Module Overview

·        Explain the concept of “long-term” regulation of BP

·        Discuss key components in the “long-term” regulation of BP

·        List and describe causes of hemodynamic shock

·        Explain the detrimental effects of hypertension on the heart

·        Explain how chest pains from cardiac causes occur

·        Discuss how the body copes with the challenge of exercise

1. Longer term control of blood pressure involves regulation of total blood volume primarily by the renin-angiotensin-aldosterone system.
2. The state when pressure is too low to sustain adequate tissue perfusion is called circulatory shock – mean blood pressure below 60 mmHg or systolic pressure below 80 mmHg.
3. Compensatory mechanisms occur to defend against a drop in pressure.
4. The state when systolic pressure is greater than 140 mmHg or diastolic pressure greater than 90 mmHg is called hypertension.
5. Hypertension is harmful because it increases the workload of the heart and leads to cardiac hypertrophy and ultimately cardiac failure.
6. Cardiac tissue extracts almost all the oxygen from blood during resting conditions. The only way for cardiac tissue to increase metabolism is to increase blood flow and oxygen delivery.
7. Cardiac myocardial oxygen consumption increases with increase in heart rate, stroke volume, arterial pressure and wall tension.
8. Blood flow through the coronary vessels supplying the left ventricle occur primarily during diastole. An increase in heart rate resulting in a decrease in diastolic time can significantly compromise blood supply in a patient with blocked coronary arteries.
9. Exercise requires a several fold increase of cardiac output to sustain the metabolic requirements of active muscles. The increase in cardiac output is maintained by a decrease in total peripheral resistance.