Blood Pressure

Blood Pressure is the pressure exerted by the blood at right angles to the walls of the blood vessels. Unless indicated otherwise, blood pressure refers to systemic arterial blood pressure, i.e., the pressure in the large arteries delivering blood to body parts other than the lungs, such as the brachial artery (in the arm). The pressure of the blood in other vessels is lower than the arterial pressure. Blood pressure values are universally stated in millimetres of mercury (mmHg). The systolic pressure is defined as the peak pressure in the arteries during the cardiac cycle; the diastolic pressure is the lowest pressure (at the resting phase of the cardiac cycle). The mean arterial pressure and pulse pressure are other important quantities.

Typical values for a resting, healthy adult human are approximately 120 mmHg systolic and 80 mmHg diastolic (written as 120/80 mmHg), with large individual variations. These measures of blood pressure are not static, but undergo natural variations from one heartbeat to another or throughout the day (in a circadian rhythm); they also change in response to stress, nutritional factors, drugs, or disease.

The function of the heart is to circulate blood around the body. The heart comprises of four chambers:

Right Atrium

Left Atrium

Right Ventricle

Left Ventricle

Functionally the heart comprises of two pumps:

The right atrium receives blood from the body (de-oxygenated blood) and the right ventricle pumps it into the lungs for aeration (removal of carbon dioxide and add oxygen).

The left atrium receives the oxygenated blood from the lungs and the left ventricle pumps it around the body.

Blood Pressure

The cardiac cycle (heart beat) consists of cardiac muscle contraction (systole) and cardiac muscle relaxation (diastole).

Blood pressure represents the force (pressure) exerted by blood against the arterial walls during a cardiac cycle. Systolic blood pressure, the higher of the two pressure measurements, occurs during ventricular contraction (systole) as the heart pumps blood into the aorta.

After systole, the ventricles relax (diastole), arterial pressure declines and the heart refills with blood. The lowest pressure reached during ventricular relaxation represents the diastolic blood pressure.

Normal systolic blood pressure in an adult varies between 110 and 140 mm Hg, and diastolic pressure varies between 60 and 90 mm Hg.

Blood Pressure ClassificationSystolic(mm Hg) Diastolic(mm Hg)

Classification

Heart Rate

The resting heart rate for the average person is between 70 and 90 beats per minute (bpm). The term tachycardia is applied to a rapid heart rate (over 100 bpm) and the term bradycardia indicates a slow heart rate (less than 50 bpm). Endurance athletes may have a resting heart rate of less than 50 bpm.

Cardiac Output

This is the amount of blood pumped from your heart and is calculated by multiplying heart rate by stroke volume (the amount of blood ejected by the heart in each beat). An athlete will have a lower resting heart rate and a larger stroke volume than a non-athlete. The cardiac output for an athlete is approx. 35 litres while that for the non-athlete is 22 litres.
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