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What are the three organizations of the
nervous system?
Central Nervous System (CNS)Peripheral Nervous System
(PNS)Autonomic Nervous System (ANS)
TERM 2
What are the two division of the central
nervous system (CNS)?
DEFINITION 2
BrainSpinal Cord
TERM 3
What is the function of the central nervous
system (CNS)?
DEFINITION 3
The functions of the CNS are:
Interpreting Sensory Input (Afferent Input)
Directing the Motor Response (Efferent Output)
*The afferent and efferent input leads to homeostasis.
TERM 4
Describe the peripheral nervous system (PNS)
and the function of the PNS
DEFINITION 4
The peripheral nervous system (PNS) is the part of the
nervous system located outside of the CNS; consisting mainly
of nerves (any nerves located outside of the spinal cord and
brain are referred to as the PNS). The function of the PNS is
to act as communication lines (how human beings sense the
world).
TERM 5
What are the two divisions (nerves) of the
peripheral nervous system (PNS)? Describe
the function of each division
DEFINITION 5
The two divisions of nerves in the PNS are:
Spinal Nerves: send information to and from the spinal
cord
Cranial Nerves: send information to and from the brain
How many cranial nerves are located within
the peripheral nervous system?
TERM 7
Describe the motor (efferent) division of the
peripheral nervous system (PNS)
DEFINITION 7
The motor (efferent) division (carrying away) of the PNS
contains nerves that are sent to effector organs (activating
muscles to contract or glands to secrete); a way to effect or
work all of the different motor responses (effect or bring
about a motor response).
TERM 8
Describe the somatic nervous system of the
peripheral nervous system (PNS)
DEFINITION 8
The somatic nervous system is composed of somatic motor nerve
fibers that conduct impulses from the CNS to skeletal muscles
(often referred to as the voluntary nervous system; conscious
control of muscles). The motor (efferent) division of the PNS is also
considered the somatic nervous system. The somatic nervous
system is made up of motor nerves, that are always attached to
muscle and innervate muscles that are voluntary.
TERM 9
Describe the autonomic nervous system
(ANS)
DEFINITION 9
The autonomic nervous system (ANS) consists of visceral
motor nerve fibers that regulate the activity of smooth
muscles, cardiac muscles and glands (innervate organs). The
ANS is an involuntary system (no control).
TERM 10
What are the two sub-divisions of the
autonomic nervous system (ANS)? What are
the functions of each sub-division?
DEFINITION 10
The two sub-divisions of the autonomic nervous system are:
Sympathetic: stimulates
Parasympathetic: inhibits
*The sub-divisions can reverse roles for specific organs.
Describe an ependymal cell. What are the two
functions of an ependymal cell?
An ependymal cell is a squamous, columnar cell will cilia (hairs)
that line the brain and spinal cord cavities. The two functions of an
ependymal cell are:
Barrier: ependymal cells act as a barrier between cerebral
spinal fluid (CSF) and the tissues of the central nervous system
(CNS); ependymal cell are one of the constructs of the blood-
brain barrier (nothing enters the spinal cord or brain)
Circulation: ependymal cells help control the circulation of
cerebral spinal fluid (CSF) with cilia (the CSF acts as
cushioning)
TERM 17
Describe an oligodendrocyte. What is the
function of an oligodendrocyte?
DEFINITION 17
An oligodendrocyte is round, with very few processes and is
located between two neurons. The function of an
oligodendrocyte is to wrap around a neuron of the CNS,
essentially forming the myelin sheath. The myelin sheath is
an insulated covering for the neuron (akin to an electrical
wiring covering).
TERM 18
What are the two types of neuroglia found
within the peripheral nervous system (PNS)?
How do the two types differ from one
another?
DEFINITION 18
Satellite CellsSchwann Cells*The two types of neuroglia
found within the PNS only differ in terms of location.
TERM 19
Describe the satellite cells of the peripheral
nervous system (PNS)
DEFINITION 19
The satellite cells surround the neuronal cell bodies located in the
peripheral nervous system (PNS); clusters of neuronal cell bodies
in the PNS are referred to as ganglia. The satellite cells of the PNS
have many of the same functions as the astrocytes from the CNS.
The satellite cells regulate and stabilize the environment around
ganglion cell bodies.*The satellite cells and Schwann Cells of the
PNS only differ in terms of location.
TERM 20
Describe the Schwann Cells of the peripheral
nervous system (PNS)
DEFINITION 20
The Schwann Cells of the PNS surround all nerve fibers located in
the PNS and form the myelin sheath for thicker nerve fibers.
Functionally, Schwann Cells are similar to Oligodendrocytes
(Oligodendrocytes form the covering for thicker nerve fibers of the
CNS). The Schwann Cells are vital to regeneration of damaged
peripheral nerve fibers (a Schwann Cell assists in the repair of
peripheral nerves).
What is an important distinct characteristic of
the peripheral nervous system (PNS), that is
absent in the central nervous system (CNS)?
An important characteristic of the PNS, that is absent in the
CNS is the ability the PNS contains to repair itself (a nerve
located within the CNS can't repair itself); destroying a nerve
in the brain or spinal cord (CNS) will render the nerve
inoperable and unrepairable.
TERM 22
Describe neurons (nerve cells)
DEFINITION 22
A neuron contains a cell body, a nucleus contained within the cell body, dendrites
that originate from the cell body and a main axon (runs away from the cell body).
The direction of a stimulus runs from a cell body, originating at the axon hillock
and initiating further travel (many points of contact to bring
information=network).Nerve cells live an entire lifetime with the proper nutrition
and are amitotic (inability to divide; once a nerve cell dies, the neuron is lost
forever).The olfactory and hippocampus (a very primitive par of the brain
participating in the storage of memories) are the only two neurons that contain
stem cells (preserving of the neurons; production of new neurons due to stem
cells, if damage has occurred)A neuron is typically very large and the structure
varies.A neuron has an exceptionally high metabolic rate and requires
continuous/abundant supplies of oxygen/glucose.
TERM 23
What are the only two neurons that contain
stem cells (ability to produce new neurons, if
damage occurs)
DEFINITION 23
Olfactory NeuronsHippocampal Neurons
TERM 24
Describe the cell body (soma) or perikaryon of
a neuron.
DEFINITION 24
The cell body of a neuron is the bio-synthetic center of a
neuron; consisting of a spherical nucleus surrounded by
cytoplasm. The cell body ranges in diameter from 5-
micrometers long. The cell body contains all of the usual
organelles (except centrioles) needed to synthesize proteins.
TERM 25
What organelle is absent in a neuron? Why is
the organelle absent from the neuron?
DEFINITION 25
CentriolesA centriole is absent from a neuron because the
organelle is necessary for division; nerve cells don't divide. A
centriole is the only organelle absent in neurons.
Describe dendrites. What is the function of a
dendrite?
A dendrite is a short arm that forms off of the cell body;
dendrites contain the same organelles found within the cell
body. The function of dendrites is to receive input, to covey
impulses to the body of the neuron (bringing information into
the cell body).*Dendrites are very short and are always
unmyelinated.
TERM 32
Do dendrites receive information via graded
potentials or action potentials?
DEFINITION 32
A dendrite receives information via a graded potential (dendrites
don't require an action potential, due to size); the information only
travels a short distance from the peripheral to the soma (graded
potentials are for local change in membrane potentials).A nearby
neuron will send information to a dendrite, the dendrite then
carries the information a short distance to the cell body.*An action
potential is much stronger than a graded potential.
TERM 33
Where does an axon originate
from?
DEFINITION 33
Cell Body (Soma)The axon is the major arm (part) of the
neuron, extending from the cell body.An axon is typically
very short, but can vary in length (a few centimeters to 3 or 4
feet). A shorter neuron contains a smaller axon hillock, while
a longer neuron contains a larger axon hillock.*Axons can be
myelinated or unmyelinated.
TERM 34
Where is a nerve impulse generated in a
neuron (the site of the originating nerve
impulse)?
DEFINITION 34
Axon Hillock
TERM 35
What is an axon collateral?
DEFINITION 35
The branching of an axon along the length at right angles
forms axon collaterals.
What is a terminus?
A terminus is located at the end of an axon; termini (more than
one terminus) can branch into numerous termini (as many as
10,000) (an axon branches profusely at the terminus or end,
referred to as terminal branches). The various termini can connect
to another neuron, a muscle or a nerve; at the end of every
terminus is a synaptic cleft, with a pre- and post-synaptic cleft.
TERM 37
What is an axon terminal?
DEFINITION 37
An axon terminal are knoblike distal endings of terminal branches (located at the
end of any branch) (also known as synaptic knobs). The axon terminal helps form
the myoneural junction. Many neurotransmitters are located within the axon
terminals (an action potential reaching the axon terminals, results in the release
of neurotransmitters into the synaptic cleft).The function of an axon terminal is
to perform as the secretory component of the axon (secreting
neurotransmitters), for the purpose of the conduction of a nerve impulse.The
released neurotransmitters will then innervate or activate whatever is located at
the end of the terminal bud (a gland, a muscle, an organ or a different nerve).The
axon terminal contains synaptic vesicles; the vesicles merge and undergo
exocytosis in response to calcium; the axon terminal then ejects the
neurotransmitters into the synaptic cleft.The neurotransmitters of the axon
terminal cross the synaptic cleft and bind to receptors on the post-synaptic cleft
(a fluid-filled space typically 35-50 nanometers wide; very small)
TERM 38
What functions as the secretory component of
the axon (secreting neurotransmitters and
conducting a nerve impulse) (the ending site
of a nerve impulse)?
DEFINITION 38
Axon Terminals
TERM 39
What two organelles do axons lack?
DEFINITION 39
Nissl BodiesGolgi Apparatus*The organelles of the axon are
the same as the dendrite, with two exceptions.*The reason
for lacking the two organelles is the lack of protein synthesis
(no repair).*The axon is dependent on the soma for repair;
repairing of the damage depends on the proximity of the
damage to the soma.
TERM 40
What are axons responsible for (in terms of
movement)?
DEFINITION 40
Axons are responsible for the movement of an impulse.
What are the two branches of a unipolar
neuron? Describe the two branches.
The two branches of a unipolar neuron are:
Proximal: conduct action potentials from the dendrite
Distal: typically associated with sensory information;
located within the PNS
TERM 47
What is an important characteristic of an
action potential?
DEFINITION 47
An action potential is self-propagating (the stimulus and
action potential are continuous, until the information is
carried where it needs to go; the process happens quickly);
once a stimulus is created, all of the nerves will self-
propagate the impulse until the particular impulse reaches
an effect
TERM 48
What is sufficient stimulus, in regards to
threshold? What is sub-threshold?
DEFINITION 48
A sufficient stimulus has to occur for threshold (threshold has to be
surpassed for an action potential to occur) to be met (the point at which
depolarization will occur; when threshold is achieved, an action potential
will occur); the neuron has to be moved from resting membrane potential
(the resting membrane potential for a cell is -70mV). A sufficient stimulus
will move the neuron from resting membrane potential.A sufficient
stimulus depends on sodium influx (sodium entering the cell), sodium
influx causes depolarization.A sub-threshold is insufficient sodium influx
(no depolarization=the nerve is not stimulated).
TERM 49
What are absolute and relative refractory
periods?
DEFINITION 49
An absolute refractory period refers to when a patch of neuron membrane is
generating an action potential and voltage gated sodium channels are open; the
neuron can't respond to another stimulus, no matter how strong the stimulus is or
how often the stimulus occurs. A relative refractory period follows the absolute
refractory period (repolarization is occurring). The axon's threshold for action
potential generation is substantially elevated; so a stimulus that would normally
generate an action potential is no longer sufficient. An exceptionally strong
stimulus will be required to generate another action potential; stronger stimuli
trigger more frequent action potential's by intruding into the relative refractory
period.
TERM 50
Neurons are (in terms of coupling)...
DEFINITION 50
Electrically Coupled*The firing of one nerve causes a large amount
of different nerves to fire, which all terminate in different areas (a
single, unifying thought is impossible due to electrical coupling of
neurons)*The electrical coupling of neurons is very important in
the CNS (more cells are electrically coupled in the CNS, than in
any other area of the body=hippocampus; the production of
cascading emotions).*The electrical coupling of neurons is
important for stereotyped movement; movements need to be fluid
and rhythmic in nature.
When does the electrical coupling of neurons
begin to occur in the human body?
Embryonic Development
TERM 52
What are the eight events that occur at a
chemical synapse?
DEFINITION 52
A depolarization occurs at the axon terminal and immediately...
A calcium channel opens and a calcium influx (coming in to the cell) occurs
(calcium enters the neuron)...
The synaptic vesicles move to fuse with the axonal membrane then...
The exocytosis of neurotransmitters occur and neurotransmitters float into the
synaptic cleft (a fluid-filled space)
The diffusion/migration of receptors (via neurotransmitters) to the post-
synaptic membrane occurs...
The binding of neurotransmitters to receptors causes channels to open,
resulting in excitation or inhibition (depending on the neurotransmitter; possibly
causing depolarization or hyperpolarization)...
The enzymes in the synaptic cleft then degrade the neurotransmitters because
a constant stimulus from the neurotransmitters is unwanted (the enzyme that
accomplishes degradation of the neurotransmitters in the synaptic cleft, is
cholinesterase)...
As soon as cholinesterase is released into the synaptic cleft, the re-uptake of
neurotransmitters back into the pre-synaptic neuron occurs; the neuron is then
ready for another synaptic potential (the cycle continues and happens quickly) TERM 53
What is the difference between temporal and
spatial summation of an excitatory post-
synaptic potential (EPSP)?
DEFINITION 53
A temporal summation of an EPSP is when one or more pre-
synaptic neurons fires (starting the summation); creating another
EPSP before the first one dissipates (keeping the nerve excited,
directly before threshold)*The efficiency of nerve conduction is
tremendously enhanced through excitatory post-synaptic
potentials (EPSP's)A spatial summation is when the post-synaptic
neuron is stimulated by a large amount of pre-synaptic neurons, in
order to enhance depolarization (facilitate depolarization)
TERM 54
How do excitatory neurotransmitters
function? How do inhibitory neurotransmitters
function?
DEFINITION 54
An excitatory neurotransmitter functions through positive
feedback mechanisms, for control.An inhibitory
neurotransmitter functions through negative feedback
mechanisms, for control.
TERM 55
Which two systems (CNS, PNS or ANS) are
neurotransmitters typically deployed within?
DEFINITION 55
Central Nervous System (CNS)Peripheral Nervous System
(PNS)
