Chapter 2 part 3 Flashcards
nerve cells and their messages
how is the neuron different from other cells in the body?
it is specialized for communication
what is a neuron?
a specialized cell of the nervous system
what is a neuron used for?
detecting information, transmitting information, and affecting muscles and glands
what is the soma of the neuron?
the round part that contains everything a regular human cell would (nucleus, mitochondria, etc.)
what is the name for the cell body of the neuron?
the soma
what do dendrites look like?
tree branches at the beginning of the neuron
what does the axon look like?
the long tube in the middle of the neuron
what do terminal buttons look like?
the little balls at the end of the neuron
what do dendrites do?
receive messages from neighboring neurons or the outside world
if a dendrite receives a message from a neuron, what does it usually consist of?
neurotransmitters (chemicals)
in what situation is there more dendrites than normal?
in a part of the brain where no chemical messages can be missed
in what situation is there less dendrites than normal?
in a part of the brain that doesn’t receive many messages
what happens to the neurons in a part of the brain that is being used more often
they can grow new spines
use it or lose it
use the pathway and grow neurons or don’t and the brain gets rid of the pathway and sometimes the neurons (like pruning trees, we need to prune the smaller branches so the big healthy ones can keep growing)
axon
conducts nerve impulse from the cell body to distant location -> carries the electrical impulse
myelin sheath
increases speed and efficiency of nerve impulse
how do axons look?
they can be short or as long as your body, some are wide tubes and others are skinny
what does myelin sheath look like?
pellet covering that wraps around sections of axon, looks white
what is myelin sheath made out of?
lipids (fat)
how does myelin sheath increase speed and efficiency?
it wraps around sections of the axon to insulate it and protect the axon from interference (like the plastic covering on a wire)
terminal buttons
release chemical messages (neurotransmitters) onto neighboring dendrites
when are neurons active?
all the time
electrochemical transmission
communication from nerve cell to nerve cell
how does a neuron generate electricity?
using charged particles called ions
what is cerebral spinal fluid?
the liquid our brains float it, it has ions and tastes salty
where do electrical signals ALWAYS start?
the cell body
where do electrical signals ALWAYS end?
terminal buttons
the inside of a neuron is more _________ than cerebral spinal fluid
negatively charged
the cerebral spinal fluid is more ________ than the inside of a neuron
positively charged
iNside
negative
outside
positive
what happens when the axon membrane won’t let sodium (Na) in?
Na lines up on the outside of the membrane
why does Na want in the axon?
because the inside of the neuron is more negatively charged than the cerebral spinal fluid, and Na is a positive ion
what is already inside the axon when it is at rest?
potassium (K)
what are the holes in the membrane for?
they sometimes allow ions to go in and out of the axon
when are the channels closed?
when the neuron is at rest and the inside is more negative than the outside
membrane potential
difference in charge (voltage) across a cell membrane
resting membrane potential
-70 millivolts (more negative than outside the membrane)
threshold
minimum amount of stimulation necessary to open channels and trigger the neural impulse
after stimulation and a channel opens ->
sodium (Na) rushes in the cell and potassium (K) is also positive so it rushes out, this is enough stimulation to open the next channel (and so on for all the other channels in the membrane)
what really is the electrical signal?
the exchange of Na and K along the axon
action potential
brief wave of positive electrical charge that sweeps down the axon
action potential is defined by what?
sodium
during the refractory period, the inside of the cell is __________
more negative than when it is at rest for a short period of time (milliseconds)
refractory period
after a neuron fires, there is a period of time where it cannot fire again
what happens during the refractory period?
pumps in the membrane work to pump K in and Na out to bring the neuron back to resting potential (basically resetting the neuron)
can a neuron fire during the refractory period?
no
all-or-none law
if threshold is reached, a full action potential occurs. if threshold is not attained, then no action potential will occur
what is the basic definition of the all-or-none law?
a neuron either fires or doesn’t fire. like a gun, it can’t half go off, it can only go off or not
when a neuron is fired, is it fired exactly the same everytime?
yes, because it can only fire or not
do neurons typically touch?
no, there is always a gap between them
synapse
the gap between neurons
are terminal buttons specialized?
yes, they only can squirt out one type of neurotransmitter
what happens when the action potential reaches the end of the axon?
it triggers a reaction in the terminal buttons that makes them squirt out neurotransmitters into the synapse
synaptic vesicles
store neurotransmitters in sacs (package them in bags)
where are receptors located?
on the dendrites
neurotransmitters
chemical messages
what do receptors do?
receive neurotransmitters
can a neurotransmitter open more than one receptor?
yes, because they are reusable
does every neurotransmitter have a different shaped molecule?
yes, and their receptors are shaped specifically for them (like locks and keys)
can a dopamine molecule go in a serotonin receptor?
no, because they aren’t the same shape (the key doesn’t fit into the lock)
chain reaction process
dendrites –> cell body –> axon –> terminal buttons –> neurotransmitter release –> dendrites –> cell body –> axon –> etc.
excitatory synapse
when neuron A releases neurotransmitters onto neuron B, neuron B will be more likely to fire
inhibitory synapse
when neuron A releases neurotransmitters onto neuron B, neuron B will stop firing or is less likely to fire
what happens when neurons fire out of control?
a seizure, this is why we need inhibitory and excitatory synapses
how do we eliminate the neurotransmitter from the synapse after is has done its job?
enzymatic degradation and reuptake
enzymatic degradation
enzymes in cerebral spinal fluid that destroy neurotransmitters. every neurotransmitter has a specific enzyme that destroys it
reuptake
neurotransmitters are pulled back into terminal buttons and get repackaged and reused (like putting your key in back in your pocket and pulling it out the next time you need it)
endogenous
made inside your body
exogenous
made outside of your body from plants in labs to mimic endogenous chemicals
7 most popular neurotransmitters
acetylcholine, dopamine, serotonin, norepinephrine, glutamate, GABA, endorphins
very 1st neurochemical ever discovered
acetylcholine
acetylcholine
involved in movement, learning, and memory
MUST have to move any muscle in your body
acetylcholine
how snake and spider venoms paralyze prey
they block acetylcholine
how does botox work?
it blocks acetylcholine in injection areas so you can’t move the muscles and create wrinkles
abbreviation for acetylcholine
ACh
dopamine
involved in movement, attention, short-term memory, planning, and reward
how does Parkinson’s work?
it is a disruption in dopamine pathways that won’t let sufferers from the disease move
what happens when you get a squirt of dopamine
you feel compelled to do that behavior again
when do we get a squirt of dopamine?
when we do something good for our species (eating, drinking, sex, etc.)
how does dopamine create a pathway to addiction
when we do specific drugs, we get a hit of dopamine and we feel compelled to use those drugs again
abbreviation for dopamine
DA
what does cocaine do to our brains involving neurotransmitters
it makes more dopamine available than our brains are used to
why is meth so addictive?
because it makes more dopamine available than any other drug
serotonin
involved in sleep, mood, and eating
abbreviation for serotonin
5-HT
how do antidepressants work?
they block reuptake so serotonin stays in the synapse longer so it can open more locks –> enhances the serotonin level in the synapse
how does MDMA (ecstasy) work?
it enhances serotonin and elevates mood
why is MDMA (ecstasy) not used as an antidepressant?
it can kill neurons
norepinephrine
involved in attention and arousal
epinephrine
adrenalin and is only in peripheral nervous system)
abbreviation for norepinephrine
NE
what does norepinephrine do?
when we are scared / excited, the brain releases NE and we become more vigilant (similar to adrenalin)
when do we have the base level of NE?
when we are awake
when do we have lower levels of norepinephrine?
when we are asleep
what neurotransmitters are also amino acids?
glutamate and GABA
glutamate
primary excitatory neurotransmitter
what happens when glutamate is released?
neurons start firing
what happens when glutamate is released in the amygdala?
we feel very anxious
GABA
primary inhibitory neurotransmitter
there is more of these two neurotransmitters than any other in the brain
GABA and glutamate
what happens when GABA is released?
neurons go silent
what happens when GABA is released in the amygdala?
we become very relaxed
anxiety meds (benzos) enhance which neurotransmitter?
GABA
we take drugs that enhance ________ and inhibit _________
GABA ; glutamate
endorphins
involved in pain inhibition and pleasure
endogenous opiods
modulates pain
do endorphins enhance or inhibit pain?
inhibit
why are endorphin drugs so addictive?
they open pathways to dopamine, which then compels us to continue the behavior
how do opiates (narcotics) work?
they mimic endorphins for when we’re in pain by inhibiting pain and the medulla
does our brain constantly release endorphins?
yes, because we experience everyday wear and tear
