Some terms Related to Circulatory System | Zoology Class 12

Biology | Zoology
HSEB Notes on Circulation
Class : 12

Some terms related to Circulation system of Heart

Heart beat

Heart beat consists of one contraction phase and one relaxation phase. During the contraction phase, there is maximum point(peak period) which is known as systole. During the relaxation phase also, there is minimum point which is known as diastole. One heart beat is completed in about 0.8 second time. 

Cardiac cycle

Cardiac cycle is the sequence of events during one heart beat. It consists of three phases.

• Atrial systole – the two atria contract simultaneously pumping blood into the respective ventricles. It lasts for 0.1 second.
• Ventricular systole - the two ventricles also contract pumping out the blood to the lungs and whole parts of body. It lasts for 0.3 second.
• Joint diastole - all four chambers of heart under go relaxation. At this time, both atria are filled with blood. It lasts for 0.4 second.

Stroke volume 

It is the volume of blood pumped out in every heart beat. It comes to be about 70 ml of blood. It is denoted by SV.

Heart rate 

It is the number of heart beats per minute time. In the normal adult, it is about 70 to 80 times. In an average, it comes to be 72 times. This is called heart rate. It is denoted by HR.

Cardiac output

It is the volume of blood pumped out in one minute time. It is given by the product of stroke volume and heart rate. It is denoted by CO

CO=SV*HR

Heart sounds

The first heart sound is lubb. It is produced due the sharp closing of atrioventricular valves like the bicuspid and tricuspid valves. At the beginning of ventricular systole, these valves are closed. 

The second heart sound is dup. It is produced due the closing of semilunar valves at the end of the aortic arch and pulmonary aorta. It occurs at the end of ventricular systole. 

Blood pressure

It is a force exerted by blood against the wall of arteries, veins and capillaries. It is called BP in short. It is of two types. Systolic blood pressure is maximum pressure during contraction. Diastolic blood pressure is minimum pressure during the relaxation. The systolic and diastolic blood pressure of a normal adult is 120/80 mm of Hg. The range of systolic blood pressure is 100 to 140. 100 is lower limit and 140 is upper limit. The range of diastolic blood pressure is 55 to 80.

Don't forget to Like and Share it. Please Join with us on Facebook and Google+ for daily notes.