Oxygen

Nutrition * Chemoheterotrophs(animals): cannot make organic molecules from inorganic carbon; need to ingest organic molecules * Cellular respiration breaks down organic molecules to co2 and h20 , releases energy * Usually cannot be aerobic for extended periods: need * If proteins are broken down: creates N-Waste * Animals need food, gas exchange, excretion * How' Influenced by size, environment, metabolism Evolution * Originated and diversified in the water * Most aquatic animals breathe ( exchange gases with water) * Diffusion is sufficient for smaller animals (whose surface area is large compared to its volume) * * Became larger and more complex * If shape is maintained, volume increases faster than surface area. Volume determines complexity, surface area determines supply * Diffusion was no longer sufficient, need bulk flow, large scale movement of materials. * Organ systems (with increased surface area ) transport materials within the body the body and to exchange materials with materials with the environment * More tissue dedicated to support and movement. * Some lineages colonized the land : molluscs, arthropods, tetrapod vertebrates * Breathe air (more O2 than h20) * Greater risk of h20 loss * Greater temperature variation; H2O has a high specific heat capacity, so it maintains a fairly constant temperature. * Tetrapod evolution * endothermy in birds and mammals: high metabolic rates and activity * Require more food produce more waste * Most other animals are ectotherms : lower metabolic rates and activity levels * Some tetrapods returned to the water : they still breathe air * Animals exist because they respond to their environment; responses can be: * Over evolutionary time: natural selection favors adaptations * within an organism’s lifetime * Seasonal * Immediate responses: physiological regulation and defenses Physiological regulation * Meets the immediate needs of cells * Most needs are met by adjusting the internal environment of the body * surrounds cells (= interstitial fluid) * Many variables the amount of 02, glucose, etc * Homeostasis: maitenance of an optimal internal environment * Even if external environment fluctuates * Metabolism-sum of chemical reactions in the cell * Degree of regulation varies * Regulators: keep variables within narrow range * Requires much energy * Conformers: allow variables to fluctuate * Common in stable environments * Requires less energy * Organism risks reaching fatal levels * Usually by negative feedback: minimizes deviation from optimal levels ( set point ) Next * Material and energy needs of animals * Emphasis * Basic processes * Diversity: size, environment, metabolism * Regulation * (Maybe a little pathology) Oxygen Chapter 42 Oxygen delivery to tissues * Determined by: * exchange with environment (air or water) * transport within body * Available processes * Diffusion: slow , along concentration gradient * Bulk flow: fast , along pressure gradient (generated by pump ) * ( no active transport across cell membranes) I. General strategies * Diffusion: small or thin organisms * Move external fluid close to cells * Water: sponges, cnidarians, flatworms * no distinct circulatory system * Air: terrestrial arthropods * External air directly conveyed to tissues * Air moves by diffusion and pumping by body wall * Circulatory system is poorly developed and not involved * Diffusion across the body surface (cutaneous respiration) plus circulation * Most aquatic invertebrates, terrestrial annelids, amphibians (water and air) * Skin must be very thin and moist * Diffusion across a specialized respiratory surface plus circulation * Gills: high surface area evaginations * Used for water (why not for air') * Many aquatic invertebrates, larval and adult fishes, larval and some adult amphibians * Surface area correlates with activity * Lungs: air sacs within body * Thin, high surface area, vascular * Some bony fishes, most tetrapods * Potential to lose water (reduced by being internal) * Complexity correlates with metabolic rate II. Gas transport * Sponges, cnidarians, insects * external fluid brought close to cells * Circulatory system absent or not ionolved in in gas transport * Other large organisms (in water and air ) * External gas exchange by diffusion * Gases are transported within body by a circulatory system A. Circulatory systems * Move gases, food, wastes * Regulation: carry hormones and heat * Protection: blood clotting and immunity * Transmit pressure Components * Specialized fluid * Muscular pump * Tubular pathways Types * Open * Blood leaves vessels: blood blood= interstitial fluid = hemolymph * Arthropods and most mollusks * Closed * Blood remains in vessels: distinct from interstitial fluid * Annelids and cephalopods * Greater control/higher pressure Focus: Vertebrate Circulation 1. Blood Vessels * Flow is unidirectional directional: vessels can be specialized 2. Heart * Muscular chambers: contract ( systole) and relax ( diastole ) * Contraction results from electrical activity within the heart * ventricular systole: generate force that pushes blood throughout the circulatory system * Cardiac output (CO)=HRxSV * Heart rate: contraction per unit time * Stroke volume: volume per contraction * Both can be modified by hormones and nerves * Both are increased by adrenaline/epinephrine 3. Blood pressure * Force exerted on vessel walls * Generated by ventricular contraction * Elastic large arteries absorb high pressure during systole * During diastole: arteries recoil * Moves blood against friction and gravity, it is a force * Determines overall blood flow (does not determine or change flow to specific organs) * Proportional to: cardiac output, blood volume, degree of vasoconstriction * Importance-maintain high flow to heart and brain, adjust to meet body needs, digestion, excersize, stress * How-constricut/dilate arterioles and precap sphincters, control by neurons and hormones, adrenaline-constriction,, more importanrtly in kidnerys, digestive tract, skin (organs that generally receive more blood). * In response to local metabolism (High CO2, low O2, nitric oxide, acidity=dilation) * Why control: BP must move blood to all organs, not to be too excessive, would cause rupture, edema(swelling) * How to change BP-change determinants * Blood volume: slow: by kidneys * Cardiac output and degree of vasconstrction * Rapid response * Receptors: baroreceptors in large arteries, detect BP * Information is sent to the brain, brain controls heart and blood vessels * Negative feedback^ 4. Exchange with tissues * At capillaries * Flow is controlled by arterioles and precapillary sphincters * Most materials move in/out by diffusion * Plasma proteins and cells remain * Water also leaves due to pressure * Most pulled back in by osmosis (due to plasma proteins ) * Not all returns to capillaries * If excess not removed: tissues will swell (edema) * Lymphatic system * Returns excess to cardiovascular system * An open circulatory circulatory system 5. Circuits Fishes * single loop * Pressure drops after gill capillaries: slow flow Tetrapods * Two circuits: pulmonary/pulmocutaneous and systemic * Blood goes through heart twice * Extra push after going through respiratory capillaries * Heart is divided into left and right * partilly : amphibians and most reptiles * Flow of two two circuits kept seperate * Potential to divert blood away from pulmonary circulation when * Possible for blood to * fully : birds and mammals * no mixing of circuits → enhanced oxygen delivery needed by endotherms (breathe continuously ) * all blood passes through lungs: blood gets completely oxygenated (importance for endotherms) * Cardiac output is the same in both sides * Circuits differ in pressure (benefit') * Pressure is higher is systemic than pulmonary----------------blood pressure is lower in the lunges because systemic has a higher pressure to push things thoughr and because we do not want edema in the lunges. 6. Regulation Blood flow to/within specific organs * Importance * Maintain high flow to * Adjust to meet body’s needs * Digestion * Exercise/stress * Temperature control * How' Constrict/dilate and pre-capillary sphincters * Control by neurons and hormones * Adrenaline/epinephrine = * More important in kidneys, digestive tract, skin (organs that generally receive blood than they need) * * In response to * High CO2, low O2, nitric oxide, acidity = dilation * Important for maintaining oxygen deliver to Blood pressure * Why control' BP must: * Be sufficient: move blood to * Not be excessive: would cause * How' Change determinants * Blood volume: * Cardiac output and degree of vasoconstriction * response * Receptors: in large arteries detect * Information is sent to * Brain controls * Negative feedback * Circulatory shock: extremely blood flow and BP * Causes (usually act quickly) * Widespread due to chemicals produced during or reactions * Heart (contractions are ) * blood volume due to blood or of body fluids (dehydration, burns) * Treatment'