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UNC-Chapel Hill BIOL 252 - Final Exam Study Guide

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BIOL 252 1st EditionExam #4 Study Guide Lectures: 21-26Respiratory SystemI. 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 membraneII. 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 III. 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 cavity v. Pleural cavity1. Holds lungs outwardIV. How significant is pulmonary elasticity?a. Pneumothorax or hemothorax is compromise of pleural membranesb. Unopposed pulmonary elasticity shrinks lungs and expands pleural cavity c. Two major forces: elastic tissues surrounding alveoli & surface tensionV. Ventilationa. When you expand your thorax, expand your lungs b. Go from neutral to decrease in pressure (-3 mmHg) – Boyle’s Lawi. Inspiration => lower intrapulmonary pressurec. When expire, decrease volume, increase pressure (+3 mmHg)i. Higher intrapulmonary pressure (762 mmHg compared to atmospheric pressure of 760 mmHg)VI. Resistance to Airflowa. Factors:i. Diameter of bronchi/bronchioles1. Bronchoconstriction: ACh, cold air, irritants, histamine (resting position)a. Why keep narrow under resting conditions?b. Smaller cross sectional diameter = smaller volume i. Anatomical dead space: all of the air not involved ingas exchange; if must move larger volume of air = more work; smaller volume – more (proportionally)gets to alveoli 2. Bronchodilation: catecholamines (E, NE) – sympathetic nervous systema. Increase diameter, decreases resistance, increases flowb. Advantage to getting air in more quickly – exchange of gases quicker ii. Pulmonary compliance1. Compliant lungs expand easily with expansion of thorax2. With aging, fibrosis = more rigid lungs (not as compliant)a. To pull in same volume, must work harder for each breathiii. Surface tension w/in alveoli 1. Each alveolus has tendency to collapse inward a. To reduce this effect, surfactant breaks/reduces surface tension – produced by greater alveolar cells (type II)b. If premature baby, cannot overcome collective inward force because not making enough surfactant VII. Respiratory Volumesa. Tidal Volume: 0.5 Lb. Inspiratory reserve volume: at top of tidal volume – if you inhale to capacity (howmuch more you can inspire)c. Expiratory reserve volume: how much more can we exhale?d. Vital capacity: inspiratory reserve volume, expiratory reserve volume, tidal volumee. Residual volume: amount of air that does not leave lungs after max exhalation (1.5 L)i. Keeps alveoli from collapsing ii. Why can’t we get rid of this air? Because we have a ribcage; this air is not usable VIII. Restrictive Pulmonary Disordersa. Restrictive disorders reduce pulmonary compliance resulting from fibrosis b. Fibrosis resulting from Tuberculosis infectionc. Result = low compliance IX. Obstructive Pulmonary Disordersa. Reduces flow (obstructs flow)b. Ex: asthma – inflammation of airways c. Blue curve – normal; red curve – obstructive disorder, takes longer to push air outd. FEV: forced expiratory volume, usually at 1 seci. Inhalation then blow out as hard as you can – 90% of vital capacity comesout after 1 secii. With obstructive disorder, flow reduced, cannot get out as quickly1. Affects diameter e. Which would result in condition resembling obstructive pulmonary disorder?i. Pulmonary fibrosisii. Insufficient numbers of great alveolar cellsiii. Bronchitis: decreases diameter, increases resistance, decreases flowiv. Broken ribsX. Gas exchangea. Happens in alveoli b. Through diffusion –


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UNC-Chapel Hill BIOL 252 - Final Exam Study Guide

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