Respiratory System Flashcards
Gas Exchange:
Facilitates the intake of oxygen and removal or CO2
Gas flow > Diffusion of gasses > Perfusion for blood flow
Acid-base balance
Regulates pH of blood, prevents alkalosis and acidosis
Phonation
Production of speech sounds
Filtration
The entire cardiac output from the right ventricle passes via pulmonary circulation.
–> Allows lungs to act as a filter and prevent air bubbles passing from left side of the heart to the systemic circulation
Metabolic
Transformation or removal of chemical substances in pulmonary circulation
i.e. Inactivates noradrenaline
Pulmonary Defence Mechanism
Protects the body from airborne threats; uses adaptive and innate immunity.
What is the lung incased in?
Parietal pleura (outtermost)
Pleural cavity (between)
Visceral pleura (innermost)
The pleurae of the Lungs: Lubrication serves to…
Reduce friction during breathing
The pleurae of the Lungs: Surface tension
helps position of the lungs against the thoracic wall
The pleurae of the Lungs: Division
isolates the respiratory system from other major organs
Fick’s Law of Diffusion
Shorter distance – Greater rate of diffusion
Greater surface area – Great rate of diffusion
Type I pneumocytes / Type 1 alveolar cells
Most abundant (97%), involved in gas exchange
Type II pneumocytes / Type 2 alveolar cells
Produce and secrete surfactant, a phospholipid
(both hydrophilic and hydrophobic) that lines the inner
alveolar surface to reduce surface tension.
Alveoli macrophages
Phagocytic cells that remove foreign debris and pathogens
The conducting zone is comprised of:
Nose –> Pharynx –> Larynx –> Trachea –> Bronchi –> Bronchioles
The respiratory system is isolated from all other systems. T/F
True
The conducing zone acts to:
- Humidifies air
- Facilitates the passage of air in & out of TRS
- Traps debris and pathogens via mucous membrane
The respiratory zone is comprised of:
Terminal bronchioles –> Alveolar ducts –> Alveolar sacs –> Plural Alveoli
The respiratory zone acts to:
Exchange of gas between the respiratory system and the circulatory system
Capillaries are wrapped around the alveolar sacs to form the respiratory membrane.
Simple diffusion of gasses between blood and air
Epithelia along the start of the respiratory tract (trachea/bronchus) consist of…
thick, pseudostratified layer with submucosal glands.
The bronchiolus consists of:
cuboidal epithelium
In the alveolus, squamous epithelial cells form a thin, single-layered continuous membrane that allows diffusion to easily occur. T/F
True
What is responsible for increasing surface area availability during gas exchange?
Alveoli
Terminal bronchi is encased in…
Smooth muscle
Pulmonary Ventilation:
Movement of gas between atmosphere and alveoli
Pulmonary Ventilation is driven by:
Volume changes in thoracic cavity –> contraction/relaxation of intercostals and diaphrag
Alveoli Macrophages:
Phagocytic cells that remove pathogens and debris
External Respiration:
Gas exchange across alveoli and blood
Internal Respiration:
Gas exchange between the blood and cells.
Via capillary-interstitial fluid-cell membrane
Gas Transport:
Transfer of O2 and CO2 via blood
Cellular Respiration:
Utilisation of O2 and production of CO2 by cells in the mitochondria
Atmospheric Pressure:
The pressure exerted by air surrounding the body
1atm = 760mmHg
Intra-alveolar & Intra-pulmonary Pressure:
Pressure within the alveoli; changes with ventilation.
Always equalises with the atmospheric pressure
Intra-alveolar & Intra-pulmonary Pressure always equalises with the atmospheric pressure. T/F
True
Intrapleural Pressure:
Air within the pleural cavity (between visceral and parietal pleura).
Fluctuates with breathing but remains relativity stable at ~-4mmHg relative to the atmosphere.
The negative pressure is generated by…
Elastic connective tissue connecting the lung to the pleura.This inward pull is counteracted by an opposing connection between the parietal (outer) pleura and the thoracic wall
Trans-pulmonary Pressure:
The difference between the intra-pleural and intra-alveolar pressures.
The inward pull from the intra-alveolar pressure and the outward tug from the intra-pleural keeps the airways open and dictates the size of the lungs.
Pneumothorax
When the intra-alveolar and intra-plaural pressure difference is zero (Ptp = 0), the lung collapses
Pneumothorax measurments:
Atmospheric pressure = 0cmH2O
Alveolar pressure = 0cmH2O
Intra-pleural pressure = 0cmH2O
A Healthy chest wall measurements
Atmospheric pressure = 0cmH2O
Alveolar pressure = 0cmH2O
Intra-pleural pressure = -5cmH2O
Humans inspire via…
-ve pressure breathing
The diaphragm and external intercostal muscles contract, causing –>
The rib cage rises –> the lungs stretch –>intra-alveolarvolume increases –> decreasing the alveolar pressure.
Δ in volume (lung) → Δ in pressure → flow of gases
Δ in volume (lung) → Δ in pressure → flow of gases
Boyle’s law:
an inverse relationship between pressure and volume (assuming that temperature is kept constant)
–> P1V1 = P2V2
Quiet Breathing or Eupnea
Without cognitive thought of the individual. Contraction of the diaphragm and external intercostals.
Deep Breathing
Requires the diaphragm to contract deeply and air passively leaves the lungs as the diaphragm relaxes.
Shallow Breathing
Requires the intercostal muscles to contract and air passively leaves the lungs as the intercostal muscle relax.
Forced Breathing or Hypernea (Inspiration)
Requires contraction of accessory muscles, in addition to the diaphragm and intercostal muscles.
During forced inspiration, muscles of the neck contract and lift the thoracic wall, increasing lung volume.
Forced Breathing or Hypernea (Expiration)
During forced expiration, musclesinthe abdomen (i.e. obliques) contract forcing abdominal organs upwards pushing the diaphragm into the thorax, and pushing more air out the lungs.
*The internal intercostals contract to compress the rib cage, which also reduces the volume of the thoracic cavity.
Which of the following describes the difference between the intra-alveolar pressure and intrapleural pressures?
Transpulmonary pressure
During quiet breathing, at the start of inspiration the intrapleural pressure is about -4 mmHg (relative to atmospheric pressure). As inspiration proceeds, intrapleural pressure reaches approximately
-8mmHg
Compliance:
The change in volume per unit change in pressure (ΔV/ΔP)
As trans-pulmonary pressure increases, lung volume…
decreases
The relationship between changes in pressure distending the alveoli and changes in lung volume determines…
How easily the lungs inflate with each breath.
Trans-pulmonary pressure:
Pressure that distends the alveoli = intra-alveolar pressure - intra-pleural pressure
The pressure difference across the whole lung
Hysteresis:
The difference between the pressure-volume curve for inflation and the curve for deflation
Reflects surfactant surface tension
The lungs have a tendency to collapse due to….
Elastic Recoil
Compliance is _____ related to elastic recoil
Inversely
i.e.
High compliance = less elastic recoil
Low compliance = more elastic recoil
Pulmonary Surfactant & Surface Tension
- Lowers elastic recoil due to surface tension
- Increases lung compliance
- Decreases work required during inspiration
Pulmonary surfactant is synthesised by…
type ll alveolar cells; consists of lipids and proteins
Surfactant reduces surface tension on alveoli –>
Reduces the collapsing pressure of small alveoli
Dipalmitoyl-phosphatidylcholine (DPPC)
Molecules of DPPC are amphoteric and align themselves on the alveolar surface with their hydrophobic portions attracted to each-other, and hydrophilic regions repelled.
DPPC breaks up the liquid molecules that were responsible for high alveolar surface tension.
–> When surfactant is present, surface tension and collapsing pressures are…
Reduced and small alveoli can be kept open.
*Surfactant stabilises alveoli
Airway Resistance
The two sources of frictional resistance; the lung and the chest wall (minor) and the resistance of airways to airflow (major)
Gas flow is a mixture of laminar and turbulent flow
Resistance increases in proportion to gas flow
Resistance is directly proportional to gas density, and inversely proportional to:
the 5th power of the radius
–> turbulent gas flow is extremely sensitive to airway calibre
The greatest resistance occurs in the medium-sized bronchi
- Resistance in large bronchi is small because of their large diameter
- Resistance in small bronchi is low because of the large cross-sectional area
Increased Airway Resistance can lead to:
- Bronchospasm
- Secretions
- Mucosal oedema
- Volume & flow related airway collapse
i.e. Asthma suffers increase airway resistance by causing spastic contraction of smooth muscles of the bronchioles –> incr. Mucus secretion, an inflammation of bronchioles
Broncho-active agents
consist of:
Acetylcholine
Nitric Oxide
Adrenergics
Histamine
Leukotrines
Acetylcholine is secreted via the ____ and acts on _____
PSNS
Acts on muscarinic receptors to mediate bronchoconstriction
Anticholinergics (atropine, bromide) are M3 receptors
Nitric Oxide is secreted via the ____ and acts on _____
PSNS and Inflammatory cells
Via guanylate cyclase, causes bronchodilation
Adrenergics is secreted via the ____ and acts on _____
SNS
Acts via beta-adrenoreceptors to mediate bronchodilation.
B-agonists: Sulbutamol
Histamine is secreted via the ____ and acts on _____
Mast cells and Inflammatory cells
Act on histamine receptors to cause bronchoconstriction
Antihistamines (fexofenadine) are H1 blockers
Leukotrines is secreted via the ____ and acts on _____
Inflammatory cells
Act on LT receptors to cause bronchoconstriction. Leukotrine antagonists and 5-lopoxygenase inhibitors are used
Factors affecting ventilation:
Pressure
Complience
Surfactant
Resistance
Pressure relationships:
The movement of gas in the respiratory system is subjected to physical determinants; i.e.
pressure, volume, temperature and the amount of gas present.
Such relationships can be empirically determined using Boyle’s Law (P vs V), Charles’ Law (V vs T), Avogadro’s Law (V vs n). A basic principle is pressure gradients determine gas flow.
Compliance:
The ease of which lungs expand affects ventilation.
Lung compliance is the volume change per unit pressure change (ΔV/ΔP).
Lung compliance depends on the elasticity of the lungs (and thorax) and the surface tension of the liquid in the alveoli. Both factors tend to decrease the lung compliance.
Factors responsible for the decrease the lung compliance:
- Elasticity of the lungs and thorax
- Surface tension in the alveoli
Surfactant:
A mixture of lipids and proteins secreted by Type II alverolar cells.
It intersperses between the water molecules in the fluid lining the alveoli, therefore, lowers surface tension.
It acts to equalises alveolar pressure throughout the lungs, preventing the collapse of alveoli and decreases the inspiratory work of breathing, increasing the compliance of lungs.
Resistance to air flow:
As airway resistance increases, breathing becomes more strenuous.
Resistance is determined by the radius of airways andalso depends on whether flow is laminar or turbulent.
With cystic fibrosis, the lung compliance…
Decreases –> alveoli become stiffer, with increasing connective tissue and the alveolar elastic recoil capacity is limited.
Individuals suffering from emphysema will experience an…
increase in lung compliance, because of the destruction of alveolar septal tissue that normally opposes lung expansion.
A deficiency in pulmonary surfactant would:
Decrease lung compliance
i) Define pulmonary ventilation.
ii) Name two factors that affect pulmonary ventilation and explain how they affect ventilation.
i) Pulmonary ventilation, or breathing, refers to the movement of air in and out of the lungs. It is driven by the contraction/relaxation cycling of intercostal and diaphragm Pressure relationships
ii) Environmental factors such as pressure, temperature, volume and amount of gas present that determines the degree of air movement in/out of the system.
Surfactant:
A mixture of lipids and proteins secreted by type II pneumocytes at the alveoli to reduce surface tension.
Compliance:
The expansion ability of the lungs that determines how much/little air enters. Resistance to air flow - The opposition of air flow int and out of the respiratory tract by friction
Inspiratory reserve volume (IRV) =
Maximal inhale
Expiratory reserve volume (ERV) =
Maximal Exhale
Residual Volume (RV) =
Air remaining post maximum exhale
Residual volume prevents…
Pneumothorax
Vital Capacity =
Inspiratory Reserve Volume + Tidal Volume + Expiratory Reserve Volume
VC = IRV + TV + ERV
Forced Vital Capacity =
Gas forcibly expelled after taking a deep breath
Expiratory Reserve Volume + Residual Volume
FVC = ERV + RV
Forced Expiratory Volume (FEV):
The amount of gas forcibly expelled at specific time intervals of FVC.
FEV1 is within the first second of FVC ~80% in healthy individuals.
COPD, Gas trapping & Obstruction of the Airway leads to:
Reduction in airflow to the lungs
Air trapping –> air remains in the lungs at expiration Hyper-inflalation –> incr. In FRC
Signs of COPD, Gas trapping & Obstruction of the Airway
- Incr. Total lung capacity –> enlarged chest
- TV remains the same
- -> IRV increases
– -> ERV decreases - RV increases
- FVC is the same, if not lower
- FRC is increased (functional Residual Capacity)
- Functional lung capacity increases
Spirometry is used to distinguish between:
Obstructive Pulmonary Diseases and Restrictive Pulmonary Diseases
Obstructive Pulmonary Diseases
Increased airway resistance from obstruction
COPD, Asthma, Cystic Fibrosis
Restrictive Pulmonary Disorders
Reduced lung capacity
Sarcoidosis, ALS, Asbestosis
Total Lung Capacity
(TLC):
The maximum amount of air contained in the lungs after maximum inspiration
Vital capacity (VC)
The maximum amount of air that can be expired after maximum inspiration effort
Measured as an index of pulmonary function
*Strength of pulmonary muscle and function
Inspiration Capacity (IC)
The maximum amount of air that can be inspired after a normal expiration
Functional Residual Capacity (FRC)
The volume of air remaining in the lungs after a normal tidal volume expiration
Anatomical Dead Space:
Air present in the airway that does not reach the alveoli for gas exchange
Alveolar Dead Space:
Air in the alveoli that does not participate in gas exchange
Total Dead Space:
Sum of Anatomical Dead Space and Alveolar Dead Space
The volume of air not used in gas exchange
When the respiratory muscles are relaxed, the lungs are at:
Functional Residual Capacity (FRC)
Compared to restrictive lung disease, obstructive lung disease has a lower…
FEV1/FVC
Overall the pulmonary circuit has the following characteristics:
- Relatively shortcircuit/vessels
- High flow rate at low pressure, due to low vascular resistance (1/10 of systemic circulation)
- Thin walled, and therefore high compliance vessels
- Minimal resting smooth muscle tone
- ‘Passive factors’play a important role in determining flow, for examplegravity when standing has a marked effect on blood flow to upper lungs
Factors influencing gas movement across the respiratory membrane:
- Structural characteristics of the respiratory membrane
- Partial pressure gradients and gas solubility
- Matching of alveolar ventilation and pulmonary blood perfusion
The “respiratory membrane” refers to:
The area between the alveolusand pulmonary capillaries lining the terminal portions of the lungs.
Features of the respiratory membrane:
- The alveolar walls are lined in thin squamous (scaley, thin, flat) epithelial cells (Type I pneumocytes).
- Pulmonary capillaries tightly encase the external surfaces of the alveoli.
- Type II pneumocytes secrete pulmonary surfactant to decrease surface tension and assist in gas exchange. A thin(approximately 0.5 µm) layer of interstitial fluid exists between the alveolar and endothelial cells.
Together, these structural properties allow for oxygen and carbon dioxide to easily diffuse between thesystems (from the atmosphere into respiratory and respiratory into circulation).
Daltons Law:
In a given system of mixed gases, the partial pressure exerted by a single gas present will, therefore, be proportional to the amount/percentage of that gas.
Henrys Law:
The amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of that gas.
Gases with a higher solubility will have more dissolved molecules than gases with a lower solubility if they have the same partial pressure.
When the PCO2 in the blood is 45 mmHg and 40 mmHg in the alveoli. What will happen to the carbon dioxide?
The carbon dioxide will diffuse from the blood into the alveoli, moving from an area of high partial pressure to an area of low partial pressure
Gases move from an area of high pressure to low pressure through diffusion. As the partial pressure of carbon dioxide is higher in the blood, the carbon dioxide from the blood moves into the lungs where it can be removed from the body by exhalation.
How do the structural characteristics of the respiratory membrane help facilitate the movement of O2and CO2across the membrane?
Pulmonary capillaries sit very close to the alveolus, with a thin layer (0.5 um) of interstitial fluid that sits between the systems.
Type II pneumocytes secrete pulmonary surfactant to assist in the gas exchange. The alveolus wall is lined with a thin sheet of squamous Type I pneumocytes.
Together, these properties allows for oxygen and carbon dioxide to easily diffuse across the respiratory membrane.
Gas Transport
Molecular oxygen diffuses across the alveoli into bloodwithin the pulmonary capillaries. It is then transported back to the heart and through to the systemic circulationwith
- Bound to haemoglobin (Hb) within the erythrocytes about 98%
- Dissolved in blood plasma/erythrocyte cytoplasm (<2%)
Haemoglobin (Hb)
- 4 protein chains
- 4 heme groups
- Fully saturated when all 4 molecules for heme are bound.
Hb02
- Vasoconstrictor
- 20ml of oxygen can be dissolved in 100ml of plasma, resulting in 235 ml O2/min being delivered to tissues. Plasma provides the remainder 15ml O2/min.
Carbon Monoxide
- 210 times greater affinity for Hb as oppose to O2
- Reduces O2-carrying capacity
- Can bind to Hb and reduces O2 release –> shifts curve to the left
- CO binding to myoglobin causes myocardial depression, hypotension, and arrhythmias and immediate death
What are some factor(s) that affect the binding/dissociation rates of oxygen with haemoglobin?
- Blood pH
- PCO2
- Temperature
John goes for a run. His body temperature increases and more CO2is produced from high rates of cellular respiration. Does the O2-Hb curve shift to the left or right?
Shifts to the right
Identify and describe the three ways that CO2can be transported in the bloodstream.
Carbon dioxide can be transported by three mechanisms: dissolved in plasma, as bicarbonate, or as carbamino-hemoglobin.
Dissolved in plasma, carbon dioxide molecules simply diffuse into the blood from the tissues. Bicarbonate is created by a chemical reaction that occurs mostly in erythrocytes, joining carbon dioxide and water by carbonic anhydrase, producing carbonic acid, which breaks down into bicarbonate and hydrogen ions. Carbamino-hemoglobin is the bound form of hemoglobin and carbon dioxide.
Transport of CO2:
- Dissolved- 7%
- Chemically bound to haemoglobin (carbaminohaemoglobin) - 23%
- Bicarbonate ions(HCO3-) - 70%
- Carbonic acid(H2CO3) - not quantitively important
- Carbonate(CO3-) - not quantitively important
The vast majority of CO2 (89%) diffuses into red blood cells. T/F
True
Most of CO2 combines with water to form carbonic acid (H2CO3), which quickly dissociates into hydrogen ions and bicarbonate ions (HCO3-) T/F
True
The majority of CO2 diffuses into erythrocytes and this process is catalysed by the enzyme…
carbonic anhydrase
*PO2 in systemic arterial blood (104 mmHg) is…
greaterthan PO2 in tissues (< 40 mmHg)
*PCO2 in systemic arterial blood (40 mmHg) is…
less than PCO2 in tissues (> 45 mmHg)
Transport of CO2: In Tissue
- Oxygen transported hereas oxyhemoglobin is released and diffuses into the tissue for cellular respiration.
- Hb binds with hydrogen ions (H+) to form HHb.
- CO2 from tissue diffuses into the plasma and RBCs.
- In the RBCs, the enzyme carbonic anhydrase rapidly converts CO2 and water into carbonic acid (H2CO3) which splits into bicarbonate (HCO3-) and hydrogen (H+).
- Bicarbonate (HCO3-) quickly diffuses from red blood cells into the plasma.
- To counterbalance the rapid outrush of negative bicarbonate ions from the RBCs, chloride ions (Cl-) move from the plasma into the erythrocytesto maintain electrical neutrality. This is known as thechloride shift.
Transport of CO2: In Lungs
- Inhaled oxygen diffusesfrom the alveoli intothe capillaries and erythrocytes,combining with HHb to form oxyhemoglobin (HbO2) and hydrogen (H+).
- Bicarbonate ions move into the RBCs and bind with hydrogen ions (H+) to form carbonic acid (H2CO3).
- Chloride ions (Cl-) diffuses out of the cell into plasma ie.reverse chloride shift.
- Carbonic acid is then split by the enzyme carbonic anhydrase to release carbon dioxide (CO2) and water (H2O).
- Carbon dioxide then diffuses from the blood into the alveoli for removal via expiration.
The Bicarbonate-Carbonic Acid Buffer system acts instantaneously and thus…
constitutes the body’s first line of defence against acid-base imbalance.
The lungs help maintain acid-base balance by:
Eliminating or retaining carbon dioxide.
This is regulated by altering the rate and depth of respiration (next module).
If H+ ion concentrations begin to rise:
excess H+ is removed by combining with HCO3 (excess CO2 exhaled)
If H+ ion concentrations begin to drop…
Carbonic acid dissociates, releasing H+
In essence, PCO2 is inversely proportional to pH
Patient X has pneumonia which causes him to breath shallowly. Due to his reduced breathing capacity patient X is unable to clear CO2effectively, which leads to an accumulation of CO2in the blood. What kind of blood pH disorder does patient X suffer from?
- Respiratory Acidosis
- The issue is of respiratory origin due to the patients shallow breathing. Higher amounts of CO2in blood will drive the formation of carbonic acid (H2CO3), which lowers the pH of the blood, creating a more acidic environment.
Central Pattern Generator:
Synaptic network that drives respiration
Premotor neurons
Motor neurons (phrenic, intercostals)
Interneurons
Inspiratory and expiratory neurons
There are three important brainstem respiratory centres that integrate signals from the periphery and send efferent signals tocontrol breathing.
- Pontine respiratory group (PRG) in the dorsal lateral pons
- Dorsal (DRG) and;
- Ventral respiratory groups (VRG) in the medulla oblongata.
Dorsal respiratory group (DRG)
- Inspiratory (discharge in inspiration), although some expiratory role
- Involuntary, rhythmic, quiet breathing
- Constant stimulation by DRG for diaphragm and external intercostal muscle contraction; results in inspiration
*When constant stimulation is interrupted (via inhibitory impulses), inspiration ceases, muscles relax and the lungs recoil for exhalation
*When constant stimulation is interrupted (via inhibitory impulses), inspiration ceases, muscles relax and the lungs recoil for exhalation
Ventral respiratory group (VRG)
- Both inspiratory and expiratory neurons that responsible for the generation of respiratory rhythm
- Neuronal group is also involved involuntary breathing by stimulating the internal intercostal and accessory respiratory muscles
Sensory input to the respiratory centres is via:
Pheripheral and central chemoreceptors
Peripheral chemoreceptors:
- Located in the carotid and aortic bodies and are innervated by the glossopharyngeal nerve, which projects to the NTS
- are primarily activated by hypoxia, but also (less so) by increased arterial pCO2, decreased pH and hypo-perfusion
The peripheral chemoreceptors are responsible for sensing large changes in blood oxygen levels.
If blood oxygen levels become quite low, PO2 < 60 mm Hg then peripheral chemoreceptors stimulate an increase in respiratory activity.
Central chemoreceptors
- located in the locus ceruleus andNTS, midline (raphe) of the ventral medulla, and ventrolateral quadrant of medulla
- respond primarily to high pCO2 mediated through the detection of a fall in the pH of the cerebrospinal fluid (CSF)
- are crucial for adequate breathing in sleep
Hering-Breuer Reflex
Pulmonary stretch receptors are localised in the smooth muscles of bronchi and bronchioles in the lung and the visceral tissue of the pleura.
These receptors are connected to medulla via afferent sensory neurons in the vagus nerveand respond to the inflation of these muscles.
In essence the sensory input prevents over-inflation. Inspiratory neurons in the respiratory CPG are inhibited, stopping inhalation, allowing for muscle relaxation and exhalation.
Propioreceptors & metaboreceptors
The intercostal muscles and diaphragm contain specialized receptors (muscle spindles) that respond to stretch.
Muscle contraction stimulates a positive feedback loop via the spinal cord that increases motor drive to the inspiratory muscles.
This response ensures that an increase in the resistance to inhalation is met with a compensatory increase in muscle recruitment.
Receptors in the muscles and joints of the locomotor system also provide positive feedback signals to the medullary controller, stimulating hyperpnoea.
Some of these receptors are stimulated by passive movement of limbs, and they are thought to play a role in the control of the exercise hyperpnoea especially at the onset of exercise.
The respiratory muscles also contain so-called metaboreceptors that responds to metabolites, such as lactate. These metaboreceptors are present in all muscles. While not directly involved in the modulation of the control of breathing,these inputs provide information regarding the metabolic state and use of your arms and limbs especially during strenuous exercise when more oxygen is required to sustain the increased rate of movement/muscle contraction.
Irritant receptors within the lungs
Within the epithelial cells of the airways are specialised nerve endings that respond to the air that is taken into the system. It responds to irritants such as dry and/or cold air, smoke, dust, pollen, chemical fumes and excess mucus. Stimulation of these receptors triggers protective reflexes. Bronchoconstriction occurs, breathing becomes more shallow, breath holding occurs before coughing strongly (this prevent these irritants from going deeper into the airways before expelling them)
Quiet breathing is primarily determined by signals from the _______
Dorsal respiratory group
Sensory feedback to the respiratory centre can be initiated by _____
Muscle spindles in the intercoastals
Which of the following is the most likely cause of high arterial PCO2
Depressed medullary respiratory centres
When you inhale…
the diaphragm and external intercostal muscles contract, the rib cage rises, the lungs are stretched, intra-alveolar volume increases, decreasing the pressure.
At inspiration
The intra-alveolar (intra-pulmonary) pressure is now below atmospheric pressure, air flows down the pressure gradient, into the lungs (negative pressure breathing) and is available for gas exchange.
Air flow continues until…
intra-alveolar pressure = Patm
The pressure that distends the alveoli is the:
transpulmonary pressure = intra-alveolar pressure minus the intra-pleural pressure.
As the transpulmonary pressure increases, lung volume increases. T/F
True
Hysteresis:
difference between the pressure-volume curve for inflation and the curve for deflation
With fibrosis the lung compliance…
decreases –> that is they become “stiffer” with increasing connective tissue and the alveolar elastic recoil capacity is limited
Describe emphysema:
increases lung compliance and the pressure-volume curve is shifted up and left, because of destruction of alveolar septal tissue that normally opposes lung expansion
in obesity chest wall compliance is reduced as moving the diaphragm downward and the rib cage up and out is much more difficult T/F
True
for laminar flow resistance is inversely related to airway radius
for laminar flow resistance is inversely related to airway radius
Dalton’s Law in respiration:
The air we breathe in is a mixture of gases
Nitrogen: 78.6%
Oxygen 20.9%
The remaining 0.5% consists of water vapour.
Carbon dioxide (CO2) takes up a mere 0.04%.
In a given system of mixed gases, the partial pressure exerted by a single gas present will, therefore, be proportional to the amount/percentage of that gas.
In a given system of mixed gases, the partial pressure exerted by a single gas present will, therefore, be proportional to the amount/percentage of that gas.
Henry’s law states that:
the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of that gas
Ventilation:
Amount of blood going into alveoli
Purfusion
Amount of blood FLOW going into the alveoli
The apex of the lung has a _____ ventilation/perfusion ratio
Higher
The base of the lung has a _____ ventilation/perfusion ratio
Lower
Within the lung, there is ____ in perfusion at the apex
Decrease (due to gravity)
“Wasted ventilation” is found at the:
Apex of the lung
Most O2 is bound to:
haemoglobin (Hb) within the erythrocytes about 98%
