Cardiovascular II

Outline

• Cardiac Cycle• Cardiac Output– Stroke Volume– Heart Rate

• Fetal Circulation• Blood Vessels• Blood Flow• Blood Pressure• Circulatory System Response to Exercise

Cardiac Cycle

• Cardiac cycle refers to all events associated with blood flow through the heart

Phases of the Cardiac Cycle

Figure 19.19b

Phases of the Cardiac Cycle

Figure 19.19a

Cardiac Output (CO) and Reserve• CO is the amount of blood pumped by each

ventricle in one minute

• CO = HR x SV

Regulation of Stroke Volume

Factors Affecting Stroke Volume

• Preload

• Contractility

• Afterload

Preload

End Diastolic Volume

Contractility

Figure 12.27

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

Afterload

Regulation of Heart Rate: Autonomic Nervous System

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

Ion Imbalances

• Hypocalcemia

• Hypercalcemia

• Hypernatremia

• Hyperkalemia

Congestive Heart Failure (CHF)

• Congestive heart failure (CHF), caused by:– Coronary atherosclerosis

– Increased blood pressure in aorta

– Successive myocardial infarcts

– Dilated cardiomyopathy (DCM)

Blood Vessels

Generalized Structure of Blood Vessels

Figure 20.1b

Blood Flow

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

Thought Questions

Radius Effects

Figure 12.21

Blood Pressure (BP)

• Force per unit area exerted on the wall of a blood vessel by its contained blood

Systemic Blood Pressure

Figure 20.5

Figure 12.30

Figure 12.31

Capillary Blood Pressure

Figure 12.40

Figure 12.41

Figure 12.47

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

Figure 12.45

Thought Question

Control of Blood Pressure

• Affecting Total Peripheral Resistance

• Affecting Cardiac Output– Affecting Stroke Volume– Affecting Heart Rate

• Affecting Total Blood Volume

Figure 12.53

Baroreceptor Activity

Total Peripheral Resistance Local Control

Local Control

Total Peripheral resistanceNeural & Hormonal Control

Total Peripheral Resistance Summary

Stroke Volume

Heart Rate

Short Term Regulation - Summary

Long Term Regulation

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

Figure 12.56

Figure 12.59

Thought Question

• What would happen if all of the vessels in your body vasodilated at the same time?

Response to Exercise

Figure 12.61

Figure 12.62

Figure 12.63

Figure 12.64

Figure 12.65

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?

Summary

• Cardiac Cycle• Cardiac Output– Stroke Volume– Heart Rate

• Fetal Circulation• Blood Vessels• Blood Flow• Blood Pressure• Circulatory System Response to Exercise