Circulation Chpt. 44 Transportation, cardiac cycle, evolution of advanced systems

Oxygen and nutrients obtained for simple organisms by diffusion Oxygen and nutrients obtained for simple organisms by diffusion cnidarians and flatworms – bodies only 2 cells thick cnidarians and flatworms – bodies only 2 cells thick Development of multi- layer tissues Development of multi- layer tissues Oxygen and nutrients transported in liquid via circulatory system Oxygen and nutrients transported in liquid via circulatory system Open – mollusks, arthropods, Open – mollusks, arthropods, no distinction between circulating fluid and fluid of body tissues no distinction between circulating fluid and fluid of body tissues Called hemolymph Called hemolymph Closed – blood enclosed in vessels, transport away and back to a pump (heart) Closed – blood enclosed in vessels, transport away and back to a pump (heart) Some invertebrates (annelids) Some invertebrates (annelids)

Vertebrate Circulatory Systems Transportation Transportation Respiratory, nutritive, excretory Respiratory, nutritive, excretory Regulation Regulation Hormone transport Hormone transport Temperature regulation (vasoconstriction/dilation, countercurrent heat exchange) Temperature regulation (vasoconstriction/dilation, countercurrent heat exchange) Protection Protection Blood clotting Blood clotting Immune defense Immune defense

Blood Composed of fluid plasma Composed of fluid plasma Interstitial fluid originates from plasma Interstitial fluid originates from plasma Matrix in which blood cells and platelets are suspended Matrix in which blood cells and platelets are suspended Metabolites, wastes, hormones Metabolites, wastes, hormones Ions Ions Proteins – carriers and clotters Proteins – carriers and clotters Red Blood Cell/Erythrocytes Red Blood Cell/Erythrocytes Oxygen transport, 45% of blood Oxygen transport, 45% of blood Doughnut shaped – increases surface area Doughnut shaped – increases surface area Hemoglobin – pigment Hemoglobin – pigment Develop from stem cells Develop from stem cells Plasma oxygen levels decrease, bone marrow creates more Plasma oxygen levels decrease, bone marrow creates more Mammalian – no nucleus, removed as age Mammalian – no nucleus, removed as age

White blood cells and platelets Immunological defenses Immunological defenses Less than 1% of blood Less than 1% of blood Larger, have nuclei, not confined to blood Larger, have nuclei, not confined to blood Several types, each have specific job Several types, each have specific job Platelets – pieces of megakaryocytes Platelets – pieces of megakaryocytes Injury – smooth muscle contracts, constriction Injury – smooth muscle contracts, constriction Platelets accumulate, stick to each other via fibrin Platelets accumulate, stick to each other via fibrin

Blood vessels Blood leaves heart via arteries which branch to reach organs, Blood leaves heart via arteries which branch to reach organs, Finest branches are arterioles, enters capillaries Finest branches are arterioles, enters capillaries Collected in venules led to veins Collected in venules led to veins Arteries, veins = same basic structure Arteries, veins = same basic structure Innermost = endothelium, elastic fibers, smooth muscle, connective tissue layer Innermost = endothelium, elastic fibers, smooth muscle, connective tissue layer Too thick to permit exchange Too thick to permit exchange Capillaries = only endothelium Capillaries = only endothelium Diffusion, filtration, transport Diffusion, filtration, transport

Arteries and arterioles Transport blood away from heart Transport blood away from heart Larger arteries = more elastic fibers Larger arteries = more elastic fibers Smaller = thick smooth muscle Smaller = thick smooth muscle Vast “tree” = frictional resistance Vast “tree” = frictional resistance Narrower vessel = more resistance to flow Narrower vessel = more resistance to flow Regulated by constriction and dilation Regulated by constriction and dilation Precapillary sphincters – limits heat loss in cold Precapillary sphincters – limits heat loss in cold

Exchange in capillaries Sufficient pressure needed to pump against resistance Sufficient pressure needed to pump against resistance Every cell is within 100 micromteres of a capillary Every cell is within 100 micromteres of a capillary Capillaries 1 millimeter long, 8 micro in diameter Capillaries 1 millimeter long, 8 micro in diameter Slightly wider than erythrocyte, must be flexible Slightly wider than erythrocyte, must be flexible Although narrow, number means greatest total area than any vessel Although narrow, number means greatest total area than any vessel Blood has more time in capillaries, releases/pick-up Blood has more time in capillaries, releases/pick-up Loses pressure and velocity, is under low pressure in veins Loses pressure and velocity, is under low pressure in veins

Venules and veins Venules-veins-heart Venules-veins-heart Less muscle because less pressure Less muscle because less pressure Can expand to hold additional blood Can expand to hold additional blood Skeletal muscles can contract to move blood back to heart – venous pump Skeletal muscles can contract to move blood back to heart – venous pump One way back to heart, venous valves One way back to heart, venous valves

Lymphatic System Closed – all vessels connected with another Closed – all vessels connected with another Some water and solutes do filter through capillaries to form interstitial fluid Some water and solutes do filter through capillaries to form interstitial fluid Supplies tissue cells with oxygen and nutrients Supplies tissue cells with oxygen and nutrients Exits near arteriolar end where pressure is higher, re- enters by osmosis (oncotic pressure) Exits near arteriolar end where pressure is higher, re- enters by osmosis (oncotic pressure) Lymphatic is open, returns rest of fluid to cardiovascular Lymphatic is open, returns rest of fluid to cardiovascular Capillaries, vessels, nodes, organs including spleen and thymus Capillaries, vessels, nodes, organs including spleen and thymus Activate some white blood cells Activate some white blood cells

Circulatory and respiratory adapatations Large body size and locomotion of animals possible because of coevolution of systems Large body size and locomotion of animals possible because of coevolution of systems Needed more efficient Needed more efficient ways to transport Circulation and respiration Circulation and respiration linked linked

Fish heart Early chordates had simple tubular hearts Early chordates had simple tubular hearts Gills of fish required chamber-pump heart Gills of fish required chamber-pump heart Peristaltic sequence, heartbeat initiated by electrical impulse Peristaltic sequence, heartbeat initiated by electrical impulse Gills oxygenate blood, but looses pressure developed by heart contraction Gills oxygenate blood, but looses pressure developed by heart contraction

Amphibian/reptilian Lungs – blood is oxygenated then returned to heart Lungs – blood is oxygenated then returned to heart Two circulations – pulmonary – heart/lungs Two circulations – pulmonary – heart/lungs Systemic – heart/body Systemic – heart/body Separates oxygenated from deoxygenated Separates oxygenated from deoxygenated Right atrium – receives deoxygenated from systemic Right atrium – receives deoxygenated from systemic Left atrium receives oxygenated from lungs Left atrium receives oxygenated from lungs Little mixing in ventricle Little mixing in ventricle Oxygenated blood to aorta, major artery Oxygenated blood to aorta, major artery One ventricle with incomplete separations One ventricle with incomplete separations Separation of pulmonary and systemic is incomplete Separation of pulmonary and systemic is incomplete Amphibians can diffuse extra oxygen Amphibians can diffuse extra oxygen

Mammalian and Birds Four chambered heart Four chambered heart Two atria and two ventricles Two atria and two ventricles Right atrium receives deoxygenated blood, delivers to right ventricle, which pumps to blood to lungs Right atrium receives deoxygenated blood, delivers to right ventricle, which pumps to blood to lungs Left atrium receives oxygenated blood from lungs, delivers to left ventricle, which pumps blood to body Left atrium receives oxygenated blood from lungs, delivers to left ventricle, which pumps blood to body Occur simultaneously – increased efficiency Occur simultaneously – increased efficiency Closed system – same amount of blood pumped by both ventricles at same time Closed system – same amount of blood pumped by both ventricles at same time More pressure generated by left ventricle More pressure generated by left ventricle Sinus venosus – pacemaker Sinus venosus – pacemaker site of heartbeat impulse site of heartbeat impulse Major chamber in fish Major chamber in fish Reduced through amphibians, Reduced through amphibians,reptiles Mammals/birds no longer Mammals/birds no longer separate chamber – tissue remains in right atrium – sinoatrial (SA) node

Cardiac cycle Two separate pumping systems within one organ Two separate pumping systems within one organ Two pairs of valves Two pairs of valves Atrioventricular (AV) valves – guard openings between atria and ventricles Atrioventricular (AV) valves – guard openings between atria and ventricles Ttricuspid valve = exit of right atrium Ttricuspid valve = exit of right atrium Bicuspid valve = exit of left atrium Bicuspid valve = exit of left atrium Semilunar valves – guard openings between ventricles and arteries Semilunar valves – guard openings between ventricles and arteries Pulmonary – right ventricle to lungs Pulmonary – right ventricle to lungs Aortic – left ventricle to body Aortic – left ventricle to body Valves open and close during cardiac cycle Valves open and close during cardiac cycle rest (diastole) and contraction (systole) rest (diastole) and contraction (systole)

Blood returns to resting heart (diastole) Blood returns to resting heart (diastole) Deoxygenated blood into right atrium Deoxygenated blood into right atrium Oxygenated blood into left atrium Oxygenated blood into left atrium Ventricles contract (systole) Ventricles contract (systole) AV valves close (lub), push semilunar valves open AV valves close (lub), push semilunar valves open Ventricles relax, semilunar close (dub) Ventricles relax, semilunar close (dub)

Veins and arteries Pulmonary arteries to lungs Pulmonary arteries to lungs Veins back to heart Veins back to heart Aorta Aorta Superior vena cava Superior vena cava Inferior vena cava Inferior vena cava

Electrical excitation Heart contains specialized autogenic depolarizing cells Heart contains specialized autogenic depolarizing cells Spreads from SA node to atria to ventricles Spreads from SA node to atria to ventricles Recorded on EKG Recorded on EKG Largest peak is polarization of ventricles Largest peak is polarization of ventricles

Blood Flow and Blood Pressure Cardiac output has normal resting rate (5L/minute) Cardiac output has normal resting rate (5L/minute) Increases during exercise (25L/min) Increases during exercise (25L/min) Vasoconstriction/dilation direct extra blood to important areas Vasoconstriction/dilation direct extra blood to important areas Increased blood pressure = increase in heart rate or vasoconstriction Increased blood pressure = increase in heart rate or vasoconstriction Can be regulated by hormones to increase blood volume Can be regulated by hormones to increase blood volume

Blood Volume Regulation ADH – antidiuretic, prevent dehydration ADH – antidiuretic, prevent dehydration Aldosterone – vasoconstriction Aldosterone – vasoconstriction Atrial Natriuretic Hormone – release Na+ and water Atrial Natriuretic Hormone – release Na+ and water Nitric Oxide – gas acts as a hormone - vasodilation Nitric Oxide – gas acts as a hormone - vasodilation