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  1. The main focus of this is to show how our muscles contract. There are 8 steps for this and it all starts with an action potential which is a change in the voltage of a cell membrane in response to a stimulus that results in the transmission of an electrical signal. To initiate an action potential in the muscle, the membrane potential needs to increase to approximately -20mV to -50mV. The signal is transmitted from the neurotransmitter to the neuromuscular junction, leading to the release of acetylcholine. The membrane then depolarizes, allowing sodium ions to enter the cell as the action potential moves through the membrane. The activation of contraction is triggered by the release of calcium ions from the sarcoplasmic reticulum (SR), a structure that stores and releases calcium, into the sarcoplasm. Calcium then binds to troponin and tropomyosin and moves by the binding sites on the actin strands. From there, cross bridges form and then ATP is used to do mechanical work. Once ATP runs out and the muscle becomes tired (or fatigued), myosin and actin stop interacting and then calcium is pumped out of the intercellular space. The exact cause of muscle
    fatigue is not known but it is thought that potassium (K+) plays a key role in why muscles can become fatigued.
    The poster board is very well put together and very easy to follow. It is extremely detailed and obvious that Ashley put a lot of time and effort into it. I really enjoyed looking at it and learning more depth about how our muscles contract!

    Jenna VanDenHeuvel

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