One of the differences between a mere accumulation of cells and a tissue or even an organ is that in organized forms (tissue, organ) cells typically communicate with each other. They coordinate their function, growth, and differentiation. In addition to cell adhesion molecules, increted hormones and local mediators, direct intercellular communication via gap junction channels plays a key role i...

Reciprocal beats between sinus node and atrium were studied in isolated rabbit heart tissue by microelectrode techniques. Early premature atrial responses which entered the sinus node frequently emerged to re-excite the atrium as "echoes." When the premature atrial beats discharged some but not all nodal areas, the atrial echoes, in turn, appeared to re-enter the sinus node. Repetitive reciproc...

In cardiac sino-atrial node (SAN) cells, time- and voltage-dependent changes in the gating of various ionic currents provide spontaneous, stable and repetitive firing of action potentials. To address the ionic nature of the species-dependent heart rate, action potentials and membrane currents were recorded in single cells dissociated from the porcine SAN, and compared with those from SAN cells ...

Postural orthostatic tachycardia syndrome (POTS) is characterized by inappropriate increase in heart rate on assuming upright position from a supine position without a necessary drop in blood pressure. Etiology of this condition is complex and multifactorial. Autonomic dysfunction,[1] hypovolemia,[2] hyper responsiveness of beta adrenergic receptors[3] with associated elevations of plasma norep...