Audio Transcript Auto-generated
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Hi I'm Brianna smith and this is my
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teaching video on the excitation contraction coupling process
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1st. The process begins with
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stimulation from the nervous system. Electrical stimulation is required
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for muscles to contract for skeletal muscle in particular,
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voluntary control is required,
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meaning that the conscious brain has to make
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decisions on exactly how the muscle will move
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a motor unit
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as an individual motor neuron and all the muscle fibers. It innovates.
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In this picture here we can see a motor neuron in orange
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finding to multiple muscle fibers.
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This process begins when electrical stimulation from the nervous system
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sends an action potential down
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the motor neuron
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and it reaches the axon terminal.
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The potential reaching the axon terminal starts the release of
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acetylcholine into the synaptic cleft.
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The synaptic cleft is a small area of space between the motor nerve and the muscle.
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A ch shown in blue on the diagram stands for acetylcholine.
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A single cooling binds to
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ion channels on the muscle membrane
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and once it binds these channels then bring
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in sodium that deep polarizes the muscle fiber.
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This deep polarization results in action potential traveling down the T. two buel
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and releasing calcium.
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This release of calcium begins the contraction of skeletal muscle.
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One thing that's important to remember here is shown under the sodium channels in
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prey sodium movements to polarize the motor
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end plate producing an end plate potential.
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So essentially what's happening here is the action potential from the motor neuron
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skips
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to the
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muscle
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end plate
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through acetylcholine and the exchange of these substances
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to stop the contraction.
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Acetylcholine Esther race is present within the synaptic cleft
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and will dispose of any extra acetylcholine
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too.
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Um Inhibit this process from occurring further.
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It's important to remember that release of calcium because we will see
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that later when we start talking about the sliding filament theory.
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But next we're going to talk about a circle near a
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sarcoma here is the smallest functional unit of a muscle.
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South
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thin filaments are called Acton and thick filaments are called myosin.
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These filaments are both present in the circle here
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and help it contract.
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Something I found interesting is the prefect sarko in myo means muscle.
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So if you ever come across these terms like sarcoma
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or medicine, you know that it relates to the muscle anatomy.
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So diving into the circle mirror here we on top, see a relaxed circle mirror
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that is very spread out.
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And on the bottom we see a contracted
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sarcoma
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which is very condensed or compressed.
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We'll start talking about
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key elements here. The M.
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Line is the center of the circle here and this remains unchanged.
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The a band which is the length of the thick filament
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also remains unchanged during contraction
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because the thin filament is essentially what is moving
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the thick filament length will stay the same.
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Um The Z desk
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show how circum ears connect to one another.
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So sir cameras are connected
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adjacent lee to other sacrum ears to create
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an entire muscle.
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Um
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So the Z. Dicks show
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from one end to another the length of just one star come here.
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The two um
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anatomical
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positionings or zones,
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bands that we need to remember are the age zone
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and I band and they are highlighted here on the contracted
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circle here.
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And this is because the H. Zone
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and the I. Banned both decrease as the muscle is contracted,
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the H zone decreases because
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the myosin
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within its own circles here pulls on the act and bringing it closer.
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And this pool of acting
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relays to the adjacent circum years,
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meaning that all the circum years are
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condensing along with the individual circumstance.
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Getting up close to the filaments themselves.
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We need to remember that act and contains two proteins.
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Troponin and triple Madison.
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And it has the binding sites for my assassin on Miocene.
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We need to remember that they have
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myosin heads that bind to these binding sites.
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So that's
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the circle near anatomy.
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And this will be helpful for explaining the sliding filament theory.
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The sliding filament theory begins when calcium
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that was released in our synaptic transition
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snap tick
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transmission
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showed in the first step of this video
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when calcium binds which opponent
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it initiates the movement of Trapani Yasin off of the binding sites.
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Troponin and shamisen are very easy to mix up.
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But the way I like to remember it is that trope amazon is
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a double stranded and it moves off of the myosin binding sites.
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So trope amaya season
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covers the mayas and binding sites.
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You can also remember it because
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it is long and double stranded
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like a medicine.
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Um and the way I remember troponin is it is within the acting.
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So it doesn't cover the full extent of it like triple medicine.
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Um Once the calcium binds such opponent trouble medicine
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is released and now these binding sites are exposed.
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Once these binding sites are exposed, the cross bridge cycling process can occur.
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So what happens first is that my son had binds
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to
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the binding site on acting.
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This forms a cross bridge.
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Once the cross bridges formed a power stroke is
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produced and this is where my son pulls on act
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in the miocene had bends and the ADP and phosphate
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that were on the mice and head are released.
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Detachment occurs when ATP binds to the Miocene head and
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this removes the mice and head from the binding site.
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This http is in hydrolyzed into ADP and phosphate,
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which allows the myosin head to be ready to power stroke again.
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So then we can see here how this process
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continues because it forms a cross bridge pulls it.
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Detaches gets ready again and repeats the cycle.
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This cycle won't stop until calcium is removed from the system.
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The removal of calcium causes proponent to move
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trouble Myerson back over the binding sites.
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It inhibits the process of the sliding filament theory.
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So here it is in its full form to go over it
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one more time calcium binds the component that moves triple miocene,
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exposing the binding sites.
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This then allows the myosin heads to form a cross bridge.
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The cross bridges then perform a power stroke which pulls on the acting.
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The deep attachment process occurs when at B binds to the mice and head
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and then
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he is then hydrolyzed to get the miocene head ready to pull another power stroke
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in this process stops once calcium
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is put back into the circle plasma particular. Um
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Now all these processes work together.
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I know we learn them a bit individualized but up here we can see the
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synaptic transmission how the action potential goes from
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the axon terminal to the motor end plate
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and then releases
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calcium. This release of calcium then
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buying such opponent moves triple myosin
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and then starts this whole process again.
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I hope you enjoyed this video and learn something from it.
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Thank you so much for watching