Physiology 3120 Lecture Notes - Lecture 11: Rigor Mortis, Calsequestrin, Rate-Determining Step

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Stavraky Lecture 11
-sarcomeres are arranged parallel to each other
-when a muscle contracts, each sarcomere shortens
-so even if each of them shortens a tiny bit, with all 100 000 sarcomeres shortening, the
muscle cell shortens as well
Very long sarcomere with no overlap of thick and thin myofilaments thus cannot grab on to
actin in thin myofilament thus no muscle contraction = 0% tension in muscle cell
As start overlap of thick and thin myofilaments, start to increase tension in muscle cell
-the more the overlap, the higher the tension
-at this point, maximize amount of cross bridges, which maximizes tensions
3. When overlap until thin myofilaments bump into each other, still a lot of tension but lower
than before
4. When thin myofilaments overlap with each other, tension down to about 80%
5. Keep contracting until thin myofilaments from opposite ends start to interfere with one
another which decreases number of cross bridges which also decreases tension
6. Contract until thick myofilaments are bumping into Z-lines to get zero tension
-in the human body, only steps 2-5 are possible ie: never gets to the extremes
2. AP in red is going down the T-tubule
-propagation occurs just like AP does in non-myelinated neurons
3. DHP is a voltage sensor that detects the AP going by in the T-tubule
4. DHP is linked physically to Ca++ channel on SR so when DHP changes shape, it opens the Ca+
+ channel on the SR membrane
-huge amount of Ca++ in the lumen of the SR diffuse out very fast into the intracellular space of
muscle cell (since conc gradient of Ca++ is huge)
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