BIOL 252 1st Edition Lecture 20 Outline of Last Lecture I. Poll EverywhereOutline of Current LectureI. Poll EverywhereCurrent LectureI. Capillary Exchangea. What moves across capillaries? Water, nutrients, wastes, ions, antibodies, hormonesi. Example of waste: urea ii. Ions: sodium, chlorideiii. Transcytosis: through endothelial cellsiv. Diffusionv. Intercellular cleftsvi. Fenestrations (filtration/reabsorption) vii. Bulk flow1. Movement of fluid component of blood plasma to leak out of capillary wall b. Filtration and reabsorptioni. Fluid filters out of arterial end of capillaryii. Fluid leaving capillary = filtration1. Opposing forcesa. Hydrostatic pressure drives fluid out of capillary (33 out)b. Osmotic pressure drives fluid into capillary (20 in)i. Force of water moving c. Net filtration pressure = 13 out iii. Fluid has forces causes it to be pulled back in1. On venous side2. Fluid reabsorbed at venous end = reabsorption 3. Net hydrostatic pressure drops (13 out)a. Lower blood pressure4. Net osmotic pressure drives fluid into capillary (20 in) 5. Net reabsorption pressure: 7 in (technically -7)iv. Capillaries reabsorb about 85% of filtered fluidThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.v. Other 15% is absorbed by lymphatic vessels and returned to the circulationvi. Edema1. Capillary filtration = capillary reabsorption + lymphatic absorptionII. Respiratory Systema. Alveolii. Squamous alveolar cellsii. Shared basement membrane1. Where O2 must traverse to get from air to bloodiii. Capillary endothelial cellb. What are the factors that affect the rate of diffusioni. Temperature ii. Surface area (greater SA = greater diffusion rate)iii. Partial pressure1. Substitute for concentration2. High concentration of O2 on one side versus the other = concentration gradient a. Greater the difference, greater diffusion rateiv. Molecule size1. Bigger = harder to movev. Diffusion distancevi. Solubility1. O2 versus CO2 solubility (CO2 more soluble)c. Respiration: exchange of gases at respiratory membraned. Ventilation: movement of air to and from respiratory membraneIII. Ventilationa. Only diaphragm is needed for relaxed ventilationb. Inhalation/inspiration: contracted diaphragmc. Expiration: relaxed diaphragmd. Other muscles there for active ventilatione. Control of ventilationi. VRG: ventral respiratory groupii. Has reverberating circuits that alternate between stimulating muscular contraction (inspiration) and allowing relaxation (expiration)iii. Can receive signals that tell it to speed up/downiv. Inspiratory neurons have spontaneous action potentials1. Trigger other neurons to cause integrating centers to cause musclecontraction2. Besides stimulating muscles, sends another signal to expiratory neuron, that has effect of turning off inspiratory neuron3. Called reverberating circuita. Why diaphragm contracts and then relaxesv. Rate factors – DRG (dorsal) and PRG (pontine) influence rate of ventilation1. Central chemoreceptors (pH)a. In CNS2. Peripheral chemoreceptors (CO2, O2)3. Stretch receptors (Hering-Breuer reflex)a. Prevents over-inflation of lung4. Irritant receptorsa. Breathe more shallow when irritants present 5. Hypothalamus and motor cortexf. Principles of ventilationi. How do we breathe?ii. Boyle’s law: pressure of given quantity of gas is inversely proportional to its volume iii. Greater volume = lesser pressureiv. Atmospheric pressure (outside) vs. alveolar pressure (inside)1. Flow outward is pressure inside > pressure outside v. How do we increase volume of our lungs?1. Balloons (lungs) expand when pressure differential2. When hand pulls down, volume increases and pressure decreases => pulling balloons open3. Applied to lungsa. Drop pressure around the lungs causes lungs to get larger b. Key to inflating lungs is space around the lungs g. What connects lungs to thoracic walli. Pleural cavity: between parietal and visceral pleura1. Adhere lungs to thoracic wallii. Visceral pleura: covering organiii. Parietal pleura iv. Plural membranes enclose pleural cavities and secrete pleural fluid IV. Expiration is easya. Around each alveolus = elastic fibersb. Unopposed elastic recoil of lungs and thorax produces a positive pressure w/in lungsc. Ribcage is ridged, providing resistance to lungs’ tendency to collapse. Which also prevents inward collapse of lungs?i. Elastic fibers surrounding alveoli1. Inward force ii. Surface tension w/in alveoli1. Force on inside of alveoli – pulls water toward itself 2. Inward force iii. Atmospheric air pressureiv. Alveolar air pressure1. Pressure inside alveoli 2. Depends upon plural cavityv. Pleural cavity1. Holds lungs