Circulation

1. Circulation

2. What is Circulation? • Tranpsort • Exchange must take place at cellular level • All cells must have access to an aqueous environment • Unicellular vs Multicellular • Circulation connects aqueous environment of cell to exchange organs • Gases, absorb nutrients, & dispose of wastes

3. Simple Circulation • GVC – no true circulation system • Cnidarians - Digest & distributeInner & outer layers bathed in fluids

4. Advanced Circulatory Systems • 3 basic components of Circulatory System • Circulatory Fluid • Set of Tubes • Muscular Pump • Pump forces fluid through tubes • Muscular heart pumps specialized fluid (such as blood) through tubular vessels • Blood or blood alternative • Carries O2 and nutrients to body tissues • Carries away CO2 and wastes

5. Open Circulatory System • Arthropods & Molluscs • No distinction between blood & interstitial fluid • HEMOLYMPH • Interconnected system of sinuses & spaces around organs for exchange • Heart is dorsal, elongated • Less energy to build & maintain; but Less effective, slowest M.R.

6. Closed Circulatory System • Earthworms, Cephalopods, & Vertebrates • Blood confined to vessels & separate from Interstitial Fluid • 1 or more hearts pump into large vessels that branch into smaller ones through organs • Exchange occurs between IF & Blood • High energy cost; more effective & supports higher metabolism

7. Focus on Vertebrate Circulation • Evolved from a heart w/ 2 chambers, 1 circuit to a double heart w/ 2 circuits • pulmonary and systemic • Vertebrate heart 1 or 2 atria & 1 or 2 ventricles • Vessels • Arteries – carry away; smallest unit - Arteriole • Capillaries – porous exchange points; arranged in beds • Veins – return to heart; smallest unit - Venule • Higher Metabolic Rate = More Complex Cardiovascular rate

8. Fish, Amphibians, Reptiles

9. Mammals and Birds • Complete division of R& L sides • Left receives & pumps only O2 rich • Right receives & pumps O2 poor • Supports endothermy • 10x as much energy & food as ectothermy

10. Double Circulation

11. Mammalian Heart • A four-chambered pump • Two atria at top • Two ventricles at bottom • Atrioventricular (AV) valves • Semilunar (SL) valves • Blood is pumped into two separate circuits • Pulmonary circuit (right heart) • Systemic circuit (left heart

12. Mammalian Heart - Valves • Connective tissue that prevents backflow & keep blood moving 1-way • Control blood flow leaving heart; 1 way doors • Forced open by pressure generated by ventricle • Close when chamber is relaxed

13. Cardiac Cycle • Systole–diastole sequence is the cardiac cycle • Systolic pressure • Contraction of ventricles pushes blood into arteries at peak pressure • Diastolic pressure • Between contractions, blood pressure in arteries falls to a minimum pressure • Neurogenic hearts (in some crustaceans) • Beat under control of nervous system • Myogenic hearts (all other animals) • Contractions initiated within the heart

14. Cardiac Cycle • Contraction of atria is initiated by signals from the sinoatrial (SA) node (pacemaker cells) • Contraction of ventricles follows, through excitation of atrioventricular (AV) node • Via Purkinje fibers • Electrocardiogram (ECG/EKG)

15. Blood Vessels

16. Blood Vessels • Arteries carry blood away from the heart • Arterioles (small branches of arteries) deliver blood to capillaries • Capillaries exchange material with interstitial fluid • Venules collect blood from capillaries • Veins return blood to the heart

17. Blood Vessels • Blood moves fastest Aorta & slowest in Capillaries • Blood Pressure – force of pressure against walls of blood vessels • ~120 mm Hg • Emptying of arteries between heartbeats is the diastolic pressure • ~80 mm Hg

18. Arteries • Artery walls • Inner endothelial layer • Middle layer of smooth muscle • Outer layer of elastic fibers • Arterioles (smallest arteries) constrict and dilate • Regulate flow and pressure of blood into capillaries

19. Capillaries • Capillary walls • Single layer of endothelial cells • Variation in contraction of smooth muscles of arterioles & pre-capillary sphincters controls blood flow through capillaries • Capillaries of brain, heart, kidneys, liver always filled to capacity; other sites vary over time • After eating  blood to Sm. Intestine • Exercise  blood directed to muscles & skin • Rings of smooth muscle – pre-capillary sphincters • Contraction in arteriole constricts vessel reducing blood flow • Controls blood flow between arteries & veins

20. Exchange Across Capillary Walls • Rate of blood flow is slower to maximizes exchange time • Blood traveling through capillaries delivers nutrients, oxygen, and removes wastes from cells • Two major mechanisms drive exchange of substances • Diffusion along concentration gradients • Bulk flow • At Arteriole end Blood pressure is greater than Osmotic Pressure • Pushes Capillary fluid out to cells – oxygen & nutrients • At Venous end Osmotic Pressure is greater than Blood Pressure • Fluid returns back into capillaries from cells – carbon dioxide & wastes

21. Capillary Function

22. Veins • Veins have thinner walls than arteries • Allows vessels to expand and contract • Veins act as blood reservoirs as well as conduits • Pressure from movements of skeletal muscles and respiration help return blood to heart • One-way valves prevent blood from flowing backward

23. The Structure of Blood Vessels

24. The Lymphatic System • Extensive network of vessels • Collects excess interstitial fluid (becomes lymph) • Returns it to the venous blood • Lymph nodes, spleen, thymus, tonsils • Remove viruses, bacteria, damaged cells, and cellular debris from lymph and bloodstream • Defend the body against infection and cancer • Returned to blood via lymphatic system • Fluid enters through lymph capillaries intertwined w/ blood capillaries • Drains back into blood @ Vena Cava • Lymph vessels resemble veins & use valves & muscle contraction to move

25. Maintaining Blood Flow and Pressure • Regulated by controlling • Cardiac output • Degree of constriction of blood vessels (arterioles) • Total blood volume • Autonomic nervous system and endocrine system interact to coordinate these mechanisms

26. Regulation of Cardiac Output • Baroreceptors detect blood pressure changes and send signals to the medulla • Brain stem sends signals (autonomic nervous system) that alter rate and force of heartbeat • Hormones secreted by several glands regulate both cardiac output and arteriole diameter • Epinephrine & norepinephrine

27. Local Controls Regulate Arteriole Diameter • Low O2 and high CO2 concentrations in tissues dilate arteriole walls • Increasing arteriole diameter and blood flow • High O2 and low CO2 concentrations have opposite effects • NO released by arterial endothelial cells increase arteriole diameter and blood flow

28. Mammalian Blood

29. Mammlian Blood • Fluid connective tissue • Blood cells (erythrocytes, leukocytes, platelets) • Suspended in a fluid matrix (plasma) • Contains water, ions, dissolved gases (O2 and CO2), glucose, amino acids, lipids, vitamins, hormones, and plasma proteins • Plasma proteins • Albumins (transport, osmotic balance, pH) • Globulins (transport, immunoglobins) • Fibrinogen (blood clotting)

30. Blood & its Parts • RBC’s – erythrocytes • Contain hemoglobin (transports O2 from lungs to body) • 5-6 million per microliter; 25 trillion per 5 L of blood • No nuclei so more room for hemoglobin • WBC’s – Leukocytes • Defend body against infecting pathogens • monocytes, neutrophils, basophils, eosinophils, & lymphocytes • Patrol Interstitial Fluid & Lymph • Platelets • Functional cell fragments that trigger clotting • Platelets – fragments of cells; no nuclei • Originate as pinched off cytoplasmic fragments of larger cells in bone marrow • Function in blood clotting; self-sealing material that plugs leaks • Inactive fibrinogen  fibrin

31. Blood & its Parts

32. Blood Stem Cells & Cellular Elements • RBCs last 3-4 months • Destroyed in liver & spleen • All blood cells develop from common source w/in bone marrow • Pluripotent stem cells • any type of BLOOD cell • EPO – naturally stimulates production of RBCs • Produced by kidney

33. Cardiovascular Disease • Cholesterol • LDL – deposits plaque in arteries • HDL – reduces deposition • Exercise  HDL’s • Atherosclerosis • Thickening of arteries • Interferes w/ circulation • Hypertension •  BP because of narrowing of vessels by atherosclerosis or reduced elasticity • Threat of heart attack or stroke increases with these diseases • Heart Attack – death of cardiac muscle • Stroke – death of nervous tissue in brain • Thrombus – blood clots or clogs in arteries

34. Gas Exchange

35. Gas Exchange • Process by which animals exchange O2 and CO2 with the environment • Two primary operating features of gas exchange • The respiratory medium, either air or water • The respiratory surface, a wetted epithelium over which gas exchange takes place

36. Respiratory Surface – Tracheal Systems • Some invertebrates, skin is the respiratory surface • Others & all vertebrates, gills or lungs are the primary respiratory surfaces • Simple diffusion of molecules drives exchange of gases across the respiratory surface • Area of respiratory surface determines total quantity of gases exchanged by diffusion • Concentration gradients of O2 and CO2 across respiratory surfaces are kept at optimal levels by ventilation and perfusion (capillaries)

37. Water Breathers • Respiratory surfaces are wetted by direct exposure to the environment • Require significant energy to keep respiratory surfaces ventilated • High density & viscosity of water • Relatively low O2 content compared with air • Sponges, Cnidarians, Flatworms • Use outer cells to form respiratory surface

38. Gills (Water Breathers) • Evaginations of the body surface • Water moves over the gills • By the beating of cilia • Is pumped over gills by contractions of body muscles • In sharks, bony fishes, and some crabs • Water moves in a one-way direction over the gills • Maximizes exchange of gases over the respiratory surface

40. Air Breathers • Air is high in O2 content • Allows air-breathers to maintain higher metabolic levels than water breathers • Air has lower density and viscosity than water • Allows air breathers to ventilate respiratory surfaces with relatively little energy

41. Insects: Tracheal System • Insects breathe by a tracheal system • Air-conducting tubes (trachea) lead from the body surface (through spiracles) and branch to all body cells • Gas exchange takes place in fluid-filled tips at ends of branches

42. Respiratory Surfaces - Lungs • Invaginations of the body surface • Allow air to become saturated with water before it reaches the respiratory surface • Reduce water loss by evaporation • Amphibians – small lungs; also use skin • Reptiles, birds, mammals – larger lungs • Size & complexity correlate w/ Metabolic Rate

43. Lung Ventilation • Positive pressure breathing • Air is forced into lungs by muscle contractions • Negative pressure breathing • Muscle contractions expand lungs, lowering air pressure inside • Allows air to be pulled into the lungs

44. Mammalian Respiratory System • Air enters the respiratory system through the nose and mouth and passes through the pharynx, larynx, and trachea • Trachea divides into two bronchi leading to lungs • Within lungs, bronchi branch into bronchioles, leading into alveoli surrounded by networks of blood capillaries

46. Mammalian Respiratory System • Negative pressure mechanism • Air is exhaled passively • Relaxation of diaphragm and external intercostal muscles between ribs • Elastic recoil of lungs (pleural membranes) • Deep and rapid breathing • Forceful expulsion of air driven by contraction of internal intercostalmuscles • Atmospheric pressure = 760 mm Hg • Oxygen in atmosphere is 21% = .21 x 760 = 160 mm Hg • Gas always diffuses from higher partial pressure to lower partial pressure • Lungs must be lower so oxygen moves in

47. Ventilating Lungs • Tidal volume • Amount of air moved in and out of lungs during an inhalation and exhalation • Vital capacity • Total volume of air a person can inhale and exhale by breathing as deeply as possible • Residual volume • Air remaining in the lungs after as much air as possible is exhaled

48. Breathing Control • Control mechanisms • Local chemical controls • Regulation centers in the brain stem • Control functions • Match rate of air and blood flow in lungs • Link rate and depth of breathing to body’s requirements for O2 uptake and CO2 release • Sensory receptors in medulla detect changes in levels of O2 and CO2 in blood and body fluids • Carotid bodies • Aortic bodies

49. Monitoring the blood • CO2 concentration – Carbonic acid – pH sensor in arteries •  pH,  CO2 so  breath deeper breaths • O2 levels measured directly •  O2,  increase breathing rate • Hyperventilating • Rapid, deep breathes caused by release of too much CO2 • Breathing control center stops signaling ribs & diaphragm • Restored when CO2  or O2  •  CO2 during exercise  Breathing Rate to  removal of CO2

50. Respiratory Pigments • Oxygen has low solubility in blood; so carried by pigments • Hemocyanin – arthropods & molluscs – uses copper as transfer element • Bluish blood • Hemoglobin – vertebrates & some inverts – uses iron is transfer element • Binding of Oxygen to hemoglobin – Bright Red • W/out Oxygen hemoglobin – dark-purplish Red