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PHGY 209 - Muscle and ANS

PHGY 209 - Muscle and ANS - But the Ca from the channels...

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Acetyl coline is released in the terminals. Nicotinic acetyl colline receptor activated by nicotine. The influx of sodium causes a EPSP flow, need 50-100 EPSPS to activate EPSP - End plate potential (30mV) Muscle fibers are covered with sodium gated channels all down the length and propagate action potential just like nerves. So the end plate potential is always big enough to propagate the signal to the WHOLE muscles. The motor neural is about at the center (middle) of the muscle fiber When the motor neuron fires a signal, the whole signal is propagated through the whole muscles. It's so fast that it looks like its done in one shot. Sarcoplasmic reticulum is packed with Ca++, it is where it is stored T-tubules: plasma membrane INSIDE the muscle fiber. Screen clipping taken: 20/10/2010, 12:01 PM T-tubule Ca++ is necessary to contract the muscle. Constraction is cause by a sudden increase of Ca++.
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Unformatted text preview: But the Ca++ from the channels that activate the muscle contraction isn’t from the tubules, it's from the sarcoplasmic reticulum. The channels in the T-tubules is voltage sensitive, that once the action potential passes by, it senses it, and the T-tubules is activated and changes shape, pushes the linkage between itself and the sarcoplasmic reticulum, and then the SR channels open. HUGE amount of Ca++ flows out of it and the concentration of Ca++ in the muscle spikes up and causes the muscle to contract by a biochemical change from the [Ca++]. 10-20-10 October 20, 2010 11:47 AM Mus. ANS Page 1 Regulation of force of the muscle fibers Slow, fast, fast glycolytic fiber. +[K+] = muscle depolarization +[ADP] 10-22-10 October 22, 2010 11:48 AM Mus. ANS Page 2...
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PHGY 209 - Muscle and ANS - But the Ca from the channels...

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