Blood is carried from the heart to all of the body's organs and tissues through vessels called arteries. Blood pressure is the pressure of the blood against the walls of these arteries as the heart pumps the blood around the body.
Blood pressure is recorded as two numbers.
The first, larger number is the systolic blood pressure. This is the pressure in the arteries as the heart squeezes out blood during each beat. The second, smaller number is the diastolic blood pressure, which is the pressure in the arteries as the heart relaxes before the next beat. Blood pressure varies all the time to meet your body's needs - from when you get up in the morning, to when you are relaxing, exercising or sleeping. Blood pressure is usually at its highest when we exercise, and lowest when we sleep.