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Understanding the Heart and Circulatory System

Explore the components of the transport system in the body, including the heart, blood vessels, and types of circulation. Learn about the structure of the heart, its functions, and how it nourishes itself. Delve into the cardiac cycle, blood composition, blood vessels, and blood pressure. Understand coronary heart disease, heartbeat control mechanisms, and the cardiac cycle in detail.

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Understanding the Heart and Circulatory System

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  1. Topic 6.2 + Option H5 Transport System • IB Biology

  2. Components of Transport System • Blood • Heart • Blood Vessels

  3. Types of Circulation • 1) Pulmonary • heart – lungs – heart • 2) Systemic • heart – body – heart

  4. Types of Circulation • 3) Coronary • blood vessels that supply heart muscle with oxygen and nutrients / remove waste products

  5. Heart Structure • 2 sides with different functions: • right: to receive + pump blood to the lungs • left: to receive + pump blood to the body • 2 types of chambers: atrium + ventricle • 4 chambers: 2 atria/2 ventricles • Cardiac muscle: involuntary • Ultimate control: • Autonomic Nervous System (ANS)

  6. Heart Valves • Allow blood to flow in only one direction • Four valves • Atrioventricular valves – between atria and ventricles • Bicuspid valve (left) • Tricuspid valve (right) • Semilunar valves between ventricle and artery • Pulmonary semilunar valve • Aortic semilunar valve

  7. Vessels of the heart • Aorta • Leaves left ventricle • Pulmonary arteries • Leave right ventricle • Vena cava • Enters right atrium • Pulmonary veins (four) • Enter left atrium

  8. Blood in the heart chambers does not nourish the myocardium • The heart has its own nourishing circulatory system • Coronary arteries • Cardiac veins • Blood empties into the right atrium via the coronary sinus

  9. Heart contractions

  10. The Heart: Cardiac Cycle • Atria contract simultaneously • Atria relax, then ventricles contract • Systole = contraction • Diastole = relaxation • Cardiac cycle – events of one complete heart beat • Mid-to-late diastole – blood flows into ventricles • Ventricular systole – blood pressure builds before ventricle contracts, pushing out blood • Early diastole – atria finish re-filling, ventricular pressure is low

  11. Blood • Plasma – fluid • Red blood cells or erythrocytes – produced in the bone marrow of large bones / transport O2 and CO2 • White blood cells (lymphocytes and phagocytes) – produced in the bone marrow / belong to immune system • Platelets - cell fragments that help blood clotting

  12. (antibodies) urea + HEAT

  13. Blood Vessels • Arteries • carry blood Away from heart; strong thick walls; smooth muscle (elastic); fibrous coat; small lumen = ↑ pressure • Veins • carry blood back to heart; large lumen; thin wall/muscle; ↓ elastic; valves • Capillaries • connect arteries and veins; no valves; pores; no muscle/not elastic extremely thin (1 cell thick) = fast exchange

  14. Blood Pressure • Blood applies pressure to the walls • If it is too low - cells might not get enough O2 • If it is too high - vessels can rupture (heart attack, stroke) • Salt can increase blood pressure • Normal blood pressure: 120/80 mm Hg

  15. Coronary Heart Disease • Slow build up of plaque (lipids, cholesterol) = ATHEROSCLEROSIS • Arteries become harder, less flexible • Less space for blood • Coronary arteries supply O2 to heart cells • Thrombosis = clot = heart attack = heart cells die • Factors affecting coronary heart disease (CHD): • Age, race, heredity, gender, cholesterol levels, blood pressure, obesity, diabetes, smoking, sedentary lifestyle, stress

  16. Heartbeat Control • Myogenic muscle contraction: • Sino-Atrial Node (SA) – specialized cells generate electrical impulse on their own with regular frequency (PACEMAKER) • Impulse spreads to both atria → atria contract together • Atrio-Ventricular node (AV) picks up the impulse in lower right atrium septum and conduces to the ventricles through fibers • Ventricles contract: AV valves close / semi-lunar valves open (SYSTOLE) • Contraction stops – ventricles relax (DIASTOLE)

  17. Heartbeat Control • Autonomic Nervous System and hormones can modify myogenic rhythm: • Nerves from brain stem (medulla) have involuntary control over heart rate = affect SA node • Exercise = ↑CO2 / ↓O2 = medulla oblongata (brainstem) takes over • Chemoreceptors detect ↑CO2 = H+ causes decrease in pH • Adrenaline targets sino-atrial node (SAN): stimulant

  18. Cardiac Cycle • One whole heartbeat • Systole = contraction / Diastole = relaxation • Valves prevent backflow • Sound = valves closing • 1st = atrio-ventricular valves (mitral, tricuspid) • 2nd = semilunar valves (aortic, pulmonary) • Important = valves open and close depending on pressure inside chambers/blood vessels • Atria systole = pressure not too great (thin walls, most blood already moved to ventricles) • Ventricular systole = pressure great inside both ventricles

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