Blood pressure

Systemic arterial blood pressure is related to cardiac output and to total peripheral resistance (in turn related to the number and calibre of small arteries and arterioles, and to blood viscosity). Arterial hypertension represents a disproportion between these two components.

Blood pressure comprises: A steady component, the mean arterial pressure, which is related to small arterial and arteriolar resistance. This in turn depends on a combination of neural mechanisms (sympathetic and parasympathetic), hormonal mechanisms (renin-angiotensin-aldosterone mechanism) and local transmitters (nitric oxide), all of which affect arteriolar calibre.

A pulsatile component, the pulse pressure, which depends on arterial stiffness and the timing of reflected waves. It represents the oscillation around mean pressure, extending from systolic to diastolic pressures.

Arterial Blood Pressure r

Cardiac Output

Stroke Volume

Total Peripheral Resistance

Figure 6.1 Determinants of arterial blood pressure.

Determinants of arterial blood pressure

Physical

Blood volume in arterial system Elastic characteristics (compliance)

Physiological

Cardiac output Peripheral resistance

Mean arterial pressure is equal to cardiac output multiplied by total peripheral resistance. Pulse pressure is equal to systolic minus diastolic pressure. It is directly proportional to stroke volume and inversely proportional to compliance. Pulse pressure increases with age due to reduced compliance.

Systolic blood pressure depends on myocardial contractility, the compliance of the great vessels and on diastolic blood pressure. Diastolic blood pressure depends on systemic vascular resistance, peripheral run-off and on heart rate.

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Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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