Outline
• Cardiac Cycle• Cardiac Output– Stroke Volume– Heart Rate
• Fetal Circulation• Blood Vessels• Blood Flow• Blood Pressure• Circulatory System Response to Exercise
Cardiac Output (CO) and Reserve• CO is the amount of blood pumped by each
ventricle in one minute
• CO = HR x SV
Afterload
• The pressure that must be overcome for the ventricles to eject blood
• Can be important in people with high blood pressure because it reduces the ability of the ventricles to eject blood
Chemical Regulation of the Heart
• The hormones epinephrine and thyroxine increase heart rate
• Intra- and extracellular ion concentrations must be maintained for normal heart function
Congestive Heart Failure (CHF)
• Congestive heart failure (CHF), caused by:– Coronary atherosclerosis
– Increased blood pressure in aorta
– Successive myocardial infarcts
– Dilated cardiomyopathy (DCM)
Resistance
• Resistance – opposition to flow – Measure of the amount of friction blood encounters
as it passes through vessels– Generally encountered in the systemic circulation– Referred to as peripheral resistance (PR)
• The three important sources of resistance are blood viscosity, total blood vessel length, and blood vessel diameter
Resistance Factors: Viscosity and Vessel Length
• Resistance factors that remain relatively constant are:– Blood viscosity – thickness or “stickiness” of the
blood – Blood vessel length – the longer the vessel, the
greater the resistance encountered
Blood Pressure (BP)
• Force per unit area exerted on the wall of a blood vessel by its contained blood
Venous Blood Pressure
• Venous BP is steady and changes little during the cardiac cycle
• The pressure gradient in the venous system is only about 20 mm Hg
• A cut vein has even blood flow; a lacerated artery flows in spurts
Control of Blood Pressure
• Affecting Total Peripheral Resistance
• Affecting Cardiac Output– Affecting Stroke Volume– Affecting Heart Rate
• Affecting Total Blood Volume
Circulatory Shock
• Circulatory shock – any condition in which blood vessels are inadequately filled and blood cannot circulate normally
• Results in inadequate blood flow to meet tissue needs
• Three types include:– Hypovolemic shock– Vascular shock– Cardiogenic shock
Thought Question
• What would happen if all of the vessels in your body vasodilated at the same time?
Thought Questions Take Home Exam Extra Credit
• What are some of the methods of treating high blood pressure and how do they affect blood pressure?
• Why do they recommend exercise to decrease high blood pressure?