BIOL 252 1st Edition Exam 4 Study Guide Lectures 21 26 Respiratory System I Respiratory System a Alveoli i Squamous alveolar cells ii Shared basement membrane 1 Where O2 must traverse to get from air to blood iii Capillary endothelial cell b What are the factors that affect the rate of diffusion i Temperature ii Surface area greater SA greater diffusion rate iii Partial pressure 1 Substitute for concentration 2 High concentration of O2 on one side versus the other concentration gradient a Greater the difference greater diffusion rate iv Molecule size 1 Bigger harder to move v Diffusion distance vi Solubility 1 O2 versus CO2 solubility CO2 more soluble c Respiration exchange of gases at respiratory membrane d Ventilation movement of air to and from respiratory membrane II Ventilation a Only diaphragm is needed for relaxed ventilation b Inhalation inspiration contracted diaphragm c Expiration relaxed diaphragm d Other muscles there for active ventilation e Control of ventilation i VRG ventral respiratory group ii Has reverberating circuits that alternate between stimulating muscular contraction inspiration and allowing relaxation expiration iii Can receive signals that tell it to speed up down iv Inspiratory neurons have spontaneous action potentials 1 Trigger other neurons to cause integrating centers to cause muscle contraction 2 Besides stimulating muscles sends another signal to expiratory neuron that has effect of turning off inspiratory neuron 3 Called reverberating circuit a Why diaphragm contracts and then relaxes v Rate factors DRG dorsal and PRG pontine influence rate of ventilation III 1 Central chemoreceptors pH a In CNS 2 Peripheral chemoreceptors CO2 O2 3 Stretch receptors Hering Breuer reflex a Prevents over inflation of lung 4 Irritant receptors a Breathe more shallow when irritants present 5 Hypothalamus and motor cortex f Principles of ventilation i How do we breathe ii Boyle s law pressure of given quantity of gas is inversely proportional to its volume iii Greater volume lesser pressure iv 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 differential 2 When hand pulls down volume increases and pressure decreases pulling balloons open 3 Applied to lungs a 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 wall i Pleural cavity between parietal and visceral pleura 1 Adhere lungs to thoracic wall ii Visceral pleura covering organ iii Parietal pleura iv Plural membranes enclose pleural cavities and secrete pleural fluid Expiration is easy a Around each alveolus elastic fibers b Unopposed elastic recoil of lungs and thorax produces a positive pressure w in lungs c Ribcage is ridged providing resistance to lungs tendency to collapse Which also prevents inward collapse of lungs i Elastic fibers surrounding alveoli 1 Inward force ii Surface tension w in alveoli 1 Force on inside of alveoli pulls water toward itself 2 Inward force iii Atmospheric air pressure iv Alveolar air pressure 1 Pressure inside alveoli 2 Depends upon plural cavity v Pleural cavity IV V VI VII 1 Holds lungs outward How significant is pulmonary elasticity a Pneumothorax or hemothorax is compromise of pleural membranes b Unopposed pulmonary elasticity shrinks lungs and expands pleural cavity c Two major forces elastic tissues surrounding alveoli surface tension Ventilation a When you expand your thorax expand your lungs b Go from neutral to decrease in pressure 3 mmHg Boyle s Law i Inspiration lower intrapulmonary pressure c When expire decrease volume increase pressure 3 mmHg i Higher intrapulmonary pressure 762 mmHg compared to atmospheric pressure of 760 mmHg Resistance to Airflow a Factors i Diameter of bronchi bronchioles 1 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 in gas exchange if must move larger volume of air more work smaller volume more proportionally gets to alveoli 2 Bronchodilation catecholamines E NE sympathetic nervous system a Increase diameter decreases resistance increases flow b Advantage to getting air in more quickly exchange of gases quicker ii Pulmonary compliance 1 Compliant lungs expand easily with expansion of thorax 2 With aging fibrosis more rigid lungs not as compliant a To pull in same volume must work harder for each breath iii 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 Respiratory Volumes a Tidal Volume 0 5 L b Inspiratory reserve volume at top of tidal volume if you inhale to capacity how much more you can inspire c Expiratory reserve volume how much more can we exhale VIII IX X d Vital capacity inspiratory reserve volume expiratory reserve volume tidal volume e 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 Restrictive Pulmonary Disorders a Restrictive disorders reduce pulmonary compliance resulting from fibrosis b Fibrosis resulting from Tuberculosis infection c Result low compliance Obstructive Pulmonary Disorders a Reduces flow obstructs flow b Ex asthma inflammation of airways c Blue curve normal red curve obstructive disorder takes longer to push air out d FEV forced expiratory volume usually at 1 sec i Inhalation then blow out as hard as you can 90 of vital capacity comes out after 1 sec ii With obstructive disorder flow reduced cannot get out as quickly 1 Affects diameter e Which would result in condition resembling obstructive pulmonary disorder i Pulmonary fibrosis ii Insufficient numbers of great alveolar cells iii Bronchitis decreases diameter increases resistance decreases flow iv Broken ribs Gas exchange a Happens in alveoli b Through diffusion partial pressures i Force exerted on walls of container ii Dalton s law each gas behaves the same way 1 Ex Oxygen is 20 9 of 760 mm Hg 159 mm Hg which is partial pressure c Alveolar air what s in your lungs i Less N2 less O2 more