When you leap up from bed suddenly, its force causes changes to your blood pressure. Your body normally adapts well to the effect of gravity and other phenomena. The heart and circulatory system regulates itself to either increase or decrease blood pressure to accommodate physical activity, temperature variation and postural changes. Sometimes circumstances hamper your body's ability to detect and react to postural changes, causing dizziness and other symptoms.
Basics
Your heart receives oxygenated blood from your lungs and then pumps the blood out via arteries and capillaries throughout your body. Blood returns to the heart via the venous system or veins and the heart sends the oxygen depleted blood to the lungs for renewal, where the process begins again. When you suddenly get up from lying down, gravity causes blood to pool or collect at the lowest part of your body, your feet.
Healthy Reaction
When blood pools in your lower extremities, less blood returns to your heart, and your blood pressure drops as a result. Ordinarily, sensitive cells called baroreceptors located near your neck arteries and heart pick up on the loss of pressure explains MayoClinic.com. The cells send signals to the heart to pump harder and blood vessels to constrict. When your heart pumps more blood into narrowed arteries, your blood pressure increases and circulation returns to normal.
Problems
Problems arise when conditions prevent your body from adapting to the postural low blood pressure. Positional low blood pressure, or orthostatic hypotension, occurs in healthy people occasionally, usually resulting from dehydration, low blood sugar or even from crossing your legs. When you experience a sudden drop in blood pressure, you feel dizzy and might feel weak and confused, according to MayoClinic.com. Syncope or fainting is the bodies' defense against inadequate blood pressure and blood supply. When you faint, you return to a horizontal position and blood flows with gravity to your brain.
Conditions
Certain conditions interfere with your body's response system to postural blood pressure changes. Your heart fails to respond adequately to drops in blood pressure when you have cardiac problems such as low heart rate or heart failure. Unchecked diabetes also wrecks havoc on blood pressure regulation due to frequent urination and resulting dehydration. Nerve damage from chronic diabetes may disrupt the signals that tell the cardiovascular system to adjust following blood pressure changes. Neurological disorders such as Parkinson's disease also undermine your body's response to changes in blood pressure.
Blood Pressure Measurements
When your physician takes your blood pressure, you should sit upright, with your legs uncrossed, according to the American Heart Association's 2005 guidelines. The doctor should provide support for your cuffed arm, and position it at the level of your heart. When you take your blood pressure at home, follow the same procedures. Doctors compare blood pressure readings of older patients when they sit up and lie down to detect problems with medications or patient health.
