chapter 12 nervous tissue
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
