Chapter 12

Nervous Tissue

Receptors are parts of the nervous system that allow it to

Receptors are parts of the nervous system that allow it to

Collect information

The nervous system controls the activity of muscles and glands. Muscles and glands can generate changes and are therefore called

Effectors

Nerves and ganglia are structures found in the

Peripheral nervous system

Which is not a general function of the nervous system

Transporting materials throughout the body

The spinal cord is part of the central nervous system

True

The afferent division of the nervous system is also known as the ____ division

Efferent

Which is not a function of the motor division of the nervous system?

Transmits impulses from the viscera

The portion of the nervous system that conducts impulses from the skin, joints, skeletal muscles, and special senses is the ___________ division.

Somatic sensory

The portion of the nervous system that has voluntary control over skeletal muscles is the _____________ division.

Somatic motor

A neuron conducting an impulse from the CNS to the detrusor muscle of the urinary bladder would be classified as a(n) __________ neuron.

Automatic motor

A neuron conducting an impulse from the stomach wall to the CNS would be classified as a(n) __________ neuron.

Visceral sensory

The motor nervous system is also known as the __________ nervous system.

Efferent

Which is not characteristic of neurons?

High mitotic rate

Conductive activity in a neuron generally causes it to secrete

A specific neurotransmitter that either excites or inhibits its target.

Which statement is consistent with the current understanding of neural tissue?

Most neurons formed in fetal development last a lifetime, but some brain regions in adults can generate new neurons.

Which part of the neuron contains the nucleus?

Soma

Where are synaptic knobs located?

At the tips of telodendria

The cytoplasm within a cell body of a neuron is called the

Perikaryon

What structures extend into the cytoplasm within a cell body of a neuron is called the

Neurofibrils

Electrical signals are conducted toward the cell body of a neuron by its __________

Dendrites

Anterograde transport is the movement of materials from synaptic knobs to the cell body.

False

Fast axonal transport is

Active (requires ATP) and can occur in either the anterograde or retrograde direction.

Vesicles and glycoproteins required at the synapse are moved down a nerve fiber by _______ axonal transport.

Fast

Based on structure, the most common type of neuron is the _______ neuron.

Multipolar

Based on function, the vast majority of neurons are

Interneurons

The neurons that are responsible for integrating information by retrieving, processing, storing, and "deciding" how the body responds to stimuli are

Interneurons

Which functional class of neurons lies entirely within the central nervous system?

Interneurons

A bipolar neurons has

One axon and one dendrite extending from the cell body

Typically, a multipolar neuron has many dendrites and one axon extending from the cell body.

True

A nerve cell that has dendrites but no axons is categorized as a(n) ___________ neuron.

Anaxonic

A mixed nerve is one that contains both

sensory and motor neurons

Spinal nerves extend from the spinal cord, whereas ________ nerves extend from the brain.

Cranial

In a mixed nerve

Some axons transmit sensory information and others transmit motor information.

Most commonly, a synapse is made between a

Presynaptic neuron's axon and a postsynaptic neuron's dendrite.

When transmission occurs at a synapse, neurotransmitter is released by

The presynaptic neuron's synaptic knob into the synaptic cleft.

Electrical synapses involve coupling of neurons by

Gap junctions

Which statement accurately compares the transmission speed of the different types of synapses?

Transmission at chemical synapses involves a brief synaptic delay, but electrical synapses are faster

Chemical synapses are more common than electrical synapses.

True

Glial cells differ from neurons in that they

Are smaller and capable of mitosis.

The nervous system contains more neurons than glial cells.

False

Glial cells help maintain the structure of synapses and they can modify neural transmission.

True

What is the most abundant glial cell in the CNS?

Astrocyte

The glial cell that helps to circulate cerebrospinal fluid is the

Ependymal cell

The glial cell that myelinates and insulates axons within the CNS is the

Oligodendrocyte

The glial cell that helps to form the blood-brain barrier is the

Astrocyte

The glial cell that myelinates and insulates axons in the peripheral nervous system is the

neurolemmocyte

The glial cell that defends the body against pathogens is the

Microglial cell

The glial cell that protects neuron cell bodies located within ganglia is the

Satellite cell

The glial cell with the responsibility of occupying the space left by dead or dying neurons is the

Astrocyte

The glial cell that provides structural support and organization to the CNS is the

Astrocyte

The glial cell with perivascular feet that wrap around capillaries in the CNS is the

Astrocyte

What do all glial cells have in common?

They assist neurons in their respective functions.

The periphery of a myelinating neurolemmocyte that contains its cytoplasm and nucleus is called the _________.

Neurilemma

The glossy-white appearance of most axons is due to

The high lipid content of the myelin sheath

Which is true regarding the action of a neurolemmocyte?

Each neurolemmocyte can wrap only a 1 mm portion of a single axon.

Which statement is true regarding the action of an oligodendrocyte?

Each oligodendrocyte can form a myelin sheath around many axons simultaneously.

The function of myelin is to

Produce faster nerve impulse propagation.

Continuous conduction of a nerve impulse occurs only along

Unmyelinated axons

Along an axon, the gaps between neurolemmocytes are called neurofibril ________.

Nodes

In the CNS all axons are myelinated, but in the PNS some are myelinated and some are unmyelinated.

False

With damage to nerve fibers, larger distances between the site of damage and the target structure innervated result in _________ chances of successful regeneration

Decreased

Which division of the nervous system shows a greater capacity for regeneration?

PNS

Following damage to axons nearby, oligodendrocytes

Secrete growth-inhibitory molecules.

Wallerian degeneration involves the breakdown of

The segments of axon and myelin sheath between the site of damage and the peripheral effector

Although severing a peripheral axon leads to some degeneration, the neurilemma remains largely intact.

True

A nerve

Is a cablelike bundle of parallel axons.

Which choice correctly orders the connective tissue wrappings of a nerve, beginning at the outermost layer?

Epineurium, perineurium, endoneurium

The endoneurium is composed of

Areolar connective tissue

The epineurium is composed of

Dense irregular connective tissue

The connective tissue wrapping that surrounds bundles (fascicles) of axons is the

Perineurium

The type of transport protein that moves a substance down its concentration gradient is a

Channel

Chemically gated ion channels are mainly found in the ________ segment of a neuron.

Receptive

A neuron's membrane contains more potassium leak channels than sodium leak channels.

True

The axon hillock makes up the ________ segment of a neuron.

Initial

The type of voltage-gated channel that possesses an inactivation gate that temporarily closes after the channel is active is the

Voltage-gated sodium channel

Potassium has a higher concentration

Inside the cell versus outside the cell, whereas sodium has a higher concentration outside versus inside the cell

Negatively charged protein molecules are more prevalent within a neuron's cytosol than in the interstitial fluid.

True

The electrochemical gradient refers to

The combination of electrical and chemical gradients between two areas

According to Ohm's law, current is

Directly related to voltage and inversely related to resistance

The separation of oppositely charged ionic particles across a resting neuron's membrane results in a potential that is measured as a

Voltage

Typically, the resting membrane potential of a neuron is

-70 mV

To measure the resting potential of a neuron, a physiologist would place

One microelecrode inside the neuron and another in the interstitial fluid

The most crucial factor determining the resting potential of a neuron is the diffusion of

Potassium out of the cell through leak channels

If there were no sodium leak channels, the resting membrane potential of a neuron would be

More negative

Maintenance of appropriate ion concentrations (especially after nerve impulses that involved ion diffusion) is primarily the job of

Sodium-potassium pumps

A depolarization is when the inside of a neuron becomes _______________ the resting membrane potential

Less negative than

Hyperpolarization of a neuron results from

Either the entry of an anion or the exit of a cation

Graded potenials generally occur only on the axon of a neuron

False

A graded potential is one that

Varies in size depending on the magnitude of the stimulus (larger voltage change for stronger stimulus)

An action potential involves a temporary reversal of polarity across the plasma membrane (that is, the inside of the axon becomes relatively positive compared to the interstitial fluid).

True

Action potentials are generated by the opening of ________ gated channels and they occur on the ________

Voltage-, axon

A postsynaptic potential is a graded potential.

True

When a neurotransmitter opens a chemically gated ion channel that allows sodium to enter the postsynaptic cell, the result is an

EPSP

As it moves from the tip of a dendrite to the axon hillock, a postsynaptic potential will maintain a constant amplitude.

False

When a neurotransmitter causes the opening of chemically gated potassium channels on the postsynaptic cell, the postsynaptic potential that results is an

IPSP, which is a hyperpolarization.

Some inhibitory neurotransmitters exert their effect by causing the opening of chloride channels, which results in the postsynaptic membrane becoming more negative.

True

The size of an EPSP is independent of the amount of excitatory neurotransmitter that is released by the presynaptic cell.

False

A graph of an EPSP would plot time against a voltage trace that would resemble

A hill where the high point approaches the threshold value.

In neurophysiology, the term "summation" refers to the addition of

Postsynaptic potentials at the initial segment

When multiple presynaptic neurons release neurotransmitter at various locations onto the postsynaptic neuron at the same time, this results in

Spatial summation