Flashcards in BIOL 0800 Reading- Chapter 13 Deck (113):
Every minute, approximately how much air and blood flows through the lungs/pulmonary capillaries?
4L air, 5L blood
What is the structure of the pulmonary system after the larynx?
Trachea, into two bronchi, into two bronchioles, into terminal bronchioles, into respiratory bronchioles, into alveolar ducts, into alveolar sacs: alveoli show up in respiratory bronchioles and increase in alveolar ducts and alveolar sacs
What is the conducting zone?
From the top of the trachea to the beginning of the respiratory bronchioles; contains to alveoli and no gas exchange
What is the respiratory zone?
From the respiratory bronchioles downwards; contains alveoli and gas exchange
What are type I alveolar cells?
One-cell thick, flat layer of epithelial cells lining the air-facing surfaces of alveolar walls
What are type II alveolar cells?
Interspersed between type I cells; thicker, specialized: produce surfactant
What is inside the alveolar wall?
Capillaries and a very small interstitial space: interstitial fluid and loose mesh of connective tissue
What are intercostal muscles?
Muscles that run between ribs
What is the pleural sac?
Completely closed sac that encloses each lung, made of thin sheet of cells called pleura
What is the difference between visceral and parietal pleura?
Internal surface touching the lung, and external surface touching the thoracic cavity interior
What is intrapleural fluid?
Fluid between the visceral and parietal pleura
What is the equation for bulk flow?
F = deltaP/R
In the equation for bulk flow, what is delta P?
Alveolar pressure (Palv) minus atmospheric pressure (Patm)
What happens when Palv is less than Patm?
Negative flow, or inspiration
What happens when Palv is greater than Patm?
Positive flow, or expiration
What is Boyle's law?
PV = PV
Lung volume depends on what two factors?
Transpulmonary pressure and lung stretchability
What is transpulmonary pressure?
The difference in pressure between the inside and outside of the lung; Palv minus Pip (intrapleural)
What are the formulas for transmural pressure on the lungs and on the chest cavity?
On the lungs is Palv - Pip, and on the chest cavity is Pip - Patm
How does transmural pressure affect inspiration/expiration?
Transmural pressure increases for inspiration (decreases Pip relative to Palv), and uses elastic recoil to drive passive expiration
When there is no airflow, why is Pip negative?
Because there is always a positive transmural pressure, so Palv > Pip, but Palv = 0
What forces cause intrapleural pressure to be zero when there is no airflow?
Elastic recoil of the lungs and the chest cavity causes the lungs to shrink and thoracic cavity to expand: pulls the pleural walls apart and decreases pressure
What is the crucial factor in keeping the lungs partially expanded between breaths?
The negative (subatmospheric) intrapleural pressure
What causes the diaphragm to contract?
Activation of the phrenic nerves
How does inspiration occur?
Thorax expands, Pip becomes subatmospheric, transpulmonary pressure increases, lungs expand, Palv becomes subatmospheric, air flows into alveoli
How does expiration occur?
Diaphragm and chest wall recoil inward; Pip returns to normal value, transpulmonary pressure decreases, elastic recoil overcomes transpulmonary pressure, and lungs passively recoil
What is lung compliance?
The magnitude of the change in lung volume produced by a given change in transpulmonary pressure
What is the formula for lung compliance?
Delta V/delta Ptp
What are two major determinants of lung compliance?
Stretchability of lung tissues, and surface tension on alveoli
What is surfactant for?
Reduces cohesive forces between water molecules on the alveolar surface: lowers the surface tension and increases lung compliance
What is the law of Laplace?
P = 2T/r
Why do alveoli of different sizes exist?
Because of Laplace's law: if the radius is smaller, then the surfactant is denser and surface tension is less, which allows for a higher pressure to prevent the small alveolus from condensing into larger ones
How does transpulmonary pressure affect resistance?
Increase in transpulmonary pressure increases airway radius, and airway resistance is decreased (inspiration)
What is lateral traction?
When the elastic connective-tissue fibers around the alveolar tissue help pull the airways open when the lungs pull on them.
How does epinephrine affect airway resistance?
Relaxes airway smooth muscle through beta-adrenergic receptors
What substance contracts airways to increase airway resistance?
Leukotriene, an eicosanoid
What is the tidal volume?
The volume of air taken in during a single expiration; usually the same volume as is expired
What is the inspiratory reserve volume (IRV)?
The maximal amount of air that can be increased above TV
What is functional reserve capacity (FRC)?
The amount of air left in the lungs after a normal tidal expiration: ERV + RV
What is expiratory reserve volume (ERV)?
The maximal amount of air that can be expired below TV
What is residual volume?
The amount of air remaining in the lungs after maximum expiration
What is the function of residual volume?
Keeps alveoli inflates between breaths, mixes with fresh air on next inspiration
What is the vital capacity (VC)?
The maximum amount of air you can exhale after a maximum inspiration; ERV + TV + IRV
What is inspiratory capacity (IC)?
Maximum amount of air that can be inhaled after a normal tidal expiration; RV + ERV
What is minute ventilation?
Total ventilation per minute: TB x RR (respiratory rate)
What is the approximate minute ventilation of a normal person?
6 L: (0.5 TV)(12 breaths each minute)
What is anatomical dead space?
The space within the airways that doesn't permit gas exchange
How do you calculate how much fresh air enters the lungs?
TV - deadspace = fresh air volume
What is alveolar ventilation?
The total volume of fresh air entering the alveoli per minute: = (TV - deadspace)(respiratory rate)
Why is breathing depth more important than breathing frequency to increase alveolar ventilation?
Because you still need to overcome dead space
What is alveolar dead space?
The volume of air that isn't used for gas exchange because alveoli have little or no blood supply; small in normal lungs
What is physiological dead space?
The sum of anatomical and alveolar dead space
What is the respiratory quotient?
The ratio of CO2 produced to O2 consumed; approximately 0.8
What is Dalton's law?
The sum of all the partial pressures of gases is the total pressure, since the pressures of different gases don't depend on each other
What is Henry's law?
The amount of gas dissolved in a liquid will be directly proportional to the partial pressure of the gas with which the liquid is in equilibrium; partial pressures at equilibrium of a gas in liquid and gas phases is identical
What are normal alveolar gas pressures?
105 for oxygen, 40 of CO2
Why are air pressures of O2 and CO2 different from alveolar pressures?
Because of diffusion in the pulmonary capillaries
What are three factors that determine the precise value of alveolar PO2?
PO2 of atmospheric air (decreased causes decrease); rate of alveolar ventilation (decreased causes decrease); rate of oxygen consumption (increased causes decrease) assuming only one factor changes at a time
What is hypoventilation?
When alveolar ventilation can't keep up with CO2 production: increase in PCO2
What is hyperventilation?
When alveolar ventilation is too great for CO2 production; decrease in PCO2
What is the major disease-induced cause of inadequate oxygen movement between alveoli and pulmonary capillary beds?
What is the major effect of ventilation-perfusion inequality?
To lower the PO2 of systemic arterial blood
Why is the PO2 of blood in circulation normally about 5 mmHg less than that of average alveolar air?
Because gravity causes a different blood flow distribution in the lung, which contributes to ventilation-perfusion inequality, which reduces PO2
What is shunt?
Blood flow to an area without ventilation
What is the main homeostatic mechanism to avoid ventilation-perfusion inequality for low ventilation and low perfusion?
When there is low alveolar PO2 (due to decrease in ventilation), the vessel vasoconstricts and directs blood elsewhere to properly ventilated areas; of when there is low alveolar PCO2, the bronchioles constrict and direct airflow elsewhere
What is hemoglobin?
Four subunits made of one polypeptide and one heme each (a globin and four heme groups); heme groups contain iron for cooperative binding to oxygen
What is percent hemoglobin saturation?
(O2 bound to Hb) / (maximal capacity of Hb to bind to O2) x 100
What factors determine the % Hb saturation?
What is the oxyhemoglobin dissociation curve?
The experimentally determined quantitative relationship between blood PO2 and the combination of oxygen with hemoglobin; sigmoid because of cooperative binding
What is the approximate shape/range of the oxyhemo dissoc curve?
Steep slope from 10-60 mmHg, plateaus at 70-100 mmHg PO2; **at a PO2 of 60 mmHg, 90% hemoglobin saturation
What is the biological significance of the plateau in the oxyhemo dissoc curve?
Safety net! Even if atmospheric PO2 decreased from 100 to 60 mmHg, total hemoglobin saturation would only decrease by 10% or so
What is the biological significance of the steep slope of the oxyhemo dissoc curve?
Allows for easy unloading of oxygen: small PO2 changes can lead to a big decrease in hemoglobin saturation
How does temperature affect the OHD curve?
Increased temperature shifts the curve right: makes it more difficult to unload oxygen
How does acidity affect the OHD curve?
Increased acidity (lower pH) shifts the curve right: makes it more difficult to unload oxygen
How does DPG concentration affect the OHD curve?
Increased DPG concentration shifts curve right: makes it more difficult to unload oxygen
How does PCO2 affect the OHD curve?
Increased PCO2 increases H+ concentration, which increases acidity: shifts curve right: lowers affinity of Hb for O2
How do CO2 and H+ affect hemoglobin's affinity for oxygen?
Allosterically modulate the globin
How does DPG affect Hb's affinity for oxygen?
DPG = released during glycolysis (only respiration for RBCs, so lots of DPG in RBCs); allosterically modulates Hb
Which is more soluble in water, CO2 or O2? Why is this important?
CO2: blood carries more dissolved CO2 than dissolved O2
How is CO2 transported in the blood?
Some by dissolving, some by binding with Hb to form carbaminohemoglobin, and most converted to bicarbonate and hydrogen ions by carbonic anhydrase
What is carbaminohemoglobin?
When CO2 binds to Hb (deoxyhemoglobin, which has a higher affinity for CO2 than for O2, than does HbO2)
Why is it important that the chloride-bicarbonate exchange removes HCO3- from the RBC?
So that the reaction still favors dissociation of bicarbonate
Why is venous blood slightly more acidic than arterial blood?
Because dissociation of bicarbonate produces H+, which binds to deoxyhemoglobin, but there's still some left: decreases the pH (more acidic)
What is associated with hypo/hyperventilation, respiratory acidosis or alkalosis?
Acidosis associated with hypoventilation, alkalosis associated with hyperventilation
What initiates nerves impulses to the respiratory skeletal muscles?
Medulla oblongata activity: in medullary respiratory center
What are the two components of the medullary respiratory center?
The dorsal and ventral respiratory groups (DRG and VRG)
What is the DRG?
Primarily fire during inspiration; input to spinal motor neurons that activate inspiratory muscles: diaphragm and inspiratory intercostal muscles
What is the nerve that innervates the diaphragm?
What is the VRG?
Rhythm generator: pacemaker cells and complex neural network that sets basal respiratory rate; respiratory rhythm generator located in the pre-Botzinger complex in the upper VRG; nerves in lower half that fire for inspiration AND expiration
What is the upper half of the VRG?
Rhythm generator in the pre-Botzinger complex; pacemaker cells; inspiratory neurons (input from DRG inspiratory neurons, from respiratory rhythm generator; output to inspiratory motor neurons)
What is the lower half of the VRG?
Expiratory neurons: important for large increases in ventilation like in exercise: active expiration through contraction
How is medullary inspiratory nerve activity modulated?
By the pons: apneustic center in lower pons, pneumotaxic center in uppon pons
What is the apneustic center?
In the lower pons: modulates medullary inspiratory activity, inhibitory to end inspiration
What is the pneumotaxic center?
In the upper pons: modulates apneustic center; smooths transition between inspiration/expiration
What are pulmonary stretch receptors for?
Cutting off inspiration: activated by large lung inflation: afferent nerve fibers send action potentials to inhibit medullary inspiratory neuron activity
What is the Hering-Breuer reflex?
When afferent nerve fibers from stretch receptors send action potentials to the brain to inhibit medullary inspiratory behavior and end inspiration; BUT only under conditions of large TV like during exercise
What are peripheral chemoreceptors for respiration?
Located in neck by common carotid arteries and in thorax on aortic arch: carotid bodies and aortic bodies (distinct from carotid and aortic baroreceptors); stimulated by decrease in arterial PO2 or increase in H+; provide excitatory input to medullary respiratory systems
What are the central chemoreceptors for respiration?
Located in medulla oblongata; provide excitatory input to medullary respiratory systems; stimulated by increase in H+
Why do changes in PCO2 trigger ventilation control reflex?
Mostly through increases or decreases in H+ concentration, which is detected by the central chemoreceptors and dealt with accordingly
Which chemoreceptors respond to H+ concentration changes, peripheral or central?
Peripheral for metabolic acidosis/alkalosis (not caused by CO2 changes), and central for respiratory acidosis/alkalosis (caused by CO2 changes)
How does H+ concentration affect chemoreceptor activity?
Increase in H+ increases chemoreceptor activation of medullary respiratory neurons, which increases respiration
What is associated with hyper/hypoventilation, metabolic alkalosis or acidosis?
Metabolic acidosis triggers hyperventilation (reduces arterial PCO2, so H+ back to normal); metabolic alkalosis triggers hypoventilation (increases arterial PCO2, so H+ back to normal)
Why doesn't arterial PCO2 increase during exercise?
Because arterial PCO2 depends on alveolar PCO2, and alveolar PCO2 depends on ratio of CO2 production to alveolar ventilation: ventilation increase proportionally with CO2 production during exercise, so no increase in alveolar PCO2
What is the limiting factor in strenuous exercise, ventilation or cardiac output?
CO: ventilation can increase enough to maintain PO2
Why is lactic acid partially responsible for hyperventilation during exercise?
Because it increases blood H+ concentration, which triggers the peripheral chemoreceptors to innervate the medullary inspiratory neurons to increase ventilation
How do J receptors act as a protective respiratory reflex?
In capillary walls/interstitium: stimulated by increase in lung interstitial pressure cased by fluid collection: rapid breathing, dry cough
What are the four kinds of hypoxia?
Hypoxic hypoxia (hypoxemia); anemic hypoxia (CO hypoxia); ischemic hypoxia; histotoxic hypoxia
What is hypoxic hypoxia?
Hypoxemia: arterial PO2 reduced
What is anemic hypoxia?
CO hypoxia; arterial PO2 normal but total oxygen content of blood is reduced because of inadequate numbers of RBCs, deficient Hb, or CO poisoning
What is ischemic hypoxia?
Blood flow to tissues is too low
What is histotoxic hypoxia?
Normal quantity of oxygen to tissues, but cell can't use it properly because of toxic agent interference
What is hypercapnea?
Increased retention of CO2 that leads to increased arterial PCO2