Exam 3 slides 2 Flashcards
- What is ventilation?
o Pulmonary Ventilation = Breathing
o Two Phases
o Inspiration: air flowing into the lungs
o Expiration: air flowing out of the lungs
- What is atmospheric pressure?
o Respiratory pressures are always described relative to atmospheric pressure (Patm)
o Patm: the pressure exerted by the gases/air surrounding the body
At sea level, atmospheric pressure is 760mmHg or 1atm
What is the relationship between intrapulmonary pressure and intrapleural pressure? What is the term for the difference between intrapulmonary and intrapleural pressure?
o Intrapulmonary Pressure (Ppul): the pressure within the alveoli
Rises/falls with the phases of breathing – always equalizes with atmospheric pressure
o Intrapleural Pressure (Pip): the pressure in the pleural cavity
Rises/falls with the phases of breathing –always about 4mmHg less than Ppul
o Pip is always negative relative to Ppul
o Term –
Transpulmonary Pressure: the difference between Ppul and Pip
o The pressure that keeps the air spaces of the lungs open and prevents lung collapse!
* A greater transpulmonary pressure means the lungs are larger in size
* Any condition that equalizes Pip with Ppul or atmospheric pressure will cause lung collapse
How are the parietal and visceral pleurae securely attached to each other?
o Secondary to the presence of pleural fluid, there is a strong adhesive force between the parietal and visceral pleurae
o Negative Intrapleural Pressure
When will transpulmonary pressure be greatest? Why?
o Transpulmonary pressure will be greatest during inhalation or inspiration
Define atelectasis and pneumothorax.
o Atelectasis
“Lung Collapse”
Occurs when a bronchiole becomes plugged
The associated alveoli will collapse
Often an extension of pneumonia
o Pneumothorax
“Air Thorax”
Presence of air in the pleural cavity
Reversed by drawing the air out via a chest tube
Lung will reinflate
- Be familiar with Boyle’s Law and be prepared to complete a simple calculation using the formula.
o Gives the relationship between pressure and volume of a gas
o At a constant temperature, pressure varies inversely with volume
o P1V1 = P2V2
o “gases always fill their container”
- What are the inspiratory muscles? What nerves deliver the impulses for contraction from the brain’s respiratory centers?
o Diaphragm + external intercostal muscles contract
o Height AND diameter of the thorax increase
o Volume of the thoracic cavity increases by ~500mL
o Lungs are stretched, intrapulmonary volume increases
o Ppul decreases
o Air rushes into the lungs
o Ppul equalizes to Patm
Phrenic nerves: The phrenic nerves arise from the cervical spinal cord (C3-C5) and innervate the diaphragm. They carry motor signals from the brain to the diaphragm, causing it to contract during inhalation.
Intercostal nerves: The intercostal nerves arise from the thoracic spinal cord and innervate the intercostal muscles (external intercostals). These nerves play a role in the contraction of the external intercostal muscles during inhalation, assisting in ribcage elevation.
In terms of volume and pressure, what happens during inspiration? During expiration?
o Inspiration
Diaphragm + external intercostal muscles contract
Height AND diameter of the thorax increase
Volume of the thoracic cavity increases by ~500mL
Lungs are stretched, intrapulmonary volume increases
Ppul decreases
Air rushes into the lungs
Ppul equalizes to Patm
o Expiration
In healthy individuals, quiet expiration is a passive process
It is dependent on lung elasticity
Inspiratory muscles relax – rib cage descends, lungs recoil
Thoracic + intrapulmonary volumes decrease
Ppul rises
When Ppul > Patm, air flows out
Name 2 muscles used for forced expiration and 3 muscles that are accessory inspiratory muscles.
o Forced expiration is an active process
o Produced through contraction of the abdominal muscles – primarily the transverse abdominis and obliques
o Intra-abdominal pressure rises, and the abdominal organs press against the diaphragm
o Internal intercostal muscles depress the rib cage and decrease thoracic volume
Know and understand the relationships between air flow, airway resistance, and change in pressure – I recommend plugging some numbers into the equations and trying it out!
What is a bronchodilator? Which branch of the autonomic nervous system is responsible for bronchoconstriction? Is epinephrine a bronchodilator or a bronchoconstrictor?
o Smooth muscle in the bronchiolar walls is extremely sensitive to neural controls and chemicals
o Inhaled irritants can activate a reflex of the parasympathetic ANS – a vigorous constriction of the bronchioles
o Asthma Attacks: histamine can cause such strong bronchoconstriction that pulmonary ventilation stops
o Epinephrine is the antidote!
o In those with respiratory disease, mucus, infectious material, or solid tumors in the passageways are important sources of airway resistance
What’s surface tension? What is surfactant? During development, when is surfactant made?
o Surface Tension: attracts liquid molecules to each other, resists any force that attempts to increase the liquid’s surface area
o Because it is composed of highly polar molecules, water has a high surface tension
o Water is always working to keep alveoli at their smallest possible size
o Surfactant: detergent-like complex of lipids and proteins produced by type II alveolar cells
o Surfactant reduces surface tension and discourages alveolar collapse – less energy is required to expand the lungs!
27 weeks gestation
What’s lung compliance? List some reasons why it might be reduced.
o Healthy lungs are very stretchy!
o Lung Compliance: measure of the change in lung volume that occurs with a given change in transpulmonary pressure
o Higher compliance = lungs that are easier to expand
o 2 Determining Factors:
Distensibility of lung tissue
Alveolar surface tension
o Lung compliance is reduced by: fibrosis, reduced amounts of surfactant, and decreased flexibility of the thoracic cage
Define tidal, inspiratory reserve, expiratory reserve, residual and minimal volumes.
o Tidal Volume (TV): air inspired/expired with normal, quiet breathing
o Inspiratory Reserve Volume (IRV): air inspired beyond TV
o Expiratory Reserve Volume (ERV): air expired beyond TV
o Residual Volume (RV): air that remains in the lungs after ERV
o Minimal Volumes (MV): small amount of air that remains in the lungs – even if the chest is opened
Define inspiratory, functional residual, vital, and total lung capacities.
o Respiratory capacities are specific combinations of lung volumes
o Inspiratory Capacity (IC): TV + IRV
o Functional Residual Capacity (FRC): RV + ERV
o Vital Capacity (VC): IRV + TV + ERV
o Total Lung Capacity (TLC): sum of all lung volumes
o VC is the total amount of exchangeable air in the lungs
o RV is the total amount of non-exchangeable air
- What are anatomic and physiologic dead space?
o Anatomical Dead Space: air that remains in the passageways and does not contribute to gas exchange; ~150mL
o Alveolar (Physiologic) Dead Space: air in non-functional alveoli
o Total Dead Space: the sum of non-useful volumes – anatomical + alveolar dead space
What’s the functional difference between obstructive and restrictive respiratory disease?
o Spirometer: instrument used for measuring respiratory volumes and capacities
o Spirometry tests can help to diagnose and differentiate between:
Obstructive Pulmonary Diseases: diseases of increased airway resistance
* TLC, FRC, RV may increase – why?
Restrictive Disorders: diseases of reduced lung capacity due to fibrosis/disease
* VC, TLC, FRC, RV may decline – why?
What is FEV1? What is a typical value for FEV1?
o Forced Expiratory Volume (FEV): determines the amount of air expelled during specific time intervals of the FVC test
o FEV1: the amount of air exhaled during the 1st second – typically, about 80%
How do you calculate alveolar ventilation? Why is it more accurate than minute ventilation?
o Minute Ventilation: the amount of air flowing in/out of the respiratory tract in 1 minute
provides a rough estimate of respiratory efficiency
Normal (Resting): 500mL x 12 breaths per minute = 6L/min
Normal (Exercising): up to 200L/min
o Alveolar Ventilation: amount of air flowing in/out of the alveoli per unit of time
a more effective measurement
AVR (mL/min) = frequency (breaths/min) x TV – dead space (mL/breath)
Dead space is typically constant
Rapid, shallow breathing decreases AVR
Define Henry’s Law
Attempts to explain how gases move in and out of solutions
Each gas will dissolve into a liquid in proportion to its partial pressure
The greater the concentration of a particular gas, the more and the faster that gas will go into solution
The direction and amount of movement of a gas are determined by its partial pressure in the 2 phases
Additional Factors:
Solubility - CO2 is 20x more soluble in H2O than O2
Temperature - as a liquid’s temperature rises, solubility decreases
Define Dalton’s Law.
Attempts to explain how gas behaves when it is part of a mixture of gases
The total pressure exerted by a mixture of gases equals the sums of the pressures exerted by each gas individually
The partial pressure of each gas is proportional to its percentage in the mixture
Example: O2 makes up 21% of the atmosphere. It has a partial pressure (PO2) of 159mmHg
20.9% x 760mmHg = 159mmHg
- Be generally familiar with the partial pressures of O2 and CO2 in the lungs + venous blood and in the body’s tissues + arterial blood. What does this mean in terms of pressure gradients and gas diffusion?
The rate of loading/unloading O2 is regulated by PO2, temperature, blood pH, and PCO2
o Under normal, resting conditions arterial blood Hgb is 98% saturated
o Under normal, resting conditions venous blood Hgb is 75% saturated
o Venous Reserve: substantial amounts of O2 still available in venous blood
Define ventilation and perfusion. Describe efficient coupling of ventilation and perfusion in the lungs.
o Perfusion: amount of blood reaching the alveoli
o Ventilation: amount of gas reaching the alveoli
o Perfusion and ventilation must be well matched for efficient gas exchange!
Define saturation in terms of hemoglobin.
o A fully saturated Hgb molecule has all 4 heme groups bound to O2
o A partially saturated Hb molecule has 1-3 heme groups bound to O2
o The rate of loading/unloading O2 is regulated by PO2, temperature, blood pH, and PCO2
o Under normal, resting conditions arterial blood Hgb is 98% saturated
o Under normal, resting conditions venous blood Hgb is 75% saturated
o Venous Reserve: substantial amounts of O2 still available in venous blood
Be familiar with the changes in Hb’s shape and the resultant changes in its affinity for O2 during loading/unloading.
o O2 is loaded/unloaded by changes in the shape of Hgb
o As O2 binds, Hgb’s affinity for O2 increases – efficient loading!
o As O2 is released, Hgb’s affinity for O2 decreases – efficient unloading!
Review the O2-Hemoglobin Dissociation Curve. Verbalize its meaning regarding the safety margin and efficient O2 unloading. What conditions can make the curve shift to the right? To the left?
o The amount of O2 carried by Hgb depends on the PO2 ( the amount of O2 available locally)
o If more O2 is present, more O2 is bound to Hgb
o If less O2 is present, less O2 is bound to Hgb
o Safety Margin: At a high PO2, Hgb stays almost fully saturated even with a large change in PO2
o Efficiency: At a low PO2, Hgb experiences sharp decreases in saturation with similar changes in PO2
o Curve will shift to the right when PCO2, temperature, or H+ rise
o Curve will shift to the left when PCO2, temperature, or H+ fall
How is most CO2 transported in blood?
o Active body cells produce about 200mL of CO2 /minute
o CO2 is transported in blood in 3 forms:
o 7-10% dissolved in plasma
o 20% bound to globin of hemoglobin (as HbCO2 or carbaminohemoglobin)
o 70% as bicarbonate ions (HCO3-) in plasma
Know how bicarbonate ions are formed. Review the two equations and the role of carbonic anhydrase.
o Most CO2 molecules entering plasma quickly enter RBCs
o Inside RBCs, CO2 combines with water to form carbonic acid
CO2 + H2O -> H2CO3
o Carbonic acid is unstable and dissociates into hydrogen and bicarbonate ions
H2CO3 -> H+ and HCO3-
o Carbonic Anhydrase: enzyme found in RBCs that catalyzes the above reactions
What happens when bicarbonate ions return to the lungs? How do they become the CO2 we exhale?
o Once generated, HCO3- moves from RBCs into plasma and is carried to the lungs
Movement of HCO3- out of the RBCs is counterbalanced by movement of Cl- into the RBCs
o Inside the lungs, HCO3- moves back into RBCs and Cl- moves out
o HCO3- will bind with H+ to form H2CO3
o H2CO3 is split by carbonic anhydrase into CO2 and H2O
o CO2 is diffused from the blood into the alveoli and expelled
Compare and contrast the Bohr and Haldane effects.
o Bohr
O2 unloading from Hgb is enhanced by an increased PCO2
Enhances O2 delivery where it is most needed
Ex: an exercising thigh muscle
o Haldane
CO2 unloading from Hgb is enhanced by an increased PO2
Enhances CO2 delivery for expiration
Ex: pulmonary circulation
Determine the role of H+ in the bicarbonate buffer system.
o Bicarbonate Buffer System: important for resisting shifts in blood pH
o If H+ concentration increases, H+ is removed by forming H2CO3
o If H+ concentration decreases, H2CO3 dissociates into H+
o Slow, shallow breathing allows CO2 to accumulate – carbonic acid forms, and pH drops – Respiratory Acidosis
o Rapid, deep breathing depletes CO2 – carbonic acid is reduced, and pH rises – Respiratory Alkalosis
o Ventilation provides a fast-acting system to adjust blood pH when it is disturbed by metabolic factors
Define respiratory alkalosis and respiratory acidosis.
o Slow, shallow breathing allows CO2 to accumulate – carbonic acid forms, and pH drops – Respiratory Acidosis
o Rapid, deep breathing depletes CO2 – carbonic acid is reduced, and pH rises – Respiratory Alkalosis
Define hypoxia. What the different types of hypoxia?
o Inadequate delivery of O2 to the body’s tissues
o Symptom: cyanosis when Hbg saturation dips below 75%
o Types:
o Anemic Hypoxia: too few RBCs or abnormal RBCs
o Ischemic Hypoxia: impaired/blocked blood circulation
o Histotoxic Hypoxia: body cells are unable to use delivered O2
o Hypoxemic Hypoxia: reduced arterial PO2
o CO Poisoning: CO outcompetes O2 for heme binding sites
Where are the ventral and dorsal respiratory groups located? Which group is responsible for setting the basal respiratory rate? Which group integrates inputs from the chemoreceptors?
o Control of respiration primarily involves neurons in the reticular formation of the medulla and the pons
o Medullary Respiratory Centers:
1- Ventral Respiratory Group (VRG): rhythm generating
* Impulses for inspiration travel along the phrenic and intercostal nerves
* Eupneic respiratory rate of ~12-16 breaths/minute
2- Dorsal Respiratory Group (DRG): integration center
* Integrates inputs from stretch and chemoreceptors and communicates them to the VRG
o Respiration stops when VRG neurons are completely suppressed
o Depth of ventilation is determined by the intensity of the stimulation to the inspiratory muscles
o Chemoreceptors: receptors responding to chemical fluctuations in the blood – the amounts of H+, CO2, O2
o The level of CO2 is the most potent and closely monitored – a rise in CO2 triggers increases in the rate + depth of respiration
What determines the depth of ventilation?
Depth of ventilation is determined by the intensity of the stimulation to the inspiratory muscles
What is the primary driver for changes in respiratory rate?
Control of respiration primarily involves neurons in the reticular formation of the medulla and the pons
Medullary Respiratory Centers:
1- Ventral Respiratory Group (VRG): rhythm generating
Impulses for inspiration travel along the phrenic and intercostal nerves
Eupneic respiratory rate of ~12-16 breaths/minute
2- Dorsal Respiratory Group (DRG): integration center
Integrates inputs from stretch and chemoreceptors and communicates them to the VRG
Respiration stops when VRG neurons are completely suppressed
Depth of ventilation is determined by the intensity of the stimulation to the inspiratory muscles
Chemoreceptors: receptors responding to chemical fluctuations in the blood – the amounts of H+, CO2, O2
The level of CO2 is the most potent and closely monitored – a rise in CO2 triggers increases in the rate + depth of respiration
Why does the respiratory rate increase during exercise? How does hypernea differ from hyperventilation?
Working muscles consume O2 and produce CO2
Ventilation will increase 10-20 fold
Hypernea: increased ventilation in response to metabolic needs
“the limitation is not the lungs”
Hyperventilation: an increase in the rate + depth of breathing – exceeds the body’s need to remove CO2
Often happens involuntarily during times of stress and anxiety
Leads to reduced levels of CO2 in the blood and vascular constriction
Symptoms: decreased perfusion, tingling/numbness, dizziness, fainting
Be familiar with the concept of hyperventilation and what it does to levels O2 and CO2.
o Hyperventilation: an increase in the rate + depth of breathing – exceeds the body’s need to remove CO2
o Often happens involuntarily during times of stress and anxiety
o Leads to reduced levels of CO2 in the blood and vascular constriction
o Symptoms: decreased perfusion, tingling/numbness, dizziness, fainting
What portions of the higher brain can temporarily override the medullary control of respiratory rate?
o Hypothalamic Controls: strong emotions and pain send signals to the respiratory centers – responses are mediated through the limbic system and the hypothalamus
Ex: gasping in shock, breath holding in anger, hyperventilation in excitement
o Cortical Controls: taking conscious control of respiratory rate - direct impulses from the cerebral motor cortex – medullary controls are bypassed
Ex: voluntary breath holding – the VRG with be automatically reinitiated when CO2 concentrations reach critical levels
Compare/contrast emphysema and chronic bronchitis. Define dyspnea.
o Emphysema or Chronic Bronchitis
Irreversible decrease in the ability to force air out of the lungs
Emphysema: permanent enlargement/destruction the alveoli and pulmonary capillaries, use of accessory muscles, hyperinflation of the lungs
Chronic Bronchitis: chronic and excessive mucus production, inflamed lower respiratory tact, obstructed airways, impaired ventilation
o Other common features:
80% of people with a COPD have a smoking history
Dyspnea: “air hunger”, labored breathing
Coughing + frequent pulmonary infections
Development of respiratory failure – hypoventilation, respiratory acidosis, hypoxemia
o Treatments: bronchodilators, corticosteroids, supplemental O2
Define asthma. Which branch of the ANS is most active during an asthma attack?
o A short-term or reversible COPD
o Affects about 1:10 Americans – children > adults
o Symptoms: coughing, dyspnea, wheezing, and chest tightness
o Active inflammation of airways proceeds bronchospasms
o Airways are inflamed by immune response, thickened with inflammatory exudate
o Common triggers: dust mites, cats, dogs, fungi
o Treatments: bronchodilators, corticosteroids
Know the difference between central and obstructive sleep apnea.
o Obstructive Sleep Apnea (OSA): collapse of the upper airway, musculature of the pharynx relaxes during sleep
o Central Sleep Apnea: reduced drive from the brain’s respiratory centers
