Blood Pressure

What is Blood Pressure? Blood Pressure is the force that blood exerts against the vessel walls.

Blood Exerts Forces on Vessel Wall As blood moves forward, it exerts an outward force on the vessel walls. Note the inner lining is called the intima, which should normally be a very smooth, laminar surface. Smoking and high blood pressure damages or “roughs up” the intima, making it easier for fats to begin to accumulate. The cross sectional diameter, or opening is called the LUMEN.

BP is the result of two forces: The first force is when the heart pumps bloods into the arteries and through the circulatory system. The second is resistance to blood flow by the arteries as smooth muscles in their walls dilate (relax; get larger) and constrict (contract; get smaller)

Vasoregulation The changing of the lumen (opening) size of a blood vessel; regulated by smooth muscle in the walls

Vasodilaton During Vasodilation, smooth muscle in blood vessel walls relax, reducing resistance to flow. Blood pressure is lowered. Vasodilation occurs near skin when it is hot to release heat and during exercise to allow blood to flow easier.

Vasoconstriction During vasoconstriction, smooth muscles in blood vessel walls contract, increasing resistance to flow. Blood pressure increases. Vasconstriction in blood vessels. next to skin to conserve heat. Caffeine and Nicotene are powerful “vasoconstrictors

Cardiac Cycle The cardiac cycle has two phases, the heart is either working or resting. Systole “the work phase” where the heart muscle contracts Diastole “the rest phase” where the heart muscle relaxes The cardiac cycle alternates: Systole, Diastole, Systole, Diastole…

Cardiac Cycle Have student hold hand over head and repeatedly make a fist and relax, saying work, rest, work, rest, then systole, diastole, systole, diastole.

Systolic BP During systole, blood is forced into the arterial system, and the pressure rises. The peak pressure during systole is called the systolic blood pressure.

Diastolic BP During diastole, the heart relaxes and the pressure falls. The pressure within your vessels during the diastole is called your diastolic BP.

Blood Pressure Curve During systole the heart muscle contracts (arrows) forcing blood into the arterial side causing an increase in BP. This peak pressure is called your systolic BP, the pressure during the work phase. In this example, what is the systolic BP? (110) When the heart muscle relaxes during diastole, the pressure drops. The pressure within your vessels during rest is your diastolic BP. What is the diastolic BP? (60)

How is BP recorded? BP is recorded as a ratio. The systolic BP, or “pressure during the work phase” is recorded in the numerator. 110 The diastolic BP is, or “pressure during the rest phase” is recorded in the denominator. 60 Ex: 110/60 mmHg

How is BP measured? BP is measured with a sphygmomanometer (blood pressure cuff) and stethoscope.

Normal BP Reponses to Exercise It is normal for systolic BP to increase during exercise, linear with heart rate. The diastolic BP remains the same or possible drops a little.

BP Responses to “Breath-holding” Avoid ‘Breathholding” during exercise such as lifting. This causes a “rise” in your diastolic blood pressure, causing blood vessels in the chest to “collapse” making blood return difficult. These high diastolic pressures could cause a weak vessel in the brain to “rupture” resulting in a stroke.