Chapter 22 - respiratory system pt2 Flashcards
What are the 2 phases in pulmonary ventilation?
- inspiration (air in)
- expiration (air out)
What is atmospheric pressure (Patm)?
- pressure exerted by air (gases) surrounding the body
- at sea level, Patm=760 mmHg or 1 atmosphere
what is the difference between positive, negative and neutral respiratory pressure?
(+) - respiratory pressure greater than Patm
(-) - respiratory pressure less than Patm (ex. -4mmHg=756 mmHg)
(+/-) - respiratory pressure is equal to Patm
What is intrapulmonary pressure (Ppul)/ intra-alveolar?
pressure in the alveoli
- fluctuates during breathing, but equalizes with Patm to end each phases of breathing - inspiration and expiration
What is the intrapleural pressure (Pip) and why is it always negative?
the pressure in pleural cavity
- fluctuates with breating, but always negative (<Patm) - 4mmHg less than Ppul
- opposing force try to pull visceral and parietal pleurae apart
What is the importance of the surface tension of the alveolar fluid?
attraction between water draws alveolar walls inwards, acting to shrink alveoli to smallest size possible
What way does the chest walls pull the thoracic wall (parietal pleura)?
outward
Intrapelural pressure - What is the function of surface tension of pleural fluid and how is it removed?
helps secure layers of pleura together
- fluid level must be kept at a minimum, excess removed by lymphatic system
- if fluid builds, Pip pressure is positive
What is transpulmonary pressure?
the difference between intrapulmonary and intrapleural pressure (Ppul-Pip)
- this pressure keeps lungs from collapsing
- size of lung is determined by transpulmonary pressure
What will happen if the transpulmonary pressure equalizes and why is it important to keep the Pip negative?
- the lung will collapse
- to keep he lungs inflated
What does the volume change in the lungs affect?
leads to pressure change, and pressure changes lead to the flow of gases to equalize the pressure
What is Boyle’s law, how does it affect air flow in the lungs, and what is the equation?
relationship between pressure and volume of a gas
- high pressure = air moves out
- low pressure = air moves in
- P1V1=P2V2
How does normal quiet inspiration affect lung volume and air flow?
thoracic volume increases by 500ml
1. Ppul decreases to -1mmHg (Ppul<Patm)
2. Until Ppul = Patm
3. Pip falls to -6mmHg
What are the 5 steps to inhalation?
- inspiratory muscles contract
- the thoracic cavity volume increases
- the lugs stretch, increasing the intrapulmonary volume
- intrapulmonary pressure drops
- air flows into lungs, down the pressure gradient
what is expiration during quiet expiration (a passive process)?
inspiratory muscles relax and thoracic cavity volume decreases (-500ml) as the lungs recoil
- air flows out until Ppul=Patm
What is forced expiration (active process)?
abdominal wall muscles to increase intra-abdominal pressure (diaphragm up) and pulls the ribs in (depression)
- internal intercoastal muscles to assist in depression
What is nonpreparatory air movement?
other processes move air into or out of lungs, altering respiratory rhythm
- voluntary or reflexive (like sneezing/ hiccup)
What are the 5 steps of breathing out?
- inspiratory muscles relax
- the thoracic cavity volume decreases
- the elastic lungs recoil passively, decreasing the intrapulmonary volume
- intrapulmonary pressure rises
- air flows out
What muscles are involved in the inspiration process?
diaphragm and external intercostals.
How does the diaphragm contribute to inspiration?
increases the height of the thoracic cavity, thus increasing its volume. It moves inferiorly and flattens out as it contracts.
What role do the intercostal muscles play during inspiration?
increase the diameter of the thorax, thus increasing its volume.
How do the intercostal muscles affect the ribs during inspiration?
pull the ribs up and out, similar to raising a bucket handle.
What causes airway resistance and what is the equation of flow (F)?
- friction
- flow (F) is proportional to the difference in pressures (Ppul-Patm) or pressure gradient (delta P)
- F= delta P/ R (resistance)
What is delta P during normal quiet breathing?
1-2 mmHg
What are the 2 reasons resistance in respiratory tree insignificant?
- conducting zone airways have huge diameters (relative to low air viscosity)
- all the bronchioles running in parallel
Where is the greatest resistance in the lungs?
medium-sized bronchi
What is the pressure difference between inhalation and expiration?
I - (-) in order to pull air in
E - (+) in order to push air out
What is the purpose of measuring pulmonary volumes?
to assess respiratory status.
- these volumes are combined to measure pulmonary capacities.
Why are pulmonary volumes often abnormal in people with pulmonary disorders?
these conditions can affect lung function and air exchange
What is a spirometer, and how is it used?
a clinical tool originally used to measure pulmonary volumes
What are pulmonary (lung) capacities and how many are there?
- are combinations of two or more lung volumes
- four main ones
What is Inspiratory Capacity (IC)?
the amount of air that can be inspired after a normal tidal expiration
- the sum of tidal volume (TV) and inspiratory reserve volume (IRV)
- IC=TV+IRV
What is Functional Residual Capacity (FRC)?
the amount of air remaining in the lungs after a normal tidal expiration
- the sum of residual volume (RV) and expiratory reserve volume (ERV)
- FRC = RV+ERV
What is Vital Capacity (VC)?
- total amount of exchangeable air
- VC= TV+IRV+ERV
What is Total Lung Capacity (TLC)?
sum of all lung volumes
- TLC = TV+IRV+ERV+RV
What are the 3 factors affecting pulmonary gas exchange?
- partial pressure gradient and gas solubilities
- thickness and SA of the respiratory membrane
- ventilation-perfusion coupling: matching alveolar ventilation with pulmonary blood perfusion
What is the partial pressure gradient?
the difference in concentration of a gas between two areas, causing the gas to move from the higher concentration to the lower concentration
- responsibility for gas coming into the body
What is the partial pressure gradients of venous blood and the alveolar?
- Po2 = 40 mmHg
- Po2 = 104 mmHg
What does it mean to have a large deltaPo2 (64mmHg), when is equilibrium across respiratory membrane reached and when have the RBC travelled across the entire pulmonary capillary?
- drives diffusion of O2 into blood
- reached at 0.25 sec
- reached at 0.75 sec (ensures all oxygenation even if blood flow increases)
What is the partial pressure gradient and gas solubility of CO2 in venous blood and the alveolar?
much smaller (5 mmHg)
- Pco2 = 45 mmHg
- Pco2 = 40 mmHg
describe the thickness and surface area of the respiratory membrane?
- very thin
- alveoli provide most of the surface area
What is the relationship between ventilation-perfusion coupling?
ventilation (amount of gas reaching alveoli) and perfusion (amount of blood flowing through pulmonary capillaries) must be coupled for optimal, efficient gas exchange
What local autoregulatory mechanisms is the ventilation-perfusion coupling controlled by?
- alveolar Po2 controls perfusion by changing arteriolar diameter
- alveolar Pco2 controls ventilation by changing bronchiolar diameter
What influences the local Po2 on perfusion?
changes in local alveolar Po2 causes change in diameters of local arterioles
- high Po2 (good ventilation), arterioles dilate to increase perfusion
- low Po2 (poor ventilation), arterioles constrict to decrease perfusion
How does local Po2 levels control blood flow?
- directs blood to go to well ventilated (high in O2, low in CO2), so blood can pick up more oxygen (and remove more CO2)
- opposite mechanisms are seen in systemic arterioles that dilate when O2 is low and constriction is high
How does the local Pco2 influence perfusion?
causes changes in diameter of local bronchioles
- when Pco2 is high, bronchioles dilate to increase alveolar ventilation (allows elimination of O2 faster)
- when Pco2 is low, bronchioles constrict
what happens when there is poor alveolar ventilation?
low alveolar Po2 (high Pco2) causes pulmonary arterioles serving these alveoli to constrict (bronchioles dilate)
Why is ventilation-perfusion never balanced?
- regional variations, due to effect of gravity on blood and air flow
- occasional (mucus) plugged alveolar ducts cause unventilated areas
What is tissue gas exchange?
involves capillary gas exchange in body tissues, where partial pressures and diffusion gradients are reversed compared to pulmonary gas exchange
Is tissue Po2 lower than arterial blood Po2?
yes
- o2 diffuses from blood to tissues until equilibrium is reached
Is tissue Pco2 higher than arterial blood Pco2?
yes
- CO2 diffuses from tissues into blood until equilibrium is reached
What does venous blood have in reactions to partial pressure?
- Po2 of 40 mmHg
- Pco2 of 45 mmHg
How do molecules carry O2 in the blood?
- 1.5% dissolved in plasma
- 98.5% bound to hemoglobin in RBC
What does O2 binding to hemoglobin change?
- O2 binds, Hb changes shape, increasing its affinity for O2
- O2 released, Hb changes shape, decreasing its affinity for O2
What is the difference between fully and partially saturated Hb?
F - 4 Hb
P - 1-3 Hb
What are the factors that influence the rate of loading and unloading of O2?
- Po2
- temp
- blood pH
- Pco2
- conc. of BPG
What are the 4 influences of Po2 on hemoglobin saturation?
- local Po2 controls loading and unloading of Hb
- % Hb sat can be plotted against Po2, producing S-shaped curve called oxygen-hemoglobin dissociation curve
- arterial blood contain 20 ml of O2/ 100 ml blood; Po2 = 100 mmHg and Hb is 98% sat.
- venous blood contains 15 of O2/ 100 ml blood; Po2= 40 mmHg and Hb is still 75% sat.
What happens when you increase the factors of that influence the rate of loading and unloading of O2?
reduces affinity of Hb for O2
- occurs in systemic capillaries (tissues)
- enhances O2 unloading, shifting the O2-Hb dissociation curve to the right (lower the sat - higher the dissociation at any Po2
What happens when you decrease the factors of that influence the rate of loading and unloading of O2?
increases the affinity of Hb for O2
- occurs in pulmonary capillaries (lungs)
- enhances O2 loading, shifting the O2-Hb dissociation curve to the left (higher sat at any Po2)
How does RBC producing BPG during glycolysis affect hemoglobin saturation?
levels rise as temperature rises (and O2 levels fall)
What is the Bohr effect?
reduced affinity of Hb for O2 resulting from falling blood pH and rising Pco2
How does the glucose and O2 cells consume to make ATP affect CO2 levels and Hb affinity?
- the more heat and CO2 they release, increasing Pco2 and H+ in local capillary blood
- increasing temperature directly and indirectly decreases Hb affinity for O2
What are the 3 ways CO2 is transported in blood?
- dissolved in plasma (small % - responsible for Pco2)
- chemically bound to hemoglobin (20%)
- forms carbaminohemoglobin - as bicarbonate ions in plasma (70%)
- forms HCO3- , then breaks into H+ and HCO3-
- primarily in RBC where enzyme (carbonic anhydrase) catalyze reaction
How is CO2 transported in capillaries?
diffuse from RBC into plasma
- outrush of HCO3- from RBC is balanced as Cl- moves into RBC from plasma
- referred to as chloride shift
How is CO2 transported in the pulmonary capillaries?
- HCO3- moves into RBC while Cl- moves out
- HCO3- binds with H+ to fomr H2CO3
- H2CO3 splits by carbonic anhydrase into CO2 and water
- Co2 diffuses into alveoli
What is the Haldane effect?
the lower the Po2 and Hb sat., the more Co2 can be carried in by blood
What does the haldane effect do?
reduced Hb buffer H+ and forms carbaminohemoglobin more easily
- process encourages CO2 exchange
What is the Dorsal Respiratory Group (DRG)?
a network of neurons located near the root of the cranial nerve
What does the Dorsal Respiratory Group (DRG) do?
it integrates input from peripheral stretch and chemoreceptors, then sends information to the Ventral Respiratory Group (VRG) neurons.
Are all the details of how the Dorsal Respiratory Group (DRG) operates known?
no, researchers are still working out the remaining details.
What does the Pontine Respiratory Centers influence?
centers in the pons that influence and modify the activity of the Ventral Respiratory Group (VRG).
How do Pontine Respiratory Centers affect breathing?
they appear to smooth out transitions between inspiration and expiration. Damage can cause prolonged inspirations, known as apneustic breathing.
What role do the Pontine Respiratory Centers play during activities like vocalization, sleep, and exercise?
they communicate with the Ventral Respiratory Group (VRG) to fine-tune breathing rhythms.
Do Pontine Respiratory Centers receive inputs from other areas of the brain?
yes, like the Dorsal Respiratory Group (DRG), they receive inputs from higher brain centers and peripheral receptors.
What is the origin of the breathing rhythm?
Not yet fully understood
What is one hypothesis regarding the generation of the respiratory rhythm?
one hypothesis suggests that pacemaker neurons in the VRG (ventral respiratory group) control intrinsic rhythmicity.
What happens when pacemaker-like activity in the VRG is suppressed?
suppressing pacemaker-like activity in the VRG doesn’t stop breathing.
What is the most widely accepted hypothesis for the generation of the respiratory rhythm?
the most widely accepted hypothesis is reciprocal inhibition of interconnected neuronal networks in the medulla.
How do pacemaker cells contribute to the respiratory rhythm?
two (possibly three) sets of pacemaker cells inhibit each other and cycle their activity to generate the rhythm.
How is breathing rate and depth fluctuations detected by chemoreceptors?
- central chemoreceptor located throughout brain stem, including medulla
- peripheral chemoreceptors found in aortic arch and carotid arteries
What is the influence of Pco2 on breathing rate?
strongest influence on ventilation
- if arterial Pco2 rises (hypercapnia), CO2 accumulation in CSF of brain and joins with water to become carbonic acid which releases H+ (triggers chemoreceptors)
What determines the depth of breathing?
depth is determined by how actively the VRG (ventral respiratory group) stimulates respiratory muscles. Greater stimulation activates more motor units, increasing the depth (tidal volume) of inspiration.
What happens if arterial Pco2 fall abnormally low?
respiration becomes slow and shallow
- periods of apnea occurs until arterial Pco2 rises again
- swimmers can control hyperventilation to hold their breath longer
How is the rate of breathing determined?
the rate of breathing is determined by how long inspiratory neurons are active or how quickly they are switched off.
What factors determine both the depth and rate of breathing?
both depth and rate of breathing are determined by the changing demands of the body.
What are the respiratory centers affected by?
- Chemical factors
- Influence of higher brain centers
- Pulmonary irritant reflexes
- The inflation reflex
What happens if arterial Po2 drops substantially?
becomes major stimulant for ventilation
What influence does arterial pH have on breathing rate and depth?
- influence ventilation (peripheral chemoreceptors)
- decrease pH may reflect Co2 retention, accumulation of lactic acid or ketones
- respiratory centers attempts to raise pH by increasing ventilation, which increases CO2 removal from body (lowers pH)
