BIOL273 Chapter Notes - Chapter 3: Endoplasmic Reticulum, Calcium Atpase, Phospholamban
11 Sep 2016
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Force generated by cardiac muscle proportional to number of number of active crossbridges. If calcium concentrations are low, some cross bridges are not activated and the contraction force is small, and vice versa. The sarcomere length: force generated is proportional to length of muscle fibre due to the degree of overlap between actin and myosin. There is an optimal amount of overlap: stretching a myocardial cell may also allow more calcium to enter through cell membrane calcium channels- which contributes to a more forceful next contraction. Cardiac muscle is also excitable tissue and has ability to generate action potentials. Calcium plays a role in the action potential. Similar to neuronal and skeletal muscle action potentials, but a little different due to calcium. Begins with a rapid depolarization caused by influx of na+ ions. Action potential opens voltage gated sodium channels, causing a rapid increase in membrane na+ permeability, then they close again, rapid depolarization.
