Segment of the ECG produced by depolarization of the atria.

(abbreviation for primary wave) body wave that causes the compression of rocks when its energy acts upon them. When the P wave moves past a rock, the rock expands beyond its original volume, only to be compressed again by the next P wave. P waves are the fastest of all seismic waves. See also S wave.

The first and faster of the body waves which moves by a series of compressions, similar to a sound wave. They can travel through both solid and liquid.

the primary body wave; the first seismic wave detected by seismographs; able to move through both liquid and solid rock; compressional waves, like sound waves, which compress and expand matter as they move through it.

Longitudinal, irrotational, push, pressure, dilatational, primary, compressional, push-pull wave.

A seismic body wave that shakes the ground back and forth in the same direction and the opposite direction as the direction the wave is moving.

Also called primary, longitudinal, irrotational, push, pressure, dilatational, compressional, or push-pull wave. P waves are the fastest body waves and arrive at stations before the S waves, or secondary waves. Their velocity in the crust varies between 5.0 and 7.0 km/s. The waves carry energy through the Earth as longitudinal waves, moving particles in the same line as the direction of the wave. P waves can travel through all layers of the Earth. P waves are generally felt by humans as a bang or thump.

The primary wave or fastest wave travelling away from a seismic event through the rock and consisting of a train of compressions and dilatations of the material.

(1)An intrinsic atrial event. (2) The portion of the ECG representing atrial depolarization.

Earliest wave in electrocardiogram in each cardiac cycle; signals electrical activation of atrial muscle.

A small rounded wave on an electrocardiogram (EKG) that indicates atrial contraction.