Chapter 12: Nervous Tissue

Which is most likely to be the threshold potential for a neuron?

-55

Which is most likely to be the resting membrane potential of a neuron?

-70 mV

Which numerical value is most likely to be the resting membrane potential of a neuron?

-70 mV

Which would cause postsynaptic stimulation to end?

-Diffusion of neurotransmitter from the synaptic cleft into extracellular fluid -Cessation of signals in the presynaptic nerve fiber -Reuptake of neurotransmitter into the presynaptic knob -Enzymatic degradation of neurotransmitter in the synaptic cleft

Which statements are true regarding postsynaptic potentials?

-They include EPSPs and IPSPs. -They are changes in the membrane potential of the postsynaptic terminal of a chemical synapse. -They are caused by neurotransmitters.

What is the approximate ratio of glial cells to neurons?

10:1

Which best describes an electrical potential?

A form of potential energy that can produce current

The all-or-none law of action potentials states which of the following?

A neuron will fire at maximum voltage if a stimulus depolarizes it to threshold.

Which best describes signal conduction in unmyelinated axons?

A wave of depolarization opens more voltage-gated channels immediately distal to the action potential.

Indicate which of the following statements are true about signal conduction along unmyelinated fibers.

A zone of depolarization excites voltage-gated channels immediately distal to the action potential. Unmyelinated fibers have voltage-gated channels along their entire length.

A cholinergic synapse uses which of the following as its neurotransmitter?

Acetylcholine

Select the four categories of neurotransmitters based on chemical composition.

Acetylcholine Neuropeptides Amino acids Monoamines

Which is true about signal conduction in myelinated axons?

Action potentials are only generated at the nodes of Ranvier. The signal moves more rapidly through the internodes than it does through the nodes of Ranvier.

Which statements are true about signal conduction along myelinated fibers?

Action potentials occur only at the nodes of Ranvier. There are few voltage-gated ion channels at the myelin-covered internodes and multiple channels at the nodes of Ranvier. Ions can be exchanged with the ECF only at the nodes of Ranvier.

How do neuromodulators alter synaptic transmission?

Adjusting the sensitivity of postsynaptic neurons to neurotransmitters Increasing the release of neurotransmitters by presynaptic neurons Altering the breakdown and/or reuptake of neurotransmitter

This picture illustrates synaptic transmission involving the release of norepinephrine. Which type of synapse is shown here?

Adrenergic synapse

Where does saltatory conduction occur?

Along myelinated nerve fibers

The neurotransmitters glutamate and GABA are examples of which of the following?

Amino acids

Which types of glial cells are found in the central nervous system?

Astrocytes Microglia Oligodendrocytes Ependymal cells

Which process of a neuron is specialized for rapid conduction of nerve signals to structures relatively far away from the neuron cell body?

Axon

Name the area of the neuron indicated by the arrow labeled A.

Axon collateral

Which term refers to the passage of proteins, organelles and other materials along an axon?

Axonal transport

Labeled line coding depends on which of the following?

Axons carrying sensory information to the brain are activated by specific types of stimuli.

Neurons that have one axon and one dendrite, such as olfactory cells, certain neurons of the retina, and sensory neurons of the inner ear, are classified as which of the following?

Bipolar

What type of neuron is shown in the image?

Bipolar

Two organ systems are dedicated to internal coordination, communication between the other systems, and maintaining the overall homeostasis of the body. They are the ___ system, which communicates by means of hormones, and the ___ system which sends quick electrical and chemical messages from cell to cell.

Blank 1: endocrine Blank 2: nervous

Sensory (afferent) neurons do which of the following?

Carry signals to spinal cord and brain

What are the two major anatomical subdivisions of the nervous system?

Central and peripheral nervous systems

At a GABA-ergic synapse, the postsynaptic receptor for the GABA neurotransmitter is which type of channel?

Chloride

This picture shows an inhibitory postsynaptic potential (IPSP). This is usually due to the opening of which type of ion channels?

Chloride or potassium

Which neurotransmitters are classified as neuropeptides?

Cholecystokinin Endorphins

Which term refers to a synapse that releases acetylcholine from the presynaptic axon terminal?

Cholinergic

Which fundamental physiological property of neurons allows them to send signals quickly over long distances?

Conductivity

The respiratory center of the brain receives input from other parts (i.e from receptors for blood chemistry in arteries and stretch receptors in the lungs) to set a pattern of breathing. This is an example of which type of circuit?

Converging

The circuit in which several input nerve fibers synapse with fewer postsynaptic neurons is what type of circuit?

Converging circuit

Which term refers to the flow of charged particles from one point to another?

Current

___ are the processes of a neuron that usually receive signals from other neurons.

Dendrites

During which part of the action potential do most voltage-gated sodium channels open?

Depolarization

Which term refers to the upward change in membrane potential during an action potential?

Depolarization

Which factors influence the speed of nerve signal conduction?

Diameter of axon Presence of myelin

A single motor neuron stimulating hundreds of skeletal muscle cells is an example of which type of circuit?

Diverging

Which term is used to describe motor neurons because they send signals away from the CNS and out to muscle and gland cells?

Efferent

Which two organ systems are primarily responsible for coordinating the other bodily systems so as to maintain homeostasis?

Endocrine system Nervous system

Choose the name of the thin layer of fibrous connective tissue found around myelin in nerve fibers of the peripheral nervous system.

Endoneurium

Which cell type if indicated by the arrow labeled A?

Ependymal

Which glial cell produces and helps circulate cerebrospinal fluid?

Ependymal cells

Which neurotransmitter is a catecholamine?

Epinephrine

List the fundamental physiological properties of neurons.

Excitability, conductivity, secretion

This picture illustrates neural transmission at which type of synapse?

Excitatory cholinergic synapse

True or false: All neurotransmitters have an excitatory effect.

False

True or false: Electrical synapses are able to integrate information and make decisions more rapidly than chemical signals.

False

True or false: Signal conduction is faster in unmyelinated axons because myelin increases the capacitance of the membrane.

False

True or false: The more synapses a neuron has, the lesser its information-processing capability.

False

Which neurotransmitters are classified as amino acids?

GABA Glutamate

In electrical synapses, electrical signals move quickly from cell to cell through which of the following?

Gap junctions

______ cells protect the neurons and help them function.

Glial

Which are characteristics of local potentials?

Graded Decremental

In a synapse, where are synaptic vesicles located?

In the axon terminal

Between the nodes of Ranvier are myelin-covered segments of axon encircled by Schwann cells. Which term refers to these segments?

Internodes

Which are true regarding the Na+-K+ pump?

It accounts for about 70% of the energy (ATP) required by the nervous system. It helps maintain the proper ion distribution across the membrane, compensating for ion leakage.

Which statements are true regarding the Na+-K+ pump?

It helps maintain the proper ion distribution across the membrane. It requires the use of ATP. It moves Na+ out of the cell and K+ into the cell.

Which correctly describe axonal transport?

It involves transport of proteins within the axon (i.e. synaptic knob enzymes or proteins that maintain the axolemma). It is bidirectional (retrograde and anterograde transport).

Which of the following contributes to the development of the resting membrane potential in neurons?

K+ is more concentrated in the ICF than in the ECF.

Different sensory receptors in the skin respond to different types of stimuli. The brain can infer the type of stimulus detected by which nerve fibers are activated. What is this called?

Labeled line coding

The myelin sheath is composed mostly of which of the following?

Lipids

Which term refers to decremental changes in electrical potential along a dendrite or the soma?

Local potentials

Which cell is indicated by the arrow labeled A?

Microglial cell

Which are usually found inside the cell body (or soma) of a mature neuron?

Mitochondria Nucleus Rough endoplasmic reticulum

Which group of neurotransmitters are synthesized from amino acids by removal of the -COOH group?

Monoamines

List the three functional classes of neurons.

Motor neurons Sensory neurons Interneurons

Neurons with numerous dendrites and a single axon are structurally classified as which of the following?

Multipolar

What are the effectors of motor neurons?

Muscle and gland cells

The pathway of neurons within a neural pool is called its what?

Neural circuit

This picture illustrates that when a stimulus strength (weight) and stretch increase at a sensory fiber, the firing frequency of the neurons increase. Which term refers to the conversion of stimulus information into a meaningful pattern of action potentials?

Neural coding

Which term describes the ability of neurons to process information, store and recall it, and make decisions?

Neural integration

Which term refers to the thick outermost coil of a Schwann cell?

Neurilemma

Which alter synaptic transmission by adjusting the sensitivity of postsynaptic neurons to neurotransmitters or by affecting the breakdown and/or removal of a neurotransmitter?

Neuromodulators

Sensory, association and motor are the three classes of what?

Neurons

The molecules shown in this picture consist of chains of 2 to 40 amino acids. To which class of neurotransmitters do they belong?

Neuropeptides

Stimulation of the postsynaptic neuron will end when nerve signals stop arriving at the presynaptic axon terminal or when which of the following occurs?

Neurotransmitter is removed from postsynaptic receptors.

Which term refers to the gaps between segments of myelin along an axon?

Nodes of Ranvier

Which are properties of action potentials?

Nondecremental (signal maintains amplitude) All or none Self-propagating

Which glial cell insulates nerve fibers from extracellular fluids and speeds up signal conduction in the brain?

Oligodendrocyte

Which type of glial cell is indicated by the arrow labeled A?

Oligodendrocytes

Inhibitory postsynaptic potentials (IPSPs) maybe result from which of the following? Select all that apply.

Opening K+ channels Opening Cl- channels

GABA has an inhibitory effect on postsynaptic neurons because it does which of the following?

Opens chloride channels

Which are the principal types of neural circuits?

Parallel after-discharge circuit Converging circuit Reverberating circuit Diverging circuit

Taken together, the sensory and motor subdivisions make up which of the following?

Peripheral nervous system

Neural integration is based on the combining together of which of the following?

Postsynaptic potentials

Which ion has the greatest influence on the resting membrane potential of most neurons?

Potassium

An electrical potential is a form of what type of energy?

Potential energy

Which term refers to the period of time after a nerve cell has responded to a stimulus in which it cannot be excited by a threshold stimulus?

Refractory period

Which term refers to the voltage difference (electrical potential) across the plasma membrane of a neuron when it is at rest and not engaged in electrical signaling?

Resting membrane potential

In a which type of circuit will one input signal cause a prolonged and repetitive output because a neuron late in the circuit restimulates a neuron earlier in the circuit?

Reverberating

Which type of circuit is shown in this figure?

Reverberating

Which term is used to describe signal conduction along a myelinated axon?

Saltatory

Which neuroglial cell is found in the peripheral nervous system?

Satellite cell

Identify the type of cell indicated by the arrow labeled A.

Schwann cell

Which type of glial cell produces the myelin sheath in the PNS?

Schwann cell

Which neurotransmitters are classified as monoamines?

Serotonin Epinephrine

Which is true about a neuron with a large diameter, myelinated axon as compared to a neuron with a small diameter, unmyelinated axon?

Signal conduction will be faster

Excitatory postsynaptic potentials (EPSPs) are usually due to the entry of which type of ion?

Sodium

Why is sodium more concentrated in the ECF than in the ICF of most neurons?

Sodium is actively pumped out of the cell by transporter proteins.

Which are names for the cell body of a neuron?

Soma Neurosoma

The sensory and motor divisions of the peripheral nervous system are further split into which two subdivisions?

Somatic and visceral

______ summation results when EPSPs occurring at multiple synapses add up to threshold at the axon hillock.

Spatial

When EPSPs from several synapses add up to threshold at the axon hillock, this process is called what?

Spatial summation

This picture illustrates a phenomenon that occurs in the trigger zone when multiple postsynaptic potentials combine their effects on a cell to produce a response. What is it called?

Summation

Which division inhibits digestion?

Sympathetic

Which term refers to the microscopic physical gap between the presynaptic and postsynaptic neurons at a chemical synapse?

Synaptic cleft

Which term refers to summation that results from a single synapse firing rapidly in sequence?

Temporal

When a single synapse generates EPSPs so quickly that each is generated before the previous one fades, what is this process called?

Temporal summation

Which part of the neuron is indicated by the arrow labeled A?

Terminal arborization

A negative membrane potential indicates which of the following?

The inside of the membrane is negatively charged relative to the outside.

Which best describes an electrical current?

The movement of charged particles like ions

Which of the following statements are true about sodium?

The resting plasma membrane is much less permeable to Na+ than to K+. Na+ is about 12 times as concentrated in the ECF as in the ICF.

Some neurotransmitters can have either excitatory or inhibitory effects depending on which of the following?

The type of receptors on the postsynaptic cell

Which statements characterize neurotransmitters?

They are synthesized by presynaptic neurons. They are released in response to stimulation. They bind to receptors and alter the physiology of the postsynaptic cell.

Which statements are true about Schwann cells?

They form the neurilemma. They assist in the regeneration of damaged nerve fibers. They form the myelin sheath in the PNS.

Which are characteristics of neural pools?

They may be concerned with a particular body function. They consist of complex patterns of interneurons.

In order for local potentials to trigger an action potential, the membrane must depolarize up to a level called which of the following?

Threshold

What is the primary function of the myelin sheath?

To increase the speed of signal conduction in the axon

True or false: Action potentials occur only where there are voltage-gated ion channels.

True

True or false: Unmyelinated nerve fibers (axons) in the PNS are enveloped in Schwann cells.

True

Which type of neuron has one single process that branches like a T into a peripheral fiber and a central fiber?

Unipolar

Which lists the structural categories of neurons?

Unipolar, bipolar, anaxonic, and multipolar

This picture shows an excitatory postsynaptic potential (EPSP). When do EPSPs usually occur?

When sodium channels open

The refractory period in which no stimulus of any strength will trigger a new action potential is the ______ refractory period.

absolute

Another term for sensory division is ______ division.

afferent

The brain and spinal cord are components of the ______ nervous system, while the nerves and ganglia are components of the ______ nervous system.

central, peripheral

The nervous system must interpret quantitative and qualitative information about its environment, thus it converts information to a meaningful pattern of action potentials. This process is called neural ___.

coding

The processes that branch from the somas of most neurons are called ______.

dendrites

The type of circuit in which one input nerve fiber synapses with multiple postsynaptic neurons is a ___ circuit.

diverging

Motor, or ___, neurons carry signals away from the CNS and they lead to effectors (muscle and gland cells).

efferent

The glial cells that line cavities of the brain and spinal cord and secrete and circulate cerebrospinal fluid are ______.

ependymal cells

The plural form of ganglion is ______.

ganglia

The knotlike swelling in a nerve where neuron cell bodies are found is called a(n) ___.

ganglion

Neuroglial cells that act as macrophages within the CNS are ______.

microglia

The picture shows the most common structural type of neuron. It contains one axon and multiple dendrites, and it is classified as a(n) ______ neuron.

multipolar

The neurons indicated by a letter "A" are structurally classified as ______ neurons. The neurons indicated by a letter "B" are structurally classified as ______ neurons.

multipolar, bipolar

The ______ (the cell body of a neuron) gives rise to branch-like processes called ______, which are the primary sites for receiving signals from other neurons.

neurosoma, dendrites

In the CNS, myelin is produced by glial cells called ___.

oligodendrocytes

At a synapse, the neuron that responds to the neurotransmitter is the ______ neuron.

postsynaptic

In a chemical synapse, synaptic vesicles full of neurotransmitter are docked at release sites on the membrane of the presynaptic neuron, while neurotransmitter receptors are found on the membrane of the ___ neuron.

postsynaptic

At a synapse, the neuron that releases neurotransmitter is the ______ neuron.

presynaptic

What is the role of neural pools in the CNS?

process information

The refractory period in which it is possible to trigger a new action potential, but only with an unusually strong stimulus is the ______ refractory period.

relative

Propagation of an action potential down a myelinated axon in which the action potential appears to "jump" from node to node is called ___ conduction.

saltatory

The sensory division of the PNS is further subdivided into the ______ sensory division, which carries signals from receptors in the skin, muscles, bones, and joints, and the ______ sensory division, which carries signals from organs of the thoracic and abdominal cavities.

somatic, visceral

There are two ways in which EPSPs can add up to produce enough activity to make a postsynaptic cell fire. They are temporal and spatial ___.

summation

The autonomic nervous system is subdivided into the ______ division which tends to arouse the body for action and the ______ division which tends to have a calming effect.

sympathetic, parasympathetic

At its distal end, an axon has an extensive complex of fine branches called a(n) ______.

terminal arborization

Neurons with a single process extending from the soma, such as the neurons that carry sensory signals to the spinal cord, are classified structurally as ______ neurons.

unipolar

An axon lacking a myelin sheath is said to be ______.

unmyelinated