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hello there everyone and welcome back to
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the mr sin channel today we are going
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into unit 2 topic 4 of ap psychology
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neural firing now if you haven't watched
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my last two videos pause this video and
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go check out my video on the endocrine
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system and also the nervous system those
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videos will be important for you to
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understand everything that's going to be
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in this video all right so by now you
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know that the nervous system is pretty
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complex and it's made up of a bunch of
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different parts each part has its own
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specific function that allow us to be us
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remember our nervous system is made up
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of different neurons we have sensory
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neurons also known as afferent neurons
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these neurons receive information and
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signals from our sensory receptors and
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they send that information up to our
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brain and spinal cord make sure you
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remember these neurons send information
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to the brain and spinal cord the two is
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important there once the brain gets that
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information it processes that
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information and then it sends the
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information back to the body through the
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motor neurons also known as the efferent
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neuron these allow information to travel
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from our brain to the rest of the body
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one way you can remember this is
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afferent approaches the brain and
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efferent exits the brain a for approach
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and e for exit we also have mirror
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neurons these neurons are why when
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someone yawns you might start to yawn
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these neurons mimic they react to the
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actions of another or our cell now in
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order for neurons to send a message they
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need to receive enough stimulation to
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cause an action potential neurons can
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only send one signal at a time and can
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only be sent at a set speed and strength
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now you might be asking well how can the
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signals then be distinguished well it's
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all about the frequency neurons can
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change the number of signals depending
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on the rate in which they're being sent
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your brain is able to understand the
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differences in the frequency and process
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the signals sent by the neuron when a
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neuron sends a message the physiological
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process is known as an action potential
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this is when a neuron fires an impulse
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down the axon now i can already hear
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some of you asking how does all this
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happen what can cause neurons to fire
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these electrical impulses well think
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about your neuron like a battery for
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example this battery right here that i'm
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holding has both a positive end and a
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negative end right now this battery has
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the potential to release energy but it
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can't do that unless there's a
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connection made between the two ends a
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neuron is similar you have in your body
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positively charged and negatively
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charged ions your cell membranes
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separate the ions and creates an
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environment on either side of the
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barrier that is overall positive or
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overall negative this gives your neurons
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potential some ions are able to cross
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the membrane more easily than others
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which is known as permeability think
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about it like having a ticket to a
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concert if you don't have a ticket you
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can't get into the venue certain ions
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have characteristics that'll allow them
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to pass more easily through the neurons
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membrane when a neuron is not sending a
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signal it has more negative ions in the
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inside than on the outside and that's
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called a resting potential when a neuron
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is resting there are a lot of positive
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ions outside the membrane waiting to
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enter neurons in a state of rest are
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polarized and in order for them to send
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a signal an action potential the process
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of depolarization must occur for a
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neuron to depolarize there has to be an
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outside stimulus let's say all of a
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sudden a plate falls on your foot this
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would stimulate sensory afferent neurons
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this would cause ion channels along the
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cell membrane of the neuron to open
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letting more positive ions inside this
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increases the positive charge inside the
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membrane which triggers the action
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potential now not all stimuli to a
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neuron causes an action potential there
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has to be enough positive ions let in if
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there are enough where the resulting
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change is strong enough to meet the
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threshold the depolarization occurs and
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the neuron fires an action potential if
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it does not meet the threshold there is
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no firing and there will be no action
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potential and the neuron will return to
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a resting state this is important to
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remember that neurons act in kind of an
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all or nothing game when an action
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potential occurs it sends a signal down
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the axon to the other neurons in the
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nervous system after one neuron goes
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through an action potential and goes
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through the process of depolarization
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the process of repolarization occurs in
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order to bring the neuron back to
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resting potential during this
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repolarization process different ion
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channels open back up to try and
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rebalance the charges by letting more
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positive ions outside of the cell
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membrane when all of this is happening
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and the signal is moving down the axon
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the neuron cannot respond to any other
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stimulus this is known as the refractory
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period when this happens the neuron
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needs another stimulus in order to meet
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the threshold or intensity level to be
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able to fire again now all right so all
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this is great and all but i can already
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hear some of you asking well what
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happens after a signal is shot down the
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axon how does the signal or action
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potential connect from one neuron to
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another neuron and to answer that we
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need to look at the synapse which is
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composed of parts of two different
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neurons remember the neuron is made up
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of dendrites the cell body the axon the
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axon terminal once the action potential
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has occurred the message has been sent
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through the axon until it reaches the
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end of the neuron called the axon
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terminal in the last video we talked
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about the process of an action potential
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reaching the axon terminal and that
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neurotransmitters were released into the
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space between the two neurons to further
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send the information this space is where
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the signal is converted and sent to
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another neuron now there are electrical
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synapses and chemical synapses
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electrical synapses are for messages
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that need to be sent quickly and
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immediately they are connected and have
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no space between neurons chemical
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synapses on the other hand take longer
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to process most of the interactions
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we're talking about are going to be
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chemical synapses chemical synapses use
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neurotransmitters which are chemical
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messengers that are diffused across the
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synaptic gap to deliver their messages
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the synaptic gap is also known as the
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synaptic cleft it's a narrow space
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between the neurons specifically the
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presynaptic terminal of one neuron and
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the postsynaptic terminal of the next
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neuron it's easy to remember if you
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break down the word pre before the
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synapse and post after the synapse the
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presynaptic terminal is the axon
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terminal of the neuron which converts
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the electrical signal to a chemical one
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and sends the neurotransmitters into the
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synaptic gap the postsynaptic terminal
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is where the neurotransmitters are
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accepted in the dendrites the receptor
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region of the receiving neuron remember
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from our last video the dendrites extend
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outward from the soma and have receptors
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at the end of them this allows them to
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be able to receive messages from
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previous neurons now since i mentioned
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neurotransmitters there are lots of
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different types that do different things
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i want to highlight the different types
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of neurotransmitters our bodies use
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before continuing with how neurons send
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signals and messages up first we have
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acetylcholine which enables muscle
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action learning and memory when you are
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moving around your body is firing off
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acetylcholine if your body is not making
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enough acetylcholine you become at risk
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for diseases such as alzheimer's next is
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dopamine it helps with our movement
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learning attention and emotion it's
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often referenced as a natural drug
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because of how it impacts your feelings
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and emotion if your body has too much
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dopamine you are at risk for
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schizophrenia and an under supply could
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lead you to develop a decrease in your
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mobility and possibly parkinson's
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disease serotonin impacts your hunger
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sleep arousal and mood if your body does
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not produce enough serotonin you are at
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risk for depression if you have too much
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serotonin you might experience obsessive
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compulsive disorder anxiety or headaches
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this is often known as the feel good
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chemical up next is endorphins which
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help with pain control this is like your
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body is producing its own morphine if
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you're lacking endorphins you'll have a
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lower pain threshold if you have an
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excess you will have a higher pain
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threshold also if you remember from the
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2.2 topic review video epinephrine or
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adrenaline and norepinephrine are also
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significant hormones and
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neurotransmitters in the body they both
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work together on the body's fight or
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flight response that will increase your
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heart rate expand the air passages of
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the lungs and redistributes blood to
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muscles you could say that they help
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with your alertness and arousal the last
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two types of neurotransmitters we're
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going to be talking about is glutamate
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and gaba glutamate is involved with
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excitatory messages it helps us with
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long-term memory and learning it is used
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more by neurons than any other
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neurotransmitter if you have an excess
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amount it might over overstimulate the
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brain which could create seizures
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insomnia or give you a migraine gaba
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helps us with sleep and movement it
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slows down your nervous system if you do
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not have enough gaba this might lead to
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seizures tremors or insomnia so you can
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see that each neurotransmitter helps
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communicate different messages and has
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different impacts on our body remember
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the nervous system sends a chemical
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signal through neurotransmitters the
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neuron sends these neurotransmitters
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across the synaptic gap also known as
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the synaptic clef and again this is the
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narrow space between the presynaptic
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terminal and the postsynaptic terminal
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now depending on which neurotransmitter
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binds to the receptor we might see the
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neuron get excited or inhibited
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excitatory neurotransmitters will
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increase the likelihood that a neuron
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will fire an action potential through
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the depolarization process in the
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postsynaptic neuron this is because the
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inside of the neuron will become more
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positive and will push the neuron
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towards the intensity or threshold
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needed for it to have an action
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potential on the other hand an
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inhibitory neurotransmitter will
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decrease the likelihood that a neuron
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will fire an action potential this leads
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to hyperpolarization to occur which is
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when the inside of the neuron becomes
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more negative which moves farther away
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from its threshold or intensity needed
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for an action potential each part of a
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neuron could have hundreds of synapses
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and each of those synapses has different
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inhibitory and excitatory
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neurotransmitters so the odds of a
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postsynaptic neuron experience an action
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potential depend on the sum of all
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excitatory neurotransmitters and
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inhibitory neurotransmitters in the area
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once the neurotransmitters have passed
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their messages onto the postsynaptic
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neuron they unbind with the receptors
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some of the neurotransmitters are
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destroyed and others get reabsorbed this
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process of taking excess
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neurotransmitters left in the synaptic
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gap is known as reuptake this is when
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the sending neuron at the presynaptic
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terminal reabsorbs the extra
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neurotransmitter in our next video we'll
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be talking more about the release and
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reabsorption of neurotransmitters as
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this is where many legal and also
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illegal drugs exploit when exciting the
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production release and reuptake of
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neurotransmitters or inhibiting it drugs
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can elicit different effects on our body
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but all of that is for the next video
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don't forget now to answer the questions
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on the screen and check your answers in
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the comments section below also if you
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need more help with ap psychology make
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sure to check out my ultimate review
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packet it has summary videos for all of
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the different topics in ap psychology it
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also has study guides answer keys
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practice quizzes and more i've included
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different documents to help you with
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unit 2 as well that look at the neuron
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the nervous system and also the brain
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hopefully this will help you get an a in
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your class and also a five on the
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national exam all right i'm mr sin thank
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you so much for watching today and as
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always i'll see you next time online
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you
