HealthKnow

Introduction

The function of the heart is to maintain a constant circulation of blood throughout the body. This is achieved by rhythmic contraction of its muscle. Cardiac cycle is the sequence of events, which occur in the heart during a single beat. The rate of heart is 72 beats per minute. So the time taken for one beat is 0.8 second. So the sequence of events occur every 0.8 second. The cardiac cycle occurs in two phases they are systole and diastole. The systole means a period of contraction and diastole means a period of relaxation.

The cycle of events occurs as follows

1.To start with, blood from the veins fill the two atria, that is superior and inferior vena cava fill the right atrium and the pulmonary veins fill the left atrium.
2. This is followed by a wave of contraction in the atria. This leads to emptying of arterial blood into the respective ventricle.
3. When the ventricles are full, they contract. Now the blood present in ventricles is forced into systemic and pulmonary circulation. At this stage, the semi lunar values guarding the aorta and pulmonary arteries are opened. At the same time, the atrio-ventricular valves are closed. This period of muscular contraction of the heart is called systole.
4. This is followed by a period of rest called diastole. During this period, there is no muscular contraction.
This sequence of events constitutes the cardiac cycle.

Pulse

Pulse is the throbbing sensation felt over the walls of arteries. It is defined as the pressure difference transmitted in the form of a wave over the arterial walls. Pulse rate is almost the same as heart rate monitor 60 to 80 minute. The wrist is the common site where pulse is usually felt. At this site, the radial artery is very superficial. This pulse is called as radial pulse. Other arteries where pulse can be felt are carotid artery, facial artery and temporal artery. In case of fever, the rate of pulse increases at the rate of ten per every rise of one degree Fahrenheit. Generally veins do not exhibit pulsation. The only vein that exhibits pulsation is jugular vein, which is nearer to heart.

Electrocardiogram

It is the recording of electrical activity of the heart. Electrocardiograph is the instrument, which is used to record the electrical current generated in the heart. By means of this instrument, the electrical current generated in the heart is conducted to remote parts of the body. The heart current can be recorded by connected any two parts of the body with this instrument. This connection is called as leads.