PHGY 216 Module 3 Exam | Complete Solutions (Answered)

PHGY 216 Module 3 Exam | Complete Solutions (Answered) What is internal respiration? - The intake of oxygen to produce ATP, creating carbon dioxide as waste What is external respiration? - All of the processes that bring oxygen from the atmosphere into the body - The transport of oxygen to the tissues - The removal of carbon dioxide from the tissues and it release back into the atmosphere What are the four steps of external respiration? - Ventilation - Exchange of O2 and CO2 between air and blood - Transport of O2 and CO2 - Exchange of O2 and CO2 between blood and tissues Describe the ventilation step of external respiration. - Air is moved in and out of the lungs by breathing - Air is moved between the atmosphere and the air sacs in the lungs Describe the exchange of O2 and CO2 between air and blood. - The diffusion of oxygen from the alveoli to the pulmonary capillaries - The movement of carbon dioxide in the opposite direction Describe the transport of O2 and CO2. - The transport of oxygen in the blood to the tissues - The movement of carbon dioxide in the opposite direction Describe the exchange of O2 and CO2 between blood and tissues. - The exchange of oxygen from the blood to the tissues and carbon dioxide from the tissue into the blood via diffusion What are the other functions of the respiratory system? - Enables speech - Defence against inhaled foreign matter - Parturition and defecation - Equalization of left and right cardiac outputs - Maintain the acid-base balance What are the three anatomical parts of the respiratory system? - The lungs - The chest wall - The pleural space What are the components of the upper airway? - Nose - Nasal cavities - Pharynx - Larynx What are the components of the lower airway? - Trachea - Left and right bronchi - Bronchioles - Alveoli What is the function of airway branching? - As each branch becomes smaller, the overall cross sectional area increases - Allows for the transition from convective flow to diffusive flow What is convective flow? - Air flow through the upper airway maintained by the energy of muscle contraction What is diffusive flow? - Passive air flow into the alveoli Where does the diffusive zone begin? - At the level of the respiratory bronchioles What is the chest wall? - Any other structures that contributes to respiration - Includes the thorax and the abdomen What are intercostal muscles? - Muscles found between the ribs - Necessary for generating pressure that allow air flow What are the divisions of the intercostal muscles? - Inner intercostals - External intercostals - Innermost intercostals What is the diaphragm? - A large sheet of skeletal muscle separating the thoracic and abdominal cavities What are the muscles of inspiration? - The diaphragm - The external intercostal muscles Describe the movement of the muscles of inspiration during inspiration. - The diaphragm descends to enlarge the thoracic cavity - The external intercostal muscles contract to elevate the ribs to further enlarge the thoracic cavity What are the muscles of expiration? - The internal intercostal muscles - Abdominal muscles When are the muscles of expiration used? - In healthy individuals they are generally inactive - Recruited during increased ventilation demands - E.g. exercise, coughing, sneezing, and vomiting What is the pleural space? - The fluid space between the parietal and visceral pleura What is the purpose of the pleural space? - Allow the membranes to rub against each other during breathing with reduced friction What are the two sub-processes of external respiration? - The ability of the respiratory muscles to generate the necessary pressure gradient to move air through the airways and to inflate the lungs - The ability of oxygen and carbon dioxide to diffuse across the alveolar-capillary barrier What it the equation that explains the physiology of the respiratory system? - ΔPressure/Resistance = Flow (V) What is the purpose of the pressure gradient? - To overcome the elastance or stiffness of the respiratory system, the resistance to flow, and the inertia of the system What are the conditions for air to flow into the alveoli? - The pressure in the alveoli must be lower than the pressure in the nose What are the conditions for air to flow out of the alveoli? - The pressure in the alveoli must be greater than the pressure in the nose What are the different pressures involved in respiratory mechanics? - Atmospheric pressure (PB) - Alveolar pressure (PA) - Pleural pressure (Ppl) - Transpulmonary pressure (Ptp) or lung recoil pressure What is atmospheric pressure? - Barometric pressure - The pressure exerted by the weight of the air in the atmosphere on the Earth's surface What is the value of atmospheric pressure? Why? - 0 mmHg - There is not enough different between the height of the lungs and nose/mouth What is alveolar pressure? - Intrapulmonary pressure - The pressure in the alveoli What is the value of alveolar pressure? - At the end of inspiration it is the same as atmospheric pressure - 0 cmH2O What is pleural pressure? - Intrapleural pressure - The pressure in the pleural space What is the value of pleural pressure? - Approximate intrathoracic pressure - -5cmH2O Why is pleural pressure negative? - Because the lungs want to collapse while the chest walls wants to expand What is transpulmonary pressure? - Lung recoil pressure - Transmural pressure - The difference between the alveolar pressure and the pleural pressure Why do the lungs have an intrinsic tendency to deflate following inflation? - Elastin fibres - Surface tension What are elastin fibres? - The connective tissues in the lunds arranged in a meshwork - Causes the elastic recoil that deflates the lungs What is surface tension? - The force exerted by the liquid lining the inside of the alveoli - Accounts for about 70% of the elastic recoil properties of the lung What are the effects of surface tension on elastic recoil? - The liquid layer resists any forces that try to increase its surface area - The surface area of the liquid shrinks as much as it possibly can What is the purpose of surface tension? - In the absence of expanding forces the alveoli can shrink as much as possible and expel alveolar gas Why don't the alveoli collapse due to surface tension? - Pulmonary surfactant - Alveolar interdependence What is pulmonary surfactant? - A complex mixture of lipids and proteins secreted by type II alveolar cells How does pulmonary surfactant prevent alveolar collapse? - The secretions help disperse the water molecules on the surface of the alveoli to decrease water-water attractions - Decreases surface tension - Decreases effort needed for inflation and increases compliance What is the law of LaPlace? - The magnitude of the collapsing pressure is directly proportional to the radius of the alveoli - 2T (surface tension)/r = P (collapsing pressure) Suppose the collapsing pressure of a smaller alveolus is larger than that of a larger alveolus. In that case, the smaller alveolus will empty into the larger one, which is detrimental to lung function. How is this prevented? - The small alveolus will secrete more surfactant Alveolar pressure must change to generate the pressure gradient, if alveolar pressure is essentially fixed at 0 mmHg, how can PA be changed? - By changing Ppl What equation describes the relationship between Pl, Ppl, and PA? - Pl + Ppl = PA Why can't PA be changed by changing Pl? - Pl is dependent on lung volume which cannot be changed How is Ppl changed? - Activating the inspiratory muscle decreased Ppl which decreased PA - Activating the expiratory muscles increases Ppl and increases PA Describe the onset of inhalation. - Alveolar pressure equals atmospheric pressure - Air does not flow in or out of the lungs - Inspiratory muscles contract, decreasing pleural pressure - Thoracic cavity enlarges - Alveolar pressure decreases allowing air to flow down its concentration gradient and inflate the alveoli - Alveolar pressure increases until it reaches atmospheric pressure Describe the onset of exhalation. - Inspiratory muscles relax - Pleural pressure and therefore alveolar pressure increase - Expiratory muscles do not need to contract since recoil forces are strong When is active exhalation necessary? - When high levels of ventilation are necessary - E.g. during exercise What is tidal volume? - The volume of air inhaled and exhaled How does activation of expiratory muscle affect tidal volume? - Increases it independent of the inspiratory muscles Describe active exhalation during routine exercise. - Muscles of the abdominal wall contract - Pressure is transferred to the pleural space - Pleural pressure is increased - Internal intercostals pull the ribe downward and inward - Size of the thoracic cavity is decreased Describe active exhalation during forced expiration. - Expiratory muscles are activated to generate a high pleural pressure - The pressure decreases because of energy lost due to resistance - Equal pressures between the airways and pleural space is reached - Transpulmonary pressure becomes negative, compressing the airway - Outward airflow can no longer be increased - Recoil pressure generates the pressure gradient for air flow Why can't outward airflow be increased when transpulmonary pressure becomes negative? - Any pressure increased is offset by a proportionate increase in airway resistance Describe the pressure-volume relationship of lung recoil pressure. - As lung volume increases its Pl increases from about 0 cmH2O at residual volume to about 30 cmH2O at total lung capacity Describe the pressure-volume relationship of chest wall pressure (Pw). - Below 65% of total vital capacity, Pw exerts inflating pressures - At 100% of total vital capacity, Pw wants to deflate What is Prs? - The combination of Pl and Pw - Represents the pressure-volume relationship of the respiratory system When is compliance the greatest? What does this mean? - At functional residual capacity - The amount of work or pressure needed to inhale or exhale is at its minimum What does low compliance mean? - More pressure is required to move air in or out How is resistance to flow determined? - Poiseuille's law What is the equation for Poiseuille's law? What is the primary determinant of resistance? - The radius of the airway How does the activity of sympathetic and parasympathetic inputs affect resistance? - At rest parasympathetic activity is dominant and promotes bronchoconstriction - Smooth muscle contract since ventilator demand is low What are other influences of bronchoconstriction? - Decreased CO2 - Histamine released - Excess mucus - Airway collapse - Oedema of the airway walls - Allergy-induced spasm of the airways (anaphylaxis) Why does sympathetic activity cause bronchodilation? - O2 demands are increased - Bronchodilation allows maximum flow rates with minimum resistance What are the mediators of sympathetic activity? - Direct and indirect innervation Describe direct innervation of sympathetic activity. - Nerve terminals release norepinephrine activating β2-receptors on the bronchial smooth muscle cells Describe indirect innervation of sympathetic activity. - Epinephrine released from the adrenal medulla circulates through the pulmonary circulation to the airway smooth muscle What other conditions can cause bronchodilation? - Increased CO2 concentrations What is asthma? - A chronic inflammatory disease of the airways that causes difficulty breathing What are the symptoms of asthma? - Shortness of breath - Chest tightness - Coughing - Wheezing What are the three ways in which airways can be impaired in asthma? - Thickening of airway walls due to histamine-induced oedema - Thick mucus secretions physically blocking the airways - Airway hyper-responsiveness causing spasms and constriction of smooth muscles in smaller airways What is chronic obstructive pulmonary disease? - Emphysema and chronic bronchitis What is chronic bronchitis? - A long-term inflammatory conditions of the lower airways - Caused by chronic exposure to cigarette smoke, allergens or air pollution - Airways become narrowed due to oedema of the airways and thick mucus secretion What is emphysema? - A reversible condition characterized by the collapse of the smaller airways and breakdown of alveolar tissues - Alveolar macrophages release trypsin as a protective measure, which destroy lung tissue What is tidal volume (VT)? - The volume of air entering or leaving the lung during a single breath - Around 500 mL at rest What is inspiratory reserve volume (IRV)? - The extra volume of air that can be maximally inspired above the resting tidal volume - Typically around 3000 mL What is inspiratory capacity (IC)? - The maximal volume of air that can be inhaled starting from the end of a normal expiration at rest - Typically 3500 mL (VT + IRV) What is expiratory reserve volume (ERV)? - The maximal volume of air that can be expelled starting at the end of a typical tidal volume - Around 1000 mL at rest What is residual volume (RV)? - The volume of air remaining in the lungs after maximal expiration - Around 1200 mL at rest What is functional residual capacity (FRC)? - The volume of air in the lungs at the end of normal passive expiration - Around 2200 mL - FRC = ERV + RV What is vital capacity (VC)? - The maximum volume of air that can be expelled during a single breath following a maximal inspiration - Around 4500 mL - VC = IRV + VT + ERV What is total lung capacity (TLC)? - The maximum volume of air the lungs can hold - Around 5700 mL What is forced expiratory volume in one second (FEV1)? - Similar to TLC - Derived from only the first second - Expressed as a ratio or percentage - Around 80% at rest What are the two categories of lung dysfunction? - Obstructive lung disease - Restrictive lung disease What is obstructive lung disease? - Inability to exhale as much - Lower FEV1 - FRC and RV are greater - VC is smaller What is restrictive lung disease? - Low lung volumes - FEV1 is reduced because the lungs are smaller - The proportion of FVC that can be exhaled (FEV1/FVC) is normal - No obstruction to airflow Describe the expiratory flow in a person with obstructive lung disease. - Start at a higher lung volume - Peak flow rate is lower - Higher residual volume Describe the expiratory flow in a person with restrictive lung disease. - Start at a lower lung volume - Peak flow rate is lower - Lower residual volume What is ventilation? - The amount of gas breathed in one minute - Minute ventilation What is the equation for ventilation? - Tidal volume x Respiration frequency = Minute ventilation Describe changes in an alveolus during inspiration and expiration - Inhaled VT is 500 mL - About 150 mL remains in the airways and cannot be used for gas exchange - About 350 mL reaches the alveoli - Exhaled VT is 500mL - Only 350 mL is expelled - 150 mL remains in the airways To increase gas exchange in the alveoli, is it better to increase frequency of breathing of or tidal volume? - VT must exceed dead space volume - The ideal breathing pattern is to use a slow deep breathing pattern How do low respiratory rates affect ventilation? - In order to maintain alveolar ventilation the tidal volume must increase - Increase the amount of work done by the inspiratory muscle - Elastic work of the lung is higher How do high respiratory rates affect ventilation? - Tidal volume can decrease with increased respiratory rates - Reduces the elastic work of the lungs - The flow-resistive work of the lung increases What are the factors that affect the work of breathing? - Decreased compliance - Increased resistance - Decreased elastic recoil - Increased demand for ventilation How does decreased compliance affect the work of breathing? - The tidal volume decreases - Respiratory rate increases