Transport & Maintenance Circulatory Systems Transport & Maintenance

Circulatory Systems transport to & from tissues nutrients, O2; waste, CO2 hormones maintain electrolyte balance of intercellular fluid transport to/from homeostatic organs small intestine delivers nutrients liver removes wastes, controls nutrients kidney controls electrolytes, dumps wastes

Circulatory Systems some animals lack circulatory systems aquatic environment fulfills same functions some animals have open circulatory systems the heart pumps interstitial fluid vessels deliver interstitial fluid to tissues interstitial fluids leave the vessels & bathe the cells of the tissues interstitial fluids return to the heart other animals have closed circulatory systems

open circulatory systems Figure 49.1

closed circulatory system of earthworm Figure 49.2

Closed Circulatory Systems components of closed circulatory systems heart(s) - pump vessels - transport conduits blood - transport medium distinct from interstitial fluid advantages over open system speed control of blood flow cellular elements of blood remain in vessels

Circulatory Systems hearts vertebrates have chambered hearts valves impose one-way flow number of chambers varies with phylogeny blood circulates through one or two circuits H => G.E.M. => B H => G.E.M. => H => B pulmonary systemic circuit circuit

Closed Circulatory Systems vessels arteries transport blood away from heart veins transport blood toward heart arterioles/venules small arteries/veins capillaries connect arterioles to venules

Closed Circulatory Systems systems with two-chambered hearts - fish one circuit atrium =>ventricle =>gills =>aorta =>body =>atrium ventricular pressure is dissipated in gill capillaries

fish circulation schematic p. 943

Closed Circulatory Systems systems with two-chambered hearts - lungfish modified for breathing air or water out-pocketing of gut acts as a lung some gill arteries supply blood to lung some gill arteries deliver blood to aorta gills exchange gases with water partially separated atrium right side => oxygenated blood => body left side => deoxygenated blood => gills/lungs

lungfish circulation schematic p. 943 * one pair of gill arteries delivers blood to lung * two gill arches deliver blood directly to aorta * “gilled” gill arches exchange gases with blood

Closed Circulatory Systems systems with three-chambered hearts - amphibians two atria left atrium receives pulmonary blood right atrium receives systemic blood ventricle anatomy limits mixing deoxygenated blood travels to lung oxygenated blood travels to body

amphibian circulation schematic p. 943

Closed Circulatory Systems reptilian hearts provide further control two atria receive blood from pulmonary & systemic circuits partially separated ventricle supplies three vessels pulmonary artery & two aortas when breathing, the right aorta carries deoxygenated blood to the pulmonary circuit when not breathing, both aortas carry blood to the systemic circuit

reptilian circulation schematic p. 944

Closed Circulatory Systems crocodilian hearts have four chambers two atria, two ventricles, two aortas two aortas are bridged near their origins when breathing, the left ventricle (& aorta) pressure is higher deoxygenated blood goes to lungs when not breathing, right aorta pressure is higher pulmonary circuit is bypassed

crocodilian schematic p. 944

Closed Circulatory Systems endotherm hearts have four chambers and one aorta systemic/pulmonary circuits are separated tissues receive highest possible [O2] (P1) under high pressure lungs receive lowest possible [O2] (P2) under lower pressure

endotherm schematic p. 945

human circulatory system Figure 49.3

Human Circulatory System circulation deoxygenated blood arrives at right atrium from inferior & superior vena cava atrium pumps blood to right ventricle ventricle pumps blood to pulmonary artery backflow is prevented by atrioventricular valve ventricle relaxes backflow is prevented by pulmonary valve

human heart anatomy Figure 49.3

Human Circulatory System circulation oxygenated blood arrives at left atrium through pulmonary veins atrium pumps blood into left ventricle ventricle pumps blood to aorta backflow is prevented by atrioventricular valve ventricle relaxes backflow is prevented by aortic valve

human heart anatomy Figure 49.3

Human Circulatory System cardiac cycle systole - contraction of ventricles maximum pressure generated major electrical event diastole - relaxation of ventricles minimum pressure characteristic electrical signatures

ventricular pressures & volumes Figure 49.4

measuring blood pressure Figure 49.5

Human Circulatory System heartbeat is myogenic pacemaker cells occur at sinoatrial node resting membrane potential depolarizes at threshold, voltage gated Ca2+ channels open K+ channels open to repolarize cells K+ channels close slowly, allow gradual depolarization autonomic nervous system regulates the rate of depolarization

autonomic control of heart rate Figure 49.6 Figure 49.8 Figure 44. 9 norepinephrine acetylcholine autonomic control of heart rate Figure 49.6 Figure 49.8 Figure 44. 9

Human Circulatory System contraction the pacemaker action potential spreads across the atrial walls atria contract action potential is transmitted to ventricles through the atrioventricular node and the bundle of His the action potential spreads to Purkinje fibers in ventricular muscle ventricles contract

origin and spread of cardiac contraction Figure 49.7

Human Circulatory System vascular system arteries carry blood from heart elastic tissues absorb pressure of heart contractions smooth muscle allows control of blood flow by neural and hormonal signals

artery structure Figure 49.10

Human Circulatory System vascular system capillaries fed by arterioles; drained by venules exchange materials between blood & intercellular fluids high total capacity; slow flow thin walls

capillary bed Figure 49.10

Human Circulatory System vascular system capillaries exchange materials by filtration, osmosis & diffusion water & solutes move through capillary walls under pressure on the arteriole side remaining solutes & diffusing CO2 produce a low osmotic potential water returns to capillaries on the venule side

water movement balanced between blood pressure & osmotic potential Figure 49.12

Human Circulatory System [lymphatics lymph vessels return excess tissue fluid to blood lymphatic capillaries collect lymph capillaries merge into larger vessels vessels contain one-way valves the major lymph vessel, the thoracic duct, empties into the superior vena cava lymph nodes participate in lymphocyte production & phagocyte activity]

vein structure Figure 49.10

Human Circulatory System veins receive blood from capillaries under low pressure contain one-way valves blood is propelled by skeletal muscle contraction or gravity

venous return by skeletal muscle contraction and one-way valves

Human Circulatory System blood - a fluid connective tissue fluid matrix - plasma dissolved gases, ions, proteins, nutrients, hormones, etc. many components found in tissue fluid cellular elements red blood cells (erythrocytes) white blood cells (leukocytes) platelets

blood components Figure 49.15

human blood samples before and after centrifugation to separate red blood cells from serum

Human Circulatory System control & regulation of circulation capillaries are subject to auto-regulation pre-capillary sphincters and arterial smooth muscle are sensitive to O2 & CO2 concentrations accumulated waste materials

local control of blood flow Figure 49.17

Human Circulatory System control & regulation of circulation simultaneous auto-regulation of capillary beds produces systemic responses changes in breathing, heart rate changes in blood distribution systemic control is neural or hormonal sympathetic stimulation contracts most arteries; dilates skeletal muscle arteries hormones constrict arteries in targeted tissues

circulatory regulation at two levels Figure 49.18

Human Circulatory System control & regulation of circulation autonomic control of circulation originates in medulla of brain stem inputs arrive from stretch receptors chemosensors higher brain centers responses may be direct - artery relaxation or contraction indirect - release of epinephrine

neural control of circulation is centered in the medulla Figure 49.19