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Cardiovascular System

Cardiovascular System. Cardiovascular System Components. Circulatory system Pulmonary system Purposes: Transport O 2 to tissues and remove waste Transport nutrients to tissues Regulation of body temperature. Circulatory System. Heart Pumps blood Arteries and arterioles

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Cardiovascular System

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  1. Cardiovascular System

  2. Cardiovascular System Components • Circulatory system • Pulmonary system • Purposes: • Transport O2 to tissues and remove waste • Transport nutrients to tissues • Regulation of body temperature

  3. Circulatory System • Heart • Pumps blood • Arteries and arterioles • Carry blood away from heart • Capillaries • Exchange nutrients with tissues • Veins and venules • Carry blood toward heart

  4. Systemic Circuit Left side of heart Pumps oxygenated blood to body via arteries Returns deoxygenated blood to right heart via veins Pulmonary Circuit Right side of heart Pumps deoxygenated blood to lungs via pulmonary arteries Returns oxygenated blood to left heart via pulmonary veins Pulmonary and Systemic Circuits

  5. Systole Contractile phase of heart Electrical and mechanical changes E.g. blood pressure changes E.g. blood volume changes Diastole Relaxation phase of heart Takes twice as long as systole E.g. resting HR = 60 Systole = 0.3 s Diastole = 0.6 s Cardiac Cycle

  6. Arterial Blood Pressure • Expressed as systolic/diastolic • Normal – 120/80 mmHg • High – 140/90 mmHg • Systolic pressure (top number) • Pressure generated during ventricular contraction • Diastolic pressure • Pressure during cardiac relaxation

  7. Blood Pressure • Pulse Pressure (PP) • Difference between systolic and diastolic • PP = systolic - diastolic • Mean Arterial Pressure (MAP) • Average pressure in arteries • MAP = diastolic + 1/3 (systolic – diastolic)

  8. Electrical Activity of the Heart • Contraction of heart depends on electrical stimulation of myocardium • Impulse is initiated on right atrium and spreads throughout the heart • May be recorded on an ECG

  9. Electrocardiogram • Records electrical activity of the heart • P wave • Atrial depolarization • QRS complex • Ventricular depolarization • T wave • Ventricular repolarization

  10. Diagnostic use of the ECG • ECG abnormalities may indicate coronary heart disease • ST-segment depression may indicate myocardial ischemia

  11. Heart Rate • Range of normal at rest is 50 – 100 b.m • Increases in proportion to exercise intensity • Max. HR is 220 – age • Medications or upper body exercise may change normal response

  12. Stroke Volume • Range of normal at rest is 60 – 100 ml.b • During exercise, SV increases quickly, reaching max. around 40% of VO2 max. • Max. SV is 120 – 200 ml.b, depending on size, heredity, and conditioning. • Increased SV during rhythmic aerobic exercise is due to complete filling of ventricles during diastole and/or complete emptying of ventricles during systole.

  13. Central Circulation Maintenance • Important for older or deconditioned adults • Moderate, continuous, rhythmic aerobic activity encourages venous return • Strenuous activity and held muscle contractions should be avoided • Taper or cool down should follow each activity session to encourage venous return

  14. Frank-Starling Law of the Heart • The heart will pump all the blood returned to it by the venous system. Central circulation must be maintained and the veins must continuously return blood to the heart.

  15. Features that Encourage Venous Return • One-way valves in veins • Vasoconstriction of blood flow to inactive body parts • Pumping action of skeletal muscles in arches of feet, calves, thighs, etc. • Pressure changes in chest and abdomen during breathing • Maintenance of blood volume by adequate fluid replacement • Siphon action of vascular system

  16. Features that Inhibit Venous return • Heat stress requiring additional blood flow to the skin for core temp. maintenance • Dehydration from sweating or from limiting fluid intake (dieting, making weight) • Held muscle contractions that cause blood to pool in the extremities • A Valsalva maneuver which increases pressure in the chest to a high level • Changing from a horizontal to a vertical position abruptly

  17. Sympathetic control Stimulates “fight or flight” response Speeds up heart rate and stroke volume Sympathetic tone > 100 bpm Parasympathetic control Connected to vagus nerves Slows down heart rate Parasympathetic tone 60 – 100 bpm Autonomic Nervous System Control of Heart Rate

  18. Skeletal Muscle Pump • Rhythmic skeletal muscle contractions force blood in the extremities toward the heart • One-way valves in veins prevent backflow of blood

  19. Components of Blood • Plasma • Liquid portion of blood • Contains ions, proteins, hormones • Cells • Red blood cells • Contain hemoglobin to carry oxygen • White blood cells • Platelets • Important in blood clotting • Hematocrit • Percent of blood composed of cells

  20. Oxygen Delivery During Exercise • Oxygen demand by muscles during exercise is many times greater than at rest • Increased oxygen delivery accomplished by: • Increased cardiac output • Redistribution of blood flow to skeletal muscle

  21. Redistribution of Blood Flow • Increased blood flow to working skeletal muscle • Reduced blood flow to less active organs • Liver, kidneys, GI tract

  22. Increased blood flow to skeletal muscle during exercise • Withdrawal of sympathetic vasoconstriction • Autoregulation • Blood flow increased to meet metabolic demands of tissue • O2 tension, CO2 tension, ph, potassium, adenosine, nitric oxide

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