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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 ...
during contraction, actin filaments move into the A bands and the H zone is filled up reducing its stretch, the I bands shorten, the Z line comes in contact with the A bands; and; the possible driving force of contraction is the actin-myosin linkages which depend on ATP hydrolysis by the myosin.
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.
Depiction of smooth muscle contraction. Muscle contraction is the activation of tension-generating sites within muscle cells. [1] [2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [1]
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.
An important property that is unique to the AV node is decremental conduction, [12] in which the more frequently the node is stimulated the slower it conducts. This is the property of the AV node that prevents rapid conduction to the ventricle in cases of rapid atrial rhythms, such as atrial fibrillation or atrial flutter.
Adenosine is an endogenous extracellular messenger that can regulate myocardial oxygen needs. [ 3 ] [ 17 ] It acts through cellular surface receptors which effect intracellular signalling pathways to increase coronary artery blood flow, slow heart rate, block atrioventricular node conduction, suppress cardiac automaticity , and decrease β ...