is treated by digoxin  (dye-GOX-in) .
The rate of this process is regulated by a 52-residue membrane protein called phospholamban. An irregularity in this process called  torsades de pointes   (tor-SAHD de PWANNT)  is treated by digoxin  (dye-GOX-in) . Two steps of this process are oddly described as "isovolumic" rather than "isovolumetric." The phases of this process are divided into points labelled P, Q, R, S, and T on a diagram where each square represents 40 milliseconds by (*)  0.1 millivolts. Signals during this process are transmitted through the bundle branches to the Purkinje  (pur-KIN-jee)  fibers. This process is regulated by the sinoatrial node and is normally divided into systolic and diastolic phases. It occurs too quickly in tachyÂ·cardia. For 10 points, name this internal process that is regulated by a pacemaker and is measured by taking one's pulse.
The rate of this process is regulated by a 52-residue membrane protein called phospholamban.
heart beat  [or heart  contraction ; or heart  expansion ; or electrical heart  conduction ; or muscle contraction ; or obvious equivalents; accept  systole  or word forms until "systolic" is read; accept  diastole  or word forms until "diastolic" is read; prompt on  pulse  until it is read]