BIO 311D 2nd Edition Lecture 26 Outline of Last Lecture I. Wrap up hormone examples (3-23 and 3-25)II. Principles of transport and exchange in animalsIII. How excretory tubules help with homeostasis?Outline of Current Lecture I. Hormones influence excretory tubules II. Where is the respiratory epithelium?III. Principles of DiffusionIV. Counter Current Exchange Current LectureI. Hormones influence excretory tubulesA. Blood pressure + leaky tubules allows for easy exchange B. Excretory tubules adapt to environment a) Structural adaptations 1. Shape, 2. Membrane proteins, 3. Cell-cell junctions 4. Length of tubule relative to water reabsorption b) Physiological Responses (under hormone control)1. If blood pressure too low2. If body dehydrated C. Kangaroo rat: highly adapted to desert conditionsa) Kidney: produces urine that is five times more concentrated than human’s… kangaroo rats never have to drink water b) Assuming that the length of the kidney tubule evolved due to selection for water conservation, rank these mammals from (expected) longest tubules to shortest tubules. [3,2, 1] 1. Beaver2. Human3. Kangaroo Rat D. When neurons in the brain’s hypothalamus detect an increase in blood solute concentration. [What conditions could lead to an increase in blood solute conditions? – dehydration, etc.], the pituitary secretes anti-diuretic hormone(ADH). ADH in blood circulation causes the transport epithelium in the kidney excretory tubules to be more permeable to water [how, possibly? – insert aquaporin (aquaporin already located on the membrane, receptors then proteins attaches to membrane creating a new aquaporin]; as a result more water is reabsorbed back into the blood and the urine produced is more concentrated.a) Explain how ADH thus helps maintain homeostasis of solute-water in the blood? Blood [Solute increased]  ADH released –more aquaporin (more reabsorption of water into blood)-- Lower solute concentration b) Alcohol inhibits ADH secretion- what results? Decreases ADH secretion –water is not reabsorbed, stays in the tubules increase urination E. One part of a response to a drop in blood pressure is secretion of aldosterone (steroid) from adrenal cortex. Aldosterone acts on nephron’s distal tubules and collecting ducts and makes them reabsorb more Na+ (how, possibly? —passive ion channels or sodium pump, from the tubule into the cell) Thus (Explain—water follows solute) more water comes in, increasing blood pressure.a) If there is an increase in blood volume and pressure, ANP hormone (atrial natriuretic peptide) inhibits NaCl reabsorption II. Where is the respiratory epithelium?A. Why do we need gas exchange? What is the gas used for? – To take in oxygen andremoving CO2B. Transport epitheliuma) Cell  bloodb) Blood  external surfaceC. No respiratory system neededa) In some animals, body wall is so thin that they simply absorb O2 and release CO2 through their skin b) Earthworms are skin breathers: they must keep their skin moist, segmented worms – circulatory system is right near the skinc) Many amphibians “breathe through their skin”. Even with gills or lungs, there are many capillaries close to the thin moist skin, and gas exchange can occur. D. Respiratory organs in many aquatic animals are gills. What happens to the O2 when it crosses the respiratory epithelium?a) Into the blood through the capillaries, into the circulatory system b) Ventilation increases flow of water over gills. How does the structure of gills optimize their function? E. Insects  (trachea) branches of respiratory tubules  Don’t have oxygen move through the tubules, they go directly to the body cellsF. List some ways that lungs can be structured to maximize gas exchange.a) Increase lung sizeb) Increase external surface area c) Increase in expansion of lungs d) Respiratory epithelium  Alveoli e) In the mammalian lung, the respiratory surface is an epithelium lining the inner walls of the alveoli. Capillary joins the cell of the alveoli  as close as you can possibly get to increase gas exchange III. III. Principles of DiffusionA. Factors affecting diffusion a) Fick’s Law for rate of gas exchange 1. Increase surface area increase diffusion2. Increase path length (diffusion distance)  decrease diffusion 3. Increase the pressure difference  increase diffusion b) How can respiratory structures be structured to maximize diffusion1. Increase surface area2. Decrease path length3. Increase in pressure difference on either side of the epithelium c) From Fick’s law, tell how each of the factors would affect the rate of diffusion across a membrane- would it:1. Increase diffusion: small temp. change, increase surface area2. Decrease diffusion: large temp. change, thicker cell membrane 3. Have no changed) Lung diseases that affect gas exchange – How?1. Emphysema: decrease in surface area2. Fibrosis: affect diffusion distance 3. Pulmonary Edema: affects diffusion distanceIV. Counter-Current ExchangeA. Increases concentration gradient B. Water comes in 100% oxygenated, blood comes in only 20% oxygenated C. More oxygen goes into the