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Adenosine is a key factor in regulating the body's sleep-wake cycle. [40] Adenosine levels rise during periods of wakefulness and lowers during sleep. Higher adenosine levels correlate with a stronger feeling of sleepiness, also known as sleep drive or sleep pressure. [41]
Multiple slow pathways can exist so that both anterograde and retrograde conduction are over slow pathways. ("slow-slow" AVNRT).Because the retrograde conduction is via the slow pathway, stimulation of the atria will be delayed by the slow conduction tissue and will typically produce an inverted P wave that falls after the QRS complex on the ...
This makes adenosine a useful medication for treating and diagnosing tachyarrhythmias, or excessively fast heart rates. This effect on the A 1 receptor also explains why there is a brief moment of cardiac standstill when adenosine is administered as a rapid IV push during cardiac resuscitation.
The A 1, together with A 2A receptors of endogenous adenosine play a role in regulating myocardial oxygen consumption and coronary blood flow. Stimulation of the A 1 receptor has a myocardial depressant effect by decreasing the conduction of electrical impulses and suppressing pacemaker cell function, resulting in a decrease in heart rate.
Calcium channel blockers such as verapamil and diltiazem have a longer half-life compared to adenosine. Although these blockers are safe when administered slowly, adenosine is considered safer and particularly useful in cases where an electrocardiogram does not provide clear information.
If the patient is stable, adenosine may be used for restoration of sinus rhythm in patients with macro-reentrant supraventricular tachycardias. It causes a short-lived cessation of conduction through the atrio-ventricular node breaking the circus movement through the node and the macro-reentrant pathway restoring sinus rhythm.
The cardiac myocyte has two general types of action potentials: conduction system and working myocardium. The action potential is divided into 5 phases and shown in the diagram. The sharp rise in voltage ("0") corresponds to the influx of sodium ions, whereas the two decays ("1" and "3", respectively) correspond to the sodium-channel ...
Such channels are important parts of the electrical conduction system of the heart and form a component of the natural pacemaker. First described in the late 1970s in Purkinje fibers and sinoatrial myocytes , the cardiac pacemaker "funny" (I f ) current has been extensively characterized and its role in cardiac pacemaking has been investigated.