by Gail Belsky. The term sleep disorder may suggest someone tossing and turning all night, but lying awake for hours with insomnia is just one example of many conditions that affect how you sleep and function during the day. In fact, you can have a sleep disorder and not even know it. Next: How long to snooze.
A U wave as seen on ECG. An electrocardiogram of an 18-year-old man showing U waves, most evident in lead V3. The U wave is a wave on an electrocardiogram that is not always seen. It is typically small, and, by definition, follows the T wave. U waves are thought to represent repolarization of the papillary muscles or Purkinje fibers.
SA node What does the ECG wave tracing represent? Electrical activity in the heart What does the ORS complex represent in the ECG wave tracing? Ventricular depolarization Contraction of the atria results from which wave of depolarization on the ECG tracing? P wave Which part of the intrinsic conduction system delays impulse briefly before it moves on to the ventricles?