Blood Pressure Part 1

Study Notes

Definitions: Blood pressure is the force exerted by blood against the walls of arteries.
Systole: The period of heart muscle contraction.
Systolic Blood Pressure: The peak maximum pressure in arteries when the left ventricle pumps blood into the aorta.
Diastole: The period of heart muscle relaxation.
Diastolic Blood Pressure: The peak minimal pressure exerted on artery walls when the heart is relaxed.
Standard Unit: Millimeters of mercury (mmHg) is used to measure blood pressure.

Normal Range: 120/80 mmHg ± 20 mmHg (systolic) and ± 15 mmHg (diastolic).
Pulse Pressure: Difference between systolic and diastolic pressure (e.g., 40 mmHg).
Hypertension: Persistent blood pressure readings above 140/90 mmHg.
Hypotension: Blood pressure readings below 100/65 mmHg.

Interrelationships: Blood pressure depends on a combination of factors.
Factors:
- Cardiac output
- Peripheral resistance
- Blood volume
- Viscosity
- Elasticity

Definition: Volume of blood pumped by the heart per minute.
Formula: Heart rate (HR) x Stroke volume (SV)
Relationship to BP: Cardiac output is a factor in determining blood pressure.

Definition: Resistance to blood flow in the arteries and arterioles.
Mechanism: Smooth muscle in the artery walls adjusts the size of the lumen to control blood flow.
Relationship to BP: Peripheral resistance influences blood pressure.

Definition: Amount of blood circulating in the vascular system.
Normal Value: Approximately 5000 ml in most adults. Generally remains constant.
Effect on BP: Changes in blood volume can affect blood pressure.

Definition: Thickness of blood.
Factor: Primarily determined by hematocrit (percentage of red blood cells in blood).
Effect on BP: Blood viscosity affects how easily blood flows through vessels.

Definition: Ability of artery walls to stretch and recoil.
Mechanism: Artery walls stretch when blood pressure increases, then recoil to maintain pressure.
Significance: Arterial elasticity helps to maintain a stable blood pressure.