Tutorial Workbook 1017MSC T3 2023 Module 3 Respiratory System

Module 3: Respiratory System 3.1: Organisation of the Respiratory System Label the following diagrams 2 Diaphragm Left lung Pharynx Left main (primary) bronchus Parietal Pleura (and Visceral Pleura covers lung surface themselves) Right main (primary) bronchus Carina of trachea Trachea Oral Cavity Larynx Nostril Nasal cavity plus Paranasal Sinuses Trachea

e) lateral cartilage ridges called false vocal folds 8) An arteriole is like a bronchiole in that both a) allow gas exchange b) allow flow in both directions c) are lined with cilia d) contain a layer of smooth muscle e) increase flow rate when constricted 5

3.2: Mechanics of breathing 1) Label the respiratory pressures and structures on the images below. Indicate changes during the phases of inspiration and expiration in one full breathing cycle, and the duration of the cycle. Label the graphs with appropriate scales and units ( relative to atmospheric pressure = atm) . 8 Intrapulmonary pressure (Ppul) 0mmHg (760mmHg) Diaphragm Lung Intrapleural pressure (Plp) – 4mmHg) 756mmHg Transpulmonary pressure 4mmHg (difference between 0mmHg and -4mmHg) Pleural Cavity Visceral Pleura Parietal pleura Thoracic wall Intrapulmonary pressure Pressure relative to atmospheric pressure (mmHg) Volume (L) 5 Seconds elapsed Intrapleural pressure Transpulmonary pressure Intrapulmonary pressure During each breath, the pressure gradients move 0.5 litre of air into and out of the lung Pleural cavity pressure becomes more negative as chest wall expands during inspiration . Returns to initial value as chest wall recoils. Pressure inside lung decreases as lung volume increases during inspiration; pressure increase during expiration. Volume of breath Intrapleural pressure

a) chest wall compliance increases b) airway resistance decreases c) alveolar surface tension increases d) amount of surfactant in the lungs increases 14. The factors responsible for holding the lungs to the thorax wall are a) the smooth muscles of the lung b) the diaphragm and the intercostal muscles alone c) adhesion forces acting between visceral and parietal pleurae d) the opposing lung and chest wall recoil forces 15. Low lung compliance tends to make inflation _______________, and low airway resistance tends to make rapid breathing ______________________. a) easy and easy b) easy and difficult c) difficult and easy d) difficult and difficult 16. Which of the following is not the case? a) gas flow equals pressure gradient divided by resistance. b) pressure gradient equals gas flow divided by resistance. c) resistance equals pressure gradient divided by gas flow d) intrapleural pressure is always negative during quiet breathing 17. Which one of the following conditions does not occur on a large inspiration? a) inspiratory muscles contract b) size of the thoracic cavity increases c) intrapleural pressure becomes more positive d) transpulmonary pressure increases 18. Compared with pressures at rest, during expiration, which of the following does not occur? 11

20. Tidal volume is air a) remaining in the lungs after forced expiration b) exchanged during normal breathing c) forcibly inhaled after normal inspiration d) forcibly expelled after normal expiration 21. The vital capacity of an average young male is around ________________. a) 2400 ml b) 3600 ml c) 4800 ml d) 6000 ml 22. The lung volume that represents the maximum volume that can be inspired or expired is a) total lung capacity b) vital capacity c) inspiratory capacity d) functional residual capacity 23. The maximal amount of air that can be inspired after a normal (not forced) inspiration is called a) inspiratory reserve volume b) inspiratory capacity c) functional residual capacity d) vital capacity 24. All of the following can be determined from a spirogram except a) expiratory reserve volume b) inspiratory reserve volume c) residual volume d) inspiratory capacity 14

3.3: Respiratory gas exchange 1. Label this diagram showing the partial pressure gradients promoting O 2 and CO 2 gas exchange across respiratory membranes (lungs) and systemic capillary membranes (body tissues). 17 Inspired air: PO2 = 160mmHg PCO2 0.3mmHg Alveoli of lungs: PO2 = 104mmHg PCO2 = 40mmHg Pulmonary Veins (PO2 100mHg) Systemic Arteries Blood leaving lungs and entering tissue capillaries: PO2 = 100mmHg PCO2 = 40mmHg Tissues: PO2 less than 40mmHg PCO2 greater than 45mmHg External respiration Internal respiration Systemic Veins Blood leaving tissues and entering lungs: PO2 = 40mmHg PCO2 = 45mmHg Pulmonary arteries Alveoli O2 CO2 O2 CO2 CO2 CO2 CO2 CO2 O2 O2 O2 O2

ii) How would (a) the pulmonary arterioles and (b) the bronchioles in this segment of the lung respond? Briefly explain the mechanisms underlying these responses. a) Pulmonary arterioles (carry blood) Pulmonary arterioles would constrict in response to low local O2 level (hypoxia) b) Bronchioles (carry air) Bronchioles would dilate in response to the raised CO2 levels (hypercapnia) iii) What benefit would the student get from these responses to inhaling a peanut? Briefly explain your answer. Vasoconstriction of pulmonary arterioles directs blood flow away from the hypoxic region to better ventilation regions improving gas exchange. Dilation of bronchioles improves ventilation somewhat in the affected area, helping to improve gas exchange. iv) What is the term used to describe this matching of blood and air supply in the respiratory system ? Ventilation and Profusion Coupling v) Briefly explain how the autoregulatory mechanism operating in this student can lead to right heart failure in a patient with chronic obstructive pulmonary disease (COPD), who has had widespread mucous blockage of airways over many years. - Widespread blockage of airways causes widespread hypoxic pulmonary vasoconstriction - Leads to pulmonary hypertension - Results in an increase in right ventricular work to maintain cardiac output - Leads too right ventricular hypertrophy and ultimately to right heart failure. 20

3.4: Gas transport Oxygen-haemoglobin Dissociation Curve 21

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Referring to the oxyhaemoglobin dissociation curve (ODC) below, answer the following questions. 1. On the PO 2 (x) axis mark the partial pressures of oxygen that you would expect to find in a healthy individual’s arterial (mark with letter a ) and mixed venous ( v ) blood at rest. (note: mixed venous blood is found in the pulmonary artery and represents the blood returning from all tissues in the body) ( a ) 100mmHg (v ) 40mmHg 2 . Using curve A (ODC at normal pH of 7.4) calculate the amount of oxygen delivered to the whole body each minute assuming that fully saturated blood carries 20mls of O 2 /100mls of blood. Assume that cardiac output is 5 L/min. Remember to calculate how much is delivered to the tissues . A fall in oxyhaemoglobin saturation from arterial (100% at 100mmHg) to mixed venous blood (80% at 40mmHg) = 20% (anything up to 25% is ok). 100mls of arterial blood carries 20mls of oxygen, - 20% x 20 = 4mls of oxygen to tissues. Thus, 1 litre of blood provides 40mls of oxygen. 5 litres (cardiac output = blood flow per minute) delivers 5 x 40mls = 200mls/min. 3. What 3 factors within the blood would cause the normal ODC (curve A ) to shift to position C ? For each factor you need to indicate whether this curve shift is associated with an increase or a decrease . i) Increase in PCO2 ii) Increase in H+ (or decrease in pH) iii) Increase in temperature 23 B A C

4. With the Bohr effect , more oxygen is released from haemoglobin at the tissues because a) a decrease in pH (acidosis) weakens the oxygen-haemoglobin bond b) a decrease in pH (acidosis) strengthens the oxygen-haemoglobin bond c) an increase in pH (alkalosis) strengthens the oxygen-haemoglobin bond d) an increase in pH (alkalosis) weakens the oxygen-haemoglobin bond 5. Summarise the homeostatic response to an increase in arterial PCO 2 (error signal) mediated by the cen t ral chemoreceptors . a) the location of receptors that are stimulated by this change Central chemoreceptors located bilaterally in the ventrolateral medulla. b) the mechanisms with i n the central nervous system that lead to a motor response An increasing arterial blood CO2 results in CO2 easily diffusing from the blood into the cerebrospinal fluid where it is hydrated and forms carbonic acid (H2CO3). As the acid dissociates, H+ is liberated. This (unbuffered) H+ excites the central chemoreceptors which stimulate the respiratory groups of neurones in the brainstem (medulla). c) the effect on breathing and how this brings a bout homeostasis of respiration Depth and rate of breathing increases, increasing alveolar ventilation. This returns the arterial PCO2 towards normal levels. 6. Fill in the Blank Activity In a healthy individual breathing room air, at sea level, at rest, the partial pressure of carbon dioxide (PCO 2 ) in inspired air is approximately 0.3 mmHg. The PCO 2 within the alveoli is approximately 40 mmHg. Arterial blood has a PCO 2 of 40 mmHg, which increases to 45mmHg in mixed venous blood. At the tissues, CO 2 diffuses down its partial pressure gradient into the capillary blood. In the blood, approximately 70% of CO 2 is transported as bicarbonate ion (HCO3-) 20% is transported as carbaminohaemoglobin and the remainder is transported dissolved in plasma. Within the red blood cell, there is a reversible reaction between CO 2 and H 2 0 which is catalysed by the enzyme carbonic anhydrase The product of this reaction diffuses out of the red cell into the plasma down its concentration gradient and ions move in the opposite direct to maintain ionic balance. KNOW THESE DIAGRAMS Transport and exchange of CO 2 and O 2 a) At the Tissues 24

b) In the lungs 7. In the plasma of arterial blood of a healthy person, the quantity of oxygen dissolved in solution a) less than 2 % of the oxygen combined with haemoglobin b) about 7% of the oxygen combined with haemoglobin c) much greater than the amount combined with haemoglobin 25

d) zero because oxygen is insoluble in aqueous solution like plasma 8. Which of the following correctly describes mechanisms of CO 2 transport ? a) 20% of CO 2 is dissolved directly into the plasma. b) 7-8% of CO 2 is carried in the form of carbaminohaemoglobin. c) the majority of CO 2 transported in the blood is in the form of carbonic acid d) the chloride shift mechanism enhances CO 2 transport 9. Which statement about CO 2 is incorrect ? a) its accumulation in the blood is associated with a decrease in pH b) CO 2 concentrations are greater in venous blood than arterial blood c) raised CO 2 levels in arterial blood stimulates central chemoreceptors d) more CO 2 dissolves in the blood plasma than is carried in the red blood cells 10. During the chloride shift in tissue capillary blood , ____________________ the red blood cell. a) HCO 3- exits b) H 2 CO 3 enters c) CO 2 exits d) Cl- exits 11. Select the correct statement about oxygen transport in blood : a) at rest, a molecule of haemoglobin returning to the lungs contains one molecule of O 2 b) during conditions of acidosis, haemoglobin will release less of its O 2 to the tissues c) 50% oxyhaemoglobin saturation level of blood returning to the lungs might indicate a physical activity level higher than normal d) binding of an O 2 molecule to a haemoglobin molecule makes subsequent binding of O 2 molecules more difficult 12. The maximum amount of oxygen that can be carried by arterial blood is decreased by a) HCO 3- b) H + c) CO 2 26

d) anaemia 13. Carbonic anhydrase is a(n) a) carrier of carbon dioxide in the blood b) enzyme that accelerates the combination of carbon dioxide and water c) enzyme that splits the bicarbonate ion d) enzyme that splits carbonic acid into hydrogen and bicarbonate ions 14. Fill in the blank activity . List the percentages for CO 2 transport in the blood: 7% dissolved in plasma 20% combined with haemoglobin 70% converted to bicarbonate ion When CO 2 binds to haemoglobin, it binds to the globin molecule and is referred to as carbaminohaemoglobin. When CO 2 binds with water it forms carbonic acid. The catalyst for this reaction is carbonic anhydrase This acid then dissociates into hydrogen ions and bicarbonate ions. When bicarbonate ions move out of the red blood cell, chloride ions move in. 27

3.5: Control of breathing Brainstem respiratory centres . Neural and chemical influences on brainstem respiratory centres . 28

1. The most powerful respiratory stimulus for breathing in a healthy person is a) increase in temperature of arterial blood b) decrease in oxygen partial pressure in arterial blood c) decrease in pH (acidosis) in arterial blood d) increase of carbon dioxide partial pressure in arterial blood 2. Which of the following is not a stimulus for breathing? a) rising carbon dioxide levels b) rising blood pressure c) decreased arterial pH d) increased body temperature 3. Respiratory groups of neurones that control breathing are located in the a) midbrain and pons b) midbrain and medulla c) midbrain and upper spinal cord d) medulla and pons 4. What kind of neuron innervates the diaphragm ? 29

a) parasympathetic neuron b) preganglionic sympathetic neuron c) postganglionic sympathetic neuron d) alpha motor neuron 5. Which of the following cells concerned with respiration are not located in the brainstem? a) dorsal respiratory group b) pontine respiratory group c) carotid bodies d) central chemoreceptors 6. Which of the following statements is correct ? a) H+ acts directly on central chemoreceptors to increase ventilation b) low arterial pH is the most powerful stimulator of respiration. c) arterial blood pH does not affect peripheral chemoreceptors directly d) H+ has little effect on the blood pH 7. Which of the conditions is the most powerful stimulant to alveolar ventilation? a) decreased PO 2 b) increased H+ concentration c) decreased arterial pH d) increased PCO 2 8. Under which condition is alveolar ventilation stimulated via peripheral chemoreceptors? a) PO 2 below 60 mmHg b) PO 2 above 60 mmHg c) PCO 2 below 20 mmHg d) PCO 2 between 20 and 40 mmHg 9. Fill in the Blanks Activity 30

At rest, spontaneous respiratory rhythm is generated in the brain stem, which comprises the medulla and the pons. Within this region, the three principal groups of respiratory neurones are the i) Ventral respiratory group ii) Dorsal respiratory group iii) Pontine respiratory group Periodic bursts of neural activity travel down the phrenic nerve innervating the diaphragm causing inhalation. Between bursts of activity, exhalation occurs by passive recoil of the lungs and chest wall. Other regions of the brain that can affect breathing include the cerebral motor cortex and the hypothalamus. REFLECTION 1. What area do I feel most confident with? Why? Respiratory volumes and capacities are my current strength as I can remember the diagrams easily. 2. What area needs improvement? How can I make this improvement? I need to study more for this content, I am feeling overwhelmed with the intricacy of the systems and the intensive pace. Have you completed your Respiratory System checklist? 31