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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]
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.
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 ...
Substrate shortage is one of the causes of metabolic fatigue. Substrates are depleted during exercise or are unable to be metabolized (e.g. metabolic myopathies), resulting in a lack of intracellular energy sources to fuel contractions. In essence, the muscle stops contracting because it lacks the energy to do so.
Chronotropic effects (from chrono-, meaning time, and tropos, "a turn") are those that change the heart rate. Chronotropic drugs may change the heart rate and rhythm by affecting the electrical conduction system of the heart and the nerves that influence it, such as by changing the rhythm produced by the sinoatrial node. Positive chronotropes ...
Ischemia, electrolyte, pH abnormalities, or bradycardia are potential causes of functionally defined re-entry due to changes in the properties of the cardiac tissue's functional core. [2] (No accessory pathway required). For reentry to occur, the path length of circuit should be greater than the wave length (ERP × conduction velocity) of impulse.
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.
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]