Chapter 12 Nervous Tissue

1. In the PNS; surround somas of neurons in ganglia, provide electrical insulation, and regulate the chemical environment of neurons 2. In the PNS; form neurilemma around all PNS fibers and myelin around most of them; aid in regeneration of damaged nerve fibers. 3. In the CNS; line cavities of the brain and spinal cord; secrete and circulate CSF 4. In the CNS; phagocytize microorganisms, foreign matter, and dead nervous tissue

1. Satellite cells 2. Schwann cells 3. Ependymal cells 4. Microglia

Acetylcholine

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

Diverging

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

unmyelinated

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

Potential energy

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

Chloride

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

presynaptic

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

postsynaptic

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

terminal arborization

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

Internodes

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

They bind neurons together and provide a supportive scaffold. They protect the neurons and help them function.

Choose the characteristics of neuroglia.

Long-term memory

Declarative and procedural memory are two types of what?

Depolarization

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

1. Both types of voltage-gated channels are closed. 2. Voltage-gated Na+ channels open 3. Voltage-gated Na+ channels inactivate

Each point in the action potential to the corresponding description of voltage-gated sodium and potassium channel activity. 1. Resting membrane potential 2. Depolarization begins 3. Repolarization begins

Sodium

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

sensory

Fiber tracts conducting impulses to the brain are called ascending or __________ tracts.

Opens chloride channels

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

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

How do neuromodulators alter synaptic transmission?

Up to a lifetime

How long can long-term memory last?

Reverberating

Immediate memory, which is the ability to hold something in mind for a few seconds, might be based on activity in which type of neural circuit?

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.

In the axon terminal

In a synapse, where are synaptic vesicles located?

gray

In cross section, the __________ matter of the spinal cord looks like a butterfly or the letter H.

Gap junctions

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

Gap junctions

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

oligodendrocytes

In the CNS, myelin is produced by glial cells called____.

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

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

Excitability, conductivity, secretion

List the fundamental physiological properties of neurons.

Interneurons Motor neurons Sensory neurons

List the three functional classes of neurons.

Binding of glutamate to NMDA receptors Entrance of calcium into the dendrite The release of nitric oxide which triggers more glutamate release

Long-term potentiation may be involved in long-term memory. The molecular changes that occur in long-term potentiation include which of the following?

Working memory

Looking up a new phone number and then dialing it from memory utilizes which type of memory?

1. Both types of voltage-gates channels are closed. 2. Voltage-gated Na+ channels open; voltage-gated K+ channels open more slowly. 3. Voltage-gated Na+ channels inactivate; voltage-gated K+ channels remain open longer.

Match each point in the action potential to the corresponding description of voltage-gated sodium and potassium channel activity. 1. Resting membrane potential 2. Depolarization begins 3. Repolarization begins

1. A mound located on one side of the soma from which the axon originates 2. Cytoplasm of the axon 3. Plasma membrane of the axon 4. Branch that originates from an axon

Match the following terms with their description. 1. Axon hillock 2. Axoplasm 3. Axolemma 4. Axon collateral

Posttetanic potentiation

Memories lasting for a few hours, such as recalling an incident earlier in the day, may be due to which of the following?

Calcium remains in the synaptic knob elevated and a later signal releases a large burst of neurotransmitter.

Memories lasting for a few hours, such as remembering what someone said to you earlier in the day may involve posttetanic potentiation. This occurs because of which of the following?

efferent

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

Axon collateral

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

Postsynaptic potentials

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

microglia

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

Bipolar

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?

unipolar

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.

Multipolar

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

"leaping" or "jumping"

Saltatory conduction means ______.

Acetylcholine Neuropeptides Amino acids Monoamines

Select the four categories of neurotransmitters based on chemical composition. Acetylcholine Neuropeptides Amino acids Monoamines Sterols Glycoproteins

Neurons

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

The type of receptors on the postsynaptic cell

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

1. Opening of calcium gates in synaptic knob as nerve signal arrives. 2. exocytosis of ACh; diffusion across synaptic cleft. 3. Binding of ACh to receptors on postsynaptic neuron. 4. Opening of sodium gates on postsynaptic membrane allowing influx of sodium. 5. Depolarization of postsynaptic plasma membrane

Starting with a signal reaching the distal end of the presynaptic axon, indicate the correct order of events that occur during transmission at a cholinergic excitatory synapse.

Neurotransmitter is removed from postsynaptic receptors.

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

plasticity

Synapses are not fixed for life. In response to experience, they can be modified to make transmission easier or harder. The ability of synapses to change is called synaptic ____.

Potentiation

Synapses in a certain pathway can be modified to allow signals to travel more easily across "trained" synapses. Which term refers to the process of making transmission easier?

Peripheral nervous system

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

Calcium

Tetanic stimulation at a synapse is due to accumulation of which of the following in the synaptic terminal?

neurosoma, dendrites

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.

central nervous system

The __________ consists of the brain and spinal cord.

Memory traces

The ability of synapses to change is called synaptic plasticity. Which term refers to the neuronal pathways formed during learning?

sympathetic, parasympathetic

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.

Central, peripheral

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

Converging circuit

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

ganglion

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

Lipids

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

Endoneurium

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

coding

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 ____.

1. information received by sensory receptors is transmitted to the CNS. 2. information is processed and an appropriate response is determined. 3. a command is issued to effectors such as muscles or glands.

The nervous system plays an important role in maintaining homeostasis. List, in order, the basic steps that describe how the nervous system carries out this task.

Amino acids

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

Neural circuit

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

multipolar

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.

ganglia

The plural form of ganglion is ______.

dendrites

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

relative

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.

Converging

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?

common fibular

The sciatic nerve divides into the tibial and __________ nerves.

Somatic and visceral

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

conus medullaris

The spinal cord extends from the foramen magnum of the skull to the first or second lumbar vertebra, where it terminates in the __________.

diverging

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

unipolar

The type of neuron shown here is ______.

summation

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

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?

Excitatory cholinergic synapse

This picture illustrates neural transmission at which type of synapse?

Neural coding

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?

When sodium channels open

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

Visceral motor

Together, the sympathetic and parasympathetic nervous systems make up the entirety of which division of the nervous system?

True

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

False

True or false: All neurotransmitters have an excitatory effect.

False

True or false: Damaged nerve fibers in the CNS regenerate very fast whereas damaged nerve fibers in the PNS never regenerate.

False

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

False

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

True

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

Muscle and gland cells

What are the effectors of motor neurons?

Central and peripheral nervous systems

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

To increase the speed of signal conduction in the axon

What is the primary function of the myelin sheath?

to process information

What is the role of neural pools in the CNS?

Bipolar

What type of neuron is shown in the image?

Tetanic

What type of stimulation is caused by rapid, repetitive signals arriving at a synaptic knob, causing progressively larger quantities of calcium to accumulate and leading to synaptic facilitation?

Temporal summation

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

Along myelinated nerve fibers. During saltatory conduction, a nerve impulse jumps from one node of Ranvier to another along myelinated fibers.

Where does saltatory conduction occur?

Neuromodulators

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

Decremental Graded

Which are characteristics of local potentials?

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

Which are characteristics of neural pools?

Neurosoma Soma

Which are names for the cell body of a neuron?

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

Which are properties of action potentials?

Diverging circuit Parallel after-discharge circuit Reverberating circuit Converging circuit

Which are the principal types of neural circuits?

Procedural Declarative

Which are types of long-term memory?

The movement of charged particles like ions

Which best describes an electrical current?

A form of potential energy that can produce current

Which best describes an electrical potential?

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

Which best describes signal conduction in unmyelinated axons?

Microglial cell

Which cell is indicated by the arrow labeled A?

ependymal cells

Which cell type if indicated by the arrow labeled A?

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 correctly describe axonal transport?

Diameter of axon Presence of myelin

Which factors influence the speed of nerve signal conduction?

Conductivity

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

Ependymal cells

Which glial cell produces and helps circulate cerebrospinal fluid?

Monoamines

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

Potassium

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

-70 mV

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

-55

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

Signal conduction will be faster

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

Unipolar, bipolar, anaxonic, and multipolar

Which lists the structural categories of neurons?

Long-term potentiation

Which may be the basis for learning and long-term memory at the neuronal level?

Satellite cell

Which neuroglial cell is found in the peripheral nervous system?

Epinephrine

Which neurotransmitter is a catecholamine?

GABA Glutamate

Which neurotransmitters are classified as amino acids?

Epinephrine Serotonin

Which neurotransmitters are classified as monoamines?

-70 mV

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

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

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

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

Which of the following statements are true about sodium?

Terminal arborization

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

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

Which statements are true about Schwann cells?

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.

Which statements are true about signal conduction along myelinated fibers?

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

Which statements are true regarding postsynaptic potentials?

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 characterize neurotransmitters?

Synaptic knobs

Which term applies to the small swellings at the distal end of the axon of a neuron that contain synaptic vesicles?

Neural integration

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

Saltatory

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

Cholinergic

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

Local potentials

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

Temporal

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

Current

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

Nodes of Ranvier

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

Synaptic cleft

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

Neurilemma

Which term refers to the outermost layer of myelin, containing the nucleus and cytoplasm of the Schwann cell?

Axonal transport

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

Refractory period

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?

Depolarization

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

Resting membrane potential

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?

Endocrine system Nervous system

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

Schwann cells

Which type of glial cell aids in regeneration of damaged peripheral nerve fibers by forming a regeneration tube to help reestablish the former connection?

Oligodendrocytes

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

Schwann cell

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

Short-term

Which type of memory allows you to remember things from up to a few hours ago?

Long-term

Which type of memory can store the most information?

Immediate

Which type of memory is important as you read (e.g. remembering the previous words in a sentence)?

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

Which would cause postsynaptic stimulation to end?

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

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

To allow easier signal transmission along pathway

Why would the synapses of a memory trace undergo synaptic potentiation?

dendrites

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

Glial

______ cells protect the neurons and help them function.

They protect the neurons and help them function. They bind neurons together and provide a supportive scaffold.

characteristics of neuroglia

1. local potential depolarizes membrane 2. threshold reached 3. depolarization spike 4. repolarization 5. hyperpolarization

events into the order in which they occur during a single action potential.