A heart beat is initiated by: Question 26 options: a) calcium entry into cardiomyocytes. b) sodium entry into cardiomyocytes. c) potassium entry into cardiomyocytes. d) sodium leaving cardiomyocytes
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A heartbeat is initiated by the electrical activity in the heart, specifically in the sinoatrial (SA) node, which is the natural pacemaker of the heart. Show more…
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Briefly describe the events leading a conducting cell to an action potential and choose the method of depolarization: sodium or calcium. Choose 4 answers. a) A few sodium channels open, voltage-gated potassium channels close, voltage-gated (slow) calcium channels begin opening, depolarizing the cell to the threshold potential. b) Rapid depolarization due to voltage-gated fast sodium channels opening and the membrane being permeable to sodium. c) Voltage-gated (fast) calcium channels close, voltage-gated potassium channels open for rapid repolarization. d) At +30 mV, fast sodium channels close and slow calcium channels open, allowing calcium ions to enter the sarcoplasm from the extracellular fluid. e) When slow calcium channels close, slow potassium channels open, resulting in a rush of potassium ions out of the cell for rapid repolarization to resting potential. f) Voltage-gated (fast) calcium channels open for rapid depolarization. g) Depend on sodium influx for depolarization. h) Depend on calcium influx for depolarization.
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The first part of the action potential of a neuron depends mostly on which movement of ions? Group of answer choices: a. Sodium ions entering the cell b. Sodium ions leaving the cell c. Potassium ions entering the cell d. Potassium ions leaving the cell
Excitation-Contraction Coupling: During the action potential in a cardiac contractile cell: a) Calcium ions enter the cell through voltage-gated calcium channels and bind to Ryanodine receptor-channels. b) Calcium ions enter the sarcoplasm through Ryanodine receptor-channels and bind to troponin. c) Calcium is pumped out of the cell into the ECF by primary active transport. d) Both a) and b) are correct, and c) is incorrect. e) a), b), and c) are all correct.
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