Theme 4: Homeostasis, PDF

Theme 4: Homeostasis to Thrive and Survive Osmoregulation, Circulation, Gas exchange and pH Homeostasis – the maintenance of a ______ ________ ___________ suitable for metabolic processes, through responses to deviations from this stable state Significance Biochemical reac...

Theme 4: Homeostasis to Thrive and Survive Osmoregulation, Circulation, Gas exchange and pH Homeostasis – the maintenance of a ______ ________ ___________ suitable for metabolic processes, through responses to deviations from this stable state Significance Biochemical reactions sensitive to: __________, __, [______], [_____], _______ Organisms must regulate many internal variables nutrients, gasses, pH, waste products, water/solutes, volume, pressure, temperature 1  Homeostasis – Negative Feedback Loops __________________– homeostasis is maintained by regulating physiological variables with reference to a __________ (generally in the integrator) 2 Homeostasis – Negative Feedback Loops 3 Homeostasis – Cell Location __________– implications for how homeostasis is approached ___________ must face the environment: Sometimes dead (i.e. superficial layers of skin) Sometimes protected by an acellular cuticle 4 Homeostasis – Cell Location Cells of exchange surfaces must be alive – control access to _______ _________ Found inside the body, but dealing with aspects of the ________ __________ Deal with wear and tear by Rapid __________ Produce ___________ ________ to microbes Covered by ________ to isolate them from the environment 5  Homeostasis – Cell Location Internal cells: homeostasis by organism regulates the ______ ____________ i.e. regulation of extracellular fluid _____________ ______ (circulating extracellular fluid) Reduces amount of work cells have to do to maintain homeostasis, if internal cells are not isoosmotic with the environment Enables them to specialize 6  Homeostasis topics _____________: regulation of the internal osmotic (water/salt/waste) environment _________: bulk flow of fluid within the body (water, solutes, nutrients, gasses) ____________: exchanging gasses with the environment ______________ controlling the [proton H+] of body fluids 7  HOMEOSTASIS and OSMOREGULATION --concepts-- Diffusion – short distances, dissolved solutes __________- Diffusion Rate = D A dC/dX Osmosis and Water Potential _______________vs ___________ ______________ – tendency of water to move Due to osmosis, hydrostatic pressure, gravity, humidity, etc Hyperosmotic, hyposmotic, isosmotic Bulk flow – mass movement over long distances due to ___________ (__________) _________ 8  Diffusion _________________- a spatial difference in the relative abundance of one type of molecule (or atom) ________ - the tendency of molecules or atoms of one kind (say, a solute) to move from a volume in which they are relatively abundant to one in which they are relatively rare This is the same as moving down a concentration gradient It is due to random movement of the particles involved It results in the diminution of the concentration gradient and the establishment of an equilibrium 9  Diffusion Fick’s Law - Diffusion Rate Across a Membrane = D A dC/dX D = _____________– depends upon characteristics of solute and solvent, temperature etc. dX A = ____________ of the membrane dC/dX: A dC – ___________ difference across membrane dX – _________ of membrane dC/dX is the force driving diffusion The ________ of particles moving across dC the membrane varies with A, all else being equal 10  Osmolality ______ – total number of dissolved particles of solute per kg of solute 1 mole NaCl dissolved in 1 kg of water yields _______ of particles – ______Na+, ______Cl- ________ – osmotic concentration of a solution, measured in osmoles 11  Tonicity Terms _________ - of a solution, having a lower ________ than the reference solution pure water is __________ to the red blood cell placed in it, which bloats 12  Tonicity Terms _____________ - of a solution, having a higher ________ than the reference solution a strong saline solution is ____________ to the red blood cell placed within it, which shrivels 13 Tonicity Terms __________ - of a solution, having the same __________ as the reference solution a bath of physiological saline is _________ to the red blood cell placed within it, which stays the same 14  Osmosis The tendency of water to diffuse across a selectively permeable membrane towards the side of ______ ______ _________ when the membrane is impermeable to the ______ 15 Semi-permeable membrae ______________ (solute potential in plants) – force exerted on water generated by differences in solute concentration across a semi-permeable membrane Pure water has an ______________ of zero – highest osmotic potential possible Lower osmotic potential is a negative number (the more solute, the more negative the osmotic potential) Water moves from ___________to __________ volumes 16 Semi-permeable membrae ______________ – hydrostatic (=_________) pressure affecting how water crosses membrane from volume of high osmotic potential to volume of low osmotic potential Pressure potential _______ low osmotic potential – flow of water across membrane decreased, reversed or stopped Pressure potential _________ low osmotic potential – flow of water across membrane increased Pressures measured in Pascals (Pa - animals) or in Ψ (Psi – plants) 17 _____________ – sum of osmotic potential, pressure potential, gravity etc. across a membrane Water moves from volumes of high ______________ to volumes of low ____________ HI POT LO POT SPM Water movement 18  Osmosis and the living cell Fresh water (high osmotic potential) Significance to animals causes cells to swell Cells will _____________if not in an isoosmotic environment (without work on the cell’s part) Significance to plants Fresh water causes Cells will develop ______ ________ hydrostatic/turgor (hydrostatic) due to cell swelling Cell wall pressure, preventing further influx of and pressing against cell wall as water water enters, which limits further influx of water  Bulk Flow and Water Bulk flow of transport fluids in ________ requires application of _________________ Affects exchange of water and solute between the bulk transport system and the extracellular fluid in ______________ systems 20  Bulk Flow and Water Animal example: _______________ exerted on blood in upstream side of capillary bed exceeds ________ ________ of extracellular fluid – water and solutes leave capillaries ______________ of blood in downstream side of capillary bed exceeds _______________ of extracellular fluid – water and solutes re-enter capillaries 21  Osmoregulation in ANIMALS Fresh water (1 mOsm) vs salt water (1000 mOsm) vs extracellular fluid (300 mOsm) Osmoconformers vs Osmoregulators _____________ strategies [Y] = [X] = [Z] Adjust osmotic potential of cells [Y] and extracellular fluid [X] to match environment [Z] [X] [Y] Examples: marine inverts, hagfish, elasmobranchs [Z] _____________ strategies: Adjust osmotic potential of extracellular fluid [X] to match cells [Y] and regulate or protect [X] against the external [Z] Generally requires thick outer layer [Y] = [X] ≠ [Z] Examples: freshwater inverts and most vertebrates [X] [Y] 22 [Z]  Osmoregulation in ANIMALS The challenge of water/salt loss and gain Terrestrial animals (water loss) water dry Aquatic animals Marine (water loss) water salt Hyperosmotic (dry!) Fresh water (water gain) water salt Hyposmotic 23 Tonicity And The Environment – Water Dwellers Body fluid _______ varies among aquatic organisms Some marine groups are ________ with seawater – osmotically stable environment 24  Tonicity And The Environment – Water Dwellers Marine bony fish - __________ to environment, lose water and gain ions, especially through the ____ Drink _________ to offset water loss ____________ in gills eliminate Na+, K+ and Cl- from blood Produce ___________ of urine, conserving water, eliminating excess solute in faeces 25  Tonicity And The Environment – Water Dwellers Freshwater bony fish – ___________ to environment, lose ions and gain water, especially through the gills Do not drink Produce large amounts of ____________ Must replace ions from food or from ________ across _____________ 26 Tonicity And The Environment – Water Dwellers Elasmobranchs - __________ to seawater, but concentrations of Na+, K+, Cl- all less than seawater – difference made up by ____ Still must deal with inward diffusion of Na+, K+, Cl- through gills __________ secretes a highly concentrated salt solution 27 Tonicity And The Environment – Land Dwellers A dry environment - constant water loss through _________: Across wet respiratory membrane Across surface of skin Water loss in urine and faeces Requires: ___________ of outer layer of body ______________of gas- exchange and digestive surfaces to air Minimizing _______________ We will deal with this in more depth when we examine adaptations to life on land 28  Summary of responses to the osmotic environment Terrestrial environments are dry: _________to the environment Consume/produce/conserve water Limit salt intake Marine environments are hyperosmotic (dry): ________to and _______from the environment Eliminate salt and consume/produce/conserve water Limit salt intake Freshwater environments are hypoosmotic: _______from and __________ to the environment Eliminate water and consume/conserve salt Limit water intake 29  Osmoregulation in ANIMALS Active _________ of water loss and gain __________: elimination of waste/toxins Aids in controlling content of ______________ (salt/water/pH) Major means: _________ into water (only in aquatic habitats) Actions of _______________ (liquid waste): __________ (non-selective) ___________ (selective) ____________ (selective) 30 Osmoregulation in ANIMALS Ion Ion pump X exchanger solutes Z X ADP filtrate ATP x z x Z ECF x filtrate z X water Co- transporter Excretory tubule composed of _________________– allows ______________of ions between ECF and filtrate Other solutes and water diffuse in either direction 31 Filtration, reabsorption, secretion result in production of urine/filtrate Water permeable Water impermeable membrane membrane Filtration Secretion Concentrated (isosmotic) Resorption (hyperosmotic) urine Different ECF/plasma unwanted Ions Ions Water functions of Sugars (hyperosmotic) excretory tubule localized along its length 32  Ammonia (NH3) excretion ________ is Toxic, we must get rid of it Aquatic ________ into the environment (across body / gills) ________ in filtrate/urine Ammonium (NH+4) / sodium exchangers Na+ water NH3 + H+ NH4+ plasma Terrestrial (and some aquatic) Terrestrial cannot use diffusion or ion exchange with air only ________ in filtrate Produce ____ (mammals, amphibians, sharks) Produce ________(land snails, insects, reptiles/birds) Key for animals that develop in terrestrial eggs 33 Ammonia (NH3) excretion 34 Protonephridium Filters extracellular fluid, eliminates waste by means of current produced by ciliated flame cell Drains into series of ducts Reabsorption takes place in the ducts 35  Metanephridium Filters coelomic fluid, __________ into circulatory system through blood vessels Associated with closed __________________ 36 Malpighian Tubules Large absorptive surface area in contact with ____________ Active secretion of uric acid, ions into lumen of tubule Water follows through osmosis Filtrate released into gut Na+ and K+ actively transported out, water follows Solid uric acid released with faeces 37 Nephron Found in __________ Filters water and solutes from blood, reabsorbs water and solutes to produce concentrated urine _____________ – important in formation of concentrated urine 38  HOMEOSTASIS and CIRCULATION Why circulate fluids? _____________ Regulate pH, osmolarity, waste, add nutrients, gas exchange _______________________________ hormones, heat, gasses, nutrients, immune components, solutes __________ is adequate in small (>1 mm thick) simple organisms, larger require a circulatory system Plants vs Animals both use a series of tubes, but differ in: Nutrient, energy and water sources Metabolic rates Cell structure Presence or absence of muscle 39 Types of Circulation in Animals 40  CIRCULATION in Animals Animals: Heterotrophs with extracellular digestion High metabolic rates demand rapid circulation Tissues require _______ and ___________ ______________must be carried away Move – vessels of system must be _______ 41  CIRCULATION in Animals ____________ and ______ ______ (vasculature) for circulation Fluids must be _____________ the vessels a cardiovascular system Pump (cardio) and vessels 42  CIRCULATION in Animals __________________: _________, ____ – suitable for taxa with slow metabolic rates May be supplemented with faster specialized transport systems, ie. tracheae in insects _________ – transport fluid in open circulatory systems, comes into ________________________ - extracellular fluid pool 43  CIRCULATION in Animals Open circulatory system: Heart(s) sit in haemolymph-filled _________ On contraction, haemolymph expelled from heart via major arteries to other haemolymph- filled spaces On relaxation, haemolymph enters heart from haemocoel Valves in heart wall maintain unidirectional flow Further distributed by body movements – directed flow to active tissues not possible Accessory hearts may supply limbs 44  CIRCULATION in Animals _______________________: Blood under __________ Blood vessels and heart form ___________________ Found in forms able to sustain prolonged high activity rates – annelids, cephalopods, some crustaceans, all vertebrates 45  CIRCULATION in Animals Closed circulatory system: Blood contained within heart and vessels of circulatory system, not coming in direct contact with any of the tissues of the body Blood plasma is part of the _____________________________ Capillary beds connect veins and arteries, permeating tissues Confinement makes _______________, ___________and _____________ possible 46  The Heart Muscular pump – creates ________ and directional flow in vasculature in closed circulatory systems, creates directional flow in open circulatory systems 47  The Heart and Blood Vessels In closed circulatory systems, heart maintains bulk flow of fluids in the face of ___________ Ohm’s law: ____ = ________ / _________ Low pressure High pressure Resistance in blood vessels (function of vessel length, diameter, smoothness) 48 The Heart and Blood Vessels In a closed circulatory system: From heart to capillaries: Blood pressure ____ with distance from heart, due to greater total volume occupied, ___________ Blood velocity ________ with distance from heart, due to smaller diameters of vessels occupied, due to resistance, decreasing diameters of vessels From capillaries to heart: Blood pressure continues to ____ Blood velocity _________ due to increasing diameters of fewer vessels 49  Blood Vessels and Blood Blood Vessels (in closed system): _______ (efferent vessels) carry fluid away from heart control blood distribution to the body by controlling vessel diameter (resistance!) depulsate pressure waves from the beating heart (elastic – expand/contract) _____ (afferent vessels) carry fluid back to heart store blood (easily expand) 50 Blood Vessels and Blood Capillaries Exchange of substances between blood and tissues (gas, fluids, solutes, nutrients, waste) Morphology of wall permits _________ Huge cumulative _______ _______ 51  Blood Vessels and Blood Blood (ECF) in vertebrates: _______ (ECF - water, ions, proteins, nutrients, gas) Key ions are Na+, K+, Cl-, HCO3-, Ca++, H+ Key proteins are globulins, albumin, fibrinogens Key gasses are O2 and CO2 ___________ (contain respiratory pigments – haemoglobin, haemocyanin, etc.) Increase capacity of fluid to carry O2 and CO2 _________ (white blood cells) – immune system _________ 52 Blood Vessels and Blood 53  Vertebrate Circulatory Systems Variation in circulatory system in vertebrates associated with: Whether or not _______ is a factor affecting blood flow (requiring higher pressure) Where ___ __________ takes place (gills, lungs, or lungs and skin) ____________ ________(endothermy or ectothermy) 54  Vertebrate Circulatory Systems Basal condition in vertebrates (“fish”) – 2 chambers: _____ – thin-walled, receives o2-poor blood from systemic circulation _______ – thick-walled, muscular, sends o2-poor blood through aorta to gills Circulatory system forms ___________ Low-pressure – effects of gravity negligible 55  Vertebrate Circulatory Systems Tetrapods evolved two separate circuits: Low-pressure ___________ between heart and lungs High-pressure ____________ between heart and rest of the body Each of these circuits required its own atrium, and increasing separation of the _________ into two chambers ________ becomes a factor 56 Vertebrate Circulatory Systems Many ectothermic tetrapods can bypass pulmonary circuit While ______ Cutaneous respiration Ectotherms tolerate some mixture of deoxygenated blood and oxygenated blood due to low ____________– thus incomplete separation of ventricle 57  Vertebrate Circulatory Systems Mammals and birds have _________________ between ventricles Blood can only pass blood between pulmonary and systemic circuits at the ______ ___________ requires efficient delivery of O2 to tissues 58  HOMEOSTASIS and GAS EXCHANGE Why is it needed? Krebs cycle and Oxidative phosphorylation Consume oxygen and produce carbon dioxide Photosynthesis Consumes carbon dioxide and produces oxygen pH regulation (via CO2 regulation, forms carbonic acid) All Plants and Animals must breathe! 59  O2 consumption and CO2 production Acetyl-CoA CO2 + NADH 60 RegisFrey/CC BY-SA 3.0 Gas Exchange with the environment ___________ (breathing): ________between the respiratory medium (air/water) and the gas exchange surface (body surface/lungs/gills/etc.) Must move large quantities of air/water over respiratory membrane Gas enters/exits extracellular fluid bulk flow system by _______ Book lung By John Henry Comstock - Scanned from the 1920 edition of The Spider Book, published by Doubleday, Page & Company in the United States (originally published in 1912), Wikimedia Public Domain, https://commons.wikimedia.org/w/index.php?curid=8754431 61 Gas Exchange and Gas Transport ____________ takes place between blood and air or water (at the respiratory membrane) and between tissues and blood - __________ in both exchanges _____________is carried out by the blood (circulatory system) 62  Atmospheric Composition and Pressure Atmospheric pressure decreases with ______ The _________ of the atmosphere remains the same Each gas making up the atmosphere contributes towards total atmospheric pressure - has a _______ ________ 63  Partial Pressure Gradients in the Body Diffusion in gas exchange is based on _______ ________ _________ Oxygen and carbon dioxide partial pressures ____ throughout the body Atmospheric oxygen = 21% Atmospheric carbon dioxide = 0.03% CO2 produced in tissues (high partial pressure) O2 consumed in tissues (low partial pressure) Gradients maintained by __________ _________ high low CARBON OXYGEN DIOXIDE partial Partial pressure pressure low high 64 Biology, Nelson 2013  Gas Exchange with the ECF Gas Exchange Surface: ________ between air/water and the ECF Surface area of gas exchange surface is proportional to mass and metabolic rate Surface area / volume relationships are important - large animals need specialized gas exchange structures - lungs, gills, book lungs/gills, trachea (not just body surface) Characteristics of a good gas exchange structure: reflected in Fick’s Law of Diffusion (Rate = D A dC/dX) Large ____________ Moist Thin 65  Gas Exchange with the ECF and Tissues ECF / cell interface: Diffusion at capillaries Small diameter (blood is never far from the walls), high total surface area, thin walls Single large blood vessel Multiple small blood vessels 66  Gas Exchange with the ECF Short distance across membrane to ECF necessary 67  Gas exchange surface area is Gas exchange surface proportional to body mass Animals with high metabolic rate (e.g. bird, mammal) Area of Animals with low metabolic rate (e.g. fish, amphibians) Body mass (size cubed) 68  Gas Exchange with the ECF Circulation: ____ ____of ECF within the animal Circulatory system must interact effectively with the gas exchange surface Mammals – ______ _____ Gas partial pressure gradient maintained by movement of blood Relatively poor gas exchange 69 Gas Exchange with the ECF Countercurrent exchange Water and blood move in opposing directions Maintains ________ _____ _______ ________ along exchange surface Highly effective gas exchange Buffin 2019, Phys. Chem. Chem. Phys., 21, 2186-2195 70 Gas Exchange with the ECF 71  Gas Exchange with the ECF ____________ ________ in birds Air flows in ___ __________ through the rigid lungs Air sac system Two cycles of ventilation necessary for one breathe to clear system Much more effective gas exchange than in uniform pool exchange 72 Gas Exchange with the ECF One-way bulk flow of air through a bird’s respiratory system 73  HOMEOSTASIS and ACID-BASE (pH) REGULATION pH is a measure of [H+] = -log10[H+] [H+] is moles H+/litre Log10 scale – [H+] changes by 10X with each successive integer on the scale H+ is continuously produced in aerobic respiration (among other metabolic activities) 74  HOMEOSTASIS and ACID-BASE (pH) REGULATION pH affects proteins involved in most cellular biochemical pathways H+ interact with charged regions, changes protein shape Tight regulation (human ECF pH = 7.4 (6.8-7.7)) 150 nM – 20 nM Regulation involves production, retention, and removal of _____ - mainly through _______ _____________ mechanism CO2 + H2O H2CO3 HCO -3 + H+ Carbonic acid Sensors monitor ECF 75  HOMEOSTASIS and ACID-BASE (pH) REGULATION 76  HOMEOSTASIS and ACID-BASE (pH) REGULATION Bicarbonate (pulmonary) buffering system: CO2 reacts with H2O to form carbonic acid - H2CO3 In vertebrates, carbonic anhydrase in red blood cells reversibly facilitates this reaction In plasma, H2CO3 readily dissociates into HCO3- (bicarbonate) and H+ - easily reversible reaction 77  Acid-Base Regulation CO2 + H2O H2CO3 HCO -3 + H+ Regulation of _________ (and thus plasma CO2) - very important route of pH control in terrestrial animals ______________ – gets rid of CO2 faster than it’s produced, shift reaction to left, lowers [H+] – alkylosis ____________ – conserves CO2, shifts equation to right, increases [H+] – acidosis 78  Acid-Base Regulation CO2 + H2O H2CO3 HCO -3 + H+ Renal and chemical buffering systems: Excretion/diffusion of HCO -3 or H+ through _________ ______or across gills, skin Proton or bicarbonate pumps – eliminate bicarbonate, shifts reaction to right, [H+] goes up – reverse pump – shifts reaction to left Chloride for bicarbonate pump Sodium for H+ pump, sodium for ammonium pump Binding of protons to other _________ 79  Recap of Theme 3 I (animals) Why is homeostasis important? Roles of osmoregulation, circulation, gas exchange, pH OSMOREGULATION Bulk flow, diffusion and osmosis/water pot. Osmosis and animal vs plant cells. Osmoconformers and osmoregulators. Water balance in terrestrial, marine and fresh-water environments. Excretory organs, osmoregulation and metabolic waste (ammonia excretion). 80  Recap of Theme 3 I (animals) CIRCULATION Moving the fluid (ECF) environment around the body Plants vs Animals Demands for animal circulation Hearts, blood vessels, blood Open and closed circulatory systems GAS EXCHANGE Why do plants and animals need to? Characteristics of a good gas exchange structure. Movements of gasses between cells and atmosphere: diffusion/partial pressures, and bulk flow 81  Recap of Theme 3 I (animals) pH REGULATION Importance of controlling [H+] Role and regulation of CO2, HCO3- (bicarbonate buffer), excretion and proton buffers. 82