, but not both. This is the false statement. A receiving neuron's membrane may receive both excitatory and inhibitory signals.

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

Schwann cells Myelin sheaths are formed when Schwann cells wrap around the axons of motor neurons.

Which of the following statements about the resting potential state of a neuron is true? The membrane potential can change from its resting value if the membrane's permeability to particular ions changes. The sodium-potassium pump plays a role in maintaining the outer membrane potential. The concentration of sodium is much higher inside the cell than outside. The neuron's plasma membrane is much less permeable to potassium than to sodium.

The membrane potential can change from its resting value if the membrane's permeability to particular ions changes. This is the basis for nearly all electrical signals in the nervous system.

Which of the following statements about resting potential is true? The concentration of sodium is much higher inside the cell than outside. The sodium-potassium pump contributes to the resting membrane potential. The resting potential exists because of differences in glucose concentration inside and outside the cell. A resting membrane allows much more sodium than potassium to diffuse across it.

The sodium-potassium pump contributes to the resting membrane potential.

What is the difference between a neuron and a nerve? Nerves are found only in the central nervous system. They consist of different numbers of cells. Neurons are made of white matter, nerves of gray matter. One is sensory in function, the other motor.

They consist of different numbers of cells.

The part of a neuron that carries nerve impulses toward the cell body is called _____. an axon a nerve a dendrite white matter

a dendrite The dendrite is defined as the part of the neuron that carries an impulse toward the cell body.

Which of the following is characteristic of vertebrate nervous systems? only partially centralized and cephalized a spinal cord that runs outside the vertebral column and gives rise to a series of cranial nerves a spinal cord with homeostatic control centers that keep the body functioning smoothly a distinct central nervous system consisting of a brain and spinal cord

a distinct central nervous system consisting of a brain and spinal cord This is characteristic of vertebrate nervous systems.

The rapid reversal of ions across the plasma membrane of a neuron is known as a(n) __________. threshold action potential membrane potential resting potential

action potential

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

an action potential reaching the end of the axon When an action potential reaches the end of an axon, vesicles fuse with the plasma membrane and release neurotransmitter into the synaptic cleft.

The threshold potential is of great significance in the physiology of neurons because if the threshold potential is not reached, _____. the neuron cannot regain its resting potential an action potential will be reached the action potential will be "inversed," with a flux of sodium out of the cell rather than into it an action potential will not occur

an action potential will not occur Stimuli that do not depolarize the membrane to the level of the threshold do not generate action potentials.

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

axon An axon is the only portion of a neuron capable of generating an action potential.

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

axons Axons conduct a nerve impulse away from the cell body.

If the dendrites are the "ears" of a neuron, and the axon is the "mouth" of the neuron, what is the "cell body" analogous to? neck hands nose brain

brain

A stimulus triggers an action potential by _____. causing sodium ions to enter the neuron causing potassium ions to enter the neuron causing sodium ions to leak out of the neuron activating the sodium-potassium pump

causing sodium ions to enter the neuron A typical stimulus will open chemically gated sodium channels, permitting sodium to enter the cell and increasing the voltage across the plasma membrane.

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

cell body The cell body is the region of a neuron where the nucleus is found.

The two major anatomical divisions of the nervous system are the sympathetic nervous system and parasympathetic nervous system. voluntary nervous system and involuntary nervous system. central nervous system and peripheral nervous system. sensory nervous system and motor nervous system.

central nervous system and peripheral nervous system.

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

dendrites Dendrites conduct an impulse from a synapse toward the cell body.

In neurons, ____________ receive signals and ____________ transmit signals. axons; dendrites cell body; dendrites cell body; axons dendrites; axons

dendrites; axons

Action potentials are generated along a neuron because _____. they are pulled along by positive-negative attraction depolarization of the membrane at one point causes an increase of permeability to sodium at the next point of cytoplasmic streaming within the neuron the neuron cytoskeleton conducts electricity as long as an ion gradient is maintained by the sodium-potassium pump

depolarization of the membrane at one point causes an increase of permeability to sodium at the next point An influx of sodium depolarizes the membrane and opens more sodium channels, causing still more depolarization; this is an example of positive feedback.

Effectors include __________. the white part of the spinal cord touch receptors the motor cortex endocrine glands

endocrine glands Effector cells are muscle or gland cells that carry out the body's response to stimuli.

The sodium-potassium pump _____. expels sodium from the cell pumps sodium and potassium into the cell expels sodium and potassium from the cell pumps sodium into the cell

expels sodium from the cell The sodium-potassium pump is a protein that expels sodium from the cell, exchanging it for potassium. Ion channels are pores that allow ions to pass through in either direction. The sodium-potassium pump brings potassium into the cell.

Action potentials relay different intensities of information due to the duration of action potentials relative to the strength of the stimulus. frequency of action potentials relative to the strength of the stimulus. shape of action potentials relative to the strength of the stimulus. amplitude of action potentials relative to the strength of the stimulus.

frequency of action potentials relative to the strength of the stimulus.

A cluster of nerve cell bodies outside the central nervous system is referred to as a(n) _____. association area ganglion cranial nerve nucleus

ganglion A ganglion is a cluster of nerve cell bodies, often of similar function, in the peripheral nervous system.

A drug that causes potassium to leak out of a neuron, increasing the positive charge on the outside, would _____. inhibit transmission of nerve signals by the neuron make it easier to trigger action potentials in the neuron cause the cell to release its neurotransmitter speed up nerve signals traveling the length of the cell

inhibit transmission of nerve signals by the neuron The additional positive charge to the outside of the neuron would require a greater stimulus to reach the threshold and trigger an action potential.

Animals that are bilaterally symmetrical, such as _____, typically _____. insects ... show cephalization and centralization sea stars ... have a radially symmetrical centralized nervous system earthworms ... have a nerve net and an uncentralized nervous system sponges ... have a radially symmetrical centralized nervous system

insects ... show cephalization and centralization The insect nervous system is concentrated at the head end, and insects have a CNS that is distinct from the PNS.

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron, the receiving neuron becomes more positive inside. ion channels in the plasma membrane of the sending neuron open. ion channels in the plasma membrane of the receiving neuron open. the receiving neuron becomes more negative 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 uniformity in the way nerve cells function within the animal kingdom is proof of neurotransmitter efficiency. is evidence that the neuron was an early evolutionary adaptation. indicates that the PNS evolved before the CNS. must have prevented the development of diversity.

is evidence that the neuron was an early evolutionary adaptation.

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

myelin sheath Myelin sheaths, formed when Schwann cells wrap around an axon, allow such neurons to conduct impulses more rapidly than unmyelinated axons.

The cell that conducts an action potential in the nervous system is a(n) _____. axon synapse cell body neuron

neuron The neuron is the functional unit of the nervous system. It is specialized for transmitting signals from one location in the body to another.

Which of the following would be present in an animal with a nerve net? cephalization fused ganglia bilateral symmetry neurons

neurons The nerve net is a weblike system of neurons.

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

neurotransmitter. Neurotransmitter molecules carry information across a synaptic cleft.

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

node of Ranvier ... node of Ranvier In myelinated neurons the impulse jumps from node of Ranvier to node of Ranvier.

The transmission of a nerve impulse 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

opening of voltage-gated sodium channels and the diffusion of sodium ions into the neuron This is the first of the events listed here. As a result of the inward flux of sodium ions, that region of the neuron depolarizes.

A nerve poison that blocked neurotransmitter receptors on the dendrites would _____. inhibit the regeneration of the neurotransmitter for use by the sending neuron inactivate the enzyme that degrades the neurotransmitter prevent transmission across the synaptic cleft cause continued stimulation of the membrane of the receiving neuron

prevent transmission across the synaptic cleft The binding of neurotransmitter molecules to their specific receptors on the postsynaptic membrane opens the ion channels, which completes the transmission of the impulse to the receiving cell. A nerve poison that blocked the neurotransmitter receptors would prevent reception of the signal.

Water held behind a dam is similar to what aspect of a neuron? dendrites resting potential threshold action potential

resting potential

The type of neuron that when stimulated by the environment transmits an impulse to the central nervous system is a(n) _____. sensory neuron motor neuron interneuron autonomic neuron

sensory neuron Sensory neurons communicate information between sensory receptors and the central nervous system about the external and internal environments.

Sarah turns quickly and sees the soccer ball hurtling toward her face. She blinks and ducks for cover. During this reaction, Sarah perceived the ball, decided what to do, and then blinked. Which choice lists the cells that were involved in this process from first to last? motor neurons, sensory neurons, and interneurons (all cells that are part of the PNS) sensory neurons, interneurons, and motor neurons (all cells that belong to the PNS) sensory neurons (part of the PNS), interneurons (part of the CNS), and motor neurons (part of the PNS) sensory neurons, interneurons, and motor neurons (all cells that belong to the CNS)

sensory neurons (part of the PNS), interneurons (part of the CNS), and motor neurons (part of the PNS)

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

sodium ... opening of voltage-gated sodium channels This describes part of the process by which an action potential travels along an axon.

The central communication conduit between the brain and the rest of the body is the nervous system. spinal cord. brainstem. nerve bundle.

spinal cord.

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

synaptic cleft "Synaptic cleft" is the name given to the space between two neurons that meet at a synapse.

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

synaptic cleft. The synaptic cleft is the small space between the sending neuron and the receiving neuron.

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

synaptic terminal Synaptic terminals contain neurotransmitter molecules that relay the nerve impulse across a synapse.

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

synaptic terminals Vesicles within synaptic terminals contain neurotransmitter that may be released into the synaptic cleft.

Which of the following best describes a nerve signal? the flow of neurotransmitter chemical along a neuron the flow of electricity along a neuron the movement of tiny filaments of protein inside a neuron the passage of ions through the membrane of a neuron

the passage of ions through the membrane of a neuron The sequential movement of ions across the plasma membrane of the neuron represents the nerve impulse.

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

the receiving neuron is less likely to generate an action potential. If the receiving neuron is more negative inside, it is less likely to generate an action potential.

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 sodium-potassium pump moving sodium ions out of the neuron and potassium ions into the neuron The sodium-potassium pump moves more sodium ions out of the cell than potassium ions into the cell; this net loss of positive ions establishes a charge differential across the plasma membrane.

Which of the following maintains the resting potential (the difference in the electrical charge inside and outside a neuron) that enables the cell to transmit a signal? the myelin sheath, which prevents ions from entering or leaving the neuron the transport and leakage of sodium ions, potassium ions, chloride ions, and various anions into and out of the cell charges that pull sodium and potassium through the membrane the opening of sodium and potassium channels in the membrane

the transport and leakage of sodium ions, potassium ions, chloride ions, and various anions into and out of the cell The resting potential is maintained by a combination of active and passive transport mechanisms.

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

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

A switch is to a light, as a ____________________ is to an action potential. membrane potential axon threshold neuron

threshold