chapter 12 nervous tissue

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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

Which would cause postsynaptic stimulation to end?

- cessation of signals in the presynaptic nerve fiber - diffusion of neurotransmitter from the synaptic cleft into extracellular fluid - reuptake of neurotransmitter into the presynaptic knob - enzymatic degradation of neurotransmitter in the synaptic cleft

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 - binding of glutamate to NMDA receptors - the release of nitric oxide which triggers more glutamate release

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 statements are true about signal conduction along myelinated fibers?

- 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 - action potentials occur only at the nodes of Ranvier

Which statements are true regarding postsynaptic potentials?

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

Which statements characterize neurotransmitters?

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

Which statements are true about Schwann cells?

- they form the myelin sheath in the PNS - they assist in the regeneration of damaged nerve fibers - they form the neurilemma

Choose the characteristics of neuroglia.

- they protect the neurons and help them function - they bind neurons together and provide a supportive scaffold

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

- unmyelinated fibers have voltage-gated channels along their entire length - a zone of depolarization excited voltage-gated channels immediately distal to the action potential

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

-70mV

A simple spinal reflex typically involves how many neurons?

3

How many pair of spinal nerves are there?

31

What is a reflex?

A stereotyped, involuntary response to a stimulus

What are the four components of a monosynaptic somatic reflex arc?

Afferent nerve fiber Efferent nerve fiber Skeletal muscle Receptor in skin, muscle or tendon

Match the following terms with their description. Axon hillock Axoplasm Axolemma Axon collateral

Axon Hillock: a mound located on one side of the soma from which the axon orginates Axoplasm: cytoplasm of the axon Axolemma: plasma membrane of the axon Axon collateral: branch that originates from an axon

Identify the regions of the spinal cord.

Cervical Lumbar Sacral Thoracic

Which neurotransmitters are classified as amino acids?

GABA, glutamate

Match the label to its corresponding structure in the figure.

Ilio-inguinal nerve

Which describes a muscle spindle?

It contains 7 or 8 modified muscle fibers and a few nerve fibers enclosed in a fibrous capsule.

Choose the name of the highlighted dermatome in the figure just above the posterior iliac crest.

L4 dermatome

What are intrafusal fibers?

Modified muscle fibers within a muscle spindle

Define extrafusal fibers.

Muscle fibers outside of a muscle spindle

Match each glial cell type with its location and function. satellite cells schwann cells ependymal cells microglia

Satellite Cells: in the PNS; surround somas of neurons in ganglia, provide electrical insulation, and regulate the chemical environment of neurons Schwann Cells: in the PNS; form neurilemma around all PNS fibers and myelin around most of them; aid in regeneration of damaged nerve fibers Ependymal Cells: in the CNS; line cavities of the brain and spinal cord; secrete and circulate CSF Microglia: in the CNS; phagocytize microorganisms, foreign matter, and dead nervous tissue

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

Schwann cell

What is the function of a muscle spindle?

To detect muscle length and body movements

A spinal nerve is formed by the union of

a dorsal and ventral root

Which best describes an electrical potential?

a form of potential energy that can produce current

What is produced when depolarization of a cell membrane reaches threshold?

a new action potential is produced

unipolar neurons

a single process

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

absolute

A recently depolarized area of a cell membrane cannot generate an action potential because of the

absolute refractory period

Synaptic vesicles of somatic neurons contain

acetylcholine

Select the four categories of neurotransmitters based on chemical composition.

acetylcholine neuropeptides monoamines amino acids

Reestablishment of the resting membrane potential occurs through

active transport of sodium and potassium ions

Sensory stimuli enter the spinal cord via

afferent axons

Which are properties of action potentials?

all or none nondecremental (signal maintains amplitude) self-propagating

Which fiber type is indicated by the arrow labeled A?

alpha motor neuron

The ______ median fissure is a longitudinal groove on the ventral surface of the spinal cord.

anterior

Which branch of the spinal nerve is indicated by the arrow?

anterior ramus

Which nerve tract is indicated in the figure?

anterolateral system

Which meninx is just below (deep to) the dura mater?

arachnoid mater

Which structure is highlighted?

axillary nerve

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 structure is highlighted?

axon

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

axon collateral

Which structure is highlighted?

axon hillock

Which structure is highlighted?

axon of motor neuron

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

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

bipolar

What type of neuron is shown in the image?

bipolar

Action potentials arriving at a presynaptic terminal cause

calcium ion channels to open

Acetylcholine is released into the synaptic cleft under the influence of

calcium ions

What is the name of the specified structure, which projects inferiorly from the spinal cord?

cauda equina

Which structure is highlighted?

cauda equina

Which sympathetic ganglion is demonstrated in the figure?

celiac ganglion

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

central and peripheral nervous systems

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

central, peripheral

Place the following regions of the spinal cord in order from superior to inferior.

cervical thoracic lumbar sacral coccygeal

Which structure is highlighted?

cervical enlargement

Which structure is highlighted?

cervical region

The spinal cord contains ascending and descending nerve fibers that send information between the CNS and the periphery. This illustrates which function of the spinal cord?

conduction

The end of the spinal cord indicated by the arrow labeled A in the figure is the medullary ________.

cone

Which structure is highlighted and indicated by the arrow?

conus medullaris

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

The __________ tract carries signals for precise, finely coordinated limb movements.

corticospinal

The ____________ tract carries signals for precise, finely coordinated limb movements.

corticospinal

The _____________ tract carries signals for precise, finely coordinated limb movements.

corticospinal

Which tract carries signals for precise, finely coordinated limb movements?

corticospinal

Which structure is illustrated?

craniosacral (parasympathetic) outflow

The tract indicated in the figure by the letter is the ________ fasciculus.

cuneate

Which structure is highlighted?

cytoplasm of Schwann cell

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

dendrites

Which structure is highlighted?

dendrites

Which structure is highlighted?

denticulate ligament

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

depolarization

Which structure is highlighted?

dorsal ramus

Name the afferent limb of each spinal nerve, as specified in the figure.

dorsal root

Which structure is highlighted?

dorsal root

Which structure is highlighted?

dorsal root ganglion

Identify the highlighted structure, which surrounds the spinal cord as well as the brain.

dura mater

Place the following layers of meninges and spaces in order from superficial to deep.

dura mater subdural space arachnoid mater subarachnoid space pia mater

Accurately describe the composition of a ventral root (highlighted in the figure).

efferent axons only

Which carries the nerve signal to the effector in a reflex arc?

efferent nerve fiber

The nerve signal for the reflex response is carried to the effector by a(n) _____________ nerve fiber.

efferent/motor

External to the neurilemma of a nerve fiber is the layer of loose connective tissue that surrounds a nerve fiber called a(n) ___________.

endoneurium

What is the loose connective tissue surrounding an individual nerve fiber called?

endoneurium

Which cell type is indicated by the arrow labeled A?

ependymal

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

ependymal cells

Which glial cell produces and helps circulate cerebrospinal fluid?

ependymal cells

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

ependymal cells microglia astrocytes oligodendrocytes

Which structure is highlighted?

epidural space

The connective tissue layer indicated by the arrow is the ______.

epineurium

What is the dense irregular connective tissue layer enclosing an entire nerve called?

epineurium

Which connective tissue layer is indicated by the arrow?

epineurium

List the fundamental physiological properties of neurons.

excitability, conductivity, secretion

This picture illustrates neural transmission at which type of synapse?

excitatory cholinergic synapse

Activation gates in the cell membrane for voltage-gated sodium ion channels open into the

extracellular fluid

At resting membrane potential, voltage-gated potassium ion channels are open.

false

The inside of the cell membrane becomes negative at the time of an action potential.

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

Within a nerve, nerve fibers are gathered into bundles called what?

fascicles

Which structure is highlighted?

femoral nerve

Which structure is highlighted?

filium terminale

Identify the specified structure.

filum terminale

In a sensory pathway, the ___________ order neuron detects the stimulus and transmits the signal to the spinal cord or brainstem.

first

Which order neurons of the spinocerebellar tract originate at muscles and tendons?

first

Which nerve fiber is indicated by the arrow labeled A?

gamma motor neuron

Which structure is highlighted?

ganglia of sympathetic trunk

The structure indicated by the arrow is called the posterior root

ganglion

______ cells protect the neurons and help them function.

glial

__________ cells protect the neurons and help them function.

glial

The tract indicated in the figure by the letter A is the __________ fasciculus.

gracile

Which nerve tract is indicated in the figure?

gracile fasciculus

Which are characteristics of local potentials?

grades, decremental

Which structure is highlighted?

gray matter

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

_______________ muscle fibers are modified muscle fibers within a muscle spindle.

intrafusal

Name the fiber type that has sarcomeres at the ends of the cell, but lack sarcomeres at the middle.

intrafusal fibers

Provide the accurate description of the cervical enlargement, which is depicted in the figure.

it contains the neurons for upper limb innervation

Which nerve tract is indicated in the picture?

lateral corticospinal tract

Acetylcholine in the synaptic cleft binds to

ligand-gated sodium channels

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

lipids

The cell membrane immediately adjacent to an action potential depolarizes because of

local currents

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

local potentials

Which are functions of the spinal cord?

locomotion reflexes conduction

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

long-term potentiation

Which structure is highlighted?

lumbar enlargement

Which structure is highlighted?

lumbar region

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

memory traces

Depolarization is initiated by a stimulus that makes the membrane potential

more positive

Depolarization of a cell membrane occurs because

more sodium ions diffuse into the cell than potassium ions diffuse out of it

The anterior root of a spinal nerve contain axons of which neurons?

motor

Which structure is highlighted?

motor end plate

The ventral horn of the spinal cord contains cells bodies of

motor neurons

Which structure is highlighted?

multipolar neuron

Which is a type of stretch receptor embedded in skeletal muscle?

muscle spindle

Which structure is highlighted?

myelin sheath

Which structure is highlighted?

myelinated axon

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

nervous system; endocrine system

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

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

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 structure is highlighted?

nissl bodies

anaxonic neurons

no axon; multiple dendrites

Which structure is highlighted?

node of ranvier

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

nodes of ranvier

Which structure is highlighted?

nucleolus of neuron

Which structure is highlighted?

nucleus of Schwann cell

Which structure is highlighted?

nucleus of neuron

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

oligodendrocyte

In the CNS, myelin is produced by glial cells called

oligodendrocytes

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

oligodendrocytes

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

oligodendrocytes

multipolar neurons

one axon; multiple dendrites

bipolar neurons

one axon; one dendrite

The absolute refractory period assures that action potential propagation is

only in one direction

The connective tissue layer indicated by the arrow is the ______.

perineurium

The connective tissue layer indicated by the arrow is the __________.

perineurium

Within a nerve, each fascicle is wrapped in which layer?

perineurium

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

peripheral nervous system

Which nerve provides all motor innervation to the diaphragm?

phrenic nerve

Which layer of the meninges is the most delicate and is composed of one or two layers of squamous to cuboidal cells and delicate collagenous and elastic fibers?

pia mater

Which meninx is closely associated with the contours of the spinal cord?

pia mater

The ______ roots are the spinal nerve roots that carry sensory nerve signals.

posterior

The branch of the spinal nerve that is indicated by the arrow is the _________ ramus.

posterior

The cuneate fasciculus is located in the ______ column of the spinal cord.

posterior

Which ramus of a spinal nerve innervates the local muscles, joints, and skin of the back?

posterior

Which spinal nerve roots carry sensory nerve signals?

posterior

Which structure is indicated by the arrow?

posterior root ganglion

Which nerve tract is indicated by the black arrow in the figure?

posterior spinocerebellar tract

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

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 factors influence the speed of nerve signal conduction?

presence of myelin; diameter of axon

Synaptic vesicles are located in the

presynaptic terminal

What type of signal does the spinocerebellar tract carry?

proprioception

Which muscles are the effectors in a patellar reflex?

quadriceps

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

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

Which of these structures is closest to the spinal cord?

rootlets

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

rough endoplasmic reticulum, mitochondria, nucleus

Which structure is highlighted?

sacral region

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

saltatory

Identify the highlighted nerve, which is located on the medial lower limb.

saphenous nerve

Which structure is highlighted?

saphenous nerve

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

schwann cells

Which structure is highlighted?

sciatic nerve

Which structure is highlighted?

sciatic nerve and branches

The release of a neurotransmitter is an example of which physiological property exhibited by a neuron?

secretion

Afferent neurons are ______ neurons.

sensory

The somas of which neurons are found within the posterior root ganglion?

sensory

A dorsal root ganglion contains cell bodies of

sensory neurons

List the three functional classes of neurons.

sensory neurons, interneurons, motor neurons

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

Which structure is highlighted?

skeletal muscle fiber

Dorsal rami of spinal nerves innervate

skin and muscles of the back

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

sodium

Which structure is highlighted?

soma of neuron

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

Interneurons are located in the

spinal cord

Which structure is highlighted?

spinal cord

Which structure is highlighted?

spinal nerve

Name the yellow highlighted structures that pass through the intervertebral foramina.

spinal nerves

In the spinal cord, where is the white matter in relation to the gray matter?

superficial

Which structure is highlighted?

sympathetic trunk

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

Which structure is highlighted?

synapse

Which structure is highlighted?

synaptic cleft

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

synaptic cleft

Which structure is highlighted?

synaptic vesicles in the presynaptic terminal

Which tract is indicated in the figure?

tectospinal

Which reflex occurs in response to excessive tension on a tendon?

tendon

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

terminal arborization

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

terminal arborization

Which best describes an electrical current?

the movement of charged particles like ions

In a sensory pathway, which neurons run from the thalamus to the sensory cerebral cortex?

third-order

Which structure is highlighted?

thoracic nerves

Which structure is highlighted?

thoracic region

Identify the specific sympathetic structures in the figure.

thoracic splanchnic nerves

Which structure is illustrated?

thoracolumbar (sympathetic) outflow

Sensory receptors are found

throughout the body

What is the role of neural pools in the CNS?

to process information

Simple spinal reflexes occur independent of the brain.

true

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 structure is highlighted?

unmyelinated axons

Which structure is highlighted?

ventral ramus

Which structure is highlighted in yellow and marked by the leader line?

ventral root

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

when sodium channels open

Which structure is highlighted?

white matter


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