Circulation and Respiration

1. Circulation and Respiration Chapter 44

2. Open and Closed Circulatory Systems Characteristics of Blood Vessels The Lymphatic System The Fish Heart Amphibian and Reptile Circulation Mammalian and Bird Hearts Cardiac Cycle How Animals Maximize Rate of Diffusion Gills Air-Breathing Animals Amphibians and Reptiles Mammals Birds Structures and Mechanisms of Breathing Outline

3. Open and Closed Circulatory Systems • Open and closed circulatory systems • open - no distinction between circulating fluid and extracellular body fluid • hemolymph • closed - Circulating fluid is always enclosed within blood vessels that transport blood away from, and back to, a pump (heart).

4. Open and Closed Circulatory Systems • Functions of vertebrate circulatory system • Functions in transporting oxygen and nutrients to tissues by the cardiovascular system. • Arteries carry blood away from the heart. • Veins return blood to the heart. • Capillaries carry blood from the arterial to the venous system.

5. Open and Closed Circulatory Systems • Principal functions • transportation • respiratory - erythrocytes transport oxygen to tissue cells • nutritive - absorbed food • excretory- metabolic wastes

6. Open and Closed Circulatory Systems • regulation • hormone transport • temperature regulation • endotherms • counter-current heat exchange - Vessels carrying warm blood from deep within the body pass next to a vessel carrying cold blood from the surface of the body.

7. Countercurrent Heat Exchange

8. Open and Closed Circulatory Systems • Protection • blood clotting • immune defense

9. Blood • Plasma is the matrix in which blood cells and platelets are suspended. • Plasma contains solutes: • metabolites, wastes, and hormones • ions • proteins • albumin • globulins • fibrinogen • serum

10. Blood Cells • Erythrocytes and oxygen transport • hematocrit - fraction of total blood volume occupied by erythrocytes • Erythrocytes develop from unspecialized cells (stem cells). • New erythrocytes are constantly formed in the bone marrow.

11. Blood Cells • Leukocytes defend the body • Less than 1% of the cells in the human body are leukocytes. • granular leukocytes • neutrophils, esinophils, and basophils • nongranular leukocytes • monocytes and lymphocytes

12. Blood Cells • Platelets help blood to clot • Platelets accumulate at an injured site and form a plug by sticking to each other and to the surrounding tissues. • reinforced by threads of protein (fibrin)

13. Blood Clotting

14. Characteristics of Blood Vessels • Blood leaves heart through arteries • Arterioles are the finest microscopically-sized branches of the arterial tree. • Blood from arterioles enters capillaries. • Blood is collected in venules that lead to larger vessels, veins, that carry blood back to the heart.

15. Structure of Blood Vessels

16. Characteristics of Blood Vessels • Arteries and arterioles • Contraction of smooth muscle layer of arterioles results in vasoconstriction which greatly increases resistance and decreases blood flow. • Relaxation of smooth muscle layer results in vasodilation, decreasing resistance and increasing blood flow. • Some organs are regulated by precapillary sphincters.

17. Characteristics of Blood Vessels • Venules and veins • made up of same tissue layers as arteries, but have thinner layer of smooth muscles • Pressure in veins is only about one-tenth that in arteries. • Skeletal muscles surrounding veins can contract to move blood by squeezing the veins. • venous valves

18. One-Way Blood Flow

19. The Lymphatic System • Lymphatic system consists of lymphatic capillaries, lymphatic vessels, lymph nodes, and lymphatic organs. • Excess fluid in the tissues drains into the blind-end lymph capillaries. • Lymph passes into progressively larger vessels with one-way valves. • encounters lymphocytes

20. Evolution of Circulatory and Respiratory Systems • Fish heart • Gills required a more efficient pump. • First two chambers sinus venosus and atrium are collection chambers. • Second two chambers ventricle and conus arteriosus are pumping chambers. • Heartbeat is peristalic sequence.

21. The Fish Heart • Greatest advantage is that the blood passing through the gills is fully oxygenated when it moves into the tissues. • Greatest limitation is that in passing through the gills, blood loses much of its pressure developed by contraction of the heart. • Limits rate of oxygen delivery to the rest of the body.

22. Amphibian and Reptile Circulation • After blood is pumped by the heart through the pulmonary arteries to the lungs, it is returned to the heart via pulmonary veins. • results in two circulations: • pulmonary circulation - between heart and lungs • systemic circulation - between heart and rest of the body

23. Heart and Circulation of a Fish

24. Amphibian and Reptile Circulation • Oxygenated blood from the lungs is kept relatively separate from the deoxygenated blood from the rest of the body due to incomplete divisions within the heart. • Amphibians in water can obtain additional oxygen by diffusion through their skin. • cutaneous respiration

25. Heart and Circulation of an Amphibian

26. Mammalian and Bird Hearts • Mammals, birds, and crocodiles have a four-chambered heart with two separate atria and two separate ventricles. • Right atrium receives deoxygenated blood from the body and delivers it to the right ventricle, which pumps it to the lungs. • Left atrium receives oxygenated blood from the lungs and delivers it to the left ventricle, which pumps the oxygenated blood to the rest of the body.

27. Heart and Circulation of Mammals and Birds

28. The Cardiac Cycle • The heart has two pairs of valves. • Atrioventricular (AV) valves guards the opening between the atria and the ventricles. • right - tricuspid valve • left - bicuspid valve • Semilunar valves guard the exits from the ventricles to the arterial system. • right - pulmonary valve • left - aortic valve

29. The Cardiac Cycle • Valves open and close as the heart goes through the cardiac cycle of rest (diastole) and contraction (systole). • Right and left pulmonary arteries deliver oxygenated blood to the right and left lungs. • Return blood to left atrium via pulmonary veins.

30. Passage of blood through the heart • Superior and inferior vena cavae bring O2-poor blood to the right atrium • Blood flows through tricuspid valve to right ventricle • From right ventricle blood passes through the pulmonary valve to the pulmonary artery • Blood picks up oxygen in the lungs and returns to the heart through the pulmonary veins • Pulmonary veins empty oxygenated blood into the left atrium • Blood flows through the mitral valve to the left ventricle • From the left ventricle blood flows through the aortic valve to the aorta • Aorta carries blood out to the body

31. The Cardiac Cycle • Aorta and all its branches are systemic arteries, carrying oxygen-rich blood from left ventricle to the rest of the body. • Coronary arteries supply the heart muscle itself. • Superior vena cava drains the upper body. • Inferior vena cava drains the lower body. • Empty right atrium and complete systematic circulation.

32. The Cardiac Cycle • Measuring arterial blood pressure • Systolic pressure is peak pressure during ventricular systole. • Diastolic pressure is minimum pressure between heartbeats. • Blood pressure is written as a ratio of systolic over diastolic pressure.

33. Measurement of Blood Pressure

34. Electrical Excitation and Contraction of the Heart • Contraction of heart muscle is stimulated by membrane depolarization. • Depolarization triggered by sinoatrial (SA) node. • Acts as a pacemaker for the rest of the heart by producing depolarization impulses spontaneously at a particular rate.

35. Electrical Excitation and Contraction of the Heart • Atrioventricular (AV) node allows depolarization to pass to the ventricles. • Depolarization is conducted rapidly over both ventricles by atrioventricular bundle (bundle of His). • transmitted by Purkinje fibers

36. Electrical Excitation and Contraction of the Heart • Electrical activity recorded on an electrocardiogram (EKG or ECG). • First peak (P) is produced by depolarization of atria (atrial systole). • Second peak (QRS) produced by ventricular depolarization (ventricular systole). • Last peak (T) produces by ventricular repolarization.

37. Electrical Excitation in the Heart

38. Blood Flow and Blood Pressure • Cardiac output • volume of blood pumped by each ventricle per minute • increases during exercise because of an increase in heart rate and stroke volume • Blood pressure and baroreceptor reflex • Arterial blood pressure depends on two factors: • cardiac output • resistance to flow

39. Blood Flow and Blood Pressure • Baroreceptors detect changes in arterial blood pressure. • Activate sensory neurons that relay information to cardiovascular control centers. • When blood pressure falls, they stimulate neurons causing arteriole to constrict and raise blood pressure.

40. Blood Flow and Blood Pressure • Blood volume reflexes involve effects of four hormones: • antidiuretic hormone • aldosterone • atrial natriuretic hormone • nitric oxide

41. Blood Flow and Blood Pressure • Cardiovascular diseases • Cardiovascular diseases are the leading cause of death in the United States. • insufficient supply of blood reaching one or more parts of the body • angina pectoris - chest pain • heart attacks – MI -blocked arteries • strokes – CVA - interference with blood supply to the brain

42. Blood Flow and Blood Pressure • Atherosclerosis - accumulation within the arteries of fatty materials and various kinds of cellular debris • Arteriosclerosis - hardening of the arteries • occurs when calcium is deposited in arterial walls • Aneurysm- ballooning of a blood vessel • Most often in abdomen or brain • Athersclerosis and hypertension can weaken walls of vessels leading to an aneurysm - Can rupture

43. Atherosclerosis

44. Speno is fine. Joe told me FOD was already lined. Steve • Flow through veins cont’d. • Varicose veins • From weakened valves • Develop due to backward pressure of blood • Phlebitis • Inflammation of a vein • Can lead to blood clots

45. Cardiovascular disorders • Atherosclerosis • Plaque formation in vessels-fats and cholesterol • Interferes with blood flow • Can be inherited • Prevention • Diet high in fruits and vegetables • Low in saturated fats and cholesterol • Plaques can cause clots to form-thrombus • If clot breaks lose from a plaque it becomes a thromboembolism

46. Cardiovascular disorders cont’d. • Stroke, heart attack, and aneurysm • Stroke (CVA)- small cranial arteriole becomes blocked by an embolism and a portion of the brain dies due to lack of oxygen. • Lack of oxygen to brain can cause paralysis or death Warning signs- numbness in hands or face, difficulty speaking, temporary blindness in one eye • Heart attack (MI – Myocardial Infarction)-portion of the heart muscle deprived of oxygen and dies • Angina pectoris-chest pain from partially blocked coronary artery Heart attack occurs when vessel becomes completely blocked • Aneurysm- ballooning of a blood vessel • Most often in abdomen or brain • Athersclerosis and hypertension can weaken walls of vessels leading to an aneurysm Can rupture

47. Cardiovascular disorders cont’d. • Coronary bypass operations • Bypass blocked areas of coronary arteries • Can graft another vessel to the aorta and then to the blocked artery past the point of blockage of blocked coronary arteries. • Gene therapy is sometimes used to grow new vessels

48. Coronary bypass operation • Fig. 12.17

49. Cardiovascular disorders cont’d. • Clearing clogged arteries • Angioplasty • Catheter is placed in clogged artery • Balloon attached to catheter is inflated • Increases the lumen of the vessel • Stents can be placed to keep vessel open • Dissolving blood clots • Treatment for thromboembolism includes t-PA • Converts plasminogen to plasmin • Dissolves clot

50. Angioplasty • Fig. 12.18