[PSYC 1100] - Midterm Exam Guide - Ultimate 49 pages long Study Guide!

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PSYC 1100
MIDTERM EXAM
STUDY GUIDE
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BIOLOGY
neural basis: reflex, nerve impulse, action potential, communication by
neurotransmitters
brain basis: nervous system structure, localization of function, disorders,
lateralization
2/10 The Neuron
reflex - an automatic, stereotyped movement produced as the direct result of a stimulus
reflex pathway
knee tap → sensory neuron from muscle → spinal cord → single synapse
in reflex → reflex, motor output cause thigh muscle to contact
also neuron going upwards to the brain
Although it can be excited by brain, response can be inhibited by the brain
inhibition - response is kept from happening
brain isn’t involved
The Neuron
means nerve cell
10 billion to a trillion neurons make up your brain
10,000 connections each
parts:
dendrites
branches
cell body (or soma)
axon
covered by myelin sheath aka covering of axon
only covering little stretches with opening in between
Nodes of Ranvier
openings /interruptions in between myelin sheath that cover
axon
terminal endings (or terminal buttons)
ending of the splitting of the axon
MS disease - immune system attacking myelin sheath
there can be different kinds of connections between neurons
How does a neuron “fire”? (What is the nurse impulse?)
Action potential
How does it cause the next neuron to fire? (How does it communicate?)
neurotransmitters
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Action potential (aka nerve impulse)
1. start with electrical RESTING POTENTIAL: inside of cell is 70 mV more negative
than outside due to Cl- ions inside and Na+ ions outside (so resting potential is -
70mV)
2. stimulation of neuron lets in Na+ (sodium) ions, which makes the inside more
positive: -70, -69, -68, -67…
as more sodium ions come inside numbers become more positively
charged
opening ion channels to allow sodium to come in, through cell membrane
3. when enough Na+ ions in get in for the potential to be reduced to -55mV,
suddenly the doors (ion gates) to the cell membrane are flung open allowing Na+
to rush in
4. so much Na+ enters that the potential doesn’t just go to 0 -- it shoots all the way
up to +40 mV, so the inside is now positive relative to the outside (the ACTION
POTENTIAL - the sudden charge/reversal in charge)
5. ion pumps work to reduce potential back to -70mV by pushing positive ions out
(actually K+ because Na+ goes out slower; then ANOTHER pump takes Na+
back out and puts K+ back in)
- note that -55 mV is a threshold: below that voltage there is no action potential -
firing is “all or none”
- more intense stimulation doesn’t cause a more intense action potential - just
more frequent ones (up to 1000/sec) and in more neurons
- action potential travels down length of axon by depolarizing neighboring areas
- travels NOT at speed of electrical current in wire, but rather at about 50 to 100
m/sec
- action potential ends at the terminal endings
Neurotransmitters - communication across the synapse
1. synapse is gap between two neurons (the presynaptic and postsynaptic
neurons); terminal ending of presynaptic neuron relay impulse to dendrites of
postsynaptic neuron
space between two neurons = synapse
presynaptic neuron generates action potential to move to the postsynaptic
neuron
2. terminal buttons contain little sacs (“vesicles”) of chemicals (“neurotransmitters”)
at action potential, vesicles burst and release neurotransmitters into synapse
3. receptor molecules on membrane of dendrite are like little locks to be opened:
neurotransmitters are the keys, and this is what opens ion gates to allow Na+
inside in the first place
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