Chapter 11; Fundamentals of the Nervous System and Nervous Tissue

Which of the following statements best describes the membrane situation in the resting state in the neuron? a. Only the voltage-gated Na⁺ channels are open. b. Only the voltage-gated Na⁺ channels are closed. c. All the voltage-gated Na⁺ and K⁺ channels are closed. d. Only the voltage-gated K⁺ are closed. e. Only the voltage-gated K⁺ channels are open.

All the voltage-gated Na⁺ and K⁺ channels are closed.

Nucleus

(1) control center of a cell; contains genetic material; (2) clusters of nerve cell bodies in the CNS

Differentiate between (1) a nerve and a tract, and (2) a nucleus and a ganglion.

-- A bundle of nerve fibers is called a tract in the CNS and a nerve in the PNS. -- A collection of cell bodies is called a nucleus in the CNS and a ganglion in the PNS.

ACh excites skeletal muscle and yet it inhibits heart muscle. How can this be?

ACh interacts with more than one specific receptor type, and this explains how it can excite at some synapses and inhibit at others.

If an axon receives two stimuli close together in time, only one action potential occurs. Why?

If a second stimulus occurs before the end of the absolute refractory period, no AP can occur because sodium channels are still inactivated.

Describe how neurons develop and form synapses.

Neuron development involves proliferation, migration, and the formation of interconnections. The formation of interconnections involves axons finding their targets and forming synapses, and the synthesis of specific neurotransmitters. Axon outgrowth and synapse formation are guided by other neurons, glial cells, and chemicals (such as N-CAM and nerve growth factor). Neurons that do not make appropriate synapses die, and approximately two-thirds of neurons formed in the embryo undergo programmed cell death.

For which cation is there the greatest amount of leakage (through leakage channels) across the plasma membrane?

There is more leakage of K⁺ than of any other cation.

Graded Potential

a local change in membrane potential that varies directly with the strength of the stimulus, declines with distance

Summation

accumulation of effects, especially those of muscular, sensory, or mental stimuli

Multiple Sclerosis (MS)

demyelinating disorder of the CNS; causes hardened patches (sclerosis) in the brain and spinal cord

Which is best described by "CNA phagocyte"? a. astrocyte b. ependymal cell c. microglial cell d. oligodendrocyte e. satellite cell f. Schwann cell

microglial cell

Which of the following diseases is directly related to demyelination? a. cerebral palsy b. muscular dystrophy c. lupus d. multiple sclerosis

multiple sclerosis

Interneuron (Association Neuron)

nerve cell located between motor and sensory neurons that shuttles signals through CNS pathways where integration occurs

Neuroglia

nonexcitable cells of neural tissue that support, protect, and insulate the neurons; glial cells

Peripheral Nervous System (PNS)

portion of the nervous system consisting of nerves and ganglia that lie outside of the brain and spinal cord

What is an exceptionally strong stimulus can trigger a response a. repolarization b. action potential c. depolarization d. relative refractory period e. absolute refractory period

relative refractory period

Involuntary Nervous System

the autonomic nervous system

Which criterion is used to structurally classify neurons? a. whether the neurons are found within the CNS or the PNS b. the number of processes extending from their cell body c. the direction the nerve impulse travels relative to the central nervous system d. whether the nerve fibers are myelinated or not

the number of processes extending from their cell body

White Matter

white substance of the central nervous system; myelinated nerve fibers

Which subdivision of the PNS is involved in (a) relaying the feeling of a "full stomach" after a meal, (b) contracting the muscles to lift your arm, and (c) increasing your heart rate?

(a) This "full stomach" feeling would be relayed by the sensory (afferent) divisions of the PNS (via its visceral afferent fibers. (b) The somatic nervous system , which is part of the motor (efferent) division of the PNS, controls movement of skeletal muscles. (c) The anatomic nervous system, which is part of the motor (efferent) division of the PNS, controls the heart rate.

Which part of the neuron is its fiber? How do nerve fibers differ from the fibers of connective tissue and the fibers of muscle??

A nerve fiber is a long axon, an extension of the cell. In connective tissue, fibers are extracellular proteins that provide support. In muscle tissue, a muscular fiber is a muscle cell.

How does a nucleus within the brain differ from a nucleus within a neuron?

A nucleus within the brain is a cluster of cell bodies, whereas the nucleus within each neuron is a large organelle that acts as the control center of the cell.

Define synapse. Distinguish between electrical and chemical synapses by structure and by the way they transmit information.

A synapse is a functional junction between neurons. The information-transmitting neuron is the presynaptic neuron; the information-receiving neuron is the postsynaptic neuron. Electrical synapses allow ions to flow directly from one neuron to another; the cells are electrically coupled. Chemical synapses are sites of neurotransmitter release and binding. When the impulse reaches the presynaptic axon terminals, voltage-gated Ca²⁺ channels open, and Ca²⁺ enters the cell and mediates neurotransmitter release. Neurotransmitters diffuse across the synaptic cleft and attach to postsynaptic membrane receptors, opening ion channels. After binding, the neurotransmitters are removed from the synapse by diffusion, enzymatic breakdown, or reuptake into the presynaptic terminal or astrocytes.

Inhibition of acetylcholinesterase by poisoning blocks neurotransmission at the neuromuscular junction because a. ACh is no longer released by the presynaptic terminal b. ACh synthesis in the presynaptic terminal is blocked c. ACh is not degraded, hence prolonged depolarization is enforced on the postsynaptic cell d. ACh is blocked from attaching to the postsynaptic ACh receptors

ACh is not degraded, hence prolonged depolarization is enforced on the postsynaptic cell

Which is bigger, a graded potential or an action potential?

Action potentials are larger than graded potentials and travel further. Graded potentials generally initiate action potentials.

An action potential does not get smaller as is propagates along the axon. Why not?

An action potential is regenerated anew at each membrane patch.

Classify neurons by structure and by function.

Anatomically, neurons are classified according to the number of processes issuing from the cell body as multipolar, bipolar, or unipolar. Functionally, neurons are classified according to the direction of nerve impulse conduction. Sensory neurons conduct impulses toward the CNS, motor neurons conduct away from the CNS, and interneurons (association neurons) lie between sensory and motor neurons in the neural pathways.

Which type of neuroglia controls the extracellular fluid environment around neuron cell bodies in the CNS? In the PNS??

Astrocytes control the extracellular environment around neuron cell bodies in the CNS, whereas satellite cells perform this function in the PNS.

What structure joins two neurons at an electrical synapse?

At an electrical synapse, neurons are joined by gap junctions.

Distinguish between excitatory and inhibitory postsynaptic potentials.

Binding of neurotransmitters at excitatory chemical synapses results in local graded potentials called EPSPs, caused by the opening of channels that allow simultaneous passage of Na⁺ and K⁺. Neurotransmitter binding at inhibitory chemical synapses results in hyperpolarizations called IPSPs, caused by the opening of K⁺ or Cl⁻ channels. IPSPs drive the membrane potential farther from threshold.

What is the difference between nerves and tracts? a. Bundles of neuron processes are called tracts in the CNS and nerves in the PNS. b. Bundles of neuron processes are called nerves in the CNS and tracts in the PNS. c. Tracts are composed of many nerves wrapped into long, rope-like extensions. d. Tracts are bundles of neuron processes and nerves are the conducting regions of neurons.

Bundles of neuron processes are called tracts in the CNS and nerves in the PNS.

Which structural and functional type of neuron is activated first when you burn your finger? Which type is activated last to move your finger away from the source of heat??

Burning a finger will first activate unipolar (pseudounipolar) neurons that are sensory (afferent) neurons. The impulse to move your finger away from the heat will be carried by multipolar neurons that are motor (efferent) neurons.

Describe common patterns of neuronal organization and processing.

CNS neurons are organized into several types of neuronal pools, each with distinguishing patterns of synaptic connections called circuits. The four basic circuit types are diverging, converging, reverberating, and parallel after-discharge.

Why does a myelinated axon conduct action potentials faster than a non-myelinated axon?

Conduction of action potentials is faster in myelinated axons because myelin allows the axon membrane between myelin sheath gaps to change its voltage rapidly, and allows current to flow only at the widely spaced gaps.

Compare and contrast graded potentials and action potentials.

Depolarization is a reduction in membrane potential (inside becomes less negative); hyperpolarization is an increase in membrane potential (inside becomes more negative). Graded potentials are small, brief, local changes in membrane potential that act as short-distance signals. The current produced dissipates with distance. An action potential (AP), or nerve impulse, is a large, but brief, depolarization signal (and polarity reversal) that underlies long-distance neural communications. It is an all-or-none phenomenon.

Define absolute and relative refractory periods.

During the absolute refractory period, a neuron cannot respond to another stimulus because it is already generating an AP. During the relative refractory period, the neuron's threshold is elevated because repolarization is ongoing.

Describe how synaptic events are integrated and modified.

EPSPs and IPSPs summate temporally and spatially. The membrane of the axon hillock acts as a neuronal integrator. Synaptic potentiation, which enhances the postsynaptic neuron's response, is produced by intense repeated stimulation. Ionic calcium appears to mediate such effects, which may be the basis of learning. Presynaptic inhibition is mediated by axoaxonal synapses that reduce the amount of neurotransmitter released by the inhibited neurons.

Which of the following is NOT true of efferent neurons? a. Efferent neurons carry impulses away from the CNS to the effector organs. b. The cell bodies of most efferent neurons are located in the CNS. c. Efferent neurons are bipolar. d. Impulses from efferent neurons cause activity in skeletal muscles and glands.

Efferent neurons are bipolar.

A neuron becomes depolarized during an inhibitory postsynaptic potential (IPSP). a. True b. False

False

A reverberating circuit involves an incoming signal that travels along a chain of neurons and quickly dies out. a. True b. False

False

Acetylcholine is released only by neurons at neuromuscular junctions. a. True b. False

False

All neurons are amitotic. a. True b. False

False

Although a variety of molecules act as neurotransmitters, amino acid neurotransmitters have NOT yet been found. a. True b. False

False

Due to the amount of space between cells, over 30% of the CNS is extracellular space. a. True b. False

False

In neural processing, input either travels along one single pathway to a specific destination (serial) or it travels along several different pathways to integrate in different CNS regions (parallel), but NOT both. a. True b. False

False

Schwann cells myelinate axons in the CNS. a. True b. False

False

Strong stimuli cause the amplitude of action potentials generated to increase. a. True b. False

False

The CNS is the control center for ALL human activities. a. True b. False

False

The end of the nerve cell axon is called the dendrite. a. True b. False

False

The sodium-potassium pump provides energy for neurons, but does NOT affect resting membrane potential. a. True b. False

False

Which ion flow through chemically gated channels to produce IPSPs? EPSPs??

IPSPs result from the flow of either K⁺ pr Cl⁻ through chemically-gated channels.

Define saltatory conduction and contrast it to continuous conduction.

In nonlyelinated fibers, APs are produced in a wave all along the axon, that is, by continuous conduction. In myelinated fibers, APs are generated only at myelin sheath gaps and are propagated more rapidly by saltatory conduction.

Distinguish between serial and parallel processing.

In serial processing, one neuron stimulates the next in sequence, producing specific, predictable responses, an in spinal reflexes. A reflex is a rapid, involuntary motor response to a stimulus. Reflexes are mediated over neural pathways called reflex arcs. The minimum number of elements in a reflex arc id five: receptor, sensory neuron, integration center, motor neuron, and effector. In parallel processing, which underlies complex mental functions, impulses travel along several pathways to different integration centers.

Explain how action potentials are generated and propagated along neurons.

In the AP graph, an AP begins and ends at resting membrane potential. Depolarization to approximately +30 mV (inside positive) is caused by Na⁺ influx. Depolarization ends when Na⁺ channels inactivate. Repolarization and hyperpolarization are caused by K⁺ efflux. If threshold is reached, and AP is generated. If not, depolarization remains local. In nerve impulse propagation, each AP provides the depolarizing stimulus for triggering an AP in the next membrane patch. Regions that have just generated APs are refractory; for this reason, the nerve impulse propagates in one direction only. APs are independent of stimulus strength: Strong stimuli cause APs to be generated more frequently but not with greater amplitude.

How is myelin sheath formed in the CNS, and what is its function?

In the CNS, a myelin sheath is formed by oligodendrocytes that wrap their plasma membranes around the axon. The myelin sheath protects and electrically insulates axons and increases the speed of transmission of nerve impulses.

What is meant by "integration," and does it primarily occur in the CNS or the PNS?

Integration involves processing and interpreting sensory information, and making a decision about motor output. Integration occurs primarily in the CNS.

Which of the following events is NOT involved in the transfer of information across a chemical synapse? a. Calcium channels open in the presynaptic region. b. Neurotransmitters bind to the postsynaptic receptors. c. A neurotransmitter is released by exocytosis. d. Ion channels open in the postsynaptic membrane. e. Ions flow directly from one neuron to the next.

Ions flow directly from one neuron to the next.

An action potential _____. a. Involves the influx of negative ions to depolarize the membrane b. Is initiated by potassium ion movement c. Is essential for impulse propagation d. Involves impulse propagation dependent on chemically gated ion channels.

Is essential for impulse propagation

Explain the importance of the myelin sheath and describe how it is formed in the central and peripheral nervous systems.

Large nerve fibers (axons) are myelinated. The myelin sheath is formed in the PNS by Schwann cells and in the CNS by oligodendrocytes. The myelin sheath gaps are also called nodes of Ranvier. Nonmyelinated fibers are surrounded by supporting cells, but the membrane-wrapping process does not occur.

Which of these ions is actively transported through the cell membrane to establish a resting potential? a. Ca b. Na c. Cl d. Mg

Na

List the types of neuroglia and cite their functions.

Neuroglia (supporting cells) segregate and insulate neurons and assist neurons in various other ways. CNS neuroglia include astrocytes, microglial cells, ependymal cells, and oligodendrocytes. PNS neurolgia include Schwann cells and satellite cells.

Which of the following is NOT a characteristic of neurons? a. Neurons are relatively small, simple-structured cells. b. Neurons require continuous and abundant supplies of oxygen, and cannot survive for more than a few minutes without it. c. In general, neurons cannot be replaced if destroyed. d. Neurons can function optimally for over 100 years.

Neurons are relatively small, simple-structured cells.

Define neuron, describe its important structural components, and relate each to a functional role.

Neurons have a cell body and cytoplasmic processes called axons and dendrites. The cell body is the biosynthetic (and receptive) center of the neuron. Except for those found in ganglia, cell bodies are found in the CNS. Most neurons have many dendrites, receptive processes that conduct signals from other neurons toward the nerve cell body. With few exceptions, all neurons have one axon, which generates and conducts nerve impulses away from the nerve cell body. Axon terminals release neurotransmitters. Bidirectional transport along axons use ATP-dependent motor proteins "walking" along microtubule tracks. It moves vesicles, mitochondria, and cytosolic proteins toward the axon terminals and conducts substances destined for degradation back to the cell body.

What is the difference between the clusters of cell bodies called nuclei and those known as ganglia? a. Nuclei exist in all cells throughout the body, and ganglia exist only within the brain and spinal cord. b. Nuclei exist in the CNS, ganglia in the PNS. c. Nuclei exist in the PNS, ganglia in the CNS. d. There is no difference between nuclei and ganglia.

Nuclei exist in the CNS, ganglia in the PNS.

Which two types of neuroglia form insulating coverings called myelin sheaths?

Oligodendrocytes and Schwann cells form myelin sheath in the CNS and PNS, respectively.

The sodium-potassium pump _____. a. Pumps two sodium ions inside the cell and three potassium ions outside. b. Pumps three sodium ions inside the cell and two potassium ions outside. c. Pumps three sodium ions outside the cell and two potassium ions inside. d. Pumps two sodium ions outside the cell and three potassium ions inside.

Pumps three sodium ions outside the cell and two potassium ions inside.

Which type of neural circuits would give a prolonged output after a single input?

Reverberating circuits and parallel after-discharge circuits both result in prolonged output.

Which is best described by "myelinates nerve fibers in the PNS"? a. astrocyte b. ependymal cell c. microglial cell d. oligodendrocyte e. satellite cell f. Schwann cell

Schwann cell

What is the difference between temporal summation and spatial summation?

Temporal summation is summation in time of graded potentials occuring in quick successions at the postsynaptic membrane. In can result from EPSPs arising from just one synapse. Spatial summation is summation in space - a postsynaptic neuron is stimulated by a large number of terminals at the same time.

For an open channel, what factors determine in which direction ions will move through that channel?

The concentration gradient and the electrical gradient - together called the electrochemical gradient - determine the direction in which ions flow through an open membrane channel.

What is the name of a growing tip of an axon that "sniffs out" where to go during development? What is the general name for the chemicals that tell it where to go??

The growing tip of an axon is called a growth cone. Neurotropins are chemicals that signal the growth cone.

Define neurotransmitter and name several classes of neurotransmitters.

The major class of neurotransmitters based on chemical structure are acetylcholine, biogenic amines, amino acids, peptides, purines, dissolved gases, and lipids. Functionally, neurotransmitters are classified as (1) inhibitory or excitatory (or both) and (2) direct or indirect action. Direct-acting neurotransmitters bind to and open ion channels. Indirect-acting neurotransmitters act through second messengers. Neuromodulators also act indirectly presynaptically or postsynaptically to change synaptic strength. Neurotransmitter receptors are either channel-linked receptors that open ion channels, leading to fast changes in membrane potential, or G protein-linked receptors that oversee slow synaptic responses mediated by G proteins and intracellular second messengers. Second messengers most often activate kinases, which in turn act on ion channels or activate other proteins.

Explain the structural and functional divisions of the nervous system.

The major functional division of the PNS are the sensory (afferent) division, which conveys impulses to the CNS and motor (efferent) division, which conveys impulses from the CNS. The efferent division includes the somatic (voluntary) system, which serves skeletal muscles, and the autonomic (involuntary) system, which innervates smooth and cardiac muscle and glands.

Define resting membrane potential and describe its electrochemical basis.

The measure of potential energy of separated electrical charges is called voltage (V) or potential. Current (I) is the flow of electrical charges from one point to another. Resistance (R) is hindrance to current flow. Ohm's law gives the relationship among these: I = V / R In the body, ions provide the electrical charges; cellular plasma membranes provide resistance to ion flow. The membranes contain leakage channels (nongated, always open) and gated channels. A resting neuron exhibits a resting membrane potential, which is -70 mV (inside negative). It is due both to differences in sodium and potassium ion concentrations inside and outside the cell and to differences in permeability of the membrane to the ions. The ionic concentration differences result from the operation of the sodium-potassium pump, which ejects 3 Na⁺ from the cell for each 2 K⁺ transported in.

A second nerve impulse cannot be generated until _____. a. The Na ions have been pumped back into the cell b. Proteins have been resynthesized c. The membrane potential has been re-established d. All sodium gates are closed

The membrane potential has been re-established

List the basic functions of the nervous system.

The nervous system bears a major responsibility for maintaining body homeostasis. It monitors, integrates, and responds to information in the environment. The nervous system is divided anatomically into the central nervous system (CNS) (brain and spinal cord) and the peripheral nervous system (PNS) (mainly cranial and spinal nerves).

Which of the following best describes the concept of integration? a. The nervous system generates neurons in order to replace or repair damaged neurons; this permits optimal communication between the CNS and the body's effector organs. b. The nervous system causes a response by activating effector organs, such as the muscles and glands. c. The nervous system processes and interprets sensory input and decides what should be done at each moment. d. The nervous system uses its millions of sensory receptors to monitor changes occurring both inside and outside the body.

The nervous system processes and interprets sensory input and decides what should be done at each moment.

Which of the following statements about the developmental aspects of neurons is INCORRECT? a. Neurons that fail to make the appropriate synaptic contact will not receive appropriate nutrients and will die. b. They develop from neuroepithelial cells. c. Axons are attached to grow toward their "target" by multiple signals such as the nerve growth factor, the nerve cell adhesion factor, and older pathfinder neurons. d. The number of adult neurons is the same as the number formed during the embryonic period. e. Neuroepithelial cells become the CNS and then go through three phases of differentiation during maturation.

The number of adult neurons is the same as the number formed during the embryonic period.

What pattern of neural processing occurs when we smell freshly baked apple pie and remember Thanksgiving at our grandparents' house, the odor of freshly roasted turkey, sitting by the fireplace, and other such memories?

The pattern of neural processing is parallel processing.

What pattern of neural processing occurs when your finger accidentally touches a hot grill? What is the response called ??

The pattern of neural processing is serial processing. the response is a reflex arc.

Which of the following statements concerning inhibitory synapses (IPSPs) is correct? a. The permeability of the postsynaptic membrane to sodium, potassium, and chloride is not changed. b. The postsynaptic membrane becomes less permeable to sodium. c. Channels allow both sodium and potassium ions to diffuse simultaneously through the membrane. d. The postsynaptic membrane becomes less permeable to potassium. e. The postsynaptic membrane becomes more permeable to potassium and chloride.

The postsynaptic membrane becomes more permeable to potassium and chloride.

What is the primary difference between the somatic nervous system and the autonomic nervous system? a. The somatic nervous system allows us to consciously control our skeletal muscles, and the autonomic nervous system controls activity that humans cannot consciously control, such as the pumping of the heart and the movement of food through the digestive tract. b. The autonomic nervous system allows us to consciously control our skeletal muscles, and the somatic nervous system controls activity that humans cannot consciously control, such as the pumping of the heart and the movement of food through the digestive tract. c. The autonomic nervous system enables us to control our involuntary muscles, while the somatic nervous system controls our glands. d. The somatic nervous system enables us to control our involuntary muscles, while the autonomic nervous system controls our glands.

The somatic nervous system allows us to consciously control our skeletal muscles, and the autonomic nervous system controls activity that humans cannot consciously control, such as the pumping of the heart and the movement of food through the digestive tract.

Which of the following is NOT true of chemical synapses? a. They communicate unidirectionally. b. They possess pre- and postsynaptic membranes separated by a synaptic cleft. c. They transmit nerve impulses directly from one neuron to another. d. Each is composed of an axon terminal and a receptor region.

They transmit nerve impulses directly from one neuron to another.

An action potential is a phenomenon that either happens completely or doesn't happen at all. a. True b. False

True

At an excitatory synapse, only one type of channel is opened, allowing both sodium and potassium to diffuse simultaneously in opposite directions. This still allows depolarization to take place. a. True b. False

True

Axons are the conducting component of the neuron, whereas dendrites are the collecting, or receptive, component. a. True b. False

True

Dendrites and axons are both arm-like processes that extend from cell bodies. a. True b. False

True

Excitatory synapses can occur anywhere on a dendrite or soma, but it is at the axon hillock where an action potential can be generated. a. True b. False

True

The firing of one neuron can produce temporal summation. a. True b. False

True

The most abundant neurotransmitter in the body is acetylcholine. a. True b. False

True

The presence of the nodes of Ranvier speeds up the velocity of conduction along the axon. a. True b. False

True

The space between the nerve cells is called the synapse. a. True b. False

True

Unipolar neurons are more accurately called pseudounipolar neurons. a. True b. False

True

Choose the statement that is most correct about membrane potential. a. Voltage would be measured by placing two electrodes on the exterior of the axon. b. Voltage would be measured by placing one electrode inside the membrane and another outside the membrane. c. Voltage would be measured by placing one electrode on the axon and grounding the other electrode. d. Voltage would be measured by placing one electrode on one end of the axon and another electrode on the other end.

Voltage would be measured by placing one electrode inside the membrane and another outside the membrane.

Events at a chemical synapse usually involve opening both voltage-gated ion channels and chemically-gated ion channels. Where are these ion channels located and what causes each to open?

Voltage-gated ion (Ca²⁺) channels are found in the presynaptic axon terminal and open when the action potential reaches the axon terminal. Chemically-gated ion channels are found in the postsynaptic membrane and open when neurotransmitter binds to the receptor protein.

Nerve

a bundle of axons in the peripheral nervous system

Neuropeptides

a class of neurotransmitters including beta endorphins and enkephalins (which act as euphorics and reduce perception of pain) and gut-brain peptides

Nitric Oxide (NO)

a gaseous chemical messenger; diverse functions include participation in memory formation in the brain, and causing vasodilation throughout the body

Inhibitory Postsynaptic Potential (IPSP)

a graded potential in a postsynaptic neuron that inhibits action potential generation; usually hyperpolarizing

Action Potential

a large transient depolarization event, including polarity reversal, that is conducted along the membrane of a muscle cell or a nerve fiber

Which of the following structures is not part of the central nervous system? a. the brain b. a nerve c. the spinal cord d. a tract

a nerve

Sodium-Potassium (Na⁺-K⁺) Pump

a primary active transport system that simultaneously drives Na⁺ out of the cell against a steep gradient and pumps K⁺ back in; also called Na⁺-K⁺ ATPase

Nerve Impulse

a self-propagating wave of depolarization; also called an action potential

Assume that an EPSP is being generated on the dendritic membrane. Which will occur? a. specific Na⁺ channels will open b. specific K⁺ channels will open c. a single type of channel will open, permitting simultaneous flow of Na⁺ and K⁺ d. Na⁺ channels will open first and then close as K⁺ channels open

a single type of channel will open, permitting simultaneous flow of Na⁺ and K⁺

The first thing needed to start an action potential is _____. a. a stimulus b. sodium c. potassium d. calcium

a stimulus

Oligodendrocyte

a type of CNS supporting cell that composes myelin sheaths

Astrocyte

a type of CNS supporting cell; assists in exchanges between blood capillaries and neurons

Microglial Cells

a type of CNS supporting cell; can transform into phagocytes in areas of neural damage or inflammation

Ependymal Cell

a type of CNS supporting cell; lines the central cavities of the brain and spinal cord

Schwann Cell

a type of supporting cell in the PNS; forms myelin sheaths and is vital to peripheral nerve fiber regeneration

Excitability (Responsiveness)

ability to respond to stimuli

Conductivity

ability to transmit an electrical impulse

The period during which the neuron cannot respond to a second stimulus, no matter how strong is a. repolarization b. action potential c. depolarization d. relative refractory period e. absolute refractory period

absolute refractory period

Biogenic amine neurotransmitters include all but a. norepinephrine b. acetylcholine c. dopamine d. serotonin

acetylcholine

Which of the following is NOT a biogenic amine neurotransmitter? a. acetylcholine b. norepinephrine c. serotonin d. epinephrine e. dopamine

acetylcholine

Which of the following substances is NOT a neurotransmitter? a. histamine b. acetylcholinesterase c. epinephrine d. carbon dioxide

acetylcholinesterase

Also called a nerve impulse transmitted by axons is a. repolarization b. action potential c. depolarization d. relative refractory period e. absolute refractory period

action potential

Which of the following electrical events occurs when a certain threshold is reached? a. IPSP b. action potential c. resting membrane potential d. EPSP

action potential

Caffeine's stimulatory effects result from blocking receptors for which neurotransmitter? a. acetylcholine b. serotonin c. dopamine d. adenosine

adenosine

Hyperpolarization

an increase in membrane potential in which the membrane becomes more negative than resting membrane potential

Pseudounipolar Neuron

another term for unipolar neuron

Which is best described by "helps regulate the ionic composition of CNS extracellular fluid"? a. astrocyte b. ependymal cell c. microglial cell d. oligodendrocyte e. satellite cell f. Schwann cell

astrocyte

Which of the following neuroglia is most responsible for helping determine capillary permeability in nervous tissue? a. oligodendrocytes b. microglia c. astrocytes d. Schwann cells e. ependyma

astrocytes

Which of the following types of glial cells are the most abundant and versatile, and aid in making exchanges between capillaries and neurons? a. oligodendrocytes b. microglia c. astrocytes d. ependymal cells

astrocytes

Reflex

automatic reaction to stimuli

Th anatomical region of a multipolar neuron that has the lowest threshold for generating an action potential is the a. soma b. dendrites c. axon hillock d. distal axon

axon hillock

Nerve Fiber

axon of a neuron

Which of the following is a rare type of sensory neuron that is found in special sensory structures like the retina of the eye? a. multipolar b. bipolar c. unipolar d. pseudounipolar

bipolar

Central Nervous System (CNS)

brain and spinal cord

Terminal Branches

branching ends of an axon that allow it to form many axon terminals; telodendria

Dendrite

branching neuron process that serves as a receptive, or input, region; transmits an electrical signal toward the cell body

Why is cyclic AMP called a second messenger?

cAMP is called a second messenger because it relays the message between the first messenger (the original chemical messenger) outside of the cell and effector molecules that will ultimately bring about the desired response within the cell.

Efferent

carrying away or away from, especially a nerve fiber that carries impulses away from the central nervous system

Afferent

carrying to or toward a center

Neuron (Nerve Cell)

cell of the nervous system specialized to generate and transmit electrical signals (action potentials and graded potentials)

Which of the following is NOT a functional classification of neurotransmitters? a. direct b. indirect c. excitatory d. chemical

chemical

Neurotransmitter

chemical messenger released by neurons that may, upon binding to receptors of neurons or effector cells, stimulate or inhibit those neurons or effector cells

Acetylcholine (ACh)

chemical transmitter substance released by some nerve endings

What type of current flows through the axolemma during the steep phase of repolarization? a. chiefly a sodium current b. chiefly a potassium current c. sodium and potassium currents of approximately the same magnitude

chiefly a potassium current

Identify the neuronal circuit described by "many neurons influence a few neurons" a. converging b. diverging c. parallel after-discharge d. reverberating

converging

The part of the cell that receives the impulse is called _____. a. axon b. soma c. dendrite d. myelin sheath

dendrite

Which of the following are the main receptive or input regions found in neurons? a. ganglia b. neurofibrils c. dendrites d. axons

dendrites

The interior of the cell becomes less negative due to an influx of sodium ions is a. repolarization b. action potential c. depolarization d. relative refractory period e. absolute refractory period

depolarization

Excitatory Postsynaptic Potential (EPSP)

depolarizing graded potential in a postsynaptic neuron

Identify the neuronal circuit described by "one or a few inputs ultimately influence large numbers of neurons" a. converging b. diverging c. parallel after-discharge d. reverberating

diverging

Which of the following circuit types is exemplified by impulses that travel from a single neuron of the brain, activate one hundred or more motor neurons in the spinal cord, and excite thousands of skeletal muscle fibers? a. converging circuits b. after-discharge circuits c. reverberating circuits d. diverging circuits

diverging circuits

Somatic Nervous System

division of the peripheral nervous system that provides the motor innervation of skeletal muscles; also called the voluntary nervous system

There are two types of synapses: chemical and _____. a. electrical b. dendritic c. axonical d. mechanical

electrical

Which of the following neurotransmitters acts as a natural opiate? a. GABA b. endorphins c. serotonin d. epinephrine e. dopamine

endorphins

The neuropeptides that act as natural opiates are a. substance P b. somatostatin and cholecystolinin c. tachykinins d. enkephalins

enkephalins

Acetylcholinesterase (AChE)

enzyme present at the neuromuscular junction and synapses that degrades acetylcholine and terminates its action

Which is best described by "lines brain cavities"? a. astrocyte b. ependymal cell c. microglial cell d. oligodendrocyte e. satellite cell f. Schwann cell

ependymal cell

Which of the following line the central cavities of the brain and spinal cord and provide a fairly permeable barrier between the CSF and nervous tissue? a. Schwann cells b. astrocytes c. oligodendrocytes d. ependymal cells e. microglia cells

ependymal cells

Which of the following types of glial cells line the central cavities of the brain and spinal cord, where they help to circulate the cerebrospinal fluid? a. oligodendrocytes b. ependymal cells c. microglia d. astrocytes

ependymal cells

Catecholamines

epinephrine, norepinephrine, and dopamine; a class of amines that act as chemical transmitters

Nervous System

fast-acting control system that triggers muscle contraction or gland secretion

Myelin Sheath

fatty insulating sheath that surrounds all but the smallest nerve fibers

Synaptic Cleft

fluid-filled space at a synapse

Relative Refractory Period

follows the absolute refractory period; interval when a threshold for action potential stimulation is markedly elevated

From where can collaterals emerge on a myelinated nerve? a. at the terminal of the axon b. from the nodes of Ranvier c. from the neuron hillock d. from the dendrite

from the nodes of Ranvier

Neuronal Pools

functional groups of neurons that process and integrate information

Synapse

functional junction or point of close contact between two neurons or between a neuron and an effector cell

The velocity of nerve impulse conduction is greatest in a. heavily myelinated, large-diameter fibers b. myelinated, small-diameter fibers c. nonmyelinated, small-diameter fibers d. nonmyelinated, large-diameter fibers

heavily myelinated, large-diameter fibers

An inhibitory postsynaptic potential (ISPS) is associated with _____. a. lowering the threshold for an action potential to occur b. opening of voltage-regulated channels c. a change in sodium ion permeability d. hyperpolarization

hyperpolarization

A potential of -90 mV is considered _____. a. hyperpolarized b. a normal resting potential c. depolarized d. a graded potential

hyperpolarized

Chemical synapses are characterized by all of the following except a. the release of neurotransmitters by the presynaptic membranes b. postsynaptic membranes bearing receptors that bind neurotransmitters c. ions flowing through protein channels from the presynaptic to the postsynaptic neuron d. a fluid-filled gap separating the neurons

ions flowing through protein channels from the presynaptic to the postsynaptic neuron

An IPSP is inhibitory because a. it hyperpolarizes the postsynaptic membrane b. it reduces the amount of neurotransmitter released by the presynaptic terminal c. it prevents calcium ion entry into the presynaptic terminal d. it changes the threshold of the neuron

it hyperpolarizes the postsynaptic membrane

Which of the following factors is associated with increased conduction velocity in an axon? a. small diameter b. presence of collaterals c. increased number of dendrites d. large diameter e. the absence of the myelin sheath

large diameter

Which of the following membrane ion channels in the neuron are always open? a. mechanically gated channels b. voltage-gated channels c. leakage channels d. ligand-gated channels

leakage channels

Which type of ion channel opens when a chemical binds to it? a. leakage channels b. mechanically gated channels c. voltage-gated channels d. ligand-gated channels

ligand-gated channels

Depolarization

loss of a state of polarity; loss or reduction of negative membrane potential

The difference in charge between the inside of the nerve cell membrane and the outside is called _____. a. differential factor b. membrane potential c. stimulus d. none of the above

membrane potential

Spatial summation occurs when _____. a. an EPSP from one terminal is activated several times in rapid order b. multiple local potentials occur at the same synapse on a cell c. multiple local potentials occur at different places on the same cell at the same time d. multiple local potentials occur at different times in the same cell

multiple local potentials occur at different places on the same cell at the same time

Neurons can be classified structurally by the number of processes extending from their cell bodies. Which of the following is the most common neuron type in humans? a. pseudounipolar b. multipolar c. unipolar d. bipolar e. multipolar and bipolar neurons are present in equal proportions

multipolar Over 99% of neurons in humans are multipolar.

Afferent (Sensory) Nerve

nerve that contains processes of sensory neurons and carries nerve impulses to the central nervous system

Unipolar Neuron

neuron in which embryological fusion of the two processes leaves only one process extending from the cell body

Axon

neuron process that carries impulses away from the nerve cell body; efferent process; the conducting portion of a nerve cell

Bipolar Neuron

neuron with axon and dendrite that extend from opposite sides of the cell body

Multipolar Neurons

neurons with three or more processes; most common neuron type in the CNS

Glial Cells

nonexcitable cells of neural tissue that support, protect, and insulate the neurons; see Neuroglia

Which is best described by "myelinates nerve fibers"? a. astrocyte b. ependymal cell c. microglial cell d. oligodendrocyte e. satellite cell f. Schwann cell

oligodendrocyte

Which of the following conditions would cause synaptic potentiation? a. closure of NMDA (N-methyl-D-aspartate) receptors b. opening of NMDA (N-methyl-D-aspartate) receptors and influx of Ca⁺⁺ c. influx of Na⁺ channels d. opening of voltage-gated K⁺ channels

opening of NMDA (N-methyl-D-aspartate) receptors and influx of Ca⁺⁺

Identify the neuronal circuit described by "may be involved in exacting types of mental activity" a. converging b. diverging c. parallel after-discharge d. reverberating

parallel after-discharge

Absolute Refractory Period

period following stimulation during which no additional action potential can be evoked

Immediately after an action potential has peaked, which cellular gates open? a. potassium b. calcium c. sodium d. chloride

potassium

The movement of which ion through leakage channels establishes the negative membrane potential? a. chloride b. potassium c. calcium d. sodium

potassium

Which of the following substances plays the major role in generating the membrane potential of a neuron through its passive movement? a. urea b. potassium c. sodium d. chloride

potassium

The interior of a nerve cell has a slight excess of negative charge because _____. a. potassium diffuses out of the cell b. potassium is actively pumped into the cell c. potassium is actively pumped out d. chloride ions are actively pumped in e. sodium is actively pumped into the cell

potassium diffuses out of the cell

Which of the following defines integration? a. increasing the level of one substance in response to a decrease in the level of another b. processing and interpretation of sensory input and determining what should be done at each moment in the body c. monitoring changes both inside and outside the body d. activating effector organs

processing and interpretation of sensory input and determining what should be done at each moment in the body

Nerve Growth Factor (NGF)

protein that promotes survival and development of neurons; secreted by their target cells and many other cell types

The sodium-potassium ion pump will _____. a. pump one potassium ion out of the cell for every ion of sodium it brings into the cell b. pump three potassium ions out of the cell for every two sodium ions it brings into the cell c. pump three sodium ions out of the cell for every two ions of potassium it brings into the cell d. pump one sodium ion out of the cell for every ion of potassium it brings into the cell

pump three sodium ions out of the cell for every two ions of potassium it brings into the cell

The specific period during which the potassium ions diffuse out of the neuron due to a change in membrane permeability is a. repolarization b. action potential c. depolarization d. relative refractory period e. absolute refractory period

repolarization

Which part of the action potential occurs when the Na⁺ channels are inactivating and K⁺ channels open? a. repolarization b. depolarization c. hyperpolarization d. resting state

repolarization

During which phase of an action potential are voltage-gated K⁺ channels open, while voltage-gated Na⁺ channels are closed? a. regeneration b. depolarizing phase c. resting state d. repolarizing phase

repolarizing phase

Resting Membrane Potential

resting membrane potential: the voltage that exists across the plasma membrane during the resting state of an excitable cell; ranges from −90 to −20 millivolts depending on cell type

Organelles for degradation or recycling are moved through the axon by _____. a. anterograde movement b. saltatory movement c. retrograde movement

retrograde movement

Identify the neuronal circuit described by "impulses continue around and around the circuit until one neuron stops firing" a. converging b. diverging c. parallel after-discharge d. reverberating

reverberating

The Nissl bodies seen in the neuron cell body represents which cellular organelle? a. mitochondria b. microtubules c. centrioles d. rough endoplasmic reticulum e. nucleus

rough endoplasmic reticulum

Which of the following is NOT a structural classification of neurons? a. sensory b. bipolar c. unipolar d. multipolar

sensory

The sensory, or afferent, division of the peripheral nervous system transmits information from the _____ to the CNS. a. heart b. skin c. stomach d. sweat glands e. kidney

skin

Which of the following characteristics is NOT associated with a myelinated nerve fiber? a. rapid conduction of nerve impulses b. slow conduction of nerve impulses c. the presence of nodes of Ranvier d. It is always associated with an axon. e. In the peripheral nervous system, it is formed by Schwann cells.

slow conduction of nerve impulses

Synaptic Vesicles

small membranous sacs containing neurotransmitter

Innervation

supply of nerves to a body part

Which of the following divisions of the nervous system is also known as the involuntary nervous system? a. the autonomic nervous system b. the peripheral nervous system c. the somatic nervous system d. the spinal division of the nervous system

the autonomic nervous system

Neuron Cell Body

the biosynthetic center of a neuron; also called the perikaryon, or soma

Axon Terminals (Terminal Boutons)

the bulbous distal endings of the terminal branches of an axon

Electrochemical Gradient

the combined difference in concentration and charge; influences the distribution and direction of diffusion of ions

Parasympathetic Division

the division of the autonomic nervous system that oversees digestion, elimination, and glandular function; the resting and digesting subdivision

Sympathetic Division

the division of the autonomic nervous system that prepares the body for activity or to cope with some stressor (danger, excitement, etc.); the fight, fright, and flight subdivision

A neuron will not respond to a second stimulus of equal strength to the first stimulus to which it has already responded because _____. a. the neuron is in the absolute refractory period b. neurons are self-propagating cells c. action potential generation is an all-or-none phenomenon d. the neuron is myelinated

the neuron is in the absolute refractory period

Axolemma

the plasma membrane of an axon

Integration

the process by which the nervous system processes and interprets sensory input and makes decisions about what should be done at each moment

Voluntary Nervous System

the somatic nervous system

Synaptic Delay

time required for an impulse to cross a synapse between two neurons

Which of the following is NOT a function of the myelin sheath? a. to electrically insulate nerve fibers b. to recapture and recycle released neurotransmitters c. to increase the speed of transmission of nerve impulses d. to protect nerve fibers

to recapture and recycle released neurotransmitters

Saltatory Conduction

transmission of an action potential along a myelinated fiber in which the nerve impulse appears to leap from gap to gap

Which of the following membrane ion channels open and close in response to changes in the membrane potential? a. mechanically gated channels b. chemically gated channels c. voltage-gated channels d. non-gated channels

voltage-gated channels