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Chapter 7: Nervous System
N/A
112
Anatomy
12th Grade
12/13/2010

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Term
Central Nervous System
Definition
brain/spinal cord
Term
Peripheral nervous system
Definition
nerves/ganglia
Term
Nerves
Definition
bundles of axons and their sheaths which extend from the CNS
Term
How many pairs of cranial nerves are in the body? 
Definition
12
Term
How many pairs of spinal nerves are there?
Definition
31
Term
Ganglia
Definition
collections of neuron cell bodies which are outside the CNS
Term
Afferent neurons
Definition
transmit action potentials from sensory organs to CNS -- sensory division
Term
Efferent neurons
Definition
transmit action potentials from CNS to effector organs -- motor division
Term
Somatic motor nervous system
Definition
transports action potentials from CNS to skeletal muscles -- voluntary
Term
autonomic nervous system
Definition
transmits action potentials from CNS to smooth/cardiac muscles -- involuntary
Term
sympathetic division
Definition
generally prepares the body for physical activity (increases rate and strength of heartbeat/raises blood pressure/stimulates liver to release more glucose)
Term
parasympathetic division
Definition
regulates resting and nutrition related functions such as digestion, defecation, and urination
Term
What two categories can the efferent division be divided into?
Definition
Somatic motor nervous system and autonomic nervous system
Term
What two categories can the autonomic nervous system be divided into? 
Definition
Sympathetic nervous system and parasympathetic nervous system
Term
What three basic units make up a neuron?
Definition
Cell body, axon, and dendrites
Term
What is another word for the cell body of a neuron?
Definition
Soma
Term
What does the axon do?
Definition
sends action potentials away from cell body
Term
Where does the action potential begin?
Definition
Axon hillock
Term
What do the dendrites do?
Definition
Bring messages into cell body
Term
Myelin sheath
Definition
Fatty wrapping the speeds up transmission of action potential down axon
Term
What produces the myelin sheaths?
Definition
Schwann cells in PNS, oligodendrocytes in CNS
Term
Node of Ranvier
Definition
gap in myelin sheath
Term
Collateral axons
Definition
branch off axon, ending in presynaptic terminals
Term
Unipolar neurons
Definition
One process, pseudodendrites, afferent neurons
Term
How many neurons do we lose every day?
Definition
7,000
Term
Bipolar neurons
Definition
Two processes, specialized afferent neurons
Term
Multipolar neurons
Definition
Several dendrites, one axon, motor or association neurons
Term
Association neurons
Definition
Conducts action potentials from one neuron to another in the CNS
Term
Oligodendrocytes
Definition
(CNS) binds neurons together and insulates axons of neurons
Term
Schwann cells
Definition
(PNS) insulate axons
Term
How are Schwann cells and oligodendrocytes different?
Definition
Schwann cells only wrap around a portion of one axon, while oligodendrocytes wrap several axons
Term
Microglia
Definition
engage in phagocytosis to fight infections
Term
Astrocytes
Definition
form the blood-brain barrier
Term
Unciliated ependymal cells
Definition
secrete cerebrospinal fluid
Term
Ciliated ependymal cells
Definition
Moves cerebrospinal fluid around and keeps it homogeneous
Term
Epineurium
Definition
shiny white wrapping around nerves (made of collagen)
Term
Fascicle 
Definition
axon bundle
Term
Perineurium
Definition
wraps fascicles
Term
Endoneurium
Definition
wraps individual axon bundles
Term
What are the 3 ways cells are classified as far as what they do?
Definition
Sensory, motor, or mixed
Term
What is the most common type of nerve?
Definition
Mixed
Term
On what conditions can a nerve regenerate once severed?
Definition
Covered by Schwann cells (in PNS), cell body must remain alive, and the two pieces of severed nerve must line up well
Term
Why can only Schwann cells regenerate nerves?
Definition
They form around severed end of axon and guide it back to the myelin sheath, while oligodendrocytes are devoted to multiple axons so they can not do this
Term
Action Potential
Definition
Electrical signal carried by an axon in a nerve
Term
Exciteability
Definition
ability to create potential response to a stimulus
Term
Which cells are excitable?
Definition
Neurons and muscle cells
Term
Potential difference
Definition
measure of charge difference across cell membrane
Term
Why does the potential difference exist?
Definition
It is a surface phenomenon
Term
What does it mean if a neuron is at rest?
Definition
No action potentials running down axon
Term
What is the charge outside the axon at rest?
Definition
Positive
Term
What is the charge inside the axon at rest?
Definition
Negative
Term
Polarized
Definition
positive and negative charges are separated
Term
Why is the membrane polarized?
Definition
It contains large negatively charged proteins that can't exit the membrane without a transport system
Term
How many sodium ions are taken out for every potassium ion brought in?
Definition
three
Term
What tends to diffuse out of the cell during the resting period?
Definition
Potassium
Term
Which ion is the plasma membrane more permeable to at rest?
Definition
Potassium
Term
When the cell is at rest, where are most of the potassium ions concentrated?
Definition
Inside
Term
When the cell is at rest, where are most of the sodium ions located?
Definition
Outside
Term
Where is the cell more negative during the resting period?
Definition
Outside
Term
What is the resting potential of a cell?
Definition
-85mV
Term
What creates an action potential?
Definition
A stimulus
Term
What is the stimulus for skeletal muscle cells?
Definition
Acetylcholine
Term
What are released at the synapses?
Definition
Neurotransmitters
Term
What does a neurotransmitter do?
Definition
Passes action potential from one neuron to another
Term
Where do synapses exist? 
Definition
Between neurons
Term
What are examples of an environment change that can trigger a stimulus?
Definition
Heat/cold, light, feel, chemicals, electric shock
Term
What does an action potential do to the charge inside the cell?
Definition
Makes it more positive than outside
Term
What does the potential difference change to once a stimulus occurs and disrupts the resting period?
Definition
+30 mV
Term
What happens to the potential difference during depolarization?
Definition
Less negative outside, more positive inside
Term
When the cell is at rest, why are there more sodium ions outside the cell than potassium ions inside the cell?
Definition
The membrane is more permeable to the potassium, so while sodium can not go into the cell, potassium can diffuse out. Also, the sodium-potassium-exchange-pump pulls more sodium out of the cell than it puts potassium into the cell
Term
What is the charge of the inside of the cell while at rest?
Definition
More negative
Term
What happens first when a stimulus is triggered?
Definition
Channel proteins in membrane open up to allow sodium to diffuse into cell
Term
Why does the inside of the cell get more positive during depolarization?
Definition
The sodium ions can now diffuse through the membrane into the cell
Term
What happens during repolarization?
Definition
The channel proteins allowing the sodium into the cell close and the potassium gates open. The potassium leaves the cell and the potential difference drops to just below -85mV
Term
How is the resting potential reestablished after the cell repolarizes?
Definition
Both the sodium and the potassium gates close, and the sodium-potassium-exchange pump brings the cell back to its original state
Term
What happens during depolarization?
Definition
The channel proteins open to allow sodium into the cell
Term
What is a stimulus called that is strong enough to trigger an action potential?
Definition
Threshold stimulus
Term
What is a stimulus called that is not strong enough to create an action potential?
Definition
Subthreshold stimulus
Term
What is a local potential?
Definition
Small charge in potential difference that dies out because the stimulus that produced it was subthreshold
Term
Does a local potential travel down the axon?
Definition
No
Term
What does the intensity of a stimulus (hot vs. warm) depend on?
Definition
Frequency of action potentials (not size)
Term
What does the refractory period do?
Definition
Keeps action potential from traveling back up axon
Term
Absolute refractory period
Definition
No action potential can be created while another is in progress
Term
Relative refractory period
Definition
Small action potential created
Term
How does the action potential move down an unmyelinated axon?
Definition
it must travel down whole axon (continuous conduction)
Term
How does action potential travel down a myelinated axon?
Definition
The signal hops down the signal using the nodes of Ranvier (saltatory conduction)
Term
What is the difference between a sharp vs. a dull ache?
Definition
Saltatory conduction vs. continuous conduction
Term
What affects the speed at which an action potential travels down an axon?
Definition
Myelinated vs. unmyelinated and width of the axon
Term
Pre-synaptic neuron
Definition
Carries signal to synapse
Term
What keeps our neurons from transmitting information we don't need?
Definition
Synapses
Term
Neuromuscular junction
Definition
Neuron-to-muscle synapse
Term
Inhibitory synapse
Definition
stops information from passing to the next neuron
Term
What synapses make up the majority of nearon-to-neuron synapses?
Definition
Inhibitory synapse
Term
Synaptic cleft
Definition
space between two neurons
Term
Excitatory chemical synapse
Definition
Uses a neurotransmitter to carry the signal across the space between neurons
Term
Temporal summation
Definition
Single axon carrying multiple action potentials in a short amount of time
Term
Spatial summation
Definition
Many axons all carry an action potential to the same neuron all at once
Term
Hyperpolarization
Definition
takes neurons farther away from creating an action potential
Term
What is the effect of inhibitory postsynaptic potentials?
Definition
Decrease the chance for an action potential
Term
If a synapse's receptors open potassium channels on the postsynaptic neuron, it is a(n) _______ synapse.
Definition
inhibitory
Term
If a synapse's receptors open sodium channels on the postsynaptic neuron, it is a(n) ___________ synapse.
Definition
excitatory
Term
Convergent neurons
Definition
Many inputs lead to one output
Term
Divergent neurons
Definition
One message gets spread to different parts of the body
Term
Oscillating neurons
Definition
message regenerates itself
Term
After-discharge response
Definition
Prolongs effect of stimulus
Term
When you flex your forearm, what division of the PNS is being used? What division of that nervous system is being used?
Definition
Efferent; somatic motor nervous system
Term
What system of the PNS is being used first when you touch a hot stove?
Definition
Afferent
Term
If a signal in a neuron traveling in the same direction as a signal in another process of that same neuron, is it traveling towards or away from the cell body? 
Definition
Towards
Term
What does it tell you if the microglia in the brain are very active?
Definition
The brain probably has an infection
Term
What are two reasons a neuron would not respond to a stimulus?
Definition
The stimulus was subthreshold; the neuron was in absolute refractory period
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