circulation chapter 23. molecular exchange o 2 & nutrients into all cells co 2 & wastes out...
TRANSCRIPT
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Circulation
Chapter 23
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Molecular Exchange
• O2 & nutrients into all cells
• CO2 & wastes out of all cells
• Necessary for large SA to volume ratio– Folds– Alternate structures
• Internal transport system facilitates
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No Circulatory System
• Exchange across PM directly with environment• Gastrovascular cavity
– Digestion, gas exchange, and distribution
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Open Circulatory System• Mollusks and arthropods
• Heart pumps hemolymph– Blood/interstitial fluid mixed– Valves prevent backflow
• Fluid directly bathes organs– Body movements help circulate– No pigment = only carries nutrients
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Closed Circulatory System
• Annelids, cephalopods, and vertebrates
• Heart pumps blood in vessels– Distinct from interstitial fluid– Control flow
• Vessels enter organs– Capillaries – Respiratory pigments
• Allows higher pressure– Larger, more complex organisms
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Evolution of Cardiovascular Systems
Single circulation Double circulation
2 chambers 4 chambersPartial 4 chambers3 chambers
• Natural selection modified according to activity levels
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The Mammalian Heart
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Human Cardiovascular System
• Process is continuous
• Double circulation– Circuits are simultaneous– Each loop/circuit must
pass through the heart
• Be able to diagram/explain
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The Working Heart• Electrocardiogram (EEG) measures
activity of heart– SA node is pacemaker– AV node relays signals to ventricles
• Cardiac cycle– Rhythmic contraction and relaxation of
heart• 0.8 sec = 72 bpm
– Systole = ventricle contract– Diastole = ventricle relax
• Listening to your heart– Lub-dub, lub-dub is AV-semilunar
contraction– Heart murmurs
• Blood moves backward
• Myocardial infarction (heart attack)– Lack of O2 kills cardiac muscle fibers
• Stroke– Artery blockage kills brain tissue
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Blood Vessels
• Direction determines– Away from or
towards the heart
• Layers vary– Endothelium
• Single cell later
– Middle layer• Smooth muscle
– Outer layer• Elastin protein
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Types of Blood Vessels
• Arteries and arterioles– Thicker walls, smaller diameter– High pressure
• Capillaries– Lowest velocity (speed)– Allows diffusion– Regulate pressure
• Venules and veins– Thinner walls, larger diameter– Lowest pressure– One way valves
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Controlling Blood Flow
• Capillaries– Sphincters to regulate flow– Active or inactive tissues
• Thoroughfare channel always open
• Arterioles (smooth muscle)– Neural and hormonal control
• Vasodilation• Vasoconstriction
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Arteriole Blood Flow• Blood pressure: force of blood
against vessel (arteriole) walls– Pulse: stretching of arteries
• Systole: increased velocity in vessels– Smaller vessels = up resistance = up
pressure • Dystole: decreased velocity, but pressure
maintained• Velocity correlates with changing
vessel types (size and number)– Capillaries allow time for diffusion
• Veins compensate for drop in pressure
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• Veins must work against gravity– One way valves– Skeletal muscle sandwich
• Standing on mats
– ‘Cankles’
• Blood pressure – Highest at heart level
• Fainting• Raising wounds
Veins, Circulation and Gravity
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Blood Composition
• Plasma (55%)– Water (90%)– Ions (balance/homeostasis)– Proteins (clotting and immunity)– Transport substances
• Cellular componenets (45%)– Red blood cells (rbc’s)– White blood cells (wbc’s)– Platelets
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RBC Count
• 3-4 month life span• Formed in bone marrow
– Low O2 = kidney’s make erythropoietin (EPO) = stimulate bone marrow
• Athletic training at high altitudes• Injections illegal
• Altering RBC numbers– Anemia is low RBC or hemoglobin– Blood doping
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Blood Clotting
• Damaged vessel constricts• Platelets form a temporary plug• Fibrin threads trap cells to seal