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Circulation

Circulation. Chapters 13 and 14. Circulatory System. Transportation nutrients, metabolic wastes (excretion), water, ions and respiratory gases (O 2 , CO 2 ), Regulatory hormonal – transportation of hormones from endocrine glands to target tissues

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Circulation

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  1. Circulation Chapters 13 and 14

  2. Circulatory System • Transportation • nutrients, metabolic wastes (excretion), water, ions and respiratory gases (O2, CO2), • Regulatory • hormonal – transportation of hormones from endocrine glands to target tissues • temperature – blood shunting to conserve or dissipate heat through the skin • Protection • blood clotting – protects against blood loss • immunity – leukocytes protect against disease

  3. Subdivisions • Cardiovascular system • heart and blood vessels • transport blood • Lymphatic system • lymph vessels and lymphoid tissues (spleen thymus, tonsils and lymph nodes) • transport lymph

  4. Cardiovascular System • Blood • transport medium (cells suspended in fluid) • Heart • pump: forces blood through BV’s • Blood vessels • tubing that carries blood (60,000 miles)

  5. Blood • Transport medium for gases, nutrients, wastes etc. • Volume • Women = 5 liters • Men = 5.5 liters • Blood is composed of: • Plasma (55% of blood volume) • fluid portion • Formed Elements (45%) • cells and cell fragments Fig 13.1

  6. Plasma • Water (90%) • dissolves materials (gases, nutrients, etc.) • acts as fluid medium for transport of blood cells and plasma proteins • Proteins (7-9%) • Maintain osmotic pressure of blood (albumins) • Lipid transport (globulins) • Immunity (antibodies, complement proteins) • Clotting factors • Various enzymes

  7. Formed Elements • Erythrocytes • Red Blood Cells • Leukocytes • White Blood Cells • Thrombocytes • Platelets Fig 13.3

  8. Erythrocytes • thin, disc-like cells • 25-30 trillion RBCs circulating at a given time • Lack nuclei and mitochondria • anaerobic respiration only • transport respiratory gases (mainly O2) Fig 13.3

  9. Erythrocytes • RBCs contain Hemoglobin • protein with 4 heme units • heme contains iron • reversibly binds O2 • Hemoglobin changes color when bound to O2 • unbound - dark maroon • bound - bright red Fig 16.33

  10. Leukocytes • Immunity • ability to resist or destroy harmful foreign invaders or abnormal cells • Functions • destroy pathogens • bacteria, viruses, protozoans and worms • destroy cancer cells • remove dead or injured cells • wound healing

  11. Leukocyte Types • Granulocytes • cytoplasmic granules • eosinophils • enhance allergic conditions chemically attack parasites (worms) • basophils / mast cells • promote inflammation response • neutrophils • phagocytes (devour pathogens and dead cells) Fig 13.3

  12. Leukocyte Types • Agranulocytes • no cytoplasmic granules • monocytes • circulating phagocytes • differentiate into macrophages in tissues • lymphocytes • found mainly in lymphatic system • specific immune responses • B Lymphocytes - produce antibodies • T Lymphocytes - destroy virally infected or cancerous cells Fig 13.3

  13. Platelets (Thrombocytes) • cell fragments from megakaryocytes in myeloid tissue • contain actin and myosin (contraction) • Formation of a blood clot to stop bleeding Fig 13.3

  14. Blood Clot Formation • platelets touch underlying collagen in connective tissue • secrete chemical messengers and “glue” • messengers induce vasoconstriction • decrease blood flow to damaged vessel • formation of platelet plug • platelets stick to collagen and to each other

  15. Blood Clot Formation • enzymatic cascade of clotting factors occurs • prothrombin (inactive enzyme)  thrombin (activated enzyme) • catalyzes fibrinogen (soluble)  fibrin (insoluble) • forms protein meshwork over the platelet clot • platelets contract to seal the breach Figs 13.7, 13.8

  16. The Heart • hollow, muscular organ • located in center of thoracic cavity • pumps constantly • variable rate Fig 13.10

  17. Blood Circuits • Pulmonary circuit • from heart (rt)  lungs  heart (left) • gas exchange with atmosphere • release CO2, pick up O2 • Systemic circuit • from heart (left)  tissues  heart (rt) • gas exchange with tissues • release O2, pick up CO2 Fig 13.9

  18. Heart Anatomy:Chambers • Four chambers • Atria (auricles) • receive blood from veins • Ventricles • pump blood into arteries Fig 13.10

  19. Cardiac Muscle • found in myocardium • striated (sarcomeres) • single nucleus in cells • fibers linked by intercalated disks • electrical synapses • allow linked fibers to contract as a unit • Atrial and ventricular fibers not linked by intercalated disks • allows atria and ventricles to contract separately Fig 12.31

  20. Heart Anatomy:Interventricular Septum • Interventricular septum • divides heart into two halves • Right side pumps deoxygenated blood • Left side pumps oxygenated blood Fig 13.10

  21. Heart Anatomy - Valves • Atrioventricular valves • Right (tricuspid) • Left (bicuspid) • Allow blood to flow from atrium to ventricle only • Chordae tendinae attached to papillary muscles • prevent valves from everting during ventricular contraction Fig 13.10

  22. Heart Anatomy - Valves • Semilunar valves • Pulmonary (Right) • Aortic (Left) • at openings of the arteries leaving the ventricles • prevent backflow of blood during ventricular relaxation Fig 13.10

  23. Blood Flow Through the Heart • Deoxygenated blood enters right side through vena cavae • right atrium • right AV valve • right ventricle • pulmonary semilunar valve • pulmonary artery • lungs (pulmonary circuit) Fig 13.9, 13.10

  24. Blood Flow Through the Heart • Oxygenated blood enters left side through pulmonary veins • left atrium • left AV valve • left ventricle • aortic semilunar valve • aorta • tissues (systemic circuit) Fig 13.9, 13.10

  25. Cardiac Cycle • contraction (systole) + relaxation (diastole) of ventricles • lasts 0.8 sec (based on 72 beats/min) Fig 13.12

  26. Cardiac Cycle - Blood Volumes • End-diastolic volume • amt of blood in ventricles at end of diastole • End-systolic volume • amt of blood in ventricles at end of systole • ~1/3 of end-diastolic vol. • Stroke volume (SV) • Amt of blood ejected by ventricles • Equal to EDV – ESV Fig 13.13

  27. Cardiac Cycle - Heart Sounds • “lub” = closing of the AV valves • “dub” = closing of the semilunar valves Fig 13.13

  28. Cardiac Excitation • Heart is generates its own APs • Pacemaker cells • undergo spontaneous depolarizations during diastole • pacemaker potentials • (-60mV  -40mV) Fig 13.17

  29. Pacemaker Potentials • Begins to depolarize due to hyperpolarization of membrane to near -60 mV • “Funny channels” – open in response to hyperpolarization • Allow Na+ and K+ to flow (depolarize) • Triggers opening of “slow” Ca2+ channels (further depolarization) • Reaches threshold for other v.g. Ca2+ channels (“fast channels”) • Ca2+ flows in • rapid depolarization and overshoot • Repolarized by opening of v.g. K+ channels and outflow of K+. Fig 13.17

  30. Pacemakers • Sinoatrial (SA) Node • pacemaker of the heart • Atrioventricular (AV) Node • Delays conduction to ventricles • Bundle of His • conducts signal through interventricular septum • Purkinje fibers • conduct signal up lateral walls of ventricle Fig 13.19

  31. Path of Cardiac Excitation • SA node cells produce APs • Atrial fibers activated • atrial contraction • APs excite AV node • delay (complete atrial contract) • APs of AV node travel down AV bundle to apex of heart • signal conducted to Purkinje fibers throughout ventricles • Myocardial fibers activated • ventricular contraction Fig 13.19

  32. Myocardial Action Potentials • Prolonged action potential duration • Influxof Na+ - depolarization • Plateau phase due to Ca2+ influxand slow opening of K+ channels • Repolarization by delayed opening of v.g. K+ channels • Prolonged refractory period ensures pumping action Fig 13.18, 13.20

  33. Cardiac Output • Amount of blood pumped by the heart in one minute • heart rate (beats/min) X stroke volume (ml) • At rest, HR = 70 bpm, SV = 70-80 ml • Cardiac Output = 5.0 - 5.5 L/min • Heart pumps entire blood volume each min. • During exercise can increase 4-5x to 25 liters/min.

  34. Heart Rate Regulation • Parasympathetic nervous system • Slows HR • Sympathetic nervous system • Speeds up HR • Hormones (Epinephrine) Fig 14.1

  35. Stroke Volume Regulation • end-diastolic volume • ↑EDV, ↑SV • function of venous return • total peripheral resistance • ↑Resistance, ↓SV • Function of blood vessel diameter

  36. Stroke Volume Regulation • contractility • function of sarcomere length in muscle fibers • sympathoadrenal stimulation (↑ Ca2+ concentrations) Figs 14.2, 14.3

  37. Blood Vessels • Tubes that conduct blood • Arteries • Aterioles • Capillaries • Venules • Veins Fig 13.25

  38. Blood Pressure • Pressure blood exerts on blood vessel walls • produced by heart contractions • main driving force for the flow of blood through the blood vessels • decreases as blood moves further from the heart Fig 14.15

  39. Arteries • Large vessel receiving blood from the heart • Functions • rapid transport of blood • large radius, high pressure • pressure reservoirs • walls expand upon systole • recoil during diastole maintains blood flow Fig 13.25

  40. Arterial Blood Pressure • Systolic blood pressure • pressure of blood in arteries during ventricular systole • Diastolic blood pressure • pressure of blood in arteries during ventricular diastole • Indicates • blood flow to the body • work load of the heart Fig 14.15

  41. Arterial Blood Pressure Regulation • Blood pressure monitored by baroreceptors in carotid sinuses and aorta • Signals sent to medulla • cardiac + vasomotor centers • response sent out via autonomic MNs • sympathetic -  HR, vasoconstriction • parasympathetic -  HR, vasodilation Figs 14.25, 14.26

  42. Arterioles • Major resistance vessels •  fluctuations in blood pressure btw systole & diastole • Control of perfusion • smooth muscle in vessel walls under autonomic control • vasoconstriction •  diameter,  blood flow • vasodilation •  diameter,  blood flow Figs 13.25, 14.15

  43. Capillaries • Single endothelial cell layer • Connect arterioles to venules • Exchange of materials between blood and interstitial fluid Fig 13.25

  44. Properties of Capillaries • Short diffusion distance • thin capillary walls • narrow diameter • High surface area • extensive branching (close to all cells) • Slow blood flow • increases time for diffusion to occur Fig 14.24

  45. Ultrafiltration • Blood passing through capillaries undergoes ultrafiltration • Blood pressure causes plasma fluid to be pushed out (proteins remain) • As fluid is pushed out, blood osmotic pressure increases • Fluid drawn back into the capillaries when osmotic pressure exceeds blood pressure • More fluid forced out than pulled in Fig 14.9

  46. Venules and Veins • Return blood to the heart after exchanging materials in capillaries • Hold most of the blood in the body • capacitance vessels • regulate rate of blood return to the heart Fig 13.25

  47. Venous Return Venous return • amt of blood veins deliver back to the heart Factors influencing return • pressure gradient • mean pressure is low • vein walls are highly elastic • large radii of veins - little resistance • modified by vasoconstriction

  48. Venous Return • Venous Valves • prevent backflow of blood • Skeletal Muscle Activity • contraction acts to “pump” veins • increases venous return with increased activity Fig 13.28

  49. Lymphatic System • Blood passing through capillaries undergoes ultrafiltration • Net loss of fluid from the blood • Must be returned to the blood Figs 14.9, 14.10

  50. Lymphatic System • Network of vessels • picks up lost fluid (lymph) and returns it to circulation • Pass through lymph nodes • Immune functions • Vessels deposit lymph into subclavian veins Figs 13.34, 13.36

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