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Nervous System Overview
Nervous System
 2 divisions
 ________________________ nervous system (CNS) – ___________________ and spinal cord
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_____________________________ nervous system (PNS) – ____________________
 2 types of ___________________
 ______________________ – ________________ cells; structural and functional unit of the
nervous system
 __________________________ cells – provide physical _________________, insulation, and
________________________ for neurons
Nervous System Functions (3)
 ______________________________
 receptors gather info from _________________________ environment (light, sound) and
_______________________ environment (body temp, blood pH, O2 conc.)
 ________________________________
 collects sensory data and makes ________________________
 ________________________
 stimulates effectors to ___________________________
 detect _______________________  make ___________________________  stimulate
________________________________
Neuroglial Cells
 fill __________________, provide __________________________ frameworks, produce
____________________, carry on ___________________________________
 4 kinds in CNS
________________________________ – support neurons and __________________________
bacteria and cellular debris
 _____________________________________ – create _______________ sheath around axons
 _____________________________ – structural support, regulation of ____________________
and ions, form __________________ tissue in CNS
 ___________________________________ – epithelia-like membrane that covers brain parts
 PNS – Schwann cells form myelin sheath
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Neuron Structure
 vary in _______________________ and __________________________
 3 basic structural components
 __________________________ – conduct impulses to cell body
 ___________________ body
 _______________ – conducts impulse away from cell body
Cell Body & Dendrites
contains __________________________ cytoplasm, mitochondria, lysosomes, Golgi apparatus.
 _____________________ (and nucleolus) centrally located
 _____________________________ – short and highly branched
 mature neurons do not _________________________
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Axon
 axonal hillock – _____________________ of axon
 ______________________ – lipoprotein sheath around an axon that ________________________
and increases the _________________ of impulse conduction
 _________________________ cells – wrap around axon like a _________________________;
myelin underneath
 neurilemma – outer portion of __________________________ cells
 nodes of _____________________ – narrow ____________ btw Schwann cells
 myelinated vs. unmyelinated
Neuron Structure Classifications
 _________________________ – cell body + __________ nerve fibers (1 axon, 1 dendrite) – rare
 ______________________ – cell body + ___________ nerve fiber w/2 branches
 __________________________ – cell body + ___________ nerve fibers (1 axon, many dendrites)
–most common
Neuron Function Classification
 __________________________ (afferent) neurons – carry nerve impulses from body into brain or
spinal cord
 most are _________________________, some bipolar
 _________________________________ – link neurons to other neurons, direct incoming sensory
impulses to the appropriate places for processing and interpretation
 multipolar
 motor (_________________________) neurons – carry nerve impulses out of the brain or spinal
cord to effectors (muscles or organs that respond to the stimuli)
 multipolar
Synaptic Transmission: How do Neurons Talk?
Synapse
 a _____________________ btw 2 communicating _________________ or between a neuron and
organ (such as muscle) that will act based on the stimulus.
 info travels from _________________________  cell body  _____________  synapse
 crossing the ____________________ is called synaptic transmission
 ____________________ neuron is the one releasing the neurotransmitter.
 _____________________ neuron is the one on the other side of the synapse taking in the
neurotransmitter.
Synaptic Transmission
 ___________________________ neuron  ____________________________ neuron
 when a nerve impulse reaches the ______________________ knobs (branching ends of the axon)
_____________________________ ( chemical signals) are released to move the signal across the
synapse.
 neurotransmitters ___________________ across the synapse and may or may not initiate a nerve
impulse on the postsynaptic neuron – depending on whether there is enough to depolarize the
postsynaptic neuron and start an action potential
Neurotransmitters
 nervous system produces about __________
 4 types
 acetylcholine
 monoamines – epinephrine, dopamine, serotonin
 amino acids
 peptides
 located in synaptic ___________________ within the ___________________ knobs
Release of Neurotransmitter
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AP travels down axon to _____________________ knob
Synaptic knob becomes more permeable to ______________________
__________________ rushes into synaptic knob
Synaptic vesicles ________________ with synaptic knob membrane
Synaptic vesicles release their __________________________________ into the synapse
Neurotransmitters are picked up by ______________________ on the postsynaptic neuron
Extra neurotransmitters are decomposed by ___________________ or removed from synapse by
_____________________ cells or reabsorbed by __________________
Action Potentials: How Do Neurons Communicate?
Cell Membrane Potential
 potential – difference in charge btw the inside and outside of the cell membrane
 Membrane is _____________________ – unequal distribution of ___________________ and
_____________________ ions across the cell membrane. At resting state inside of axon is
negative while outside is positive.
 ions enter or leave the cell through _____________ or ____________________
 cell membrane is the cell’s _________________________
 Sodium/potassium pump (Na/K) pumps sodium (Na) out of the cell resulting in (+) outside and
(-) inside. Result of Na/K pump is polarization of the membrane in the resting potential state.
Resting Potential = ____________mV
 Na/K pump is on when the neuron is at rest.
 lots of Na+ ___________________ cell; less K+ ___________________ the cell
 in a resting cell, more _______________________ ions leave than _________________  outside
becomes more ___________________ while the inside becomes more ___________________
 Potential of neuron that is not yet stimulated is called the ___________________ potential
(-70mV)
Potential Changes
 Electrical ___________________(nerve impulse) of the cell membrane affects the membrane’s
resting potential
 When the threshold is reached (-60 mV) the axon becomes depolarized, changing the charges so
that the inside becomes _________ while the outside is now ______________. The stimulus
turned off the Na/K pump to allow the depolarization of the membrane.
 Depolarization moves the action potential down the axon as each successive charge reversal
causes the charge next to it to reverse.
Action Potentials
 rapid change in potential as the pulse passes down the axon  __________________ potential
 at threshold, ____________ channels open and Na+ diffuse __________________, depolarizing
the membrane. This happens in a forward moving line, moving the action potential forward.
 Just after the action potential passes, ____________ channels open and K+ diffuse
_______________________, _____________________________ the membrane
 many AP can occur before active transport, Na/K pump (requires energy), is needed to
reestablishes the ____________________ potential
 nerve impulse – wave of ____________________ potentials
Events of a Nerve Impulse
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____________________ potential = _________mV
______________________ stimulus; _____________________ reached = _________mV
Na+/K+ pump turned _______________ at point of stimulus
Na+ rushes ____________ cell  __________________________
As the action potential passes, K+ rushes __________ of cell  _________________________
The action potential is a bioelectric current that provides the electrical stimulus needed to
“_________” the adjacent membrane potential to reverse that charge, which then reverses the
next charge and continues until the action potential wave reaches the end of the axon.
 Wave of AP travels down the axon to the ends which are synaptic knobs. Synaptic transmission
moves the signal to the next neuron.
Impulse Conduction
 _____________________________ fibers conduct impulses over their entire surface (0.5 m/sec)
 travels entire ___________________
 _________________________ fiber conduct impulses only at exposed areas (nodes of
_________________); impulses “_____________” from node to node and increase rate of
conduction (120 m/sec)
 like skipping a rock on water
All-or-None Response
 if nerve fibers ________________, they respond _______________________
 like muscle fiber contraction
 increases in ____________________ (above threshold) increase the ___________________ of
impulses per second, not the ______________________ of impulse
Review Questions
 What does “polarized” mean?
 What is a potential?
Explain what is a resting potential in a neuron?
Explain what is an action potential in a neuron?
 What is the role of Na+ and K+ during resting potential?
What is the role of Na+ and K+ during an action potential?
 What causes the neuron axon membrane to be polarized?
What causes the neuron axon membrane to be depolarized?
What causes the neuron axon membrane to be repolarized?
 List the major events that occur during an action potential.
 How does impulse conduction differ in myelinated vs unmyelinated nerve fibers?
NS: The Rest
Reflexes
 a _____________, ______________________ response to stimuli. e.g. withdrawal reflex when
something painful is touched.
 help maintain _______________________ and are _______________________
 reflex arcs -- the path of the stimulus (nerve impulse) is ________________, sensory neuron,
interneuron, motor neuron, _________________. It does not go through the central nervous
system up to the brain.
Peripheral Nervous System
nerves that branch out from the __________ and connect it to other body parts
_________ pairs of cranial nerves
_________ pairs of spinal nerves
Informs the Central Nervous System of changing conditions inside and outside the body, and then
transmits the CNS response to the organ (muscles or glands) to make the needed adjustment.
 Includes (1) the nerves that control skeletal muscles – somatic division of the PNS and (2) the
Autonomic Nervous System.
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Autonomic Nervous System (ANS)
 part of the _________ that functions independently and continuously without
____________________ effort. Controls involuntary muscles (___________ and _________) and
gland organs.
 2 divisions: _______________________ and ___________________________
 sympathetic: prepares body for ______________-expending, stressful, or emergency situations
– flight or fight response to stimulus.
 parasympathetic: operates under _________________, restful situations; balances the effects
of sympathetic and restores the body to a __________________ state following a stressful
experience.
 Meninges
 protect the ________________ and ________________ cord
 3 layers –
 ___________ mater: outermost layer; connective tissue that contains many ________________
vessels and nerves
 _______________________ mater: middle layer; thin web-like mem that lacks blood vessels
 _________ mater: innermost layer; very thin with many blood vessels and nerves that
__________________ underlying cells of the brain and spinal cord
Spinal Cord
from _____________________ magnum to 1st or 2nd ___________________ vertebrae
___________ segments each with a pair of spinal nerves
made mostly of ___________________________
core of ______________ matter within _______________ matter
 looks like a butterfly
 a central _______________ runs down the middle and is filled with cerebrospinal fluid
 2 enlargements: _______________ and __________________ back
 cauda equina (________________ tail)
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Functions of the Spinal Cord
 conducting _________________ impulses to and from _______________
 center for spinal ___________________