Answers Objectives-4, BIO 3360
RESPIRATION – I – INTRODUCTION to OXYGEN and CARBON DIOXIDE
- A unicellular organism can use just plain diffusion to exchange gases. Multicellular animals use diffusion plus convection which is movement in bulk.
- Diffusion is movement from high concentration to low, flux is movement of materials through a pathway and convection is movement in bulk.
- Diffusion is between alveoli and pulmonary capillaries as well as systemic capillaries and body tissues; convection is alveolar gas exchange (lung and environment) and blood circulation.
- 760 and 630 mmHg
- The pressure contribution by each gas in the atmospheric pressure; PO2is 150 mmHg and PCO2 is about 0.
- [G] = P Gas x S Gas ; This says that the concentration of gas in a solution is dependent on the pressure gradient of the gas and how soluble that gas is in liquid.
- Compare oxygen solubility in air vs. aqueous solution: oxygen is much more soluble in air than in an aqueous soln. As temperature increases, solubility decreases. As salinity increases, oxygen solubility decreases.
RESPIRATION – II – GAS TRANSFER
- Ventilation is breathing or pumping water across another respiratory surface such as gill/skin. Elastic recoil is like letting go of a rubber band causing a structure to get smaller back to its resting shape while compliance is how easy it is to stretch a structure. Surface tension is by like molecules (water) being attracted to each other and it hurts lung compliance by making the lungs wanting to collapse. Surfactant is a fatty substance that gets between the like molecules that are causing surface tension and thus reduces it. Hemoglobin is the respiratory pigment that most commonly transports oxygen in the bloodstream.
- Diffusion is the key principle behind oxygen and carbon dioxide exchange. Gases move from an area of higher pressure to an area of lower pressure across very thin membranes.
- Each is only one cell layer thick and very thin.
- Inhalation involves contraction of respiratory muscles which increases the size of the lungs and lowers their pressure so that air moves in from a higher atmospheric pressure to a lower one in the alveoli; Exhalation involves relaxing those respiratory muscles allowing them to pop up and in resulting in a smaller lung volume with a higher pressure than atmospheric pressure. This causes air to move out.
- Tidal volume is the amount of air moving in or out in a quiet breath; dead air volume is that amount of air not in the alveoli. Alveolar ventilation rate would be the respiratory rate x (the tidal volume-dead air volume).
RESPIRATION III – NON-MAMMALIAN RESPIRATION and GAS TRANSPORT IN BLOOD
- Diffusion is slower and water has less oxygen than air.
- Fish use countercurrent water flow from inside to out and blood flow across the gills goes outside to in ensuring a gradient across the entire gill. Birds have secondary bronchi connected by parabronchi that have air capillaries in their walls leading to one way air flow and a tremendous surface area for gas exchange. They have tremendous surface area and one way air flow and continuous ventilation of the bronchi. A reptile uses negative pressure, but the frog uses a pulse pump in which it gulps air and then squeezes into to airways.
- External gill is an evagination of the pharyngeal area whereas an internal gill is within the contours of the pharynx. The birds have secondary bronchi connected by parabronchi that have air capillaries in their walls leading to one way air flow and a tremendous surface area for gas exchange. Air sacs in birds provide continuous ventilation of the bronchi. The tracheal system in insects includes tracheas that branch to smaller tracheoles which are blind tubes located near tissue cells. The opening is termed the spiracle. The chloride shift keeps ionic balance in a red blood cell. A bicarbonate ions (negatively charged) move in or out of a RBC, the chloride ions (negatively charged) move in the opposite direction.
- Gill lamellae and filaments.
- Water and blood are moving in opposite directions such that there is always a concentration gradient and this maximizes efficiency.
- Some amphibians.
- Hemoglobin transports oxygen in most vertebrates and some invertebrates. Hemocyanin transports oxygen in mollusks and arthropods. Chlorocruin transports oxygen in marine annelids. Hemerythrins transport oxygen in hard-valved invertebrates and other marine worms.
- It is the PO2levels that determine whether oxygen and hemoglobin bind (=saturates) or dissociate in the oxygen-hemoglobin dissociation curve. The Bohr effect which reflects conditions of exercise & metabolic activity (low pH, high temp, High CO2 levels…) that shifts it to the right and opposite shifts it to the left. Shifting the curve to the right which means that high metabolism tissues get the oxygen they need. The Root effect demonstrates that increasing CO2 or decreasing pH decreases affinity of oxygen and hemoglobin.
- Some free in plasma, some bound to the globin portion of hemoglobin but most in the form of bicarbonate ions.
- CO2+ H2O <–> H2CO3 <–> HCO3– + H+
- Deoxygenated blood can carry more CO2than oxygenated blood. The CO2 equilibrium curve of deoxygenated blood is shifted to the left. Why? Deoxygenated hemoglobin tends to bind H+ ions, increasing the pH and HCO3–, and increasing the total amount of CO2 that can be carried. The Haldane effect is that deoxygenation of hemoglobin at the tissues promotes CO2 uptake by the blood whereas oxygenation of the hemoglobin at the respiratory surface promotes CO2
- An acid is a proton donor and has a pH 0-7; a base is a proton acceptor and has a pH 7-14.
- Inverse relationship. As hydrogen concentration increases, pH decreases.
- H+ and OH– form water.
- Neutrality is when the positive ions equal the negatives; ion has a charge to it – an unequal number of positive vs. negatives; an electrolyte is a salt that ionizes in water.
- SID is the sum of all positive strong ions minus the sum of all negative strong ions. A negative SID is an acid and a positive SID is a base.
- Buffers resist changes of pH by converting strong acids/bases to weak ones.
- Controlling PCO2levels through respiratory system, controlling SID through urinary system and through buffer systems. A physiologic buffer is a body system such as the respiratory or urinary system. A chemical buffer system, such as the bicarbonate buffer system can quickly bind or release hydrogen ions. Respiratory through increasing/decreasing PCO2levels and urinary primarily through hydrogen ion excretion.
- Bicarbonate Buffer System: CO 2+ H 2 O <–> H 2 CO 3 <–> HCO 3 – + H+ , Phosphate Buffer System: H 2 PO 4 – <–> HPO 4 2– + H+ , Protein Buffer System: Carboxyl groups on amino acids –COOH –> –COO– + H+ or Amino groups on amino acids –NH2 + H+ –> –NH3 +.
IONIC & OSMOTIC BALANCE and NITROGEN EXCRETION
- Freshwater fish must conserve & acquire salt and expel water, saltwater fish must expel salt against the concentration gradient and obtain water. Organs used for this balance include kidneys, gills, skin, digestive tract. Waterproofing can occur through a waxy cuticle in insects, keratin in tetrapods, close proximity of adjacent epithelial cells, hair. Salt gland excrete salt and use countercurrent mechanisms, in that blood and salt flow of gland run in opposite directions maximizing salt concentrations in the lumen of the gland.
- Ionoconformer conforms to external environment levels and an ionregulator keeps internal homeostasis regardless of environment. Osmoconformer keeps water levels about equivalent to external environment and osmoregulator maintains water homeostasis regardless of external environment. Regulatory volume increase is importing ions resulting in influx of water. Regulatory volume decrease is ions leave the cell and therefore water follows.
- Water in the environment, diet and metabolism.
- Organs used for this balance include kidneys, gills, skin, digestive tract.
- Ammonia, uric acid, urea.
- Protein catabolism.
- Ammonia is most toxic but requires the fewest steps and the smallest amount of energy to form. Uric acid needs more energy to form and is very concentrated; urea requires even more energy to form but is less concentrated and less toxic.
- Lungfish can convert from ammonia excretion to urea excretion depending on surroundings (water vs. air).
THE MAMMALIAN KIDNEY
- Rid body of liquid waste, water balance, filter blood, vitamin D activation, regulates blood pressure and regulates erythropoiesis.
- Outer part of kidney, inner part of kidney, triangular regions in the medulla, funnel collecting urine to transport out of the kidney.
- Nephron; Glomerulus & Glomerular capsule (Glomerulus is a tuft or network of permeable blood capillaries. It is surrounded by the capsule (Bowman’s Capsule) and these two structures comprise the renal corpuscle.), Renal tubules including proximal convoluted tubule, descending limb of the loop of Nephron, loop of nephron, ascending limb of loop of nephron, distal convoluted tubule, followed by collecting ducts or tubules.
- Glomerular hydrostatic pressure (is blood pressure in glomerulus) drives filtration. Opposing factors are not strong enough to oppose filtration, but include the osmotic pressure in the glomerulus as well hydrostatic pressure in the glomerular capsule.
- Filtration occurs from the glomerulus into the glomerular capsule. It is a passive process influenced by the size of the particles & whether or not they can fit through the pores of the glomerulus and not based on need. Blood pressure in the glomerulus certainly is a driving force. ADH is made by the hypothalamus but stored in the posterior pituitary gland. It causes water reabsorption in the nephron. The distal convoluted tubule is ADH (antidiuretic hormone) and aldosterone If ADH is present, water is reabsorbed. If aldosterone is present, sodium is reabsorbed and water passively follows. The collecting duct is also hormone dependent. If ADH is present, you will have significant water reabsorption resulting in small amounts of highly concentrated urine. Aldosterone is made by the adrenal cortex. It causes sodium reabsorption from the nephron and water passively follows. Nephrons filter blood to make liquid waste, or urine. They control blood pressure, volume and pH. They remove waste from bloodstream such as protein metabolic waste called urea. Urine is the liquid waste as a result of the filtration/reabsorption process. Nephrons are the functional and structural units of the kidneys. They filter blood to make liquid waste, or urine. They control blood pressure, volume and pH. They remove waste from bloodstream such as protein metabolic waste called urea. The proximal convoluted tubule is where most reabsorption occurs. Most nutrients and water are reabsorbed here. As you descend the limb of the nephron, it is permeable to water and water is reabsorbed. At the loop, urea enters the loop from the interstitial region & is recycled back into the urine. The ascending limb is permeable to salt but not water. As you ascend into a weakly concentrated interstitial region the salt will be reabsorbed. The distal convoluted tubule is ADH and aldosterone dependent. If ADH is present, water is reabsorbed. If aldosterone is present, sodium is reabsorbed and water passively follows. The collecting duct is also hormone dependent. If ADH is present, you will have significant water reabsorption resulting in small amounts of highly concentrated urine. It gets so concentrated, that near the bottom of the collecting duct, even urea is reabsorbed into the interstitial region. Secretions of substances such as hydrogen ions, ammonia, and drugs occur primarily in the convoluted tubules. Here substances can pass directly from the bloodstream into these tubules.
- Two parallel tubes running in opposite directions benefit each other. For example if salt is pulled out of one tube, it facilitates pulling water out of the parallel tube. Vasa recta serve the limbs of the nephron. They are parallel tubes of blood flow running in opposite direction.
- There is a vast decrease in volume and increase in concentration upon traveling through the proximal convoluted tubule. After descending the limb, the concentration increases and volume decreases. After ascending the limb, the concentration decreases and volume is unchanged. After the DCT and collecting tubule, if ADH is present, the volume decreases and concentration increases. The significance is that as you descend into the medulla, the interstitial fluid is very concentrated which offers some great “drawing” power for pulling water out of the kidney tubules. The concentration is maintained by having the vasa recta operate in a countercurrent mechanism so that all of the solutes are not removed from the interstitial region. Additionally, urea adds to the interstitial concentration, as does differential permeability of the different portions of the nephron.