Diastole refers to relaxation of a heart chamber before and during filling of the chamber Systole refers to contraction of a heart chamber in the process of emptying. Recording of electrical activity of the heart. ECG is altered when heart muscle is damaged or ventricle walls are thickened. T wave represents ventricular repolarization When viewing an electrocardiogram, it can be seen that deflections of the waves whether positive or negative occur occur from a common line known as the isoelectric line. Sounds are repeated for each cardiac cycle.
Second sound is ventricular relaxation and closure of semilunar valves.
Abnormal heart sounds are called murmurs and are usually associated with valve disorders Heart Rate and Its Control Heart rate refers to frequency of cardiac cycles Usually measured as beats per minute Generally, smaller animals have higher heart rates Consequence of metabolic rate and oxygen consumption Larger surface area to body mass ratio in smaller animals Physical conditioning lowers heart rate as a result of cardiac Hypertrophy. Young animals have a higher heart rate than adult animals higher metabolic rate Tonic vagal inhibition is less developed in young animals. Autonomic Nervous System regulates heart rate Sympathetic innervation occurs via efferent fibers from the stellate ganglia of the sympathetic trunk. Increases heart activities Parasympathetic innervation is supplied by fibers from the vagus nerves. Decreases heart activities Heart activities include rate of contraction, force of Contraction, rate of impulse conduction and amount of coronary blood flow.