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In heart pacemaker cells, phase 0 depends on the activation of L-type calcium channels instead of the activation of voltage-gated fast sodium channels, which are responsible for initiating action potentials in contractile (non-pacemaker) cells. For this reason, the pacemaker action potential rising phase slope is more gradual than that of the ...
The section shows: 1) the opened ventricles contracting once per heartbeat—that is, once per each cardiac cycle; 2) the (partly obscured) mitral valve of the left heart; 3) the tricuspid and pulmonary valves of the right heart—note these paired valves open and close oppositely. + (The aortic valve of the left heart is located below the ...
Ectopic beat is a disturbance of the cardiac rhythm frequently related to the electrical conduction system of the heart, in which beats arise from fibers or group of fibers outside the region in the heart muscle ordinarily responsible for impulse formation (i.e., the sinoatrial node).
In another notable Times crossword, 27-year-old Bill Gottlieb proposed to his girlfriend, Emily Mindel, via the crossword puzzle of January 7, 1998, written by noted crossword constructor Bob Klahn. [ 55 ] [ 56 ] The answer to 14-Across, [Microsoft chief, to some] was BILLG, also Gottlieb's name and last initial. 20-Across, [1729 Jonathan Swift ...
A crossword creator might choose to clue the answer SEN (as in the abbreviation for "senator") as "Washington bigwig: Abbr." or "Member of Cong.", with the abbreviation in the clue indicating that the answer is to be similarly abbreviated. [7] The use of "Var." indicates the answer is a variant spelling (e.g., EMEER instead of EMIR), while the ...
Each heartbeat originates as an electrical impulse from a small area of tissue in the right atrium of the heart called the sinus node or sinoatrial node (SA node). The impulse initially causes both atria to contract, then activates the atrioventricular node (AV node) , which is normally the only electrical connection between the atria and the ...
Sinus node dysfunction also known as sick sinus syndrome is a group of irregular heartbeat conditions caused by faulty electrical signals of the heart. When the heart's sinoatrial node is defective, the heart's rhythms become abnormal—typically too slow or exhibiting pauses in its function or a combination, and very rarely faster than normal ...
The heart is the first functional organ in vertebrate embryos. The tubular heart quickly differentiates into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and the sinus venosus. The truncus arteriosus splits into the ascending aorta and the pulmonary trunk. The bulbus cordis forms part of the ventricles.