UH BIOL 1344 - Cell Polarization and Depolarization (2 pages)

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Cell Polarization and Depolarization

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Cell Polarization and Depolarization


Continues lecture notes on the chapter on the heart. Covers generating action potential in cardiac and pacemaker cells

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University of Houston
Biol 1344 - Hum Anat Physiol

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BIOL 1344 Lecture 6 Outline of Last Lecture I Layers of the Heart II Valves in the Heart and Conditions with Malfunctioning Valves III Coronary Arteries and Blood Pressure IV Cardiac Muscle Cells Outline of Current Lecture V Cell Polarization and Depolarization VI Generating Action Potential A Sodium potassium Pump B mV Levels in Cardiac Muscle Cells VII Pacemaker Cell Cycle Generating Action Potential Current Lecture Cells are either polarized or depolarized based on whether they are positive or negative on the inside Cells contain proteins and phosphate which make them negative However they also contain potassium or K which are positive but flow out of the cell through leak channels If a cell is negative inside it is called polarized If it is positive it is called depolarized The sodium potassium pump regulates these levels and restores ionic conditions in the cell This pump uses ATP to continually pump out 3 Na and pump in 2 K in This is why cells require food and oxygen for energy to maintain this system of homeostasis Cardiac muscles generate action potential using this system of active transport in cells There is a cycle that these cells go through which has four stages and lasts 250 350 milliseconds These cells begin at about 90 mV then there is a rapid influx of Na through voltage gated Na channels which shoots the cell up to 20 mV This is the peak of the cycle and where the point of action potential is This is the stimulus required to start the muscle contraction systole The next stage is slow Ca 2 entry through voltage gated Ca 2 channels The positive level of the cells drops a little bit during this stage The third stage is fast K exit or efflux through voltage gated K channels The mV level of the cell drops almost back to 90 at this point The last phase is the restoring of ionic conditions through the sodium potassium pump so Na and Ca are pumped These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a

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