Respiratory System Flashcards
What are the 4 key functions of the respiratory system
Exchange of gases between the atmosphere and blood, homeostatic regulation of body pH, protection from inhaled pathogens and irritating substances, and vocalization
What is external respiration
Movement of gases between atmosphere and body’s cells
What are the 4 parts of external respiration
Ventilation, gas exchange between lungs and blood, gas transport, and gas exchange between blood and body tissues
What is ventilation
Exchange of air between atmosphere and lungs (inspiration and expiration) in airways
What does gas exchange between the lungs and blood happen
O2 and CO2 exchanged between alveoli and pulmonary capillaries
Where does gas exchange between blood and body cells occur
O2 and CO2 exchanged between capillaries and cells
What is cellular respiration
Intracellular processes (Krebs cycle, etc.) using O2 to generate ATP, CO2, and H2O
What do the conducting airways do
Warm air to body temperature, add water vapor until the air reaches 100% humidity, and filter out foreign material
Why do the conducting airways branch
To increase surface area and thus diffusion (Fick’s Law)
What are alveoli
Air sacs and capillaries made of 1 epithelial layer for pulmonary circulation
What are the 2 cell types of the alveoli epithelial layer and what do they do
Type I (95%) is involved in gas exchange, and type II secretes alveolar fluid and surfactant
What is surfactant
Mixes with alveolar fluid (saline-like) to decrease surface tension (helps lungs inflate and expand), be a protective layer, solvent, and environment for macrophages
What is airflow proportional to
Pressure gradient/R
What drives airflow (ventilation)
Muscular contractions create pressure gradient (quiet breathing and forced expiration)
What are the 2 phases of the respiratory cycle
Inspiration (inhalation) and expiration (exhalation)
What is Boyle’s law
P1V1 = P2V2 –> Pressure is inversely related to the size of the container
How do the diaphragm and thoracic cage change during inspiration
Diaphragm contracts and flattens, while ribs move up and away from the spine like a water lever
How do the diaphragm and thoracic cage change during expiration
Diaphragm relaxes, thoracic volume decreases as ribs move outward laterally (like water bucket handle)
What contributes to 60-75% of inspiratory volume change
Diaphragm movement
What contributes to remaining 25-40% of inspiratory volume change?
Movement of the rib cage (external intercostals and scalenes)
What are pleural sacs
Balloon like structures surrounding each lung
What is the space between the lungs and the pleural membrane called
Intrapleural space filled with pleural fluid
What are the 2 functions of pleural fluid
To create a moist, slippery surface that allows pleural membranes to slide across each other (pleurisy when lack of pleural fluid), as well as keep lungs adhered to the chest wall
What happens if the pleural cavity is opened to the atmosphere
Air flows in (because of smaller subatomic pleural cavity pressure), the bond holding the lung to the chest wall is broken, and the lung collapses (pneumothorax)
What is most of the work in breathing
Overcoming resistance of elastic lungs to stretching (like a rubber band)
What is compliance
Ability of the lungs to stretch (high = easy, low = needs more force)
What are restrictive lung diseases
The lungs have low compliance and require more work to expand, eg. with fibrotic lung diseases (scar tissue/collagen) or inadequate surfactant production (like in newborn respiratory distress system)
What is elastance
The ability of the lungs to return to normal after stretch (elastic recoil)
What decreases elastance
Smoking (macrophages degrade elastic fibers) and emphysema (high compliance but poor elastance)
What paracrine influence the smooth muscle of bronchioles
Primarily CO2, but also histamines and the ANS
How does CO2 affect bronchioles
Increased concentrations in expired air relaxes smooth muscles and causes dilation (less resistance and more flow)
How does histamine affect bronchioles
Released by mast cells (due to damage or allergic reaction) it causes constriction to prevent pathogens from coming in (increase resistance, decrease flow)
How does the ANS affect bronchioles
PSNS bronchioconstricts while SNS (epinephrine and B-2) has no direct innervation
What device measures volume of air moved with each breath
Spirometers
What is the difference between end of normal inspiration and end of normal expiration
Tidal volume (~500 mL)
What is minute (total pulmonary) ventilation (VeATP)
Volume of air moved in or out of the lungs each minute (~6L/min)
What is the equation for minute ventilation
VeATP = breathing rate (breaths/min) * tidal volume (ml/breath)
What is hypoxia
Insufficient O2 availability to cells
What is hypercapnia
Elevated CO2 levels that change blood pH
What is it called when alveolar ventilation decreases
Hypoventilation
What is it called when alveolar ventilation increases
Hyperventilation
What happens during hypoventilation
Alveolar P(O2) decreases and (P(CO2) increases
What can cause hypoventilation
CNS depression (alcohol poisoning, drug overdose)
What happens during hyperventilation
Alveolar P(O2) increases and P(CO2) decreases
What can cause hyperventilation
Anxiety, panic stress, stimulants, and/or severe pain
What is P(O2) and P(CO2) in the alveoli
P(O2) = 100mmHg
P(CO2) = 40mmHg
What is P(O2) and P(CO2) in the arterial blood
P(O2) = 100mmHg
P(CO2) = 40mmHg
What is P(O2) and P(CO2) in the cells
P(O2) <= 40mmHg
P(CO2) >= 46mmHg
What is P(O2) and P(CO2) in the venous blood
P(O2) <= 40 mmHg
P(CO2) >= 46mmHg
What is the concentration of gases in the atmosphere
79% N2, 21% O2, 0.03% CO2
What is Dalton’s law
Total pressure exerted by a mixture of gases = sum of pressures exerted by the individual gases
What is partial pressure
The pressure of a single gas
What is the equation for partial pressure
P(gas) = P(atm) * % of gas in atmosphere
Does the % of gas in the atmosphere ever change
No, but P(atm) does
What 3 things does alveolar gas exchange (diffusion rate) depend on
Partial pressure (concentration) gradient (directly proportional), surface area available for gas exchange (directly proportional), and diffusion distance including membrane thickness (inversely proportional) –> None usually vary
What is emphysema
Damage from smoking, etc. to alveolar sacs that merges them to decrease surface area)
What affects partial pressure gradients of gases (respiratory system)
Altitude and hypoventilation
What effects diffusion distance
Fibrotic lung disease and pulmonary edema
What is pulmonary edema
Fluid in the lungs (e.g congestive heart failure, pneumonia)
What is Henry’s Law
Movement of gases from air to liquid is proportional to the pressure gradient, temperature, and solubility (how easily gas dissolves in a liquid)
Which is more soluble, O2 or CO2
CO2 (20x more soluble)
How is O2 carried in blood
98% is reversibly bound to hemoglobin in red blood cells, the rest is dissolved
What is the law of mass action
High O2 (PO2) concentration = high binding vs. low O2 concentration = low binding = O2 released to diffuse into cells
How many O2 can 1 hemoglobin bind
4
What is % Hb saturation
% of available binding sites that are being used (normal is 98%)
What is the primary determinant of %Hb saturation
Plasma PO2
What is affinity
Degree to which a protein is attracted to it’s ligand, affected by protein shape (allosteric modulation)
What effect does pH have on hemoglobin’s affinity for O2
Bohr effect/shift: Decrease in pH, increases H+, increases O2 release at tissues (left shift)
What effect does temperature have on hemoglobin’s affinity for O2
Increase in temp increases O2 release at tissues
What effect does PCO2 have on hemoglobin’s affinity for O2
Increase in PCO2 increases O2 release at tissues
What effect does 2,3-BPG have on hemoglobin’s affinity for O2
Released in response to prolonged hypoxia (from altitude or anemia): Increase in BPG increases O2 release at tissues
What 3 ways is CO2 transported in the blood
Dissolved in plasma (7%), bound to hemoglobin different from O2 binding site(23%), converted to bicarbonate ion (70%)
Describe bicarbonate ion (HCO3-)
Buffers metabolic acid, reversible bicarbonate buffering reaction driven by carbonic anhydrase enzyme (antiporter transports HCO3-)
What is hypercapnia
Too much CO2
What effect does hypercapnia have on the bicarbonate buffering reaction
Right shift, increases H+, decreasing pH, and causing acidosis
What effect does alkalosis have on the bicarbonate buffering reaction
Right shift, increases CO2, increases H+, decreasing pH
How are respiratory skeletal muscles activated
By somatic motor neurons controlled by CNS
What neurons drive the rhythmic breathing pattern
Central pattern generating network (pre-Boetzinger complex) in the medulla oblongata
What is the pre-Boetzinger complex
Pacemaker neurons controlling inspiratory (DRG) and expiratory (VRG) muscles
What 3 sensory signals modify output signals for breathing
Chemoreceptors (O2, CO2, and H+), limbic (emotions), and fever
What are the 2 types of chemoreceptors that change output signal for breathing and what do they do
Central chemoreceptors (medulla) sense change in CO2 and H+ in cerebrospinal fluid, and peripheral chemoreceptors (carotid and aortic arteries) that sense changes in PO2, pH, and PCO2 in blood
What is the primary stimulus for changes in ventilation
Changes in CO2 affect tidal volume and breathing rate (sensed by peripheral and central chemoreceptors)
