Chapter 12: Nervous Tissue

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

-55

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

-70 mV

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.

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.

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

1. Local potential depolarizes membrane 2. Threshold is reached 3. Depolarization spike 4. Repolarization 5. Hyperpolarization

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.

1. Opening of calcium 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 post-synaptic membrane allowing influx of sodium 5. Depolarization of postsynaptic plasma membrane

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

Axon hillock

A mound located on one side of the soma from which the axon originates

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 Amino acids Neuropeptides Monoamines

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?

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

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

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

Axon terminals

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

Axonal transport

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

Axon collateral

Branch that originates from an axon

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

Calcium

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

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

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

Current

Axoplasm

Cytoplasm of the axon

Which are types of long-term memory?

Declarative Procedural

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 are the principal types of neural circuits?

Diverging circuit Converging circuit Reverberating circuit Parallel after-discharge circuit

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

Endocrine system Nervous system

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

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

Which would cause postsynaptic stimulation to end?

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 glial cell produces and helps circulate cerebrospinal fluid?

Ependymal cells

List the fundamental physiological properties of neurons.

Excitability, conductivity, secretion

All neurotransmitters have an excitatory effect.

FALSE

Damaged nerve fibers in the CNS regenerate very fast whereas damaged nerve fibers in the PNS never regenerate.

FALSE

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

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

Which are characteristics of local potentials?

Graded Decremental

Short-term memory allows you to remember things for up to how long?

Hours

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

Immediate

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 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.

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 type of memory can store the most information?

Long-term

Declarative and procedural memory are two types of what?

Long-term memory

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

Long-term potentiation

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

Memory traces

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

Neural circuit

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

Neural integration

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

Which are names for the cell body of a neuron?

Neurosoma Soma

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.

Anaxonic neurons

No axon; multiple dendrites

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) Self-propagating All or none

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

Oligodendrocyte

Multipolar neurons

One axon; multiple dendrites

Bipolar neurons

One axon; one dendrite

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

Peripheral nervous system

Axolemma

Plasma membrane of the axon

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

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?

Potentiation

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

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?

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

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

Schwann cell

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

Schwann cells

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

Short-term

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

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

Somatic and visceral

Which division inhibits digestion?

Sympathetic

Action potentials occur only where there are voltage-gated ion channels.

TRUE

Unmyelinated nerve fibers (axons) in the PNS are enveloped in Schwann cells.

TRUE

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?

Tetanic

Which best describes an electrical current?

The movement of charged particles like ions

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

The type of receptors on the postsynaptic cell

Two organ systems are dedicated to internal coordination, communication between the other systems, and maintaining the overall homeostasis of the body.

They are the endocrine system, which communicates by means of hormones, and the nervous system which sends quick electrical and chemical messages from cell to cell.

Which statements are true about Schwann cells?

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

Choose the characteristics of neuroglia.

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

Which statements characterize neurotransmitters?

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

Which statements are true regarding postsynaptic potentials?

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

Which are characteristics of neural pools?

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

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

To allow easier signal transmission along pathway

What is the primary function of the myelin sheath?

To increase the speed of signal conduction in the axon

What is the role of neural pools in the CNS?

To process information

How long can long-term memory last?

Up to a lifetime

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

Visceral motor

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

Working memory

Dendrites

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

A neuron with one axon and one dendrite is structurally classified as a

bipolar neuron

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

diverging circuit

Unipolar neurons

have a short single process leaving the cell body

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

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

plasticity

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

postsynaptic neuron

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

presynaptic

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

Afferent neurons are ______ neurons.

sensory

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

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

unmyelinated