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The funny current is highly expressed in spontaneously active cardiac regions, such as the sinoatrial node (SAN, the natural pacemaker region), the atrioventricular node (AVN) and the Purkinje fibres of conduction tissue. The funny current is a mixed sodium–potassium current that activates upon hyperpolarization at voltages in the diastolic ...
In the heart's conduction system electrical activity that originates from the sinoatrial node (SAN) is propagated via the His-Purkinje network, the fastest conduction pathway within the heart. The electrical signal travels from the sinoatrial node, which stimulates the atria to contract, to the atrioventricular node (AVN) , which slows down ...
It employs pacemaker cells that produce electrical impulses, known as cardiac action potentials, which control the rate of contraction of the cardiac muscle, that is, the heart rate. In most humans, these cells are concentrated in the sinoatrial (SA) node, the primary pacemaker, which regulates the heart’s sinus rhythm.
This rate can be altered, however, by nerves that work to either increase heart rate (sympathetic nerves) or decrease it (parasympathetic nerves), as the body's oxygen demands change. Ultimately, muscle contraction revolves around a charged atom (ion) , calcium (Ca 2+ ) , [ 3 ] which is responsible for converting the electrical energy of the ...
An increase in sympathetic stimulation to the heart increases contractility and heart rate. An increase in contractility tends to increase stroke volume and thus a secondary increase in preload. An increase in preload results in an increased force of contraction by Starling's law of the heart; this does not require a change in contractility.
This can lead to sustained or tetanic contraction. In the heart, contractions must be spaced to maintain a rhythm. Unlike in muscle, repolarization occurs at a slow rate (100 ms). This prevents the heart from undergoing sustained contractions because it forces the refractory period and cardiac action potential firing to be of the same length of ...
World's Craziest Fools is a clip show made by Roughcut TV for BBC Three, presented by Mr. T.It showcases clips, sometimes viral, of people making themselves look like "Fools" (a reference to Mr. T's catchphrase), often by accident.
Asystole (New Latin, from Greek privative a "not, without" + systolē "contraction" [1] [2]) is the absence of ventricular contractions in the context of a lethal heart arrhythmia (in contrast to an induced asystole on a cooled patient on a heart-lung machine and general anesthesia during surgery necessitating stopping the heart).