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82 Cards in this Set

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  • Back
What is the main function of the nervous system?
Enables organisms to receive and respond to stimuli.
Neurons
are the functional units of the nervous system, they convert stimuli into electrochemical signals that are conducted throughout the nervous system
What are the three main parts of a neuron?
dendrites
cell body
axon
Dendrites
receive information and transmit it toward the cell body

(they are cytoplasmic extensions)
Soma
cell body, contains the nucleus and controls the metabolic activity of the neuron
Axon
nerve fiber
Axon hillock
connects the cell body to the axon
Myelin
insulating substance
Glial cells
produce myelin
Where do oligodendrocytes produce myelin?
central nervous system
Where do Schwann cells produce myelin?
peripheral nervous system
What are the gaps called between segments of myelin?
nodes of Ranvier
What are the ends of axons called?
synaptic terminals
What do synaptic terminals release into the synaptic cleft?
neurotransmitters
Where is the synaptic cleft located?
between the axon terminal of one cell and the dendrites of another
What is multiple sclerosis (MS)?
demyelinating disorder, where the myelin of the brain and spinal cord is selectively targeted

-results in weakness, lack of balance, vision problems and incontinence
What are action potentials?
impulses that travel along the axon
What do action potentials cause?
release of neurotransmitters into the synapse
What is the resting potential?
Potential difference between the extracellular space and the intracellular space when a neuron is at rest.
What is a typical resting potential?
-70 mM

(inside of the cell is more negative than the outside)
How is the potential difference maintained?
Sodium-potassium pump
(aka: Na+-K+ ATPase)
T/F

During resting potential the concentration of K+ is greater on the inside.
T
How does the cell become polarized?
K+ diffuses down its concentration gradient into the cell, creating a net negative charge on the inside.
What type of transport does the Na+/K+ pump do?
3 Na+ out for every 2 K+ in
T/F

A nerve cell receives both excitatory and inhibitory impulses from other cells.
T
What does depolarization cause?
the inside of the cell becomes less negative
What is the minimum threshold membrane potential?
the level at which an action potential is created (-50 mV)
How does an action potential begin?
when voltage-gated Na+ open in response to depolarization
What happens when voltage-gated Na+ channels open in response to depolarization?
it allows Na+ to rush down its electrochemical gradient into the cell
What causes repolarization?
voltage-gated K+ channels open and allow K+ to rush out, down its electrchemical gradient
Hyperpolarization
more polar than normal (more negative)
Refractory period
immediately after an action potential when it may be impossible to initiate another action potential
T/F

Neuronal information is coded by the frequency and number of action potentials rather than the size of the action potential.
T
Electrical gradient
Na+ wants to go into the cell because it is more negative inside the cell
Chemical gradient
Na+ wants to go into the cell because there is less Na+ inside the cell
Where is tetrodotoxin found?

(TTX)
Puffer fish
What does tetrodotoxin do?
blocks voltage-gated Na+ channels thereby blocking neuronal transmission
T/F

The harder you hit your thumb with a hammer the more action potentials will travel up your pain fibers, but the size and duration of each individual action potential will remain the same.
T
What is the membrane potential of an action potential?
+ 35 mV
How do local anesthetics work?
blocking of the voltage-gated Na+ channels
Why do local anesthetics work well on pain neurons?
pain neurons have small axonal diameters and little or no myelin
Where does action potential get initiated?
axon hillock
What makes the backward travel of action potential impossible?
refractory periods
T/F

Different axons can propagate action potentials at different speeds.
T

the greater the diameter of the axon and the more heavily it is myelinated: the faster the impulse travels
How does myelin increase the conduction velocity?
by insulating segments of the axon so that the membrane is permeable to ions only in the nodes of Ranvier
Saltatory conduction
action potential "jumps" from node to node
Effector cells
postsynaptic cells found in muscles and glands
What are the vast majority of synapses in humans?
chemical synapses
How does cocaine affect one?
blocks neuronal uptake carriers
What does acetylcholinesterase do?
inactivates the neurotransmitter acetylcholine
Synapse
the gap between the axon terminal of one neuron and the dendrites of another
What are afferent neurons?
sensory neurons
What are efferent neurons?
motor neurons
What does amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease) affect?
motor neurons
Interneurons
participate only in local circuits
Nerves
bundles of axons covered with connective tissue
What makes up the central nervous system?
brain and spinal chord
What makes up the peripheral nervous system?
somatic and autonomic
What makes up the autonomic
sympathetic and parasympathetic
What are the three regions of the brain?
forebrain, midbrain and hindbrain
What is gray matter?
cell bodies
What is white matter?
myelinated axone
What can the forebrain be divided into?
telencephalon and diencephalon
What does the corpus callosum allow?
communication between the right and left cerebral cortices
What does the diencephalon contain?
thalamus and hypothalamus
What does the thalamus do?
it is a relay and integration center for the spinal cord and cerebral cortex
What does the hypothalamus control?
visceral functions like hunger, thirst, sex drive, water balance, blood pressure and temperature regulation
What does the midbrain do?
it is a relay center for visual and auditory impulses and plays an important role in motor control
What is the hindbrain of?
cerebellum, pons and medulla
What does the cerebellum do?
-modulate motor impulses initiated by the motor cortex

-important in maintenance of balance, hand-eye coordination and the timing of rapid movements
From what does the pons act as a relay center?
to allow the cortex to communicate with the cerebellum
What does the medulla oblongata control?
breathing, heart rate and gastrointestinal activity
What makes up the brainstem?
midbrain, pons and medulla
Into what regions is the spinal cord divided?
cervical, thoracic, lumbar and sacral
What type of reflex is the knee-jerk reflex?
monosynaptic
Give an example of the withdrawal reflex (it is polysynaptic)?
A person steps on a nail
-the injured foot pulls back in pain while the other foot steps forward to maintain balance
What does the autononmic nervous sytem control (ANS)?
Involuntary nervous system-regulates the body's internal environment without the aid of conscious conntrol

-controls cardiac and smooth muscle
Where is smooth muscle located?
blood vessels, digestive tract, bladder and bronchi
"Fight or flight" is part of which nervous system?
sympathetic
"Rest and digest" is part of which nervous system?
parasympathetic
"One very important parasympathetic nerve that innervates many of th thoracic and abdominal viscera is called the ..."
vagus nerve
What do both the ganglionic and postganglionic neurons release?
acetycholine