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What does the acronym CNS stand
for?
Central Nervous System
TERM 2
What does the acronym ANS stand
for?
DEFINITION 2
Autonomic Nervous System
TERM 3
What does the acronym PNS stand
for?
DEFINITION 3
Peripheral Nervous System
TERM 4
Which of the systems (CNS, ANS or PNS) are
voluntary?
DEFINITION 4
The central nervous system (CNS) and peripheral nervous system
(PNS) are under voluntary control.*The book states that the
somatic nervous system (composed of somatic nerve fibers that
conduct impulses from the CNS to skeletal muscles) is known as
the voluntary nervous system, because the system allows
conscious control of skeletal muscles. The book states that the
somatic nervous system is a part of the motor (efferent) division of
the PNS.
TERM 5
What system (CNS, ANS or PNS) is
involuntary?
DEFINITION 5
The autonomic nervous system (ANS) is under involuntary
control.
Explain afferent neurons
The afferent (sensory) nerves move information towards the
spinal cord and brain; all afferent (sensory) nerves are
directed towards the spinal cord and brain.
TERM 7
Explain efferent neurons
DEFINITION 7
The efferent (motor) neurons move information towards
effector organs; efferent (motor) nerves are a way to effect
or work all of the different motor responses.
TERM 8
How do spinal nerves differ from cranial
nerves?
DEFINITION 8
The spinal nerves send information to and from the spinal
cord. The cranial nerves send information to and from the
brain (12 cranial nerves).
TERM 9
What are the two sub-divisions of the
autonomic nervous system (ANS)? Explain the
function of the two sub-divisions.
DEFINITION 9
The two sub-divisions of the autonomic nervous system
(ANS) are the sympathetic and parasympathetic divisions.
The sympathetic division stimulates, while the
parasympathetic division inhibits.*The roles of the two sub-
divisions can reverse for certain organs.
TERM 10
What role do glial cells provide?
DEFINITION 10
The glial cells function as support cells; supporting and
maintaining the health of a neuron through various activities
(confirming the neuron fires properly, helping to maintain a
consistent pH level and maintaining a proper amount of fluid
in the space between cells).
What is the function of satellite cells? How do
satellite cells differ from neurolemmocytes
(Schwann Cells)?
The satellite cells surround the neuronal cell body in ganglia;
ganglia are intersections for nerves (a traffic jam). The
function of a satellite cell is to regulate and stabilize the
environment around ganglion cell bodies. The satellite cells
only differ from neurolemmocytes (Schwann Cells) in terms
of location.
TERM 17
What are the two types of neuroglia present
in the autonomic nervous system (ANS)?
DEFINITION 17
The two types of neuroglia present in the autonomic nervous
system are satellite cells and neurolemmocytes (Schwann
Cells).
TERM 18
How many types of neuroglia are found in the
human body? How many types of neuroglia
are in the central nervous system (CNS) and
the autonomic nervous system (ANS)?
DEFINITION 18
The amounts of the various types of neuroglia present in the
human body are as follows:
6 types of neuroglia are present in the human body
4 types of neuroglia are found in the central nervous
system (CNS)
2 types of neuroglia are found in the autonomic nervous
system (ANS)
TERM 19
What are the four types of neuroglia present
in the central nervous system (CNS)?
DEFINITION 19
The four types of neuroglia present in the central nervous
system are:
Astrocytes
Microglia
Ependymal Cells
Oligodendrocytes (Few Processes)
TERM 20
What is the structural unit of the nervous
system?
DEFINITION 20
A Neuron
What does amitotic refer
to?
The term amitotic refers to the inability to divide; nerve cells
are amitotic (once a nerve cell dies, it is lost forever).
TERM 22
What is the longevity of a neuron?
DEFINITION 22
The longevity of a neuron is a lifetime, with the proper
nutrition.
TERM 23
Explain the cell body of a neuron
DEFINITION 23
The cell body of a neuron (also called the soma or perikaryon)
is the major bio-synthetic center of a neuron (the center of
metabolic activity in a neuron) (contains the usual organelles
needed to synthesize proteins); the cell body is typically 5-
140 micrometers long.
TERM 24
Are centrioles present in a
neuron?
DEFINITION 24
No, centrioles are not present in a neuron because centrioles
are necessary for division; nerve cells don't divide. The
centrioles are the only cell component absent in nerve cells;
all other organelles are present in neurons.
TERM 25
Explain the endoplasmic reticulum of a
neuron
DEFINITION 25
A neuron contains both rough and smooth endoplasmic
reticulum's; the rough endoplasmic reticulum of a neuron
contains Nissl Bodies (chromatophilic substances which are
the sites for protein synthesis). The reticulum's are a system
of tubes associated with the transportation of materials
within the cytoplasm.
What typical organelles are lacking in the
axon? Why is the axon lacking these specific
organelles?
The axon is lacking:
Nissl Bodies
Golgi Apparatus
The axon is lacking these specific organelles because the
axon lacks the ability for protein synthesis (the inability to
repair itself). The axon is dependent on the soma (cell body)
for repair.
TERM 32
Explain the Nodes of Ranvier, pertaining to a
myelinated neuron
DEFINITION 32
The Nodes of Ranvier are myelin sheath gaps that occur at
regular intervals along a myelinated axon (approximately 1
millimeter apart). The Nodes of Ranvier participate in the
exchange of ions necessary required to generate an action
potential. The neurolemma is exposed where there is no
myelination, located at the Nodes of Ranvier.
TERM 33
Explain the Golgi Apparatus of a neuron
(absent in the organelles of a axon)
DEFINITION 33
The Golgi Apparatus of a neuron is well developed and forms
an arc (or a complete circle) around the nucleus of a neuron.
The Golgi Apparatus plays a role in packaging peptides and
proteins into vesicles.
TERM 34
Explain the nucleus and nucleolus of a neuron
DEFINITION 34
The nucleus of a neuron contains the cell's history and all of the
basic information necessary to manufacture all of the proteins,
that are characteristic of the specific neuron; synthesizes RNA and
DNA for shipment to the cytoplasm.The nucleolus is an organelle
within the nucleus that is involved in ribosome synthesis and the
transfer of RNA to the cytosol.
TERM 35
Explain the cytosol of a neuron
DEFINITION 35
The cytosol of a neuron is watery, salty fluid with a
potassium-rich solution inside the cell containing enzymes
responsible for metabolism.
Explain the mitochondria of a neuron
The mitochondria of a neuron is responsible for the supply of
energy in the form of ATP (adenosine triphosphate); neurons
require an enormous amount of energy (the brain is one of
the most metabolically active tissues in the body). The
chemical energy stored in ATP is used to fuel most of the
biochemical reactions within the neuron
TERM 37
Explain the polyribosomes of a neuron
DEFINITION 37
The polyribosomes of a neuron are several free ribosomes
attached by a thread; the thread is a single strand of mRNA
(messenger RNA), which is a molecule involved in the
synthesis of proteins outside of the nucleus. The associated
polyribosomes work to make multiple copies of the same
protein.
TERM 38
Explain the neuronal membrane of a neuron
DEFINITION 38
The neuronal membrane of a neuron is made up of lipids and proteins (fats and
chains of amino acids); a bi-layer (or sandwich) of phospholipids arranged with
the polar (charged) regions facing outward and the non-polar (uncharged)
regions facing inward. The neuronal membrane serves as a barrier to enclose the
cytoplasm within the neuron and to exclude specific substances. The membrane
contains a mosaic of proteins responsible for:
Containing specific ions and small molecules within the cell and excluding
other ions and small molecules
Catalyzing enzymatic reactions
Accumulating nutrients and rejecting harmful substances
Establishing an electrical potential within the cell
Conduction of an impulse
Sensitivity to particular neurotransmitters and modulators
TERM 39
Explain the axon of a neuron
DEFINITION 39
The axon is the main conducting unit of a neuron; capable of conveying
electrical signals across a variety of distances (an axon can be either
short, long or absent=amacrine neurons) and affecting different targets
(major arm of the neuron extending from the body)*Axons are typically
very short, but can be long (ranging from a few centimeters to 3 or 4
feet). A shorter neuron has a smaller axon and axon hillock, while a
longer neuron has a larger axon and axon hillock.*Axons also typically
branch forming axon collaterals; terminal branches of axons form
telodendrions. Axons can be myelinated or unmyelinated.
TERM 40
Explain the axon hillock of a neuron
DEFINITION 40
The axon hillock of a neuron the point at which the axon is
joined to the cell; electrical firing known as an action
potential typically occurs (a nerve impulse is generated).*The
axon hillock is the site of origination for a nerve impulse
within a neuron.
What systems (CNS, PNS or ANS) contain
myelinated axons?
The central nervous system (CNS) and peripheral nervous
system (PNS) contain myelinated axons, because the need
for a faster stimulation and generated impulse is greater.
TERM 47
What are the three classes of neurons? How
many processes does each class contain?
Explain the three classes of neurons.
DEFINITION 47
The three classes of neurons are:
Multipolar Neurons: contains three or more processes; multipolar neurons are
the most numerous in the body (99%) and are mainly located in the central
nervous system (CNS)
Bipolar Neurons : contains two processes (an axon and a dendrite); typically
located in special sense organs (vision and olfactory)
Unipolar Neurons : contains a single, short process; unipolar neurons branch
into two peripheral branches (a proximal and a distal branch). The proximal
branch of a unipolar neuron conducts action potentials from the dendrite
(self-definition). The distal branch of a unipolar neuron is always associated
with sensory information and is found in the peripheral nervous system
(PNS).
TERM 48
Explain the difference between white matter
and grey matter
DEFINITION 48
The white matter of a neuron refers to dense collections of
myelinated fibers, typically located in regions of the brain
and spinal cord. The grey matter of a neuron contains mostly
unmyelinated fibers and neuronal cell bodies.
TERM 49
Explain a pseudomonopolar
neuron
DEFINITION 49
A pseudomonopolar neuron is a different type of unipolar
neuron that originates as a bipolar neuron, but the bipolar
section fuses and becomes a single/unipolar neuron.
TERM 50
Which class of neuron is the most numerous
in nature?
DEFINITION 50
Multipolar Neurons (99% of all neurons)
Which class of neuron is typically associated
with special senses?
Bipolar Neurons
TERM 52
Which type of neuron lie between a sensory
neuron and a motor neuron?
DEFINITION 52
Interneurons or Association Neurons
TERM 53
Where are interneurons or association
neurons located?
DEFINITION 53
The interneurons or association neurons lie between sensory
and motor neurons.
TERM 54
What does irritability of a neuron refer
to?
DEFINITION 54
The irritability of a neuron refers to the response to a
stimulus.
TERM 55
What is the definition of a potential
difference, in reference to a neuron?
DEFINITION 55
A potential difference in a neuron, refers to the difference in
charges (electrical potential) between two points (the
outside of a neuron is positive and the inside of a neuron is
negative).
What is the difference of a resting membrane
potential, in reference to a neuron?
The resting membrane potential of a neuron is the potential
difference of charges in a neuron (the neuron is positively charged
on the outside and negatively charged on the inside); the
membrane is said to be polarized and the resting potential only
exists across the membrane. The average resting membrane
potential of a neuron is -70mV. The two factors that generate the
resting membrane potential are the differences in ionic
composition of the intracellular and extracellular fluids; the
differences in the permeability of the plasma membrane to these
specific ions.
TERM 62
What is an action potential?
DEFINITION 62
An action potential is a change in membrane potential (a signal
type) that signals over long distances; a brief reversal of
membrane potential (depolarization follows the action potential;
followed by repolarization and typically a brief period of
hyperpolarization; lasting only a few milliseconds). An action
potential doesn't decay with distance like a graded potential. An
action potential is stronger than a graded potential and is the
primary way of communication for a neuron.
TERM 63
What is a graded potential?
DEFINITION 63
A graded potential is a short-lived, localized change in
membrane potential; weaker than an action potential and
only capable of signaling over short distances (local)
(decreases in magnitude with distance). A graded potential
can either be depolarization or hyperpolarization and are
triggered by a change in the neuron's environment.
TERM 64
What occurs if a neuron depolarizes? What
are the ions involved in depolarization?
DEFINITION 64
A neuron's depolarization is a reduction in membrane potential (a
decrease); the inside of the membrane becomes less negative,
than resting potential. A change in resting potential from -70mV to
-65mV is depolarization. Depolarization also includes events in
which the membrane potential reverses and moves above zero to
become positive. Depolarization increases the production of nerve
impulses. The ions involved in depolarization are sodium and
potassium.
TERM 65
Is the firing threshold the same for all neurons
of the body?
DEFINITION 65
No, the firing threshold is not the same for all neurons of the
body because all neurons (like muscles) have a different
point at which depolarization will occur; a sufficient stimulus
has to occur for a neuron's threshold to be met (the neuron
has to be moved from resting membrane potential).
What does repolarization of a neuron refer
to?
The repolarization of a neuron refers to a return to resting
membrane potential; a decrease in sodium permeability
occurs. The cause of repolarization is an abrupt decline of
sodium permeability and an increase in potassium
permeability. During repolarization, the internal negativity of
a neuron returns.
TERM 67
What is hyperpolarization of a neuron?
DEFINITION 67
The hyperpolarization of a neuron is an increase in membrane
potential; the inside of the membrane becoming more negative. A
change from -70mV to -75mV is hyperpolarization.
Hyperpolarization reduces the probability of nerve impulses.
Hyperpolarization of a nerve refers to the continuation of
potassium permeability outside of the neuron; caused by
excessive potassium efflux (leaving the cell) (the flowing of
positive ions outside of the neuron; causing the membrane
potential inside of the cell, to become more negative).
TERM 68
What does saltatory conduction refer to?
Which neuron uses saltatory conductions
(myelinated or unmyelinated)?
DEFINITION 68
A saltatory conduction is used by myelinated neurons and is
the jumping from each Node of Ranvier, to a subsequent
Node of Ranvier(each subsequent gap of the myelin sheath)
(a quicker traveling of the impulse)
TERM 69
Which method of conduction is faster,
saltatory or continuous conduction?
DEFINITION 69
Saltatory Conductions used by Myelinated Neurons
TERM 70
What does continuous conduction refer to?
Which neuron uses continuous conduction
(myelinated or unmyelinated)?
DEFINITION 70
A continuous conduction is used by unmyelinated neurons
and is the continuous conduction (continuous travel) of an
impulse, down the entire unmyelinated neuron.
What are the two different methods, in which
synaptic transmissions occur? Explain the two
varieties of synaptic transmissions.
The two different varieties of synaptic transmissions are:
Chemical Synapses: the most common type of synapse; allowing the release
and reception of chemical messengers known as neurotransmitters into the
synaptic cleft (a fluid-filled gap or space). A typical chemical synapse is
made up of an axon terminal (containing synaptic vesicles full of
neurotransmitters) and a neurotransmitter receptor region on the post-
synaptic neuron's membrane (typically located on the dendrite or soma).
Chemical synapses prevent a nerve impulse from being directly transmitted
from one neuron to another; instead depending on the release, diffusion and
receptor-binding of neurotransmitter molecules (unidirectional
communication).
Electrical Synapses: much less common than chemical synapses; consisting
of gap junctions and the connexons (the channel protein); connects the
cytoplasm of adjacent neurons, allowing ions and small molecules to flow
directly from one ion to the next (electrically coupled) (rapid transmissions of
either unidirectional or bidirectional movements) (synchronizing the activity
of all interconnected neurons). Electrical synapses are far more abundant in
embryonic nervous tissue; retina and hippocampus. TERM 77
What is a pre-synaptic neuron?
DEFINITION 77
A pre-synaptic neuron brings the impulse to the synapse
(pre-synaptic cleft); conducting impulses towards the
synapse.
TERM 78
What is a post-synaptic neuron?
DEFINITION 78
A post-synaptic neuron receives the impulse and may
undergo an action potential; transmitting the impulse away
from the synapse.*A post-synaptic neuron can be a pre-
synaptic neuron to a different neuron, with enough
stimulation.
TERM 79
What chemicals move across the synaptic
cleft (a fluid-filled space), to bind with
receptors on the post-synaptic neuron?
DEFINITION 79
Neurotransmitters
TERM 80
What happens to extra neurotransmitters in
the synaptic cleft?
DEFINITION 80
The enzyme cholinesterase (located within the synaptic cleft) will
degrade neurotransmitters once an action potential has been
established, to prevent constant stimulation. Once degradation
occurs, the re-uptake of neurotransmitters back into the pre-
synaptic neuron occurs as well; the neuron is then read for another
synaptic potential (the cycle then continues).
What is an excitatory post-synaptic potential
(EPSP)?
An excitatory post synaptic potential (EPSP) (a gas pedal) excites
the nerve up to the point of firing (an action potential occurring),
so an action potential can occur very quickly. The action potential
will then occur as soon as a small amount of sodium influxes
(enters the cell) and a small amount of potassium effluxes (leaves
the cell).*Both excitatory and inhibitory post-synaptic potentials
(EPSP's and IPSP's) are required for fine motor control of the body;
the ability to control nervous conductions (a brake and gas pedal
for a car offers fine control of the vehicle).
TERM 82
What is an inhibitory post-synaptic potential
(IPSP)?
DEFINITION 82
An inhibitory post-synaptic potential (IPSP) (a brake pedal) moves the neuron
away from threshold and will result in hyperpolarization (the nerve shutting
down); reducing a post-synaptic neuron's ability to generate an action potential.
An IPSP is based around the permeability of potassium and chloride ions;
potassium begins to efflux (leaving the cell) and chloride begins to influx (coming
into the cell). The two neurotransmitters that affect chloride channels to inhibit
neurons are GABA and Glycine.*Both excitatory and inhibitory post-synaptic
potentials (EPSP's and IPSP's) are required for fine motor control of the body; the
ability to control nervous conductions (a brake and gas pedal for a car offers fine
control of the vehicle).
TERM 83
Which post-synaptic potential (response) are
chloride ions associated with, excitatory or
inhibitory?
DEFINITION 83
Inhibitory Post-Synaptic Potential (IPSP)
TERM 84
Why would an excitatory post-synaptic
potential (EPSP) come into summation?
DEFINITION 84
The summation of an excitatory post-synaptic potential
(EPSP) would generate a pre-excitation of the neuron; the
function of a summation is to enhance depolarization
(facilitate depolarization). A single EPSP can't induce an
action potential in the post-synaptic neuron (nerve impulses
would never result without summation).
TERM 85
What are the two types of summation for an
excitatory post-synaptic potential (EPSP)?
Describe the two types of summation.
DEFINITION 85
The two types of summation for an excitatory post-synaptic potential are:
Temporal Summation: a summation of the EPSP when one or more pre-
synaptic neurons fires (starting the summation); creating another EPSP
before the first one dissipates (essentially keeping the nerve excited; directly
before threshold). The post-synaptic membrane depolarizes more than it
would from a single EPSP.
Spatial Summation: the summation of an EPSP when the post-synaptic
neuron is stimulated by a large amount of pre-synaptic neurons; huge
amounts of receptors bind neurotransmitters/simultaneously initiating
EPSP's, which summate and dramatically enhance depolarization.
*The efficiency of nerve conduction is tremendously enhanced with the
summation of EPSP's.
Explain acetylcholine (a neurotransmitter
pertaining to a neuron)
The locations (secretions) of acetylcholine are in the central nervous system
(CNS), autonomic ganglia and visceral effectors. The functional classes of
acetylcholine are excitatory with direct action in the central nervous system
(CNS); excitatory or inhibitory (depending on sub-type of receptor) with indirect
action (via second messengers) in the peripheral nervous system (PNS).
Acetylcholine is widespread throughout the CNS; occurring in the cerebral cortex,
hippocampus and brain stem. Acetylcholine is within all neuromuscular junctions
and some autonomic motor endings of the PNS. The effects of acetylcholine
include functioning as a neurotransmitter; a chemical released by nerve cells to
signal different nerve cells
TERM 92
Explain epinephrine (a neurotransmitter
pertaining to a neuron)
DEFINITION 92
The neurotransmitter epinephrine is also commonly known as
adrenaline; epinephrine is a hormone released by the adrenal
medulla and aids in the regulation of a sympathetic branch of the
ANS. Epinephrine typically increases blood pressure, heart rate
and cardiac output; increases the release of glucose from the liver
(increased feeling of muscular strength and aggressiveness).
TERM 93
Explain norepinephrine (a neurotransmitter
pertaining to a neuron)
DEFINITION 93
The neurotransmitter norepinephrine is secreted in the brain stem
and areas of the cerebral cortex of the CNS; the main
neurotransmitter of postganglionic neurons in the
parasympathetic nervous system of the PNS. Norepinephrine is
either excitatory or inhibitory (depending on receptor type) in the
CNS; expresses indirect action (through second messengers) in
the PNS. A neurotransmitter typically causing the effect of
happiness (feeling good).
TERM 94
Explain dopamine (a neurotransmitter
pertaining to a neuron)
DEFINITION 94
The neurotransmitter dopamine is secreted in the midbrain and
hypothalamus of the CNS; located occasionally in sympathetic
ganglia of the PNS. Dopamine is either excitatory or inhibitory
(depending on receptor type) in the CNS; expresses indirect action
(through second messengers) in the PNS. A neurotransmitter
typically causing the effect of happiness (feeling good).
TERM 95
Explain serotonin (a neurotransmitter
pertaining to a neuron)
DEFINITION 95
The neurotransmitter serotonin is secreted in the brain stem,
midbrain, hypothalamus, cerebellum, pineal gland and spinal
cord of the CNS. Serotonin is mainly inhibitory (indirect
action via second messengers with direct action at
receptors). Serotonin plays a role in sleep, appetite, nausea,
migraine headaches and regulating mood.
Explain GABA (a neurotransmitter pertaining
to a neuron)
GABA is secreted from the cerebral cortex, hypothalamus,
spinal cord and retina of the CNS. GABA is generally
inhibitory (direct and indirect actions via second
messengers). GABA is a principal inhibitory neurotransmitter
in the brain; important in pre-synaptic inhibition at
axoaxonal synapses.
TERM 97
Explain glycine (a neurotransmitter pertaining
to a neuron)
DEFINITION 97
The neurotransmitter glycine is secreted in the brain stem,
spinal cord and retina of the CNS. Glycine is typically
inhibitory with direct actions. Glycine is the principal
inhibitory neurotransmitter of the spinal cord.
TERM 98
Homeostatic Imbalance: What type of
transport do specific viruses and bacterial
toxins (that damage neuronal tissues) use to
reach the cell body?
DEFINITION 98
Specific viruses and bacterial toxins (that damage neuronal
tissues) use retrograde axonal transport to reach the cell
body (soma). The retrograde axonal transport system has
been demonstrated in polio, rabies, herpes simplex viruses
and for the tetanus toxin.
TERM 99
Homeostatic Imbalance: What is the cause of
impaired impulse propagation?
DEFINITION 99
The cause of impaired impulse propagation is a variety of chemical and
physical factors. Local anesthetics (used by medical professionals) act by
blocking voltage gated sodium channels; no sodium entry into the
cell=no generation of an action potential. Cold and continuous pressure
interrupts blood circulation, by hindering the delivery of oxygen and
nutrients to neuron processes and impairing the neurons ability to
conduct impulses (numbing of a finger with an ice cue or an appendage
becoming numb after sitting on the appendage for a long period of time).
Removing the cold object or pressure, leads to the transmission of
impulses again; leading to an unpleasant prickly feeling.
TERM 100
What is the definition of the nervous system?
DEFINITION 100
The nervous system is the master controlling and
communicating system of the body.
