PHYL 1010X Final: Block XC Study Guide
Document Summary
The sarcoplasm reticulum pumps calcium back into its lumen using calcium atpase. The addition of net positive charge to the muscle fiber depolarizes the membrane. They always reach the threshold and initiate a muscle action potential: action potential- travels across the surface of the muscle fiber into the t-tubules by the sequential opening of voltage gated sodium channels. The action potential that moves down the t-tubules causes calcium release from the sarcoplasmic reticulum. free cytosolic calcium levels in a arresting muscle are normally quite low, but after an action potential, they increase about 100 fold. When cytosolic calcium levels are high, calcium binds to troponin, tropomyosin moves on the on position and contraction occurs. Transduction of the electrical signal into a calcium signal requires 2 key membrane proteins. The t-tubule membrane contains voltage sensing l-type calcium channel called dhp receptor. The ends of the thick and thin filaments overlap slightly.
