Physiology Review Flashcards
Where in the brain is CO2 O2 and pH of arterial blood sensed?
Respiratory centers in the medulla
How is the metabolic demand of the body sensed by the peripheral chemoreceptors?
CO2, O2 and pH
Peripheral chemoreceptors send information along which nerve to the medulla for integration?
CN IX and X
What do the central chemoreceptors detect? Where does this send signals to?
pCO2
What is the respiratory center in the brain called? What does this do?
Central pattern generator
Generates spontaneous rhythmic discharge to keep the diaphragm functioning at a reasonable rate based on metabolic demands
What nerves does the central pattern generator send efferent signals to, to affect the respiratory muscles?
7 9 10 11 12
Where in the breathing control mechanism can the higher CNS exerts effects? Along what tracts does it send signals?
At the level of the spinal cord (bypasses the central pattern generator)
corticospinal tract
Along which tract does the ANS send signals to the diaphragm?
White matter of the spinal cord
The diaphragm sends afferent signals to the brain via which nerve?
CN X
What are the smallest airways that do not have alveoli?
Terminal bronchioles
Where does the majority of the resistance to airflow come from? Why?
The bronchus and the bronchioles
This is where smooth muscle is
What are the three major histological areas that comprise the conducting airways?
Inner mucosal surface
Smooth muscle layer
Outer connective tissue layer (cartilage)
Where is the airways is cartilage found?
Main bronchi
What type of epithelium covers the bronchial wall?
Ciliated pseudostratified epithelium
What are the main components of the bronchial wall?
Epithelium Smooth muscle cells Mucus glands CT Cartilage
What are the main components of the smaller bronchial walls?
Simple cuboidal epithelium
No cartilage
Is there cartilage in the bronchioles?
No
What are the four major obstructive lung diseases?
- Inflammation (bronchitis)
- Increased secretion (Asthma)
- Constriction of the smooth muscles
- Physical blockade (tumors)
What is the equation for the resistance to airflow?
R = {8nl / pi(r)^4 | n = viscosity of inspired air, l = length of airway, r = radius of the airway}
What happens with M3 activation in the lungs?
SM constriction
What happens with Beta 2 activation in the lungs?
SM relaxation
What is the most influential factor that controls resistance to airflow?
radius of the bronchiole
What are the three conditions that result in obstruction from the airway wall?
Asthma
Acute and chronic bronchitis
What is the pulmonary disorder that results in obstruction of the airway d/t a loss of lung parenchyma?
COPD
What are the pulmonary disorders that result in obstruction of the airway due to an obstruction in the airway lumen? (5)
bronchiectasis Bronchiolitis CF Epiglottitis Croup
Where does respiration take place?
At the respiratory unit
What comprises the respiratory unit?
Respiratory bronchiole
Alveolar ducts
Atria
Alveoli
What describes the capillary flow around the alveoli?
“sheet of flow”
What comprises the respiratory membrane?
The cell membrane between type I alveolar cells and the capillary bed
True or false: Like the tight junctions between endothelial cells, the junctions between endothelial cells are tight, not allowing much to pass through them
False–Unlike the tight junctions
between adjacent epithelial cells, which constitute a tight seal, the junctions between endothelial cells are leaky, allowing water and solutes to move back and forth between plasma and the interstitial space, the region between epithelial and endothelial basement membranes.
What are the components of the respiratory membrane?
- Surfactant
- Alveolar epithelium
- Epithelial BM
- Interstitial space
- Capillary basement membrane
- Capillary endothelial membrane
What is contained within the interstitial space in the respiratory membrane
Elastin and collagen (fibroblasts)
SM
Lymphatics
Capillaries
What is Goodpasture syndrome?
Autoimmune attack against type IV collagen in the kidneys and lungs, resulting in failure
What are the two major ways that pulmonary edema can result?
Damage to the respiratory membrane, or increased hydrostatic pressure in the capillaries
What happens with an increased deposition of collagen in the respiratory interstitial space?
harder to expand
What is the equation that relates to diffusion of gas across the respiratory membrane?
(dP)(A)(S) / d (MW)^0.5
A = surface area S = solubility of gas d = distance between two sides of the membrane
What are the factors that you can change clinically to alter the diffusion of gas across the respiratory membrane?
dP
What happens to dP in restrictive lung diseases?
Decreases
What are the factors that can affect d in the diffusion equation?
Pneumonia
Pulmonary edema
Which is more soluble in blood: CO2 or O2? What is the significance of this?
CO2
Needs a smaller partial pressure to enter the blood than oxygen does
What are the two major factors mentioned in class that can alter the surface area of the respiratory membrane?
Atelectasis
Tumor
What allows for the smooth movement between the visceral and parietal pleura?
1 mL of fluid
Which has stomata, the visceral or parietal pleura? What is the function of these?
parietal pleura
Serve as exit points for the pleural liquid, protein, and cells from the pleural space, to the lymphatics
What happens to the pleural capillaries in the visceral pleura during CHF? What does this cause?
Increased hydrostatic pressure
Causes a pleural effusion
What is the blood supply to the visceral pleura?
Bronchial circulation with venous return via the sub visceral pleural cavities
What is the blood supply to the parietal pleura?
branches of the intercostal arteries, with venous return via the bronchial veins
True or false: normally, there is a steady and balanced influx and efflux of fluid into the parietal space
True
What is the only significant barrier to solute and water exchange in the pleural space?
Pleural interstitium
The contribution to pleural liquid and protein formation from the visceral pleura in humans is minimal. Why?
Because the distance between the microvessels and the mesothelium is
relatively large and because of the lower filtration pressure in the visceral pleural
microcirculation as bronchial venules empty into the pulmonary veins with their lower
pressure.
What are the three main mechanisms by which there is a buildup of fluid in the pleural space?
Increased effusion
Decreased clearance
Combination
Decreased oncotic pressure within the parietal capillaries will lead to pleural effusion. What can cause this? (3)
Hepatic failure
Kwashiorkor
Renal disease
What is the cause of atelectasis induce pleural effusion?
Collapse of the visceral pleura d/t decreased oxygenation leads to collapse
What is the most important cause of pleural effusions in CHF?
Increased pulmonary venous pressure causes fluid to move across the visceral mesothelium
What is the effect of inflammation of the pulmonary and pleural microvessels?
Pleural effusion d/t increased movement of fluid
How could a diaphragmatic defect result in a pleural effusion?
Fluid movement from the peritoneal to the pleural cavity
What are the two major mechanisms by which there is a decreased clearance of lymphatic drainage?
Systemic venous HTN
Blockage
What is the definition of lung compliance?
the extent to which the lungs will expand for each unit increase in transpulmonary pressure
What happens to lung volume as transpulmonary pressure increases?
increases
What accounts for the steep and sudden upward slope of the lung pressure to volume curve?
Max stretching is occurring
How is lung compliance represented on a pressure-volume curve?
Slope between two points, with steeper slopes reflecting more compliance
What is the relation between compliance and elasticity?
Inverse
What are the factors that determine compliance of lung tissue?
Elastic forces of lung tissue (elastin and collagen)
Elastic surface forces of surface tension
What are the four main categories of restrictive lung disease?
- Lung parenchyma disorders
- Pleural space disorders
- Neuromuscular/chest wall disorders
- Infection or inflammation of the lungs
What are the two main lung parenchyma disorders?
Fibrotic interstitial lung disease
Atelectatic disorders
What is fibrotic interstitial lung disease?
Diffuse interstitial lung disease or sarcoidosis
What are the atelectatic disorders?
ARDS, IRDS
What are the two major pleural space disorders?
Pneumothorax
Pleural effusion
What are the neuromuscular disorders?
Polio
ALS
Guillain-barre
What are the major chest wall deformities?
Scoliosis
Ankylosing spondylitis
Flail chest
What is the effect of adding collagen to the lung in terms of compliance? Why?
Decreases compliance
This is due to more pressure needed to pull on inelastic collagen to get the same drop in pressure in the alveoli
Why will pneumonia decrease the compliance of the lung?
Increased fluid between the two pleural surfaces (pressure changes has to transmit through more liquid/space
What is the largest vascular bed in the body?
Pulmonary circulation
What allows the pulmonary vasculature to be compliant enough to accommodate all of the cardiac output?
Large numbers
Thin wall
Lower muscularity
How does the pulmonary vasculature change in response to increases/decreases in CO?
Changes compliance
Change number of arteries open (recruitment and distention)
What is the blood supply to the lungs?
Bronchial arteries
What percent of CO does the bronchial circulation receive? What happens in diseases like CF?
1-2%
CF increases the amount of blood received, causing hemoptysis
Where does the blood in the bronchial circulation go after circulating through the alveoli?
1/3 goes straight back to the RA, other 2/3 goes to the LA via the pulmonary vein
Why is there a small decrease in blood pO2 in the pulmonary vein as it returns to the heart?
Dumping of the bronchial circulation (physiological shunt)
What is the general MOA of hypoxic pulmonary vasoconstriction?
If a pulmonary capillary gets less oxygen supply (less than 70 mmHg), it will constriction so blood goes to better aerated areas
Do pulmonary veins constrict with hypoxia?
No
What are the 5 major clinical scenarios in which there is an abnormal HPV response?
- Airway obstruction
- Failure of ventilation
- Acute lung damage
- High altitude
- COPD
What is the normal, average value of V/Q?
0.8
What is the “dead space” in the lungs?
Ventilation of those lung regions that are not perfused
What is the common pathological state that leads to dead space formation?
pulmonary embolism
What are shunts?
a portion of the cardiac output or blood flow that is diverted or
rerouted.
What are the two components of the physiologic shunt?
Bronchial blood flow
Coronary circulation that drains directly into the LV through the thebesian veins
What are the thebesian veins?
Veins from the coronary circulation that drain into the LV
What are the causes of right to left shunts?
VSDs or ASDs
Why is it that hypoxia always occurs with a right to left shunt?
Because a significant fraction of the cardiac output is not delivered to the lungs for oxygenation.
What is the defining characteristic of a right to left shunt /a way to test for one?
It cannot be
corrected by having the person breathe a high O2 gas (e.g., 100% O2) because the shunted blood never goes to the lungs to be oxygenated.
What are the two fairly common causes of left to right shunts?
PDA
Trauma
V/Q = 0 means what?
Shunt
V/Q = infinite means what?
Dead space
What is the tidal volume (Vt)? What determines this?
the volume of air entering or leaving the nose or mouth per breath.
VT is determined by the activity of the respiratory control centers in the brain as they affect the
respiratory muscles and by the mechanics of the lung and the chest wall.
What is residual volume? What determines this?
RV is the volume of gas left in the lungs after a maximal forced expiration.
RV is determined by the force generated by the muscles of expiration and the inward elastic
recoil of the lungs as they oppose the outward elastic recoil of the chest wall.
What happens to residual volume with COPD? Why?
Increases dramatically d/t increased trapping of air in the alveoli
What is the importance of residual volume?
Prevents the lungs from collapsing with total expiration
What is the expiratory reserve volume?
the volume of gas that is expelled from the lungs during a maximal forced expiration
What is the inspiratory reserve volume? What determines this?
the volume of gas that is inhaled into the lungs during a maximal forced inspiration
starting at the end of a normal tidal inspiration.
IRV is determined by the strength of contraction of the inspiratory muscles
What is the functional residual capacity? How does this relate to the elastic recoil in the lungs?
the volume of gas remaining in the lungs at the end of a normal tidal expiration.
Represents the balance point between
the inward elastic recoil of the lungs and the outward elastic recoil of the chest wall.
What is the inspiratory capacity?
the volume of air that is inhaled into the lungs during a maximal inspiratory effort that
begins at the end of a normal tidal expiration (the FRC)
VT + IRV = ?
IC
What is the total lung capacity? What determines this?
TLC is the volume of air in the lungs after a maximal inspiratory effort.
TLC is determined by the strength of contraction of the inspiratory muscles and the inward
elastic recoil of the lungs and the chest wall.
RV + VT + IRV + ERV = ?
TLC
What is the vital capacity?
VC is the volume of air expelled from the lungs during a maximal forced expiration starting after
a maximal forced inspiration
TLC - RV = ?
VC
What lung volumes cannot be measured with a spirometer?
RV
FRC
TLC
What is the forced vital capacity (FVC)?
is the total volume of air that can
be forcibly expired after a maximal inspiration.
What is FEV(1)?
FEV in the first second of exhalation
What is the FEV1/FVC? What is the normal value of this? What does this represent?
he fraction of total FVC that can be expelled
in the first second. Normal value is 0.8. This ratio
reflects the resistance to airflow.
What is he forced expiratory flow (FEF(25-75%))?
is the flow rate at 25 – 75% of the exhaled vital capacity
What is the peak inspiratory flow (PIF)?
point of maximal flow during inspiration
Draw out the flow/volume curve.
Draw
What is represented by the area under the curve in the peak flow curve prior to the PEV? After>
Before PEF = large airways
After PEF = Small airways
What happens to the flow-volume curve with obstructive lung diseases?
PEF occurs sooner, is not as high, and drops faster
What happens to the flow-volume curve with an upper airway obstruction?
Flat peak at a much lower flow, as well as lower PIF. Volumes about the same.
What happens to the flow-volume curve with a restrictive lung disease?
Lower peaks, much lower volumes
What is the normal FEV1/FVC?
0.8
What is the FEV1/FVC in obstructive lung diseases?
Less than 0.7
What is the FEV1/FVC in restrictive lung diseases?
Increases
