Unit 2 Outline
Unit 2
Structure and Functions of
Cells of the Nervous
System
1
Cells
Communication
Within a Neuron
Communication
Between Neurons
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2
Divisions of the Nervous
System
of the Nervous System
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The Nervous System
__________Nervous System (CNS)
• Comprised of the brain and spinal cord
• Encased within the _________________________
__________Nervous System (PNS)
• Comprised of nerve tissue located ________of the brain
and spinal cord.
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Cells of the Nervous
System
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Cells of the Nervous
System
__________neuron
• A neuron located within the central nervous system
__________neuron
• A neuron that ________________in the external or
internal environment and sends information about
these changes to the central nervous system.
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that controls the
______________________________________________
__________________________________________.
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Cells of the Nervous
System
Neuron
Basic Structure
__________or “cell body”
• The cell body of a neuron, which contains the
nucleus.
___________________
• A neuron located entirely within the central nervous
system.
__________
• A branched treelike structure attached to the soma
of a neuron; receives information from the terminal
button of other neurons.
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Neuron
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Basic Structure
__________
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Cells of the Nervous
System
• The long thin cylindrical structure that conveys
information from the soma of a neuron to its terminal
button.
__________neurons
• A neuron with one axon and many dendrites attached to
its soma.
__________
• A junction between the terminal button of an axon
and the membrane of another neuron.
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Cells of the Nervous
System
__________neurons
• A neuron with one axon and one dendrite attached
to its soma.
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Cells of the Nervous
System
__________neurons
• A neuron with one axon attached to its soma; the axon
divides, one branch receiving sensory information and the
other sending the information into the central nervous
system.
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Neuron
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Basic Structure
__________ button
• The bud at the _____ of a branch of an axon; forms
synapses with another neuron; sends information
to that neuron.
______________
• A chemical that is released by a terminal button;
has an excitatory or inhibitory effect on another
neuron.
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Cells of the Nervous System
Cells of the Nervous System
Internal structure
Internal structure
__________
Mitochondria
• A structure consisting principally of lipid molecules
• An organelle that is responsible for extracting
that defines the outer boundaries of a cell and also
constitutes many of the cell organelles.
__________ from nutrients.
Adenosine triphosphate (ATP)
• A molecule of prime importance to cellular energy
__________
• The viscous, semi-liquid substance contained in the
metabolism; its breakdown liberates energy.
interior of a cell.
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3
Mitochondria
Originated as independent free-living organisms
that “__________” larger cells.
Produce____ – an energy source.
Very efficient in energy extraction, and this
benefited the host cells.
Inherited only from our ________ (Eve’s DNA).
Multiply independent within the cells in which they
live.
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Internal structure
Deoxyribonucleic acid (_____)
Internal structure
__________
• A structure in the central region of a cell, containing
the nucleolus and chromosomes.
• A strand of DNA, with associated proteins, found in
the nucleus; carries __________ information.
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Cells of the Nervous System
Internal structure
Cytoskeleton
• Formed of microtubules and other protein fibers,
• A long complex macromolecule consisting of two
linked to each other and forming a cohesive mass
that gives a cell its ______.
interconnected helical strands; along with associated
proteins, strands of DNA constitute the chromosomes.
__________
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Cells of the Nervous System
Cells of the Nervous System
_____
__________
• A molecule that controls a chemical reaction,
• The functional unit of the chromosome, which directs
combining two substances or breaking a substance
into two parts.
synthesis of one or more proteins.
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Cells of the Nervous System
Internal structure
Microtubule
• A long strand of bundles of protein filaments
arranged around a hollow core; part of the
cytoskeleton and involved in transporting
substances from place to place within the cell.
____________________________
• An active process by which substances are propelled
along microtubules that run the length of the axon.
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Cells of the Nervous System
Supporting Cells
_______ cells
• Also known as neuroglia or “neural glue”.
• The supporting cells of the central nervous system.
__________ or “star cell”
• A glial cell that provides support to neurons of the
central nervous system, provides ________ and
other substances, and regulates the chemical
composition of the __________ fluid.
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Asrocytes
•Receive nutrients from
capillaries.
Release nutrients to neurons as
needed.
________ around the CNS like
amoebas.
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Cells of the Nervous
System
__________
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Cells of the Nervous
System
• The smallest glial cells; act as phagocytes and
__________sheath
• A sheath that surrounds axons and insulates them,
protect the brain from invading microorganisms.
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preventing messages from spreading between
adjacent axons.
__________
• The process by which cells engulf and digest
other cells or debris caused by cellular degeneration.
_____________________
• A naked portion of a myelinated axon, between
adjacent oligodendrocytes or Schwann cells.
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Forming Myelin
___________________
• A type of glial cell in the central nervous system
that forms myelin sheaths.
_______________ cell
• A cell in the peripheral nervous system that is
wrapped around a myelinated axon, providing
one segment of its myelin sheath.
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The Blood-Brain Barrier (BBB)
Features of the blood-brain barrier
• Paul Ehrlich injected blue dye into the bloodstream of
animals and found dye everywhere except in the brain
and spinal cord.
• __________________________that can enter the CNS
from the blood.
• Helps the CNS maintain the proper composition of
fluids inside and outside the neurons.
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The Blood-Brain Barrier (BBB)
Features of the blood-brain barrier
Blood-brain barrier
• A _________________ barrier between the blood and
the brain produced by cells in the walls of the brain’s
capillaries.
___________________
• A region of the medulla where the blood-brain barrier
is weak; poisons can be detected there and can initiate
vomiting. (Prevent food poisoning)
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Neural Communication
The Withdrawal Reflex
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Communication Within a Neuron
Measuring electrical potentials of axons
Electrode
• A conductive medium that can be used to apply
electrical stimulation and record electrical potentials.
Microelectrode
• A very fine electrode, generally used to record activity
of individual neurons.
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Some Marine Invertebrates Have
Very Large Axons
_______ axons are 100’s of times
larger than mammalian axons, were
easy to keep in a lab, and were easy to
study.
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Communication Within a Neuron
Measuring electrical potentials of axons
____________ potential
• The electrical charge across a cell membrane; the
difference in electrical potential inside and outside the
cell.
Oscilloscope
• A laboratory instrument that is capable of displaying a
graph of voltage as a function of time on the face of a
cathode ray tube.
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Communication Within a Neuron
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Communication Within a Neuron
Measuring electrical potentials of axons
Measuring electrical potentials of axons
Axons have two basic electrical potentials
Resting membrane potential
• __________ membrane potential
• __________ potential
• The resting membrane potential of a neuron when
it is not being altered by excitatory or inhibitory
postsynaptic potentials; approximately _______ mV in
the giant squid axon.
The membrane potential can change
• Depolarization
• Hyperpolarization
• Threshold of excitation
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Communication Within a Neuron
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Communication Within a Neuron
Measuring electrical potentials of axons
Measuring electrical potentials of axons
_____________
__________ potential
• Reduction (toward zero) of the membrane potential
• The brief electrical impulse that provides the basis for
conduction of information along an axon.
of a cell from its normal resting potential.
_____________
• An increase in the membrane potential of a cell,
relative to the normal resting potential.
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__________ of excitation
• The value of the membrane potential that must be
reached to produce an action potential.
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Communication Within a Neuron
The force of diffusion
Diffusion
• Movement of molecules from a region of _____
concentration to regions of _____ concentration.
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Communication Within a Neuron
The force of electrostatic pressure
Electrolyte
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• An aqueous solution of a material that ionizes
Communication Within a Neuron
The force of electrostatic pressure
Electrostatic pressure
• The attractive force between atomic particles charged
a soluble acid, base, or salt.
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with __________ signs or the repulsive force between
two atomic particles charged with the ______ sign.
Ion
• A charged molecule.
• Cations are ________ charged, and anions are
________ charged.
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Communication Within a Neuron
Ions in the extracellular and intracellular fluid
__________ fluid
• The fluid contained within cells.
__________ fluid
• Body fluids located outside cells.
Sodium-potassium transporter
• A protein found in the membrane of all cells that
extrudes sodium ions.
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Communication Within a Neuron
The
__________ potential
____
channel
• A specialized protein molecule that permits
specific ions to enter or leave the cell.
Voltage-dependent
ion channel
• An ion channel that opens or closes according
to the value of the __________ potential.
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Communication Within a Neuron
Conduction of the action potential
_______________ law
• The principle that once an action potential is
triggered in an axon, it is propagated without
decrement to the end of the fiber.
______ law
• The principle that variations in the intensity of a
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stimulus or other information being transmitted in
an axon are represented by variations in the rate
at which that axon fires. 60
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Communication Within a Neuron
Conduction of the action potential
__________ conduction
• Conduction of action potentials by myelinated axons.
•
The action potential appears to jump from one node of
Ranvier to the next.
The fastest action potentials are conducted 120 m/s (266
mph).
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Communication Between Neurons
Communication Between Neurons
The concept of chemical transmission
The concept of chemical transmission
Postsynaptic potentials
Binding site
• Alterations in the membrane potential of a
• The location on a receptor protein to which a ligand
postsynaptic neuron, produced by the liberation
of a ________________ at the synapse.
binds.
Ligand
• A chemical that binds with the binding site of a receptor.
Neurotransmitters and “drugs” are ligands.
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Communication Between Neurons
Structure of synapses
Dendritic _______
• A small bud on the surface of a dendrite, with which a
terminal button of another neuron forms a synapse.
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Communication Between Neurons
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Communication Between Neurons
Structure of synapses
Structure of synapses
__________________ membrane
Synaptic _________
• The membrane of a terminal button that lies
• The space between the presynaptic membrane
adjacent to the postsynaptic membrane and
through which the neurotransmitter is released.
___________________ membrane
• The membrane located on the dendrite of the
neuron that receives the information.
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and the postsynaptic membrane that is about
20 nm wide.
Synaptic ____________
• A small, hollow, beadlike structure found in the
terminal buttons; contains molecules of a
neurotransmitter.
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Communication Between Neurons
Communication Between Neurons
Structure of synapses
Activation of receptors
Release zone:
Postsynaptic receptor
• A receptor molecule in the postsynaptic membrane
• A region of the interior of the presynaptic membrane
of a synapse that contains a binding site for a
_________________.
of a synapse to which synaptic vesicles attach and
release their neurotransmitter into the synaptic cleft.
Neurotransmitter-dependent ion channel
• An ion channel that opens when a molecule of a
neurotransmitter binds with a postsynaptic receptor.
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Communication Between Neurons
Activation of receptors
Ionotropic receptor ( __________ Method)
• A receptor that contains a binding site for a
•
neurotransmitter and an ion channel that opens
when a molecule of the neurotransmitter attaches
to the binding site.
_____ latency & _____ duration event.
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Communication Between Neurons
Activation of receptors
Metabotropic receptor ( __________ method)
• A receptor that contains a binding site for a
•
•
neurotransmitter; activates an enzyme that begins a
series of events, opening an ion channel elsewhere in
the membrane of the cell when a molecule of the
neurotransmitter attaches to the binding site.
The neurotransmitter activates a __ protein, and this
stimulates the production of a chemical called a
“_______ messenger”.
_____ latency & _______ duration event.
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Communication Between Neurons
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Communication Between Neurons
Activation of receptors
Postsynaptic potentials
G protein
__________ postsynaptic potential (EPSP)
• A protein coupled to a metabotropic receptor; conveys
• An excitatory depolarization of the postsynaptic
messages to other molecules when a ligand binds with
and activates the receptor.
Second messenger
membrane of a synapse caused by the liberation of a
neurotransmitter by the terminal button.
• A chemical produced when a G protein activates an
enzyme; carries a signal that results in the opening of the
ion channel or causes other events to occur in the cell.
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__________ postsynaptic potential (IPSP)
• An inhibitory hyperpolarization of the postsynaptic
membrane of a synapse caused by the liberation of a
neurotransmitter by the terminal button.
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Communication Between Neurons
Termination of postsynaptic potentials
__________
• The reentry of a neurotransmitter just liberated by a
terminal button back through its membrane, thus
terminating the postsynaptic potential.
Enzymatic __________
• The destruction of a neurotransmitter by an enzyme
after its release, for example, the destruction of
acetylcholine by acetylcholinesterase.
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Communication Between Neurons
Communication Between Neurons
Termination of postsynaptic potentials
Effects of postsynaptic potentials:
Acetylcholine (____)
Neural __________
• A neurotransmitter found in the brain, spinal cord, and
• The process by which inhibitory and excitatory
parts of the peripheral nervous system; responsible for
muscular contraction.
postsynaptic potentials summate and control the
rate of firing of a neuron.
Acetylcholinesterase (AChE)
• The enzyme that destroys acetylcholine soon after it is
liberated by the terminal buttons, thus terminating the
postsynaptic potential
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Communication Between Neurons
__________
• A receptor molecule located on a neuron that
responds to the neurotransmitter that they themselves
release.
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Communication Between Neurons
Autoreceptors have a variety of functions:
• Regulate internal processes of the cell
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Communication Between Neurons
Axoaxonic synapses
Presynaptic __________
• The action of a presynaptic terminal button in an
• Regulate __________ of the neurotransmitter
axoaxonic synapse; reduces the amount of
neurotransmitter released by the postsynaptic terminal
button.
• Regulate the __________ of a neurotransmitter
• Generally serve to ______ the activity of a transmitter
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Presynaptic __________
• The action of a presynaptic terminal button in an
axoaxonic synapse; increases the amount of
neurotransmitter released by the postsynaptic terminal
button.
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Communication Between Neurons
Nonsynaptic chemical communication
____________
• A naturally secreted substance that acts like a
neurotransmitter except that it is nor restricted to the
synaptic cleft but diffuses through the extracellular fluid.
Peptide
• A chain of amino acids joined together by peptide bonds.
Most neuromodulators, and some hormones, consist of
peptide molecules.
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Communication Between Neurons
Nonsynaptic chemical communication
__________
• A chemical substance that is released by an endocrine
gland and that has effects on target cells in other organs.
__________ gland
• A gland that liberates its secretions into the extracellular
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The Endocrine System:
Hormonal Regulation
1. Pituitary gland “master gland”
controls other bodily
glands and is under
control of the
hypothalamus
fluid around capillaries and hence into the bloodstream.
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Hierarchy of Control over the Endocrine System
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The Endocrine System
2. Adrenal glands - release adrenaline and cortisol
during physical and psychological stress
– activated by the sympathetic nervous system
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The Endocrine System
3. Sexual reproductive glands
Testes in males produce testosterone
Ovaries in females produce estrogen
However, both sexes release some sex hormone
associated with the opposite sex
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Endocrine System
Hormones are like a neurotransmitter that are
distributed to receptor sites via the blood
supply.
Hormones orchestrate and coordinate
responses in a diverse number of structures.
Long delay between release of the hormone
and the response, and a slow return to
baseline.
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