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Lecture 10

CAS BI 106 Lecture 10: Anatomy Lecture 10

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CAS BI 106
Dale Pasino

Lecture 10 21717 Contraction Muscle contraction controlled by neurological input Solid connection between 2 cells is called a synapse Synapse between neuron and muscle cell is called neuromuscular junction (NMJ) At the NMJ (neuron comes adjacent to the muscle very close but not touching), the neuron releases a chemical onto the (surface) plasma membrane of the muscle cell Triggers a muscle impulse to contract Both your neuron and muscle cells have the ability to create small electrical impulses o In muscle cells the electrical impulses make the mechanism for contraction Sarcolemma on the outside. Connection between the sarcolemma and neuron close but not touching. When the electrical signal travels down the neuron and releases the chemical, the chemical doesnt have far down to go. Calcium is stored within sarcoplasmic reticulum. When the electrical signal comes by it forces calcium to flow out and make contraction possible Because of T tubules the electrical signal can go deep down in the membrane T tubules are always next to the sarcoplasmic reticulum Contraction happens when thick filaments reach and pull the thin filaments. The muscle cell plasma membrane has invaginations into the cell called T tubules These structures carry the muscle impulses deep into cell Ttubules are adjacent to sarcoplasmic reticulum (modified endoplasmic reticulum unique to muscle cells) SR stores calcium Muscle impulse triggers release of calcium from SR Making muscles move Calcium is necessary to allow the the myofilaments to interact In the absence of calcium, muscle contraction is impossible ATP (cellular energy) is necessary for both contraction and relaxation to occur If you run out of ATP during contraction you wont be able to take back the calcium (called a cramp) Rigor Mortis stiff state, energy ran out and calcium allowed out into the muscle and no atp to take back the calcium. Changes in striations during contraction When contracted you dont see difference in striation Muscular innervation When your brain decides to contract a muscle, it sends 2 neurons, one from the brain to the spinal cord and one from the spinal cord to the muscle. That second neuron forms a NMJ with a muscle cell. you dont have 1 neuron for every
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