Drop/Add and Withdrawal Deadlines. Registration deadlines determine the last day you are able to add, drop or withdraw from classes. Each class has its own set of registration deadlines which are based on the length of the class as well as the session in which the class is held.
cardiac pacemaker - a specialized bit of heart tissue that controls the heartbeat. SA node, sinoatrial node, pacemaker. cardiac muscle, heart muscle - the muscle tissue of the heart; adapted to continued rhythmic contraction.
Medical Definition of Natural pacemaker Natural pacemaker: The natural pacemaker of the heart is the sinus node, one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood.