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Chapter 34 The Nervous System


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Name the 4 basic functions of the Nervous System
1)percieve a stimulus
2)transform it into an "impulse"
3)conduct the impulse
4)trigger a response or not (selective to the stimuli you percieve)
The nervous system is composed of neurons and associated cells, and the functions are reflected in the structural arrangements of _______, ____________, and ___________ into pathways
neurons, receptor cells, effector cells
Function of a dendrite
recieve signals
Function of an axon
conducts signals
Function of a cell body
holds ions and decides whether to conduct a stimulus or not
Function of sensory neuron
(receptor cells) picks up sensation or stimulus and conducts it to an interneuron
Function of association (interneuron)
in b/w sensory and motor decision making to respond or not, found in CNS
Function of motor neuron
carries out the response by stimulating the effector cell, found in the PNS
Function of the effector cell
muscle or anything actually stimulated
Reflex arc
simplest pathway, contains only 2 neurons, one sensory and one motor, doesnt have to travel all the way to the brain for a reflex, used a defense mechanism
Difference b/w divergent and convergent pathways
Divergent- one neuron affects many
Convergent- alot of pathways are converging upon one neuron
What is a resting potential?
potential to do work
Why do all living cells have a negative resting potential?
needs to be negative to have the ability to conduct an impulse
What 2 forces maintain this distribution of charged ions
1) attractions of (-) and (+) charges high concentration
2) diffusion
What is an action potential?
Na+ rushes in and K+ rushes out (gates open)and makes the inside (+)
What events occur in quick succession during an action potential?
depolarization-goes from (-) and (+) inside Na goes in
repolarization-return to (-) inside the cell
travels down the axon to the bouton and diffuses to the next dendrite
How is the ion distribution inside the cell and outside the cell returned to the original state so the cell is always ready for an action potential
the Na/K pump uses active transport restores the correct ion distribution (repolarization)
Why does repolarization require energy?
active transport- uses atp to move things against the concentration gradient, requires a transport protein
How is impulse conduction along an axon speeded up when satellite cells are present?
they allow the impulse to skip from node to node instead of all the way down the axon
What are the 3 functions of satellite cells?
1)give physical support and protection
2) help nourish the neurons
3)provide insulation and speed up conduction (50X) faster if mylenated
How are impulses conducted across the synaptic gap?
action potential goes from electrochemical to just chemical thru diffusion, neurotransmitter, ion channels open and recieve the right neurotransmitters
What is a bouton?
end of an axon swollen
What are vesicles?
store neurotransmitters
Name some neurotransmitters produced by the nervous system.
epinephrine(organs and involuntary muscle)
serotonin (pain, mood, sleep)
dopamine (stimulates hypothalamus)
GABA (major inhibitory)
Which is the one neurotransmitter used primarily in teh stimulation of skeletal muscle?
acetylcholine- prominent in many CNS synapses
How are neurotransmitters removed from the gap after conduction?
some simply diffuse away
some actively taken back up by the presynaptic axon
some is broken down by an enzyme
Which is faster: a conduction along the length of an axon, or conduction across the tiny synaptic gap?
axon b/c there is no diffusion
Why can impulses only travel in one direction along a neural pathway?
1)only one end of the neuron has neurotransmitters
2)axon doesnt recieve a stimulus
3) impulse cant double back due to refractory period (recovery time from de/repolarizing
What is meant by intergration of signals that occurs in the cell body?
summing up exhibitory and inhibitory signals to see if an action potential occurs

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