PHYSIOLOGY - Respiration Flashcards
1
Q
What is respiration?
A
Respiration is the process by which oxygen is extracted from the external environment and delivered to cells for aerobic respiration
2
Q
Which breathing pattern is used by mammals?
A
Tidal breathing
3
Q
What is a respiratory cycle?
A
A respiratory cycle is one sequence of inspiration and expiration (i.e. one breath)
4
Q
What is total lung capacity (TLC)?
A
Total volume of air the lungs can hold
5
Q
What is tidal volume (Vt)?
A
Total volume of air moved within one respiratory cycle during quiet breathing
6
Q
What is functional residual capacity (FRC)?
A
Total volume of air remaining in the lungs following quiet expiration
7
Q
What is vital capacity (VC)?
A
Total volume of air moved within one respiratory cycle during forced breathing
8
Q
What is residual volume (RV)?
A
Total volume of air remaining in the lungs following forced expiration
9
Q
What is minute ventilation?
A
Minute ventilation is the total volume of air inhaled and exhaled per minute
10
Q
What is the formula for calculating minute ventilation?
A
Tidal volume (Vt) x respiratory frequency (f)
11
Q
What increases minute ventilation?
A
Increased metabolic rate increases oxygen demand and thus increases minute ventilation
12
Q
What is dead space?
A
Dead space in the volume of air that does not participate in gaseous exchange
13
Q
What is anatomic dead space?
A
Anatomic dead space is the volume of air within the conduction respiratory pathways that does that participate in gaseous exchange
14
Q
What is alveolar dead space?
A
Alveolar dead space is the volume of air which enters alveoli which are not perfused that thus do not participate in gaseous exchange
15
Q
What is physiologic dead space?
A
Physiologic dead space is the sum of the anatomic and alveolar dead space
16
Q
What is the formula for calculating tidal volume (Vt)?
A
Volume of air entering perfused alveoli (Va) + Physiologic dead space (Vd)
17
Q
What is panting?
A
Panting is a thermoregulatory mechanism involving a controlled decrease is tidal volume and increase in respiratory frequency
18
Q
How does panting act as a thermoregulatory mechanism?
A
Decreased tidal volume decreases the volume of air reaching the alveoli for gaseous exchange and thus more air will ventilate the dead space and increase the evaporation of the moistened air - cooling the dog down. Increased respiratory frequency will compensate the decreased tidal volume to ensure enough air reaches the alveoli for gaseous exchange
19
Q
What is Boyle’s law?
A
Boyle’s law states that as the volume of gas increases, the pressure exerted decreases, and vice versa
20
Q
What is atmospheric pressure?
A
Atmospheric pressure is the force exerted by the air surrounding the body
21
Q
What is intra-alveolar pressure?
A
Intra-alveolar pressure is the force exerted by the air within the alveoli
22
Q
What drives pulmonary ventilation?
A
The difference in atmospheric and intra-alveolar pressure drives airflow in and out of the lungs as air flows down a pressure gradient (high to low pressure)
23
Q
Describe briefly the process of inspiration
A
Contraction of the diaphragm and intercostal muscles increases the volume of the thoracic cavity and consequently the volume of the lungs, causing a decrease in intra-alveolar pressure relative to atmospheric pressure, driving airflow down its pressure gradient into the lungs
24
Q
Describe briefly the process of expiration
A
Expiration is a passive process where relaxation of the diaphragm and intercostal muscles following inspiration causes the lungs to recoil, decreasing the volume of the thoracic cavity and the lungs, causing an increase in intra-alveolar pressure relative to atmospheric pressure, driving airflow down its pressure gradient into the atmosphere
25
Describe the structure of alveoli
Alveoli are small sac-like structures surrounded by a network of pulmonary capillaries
26
What are the two cell types which line the walls of alveoli?
Type 1 pneumocyte
Type 2 pneumocyte
27
What is the function of type 1 pneumocytes?
Gaseous exchange
28
What is the function of type 2 pneumocytes?
Secretion of surfactant
29
What is alveolar gaseous exchange?
Alveolar gaseous exchange is the diffusion of oxygen from the alveoli into the pulmonary capillaries and diffusion of carbon dioxide from the pulmonary capillaries into the alveoli along a pressure gradient (high to low pressure)
30
What are the three components of the gas exchange membrane?
Type 1 pneumocytes
Fused alveolar and endothelial basement membranes
Pulmonary capillary
31
What is the partial pressure (PO2) of oxygen in the alveoli and the pulmonary capillaries?
Alveolar PO2 = 100
Blood PO2 = 40
32
What is the partial pressure (PCO2) of carbon dioxide in the alveoli and the pulmonary capillaries?
Alveolar PCO2 = 40
Blood PCO2 = 45
33
Describe gaseous exchange between cells and the systemic circulation
Diffusion of oxygen from systemic capillaries into cells and the diffusion of carbon dioxide from cells into the systemic capillaries along a pressure gradient (high to low pressure)
34
Which two factors can alter the partial pressure of oxygen (PO2)?
Atmospheric pressure
Humidity
35
How can the partial pressure of oxygen (PO2) be calculated?
Atmospheric pressure (Patm) x Fractional concentration of oxygen in the environment (FO2)
36
What is the fractional concentration of oxygen (FO2) in the environment?
0.21 (21%)
37
How should you calculate the partial pressure of oxygen (PO2) in the presence of water vapour?
(Atmospheric pressure - Water vapour pressure) x Fractional concentration of oxygen in the environment
(Patm - PH2O) x FO2
38
Why is the alveolar partial pressure of oxygen (PO2) lower than the atmospheric partial pressure of oxygen (PO2)?
As air travels down the respiratory tract to the lungs, the respiratory epithelium humidifies the air and reduces the PO2. Furthermore, there is a continual diffusion of oxygen out of the alveoli into the pulmonary capillaries and a continual diffusion of CO2 from the pulmonary capillaries into the alveoli, also reducing the alveolar PO2
39
How can you calculate the partial pressure of oxygen in the arterial blood?
(Atmospheric pressure - Water vapour pressure) x Fractional concentration of oxygen in the environment - partial pressure of arterial carbon dioxide
(Patm - PH2O) x FO2 - PaCO2
| remeber brackets then multipy before subtraction
40
What are the two methods of oxygen transport within the blood?
Dissolved in the plasma
Bound to haemoglobin
41
Which three factors can influence oxygen transport within the blood?
Concentration of haemoglobin
Cardiac output
Haemoglobin affinity for oxygen
42
How does oxygen partial pressure (PO2) influence haemoglobin affinity for oxygen?
Increased PO2 increases the affinity of haemoglobin for oxygen whereas decreased PO2 decreases the affinity of haemoglobin for oxygen
43
What is an oxygen dissociation curve?
An oxygen dissociation curve plots the relationship between the partial pressure of oxygen (PO2) and the percentage (%) of haemoglobin oxygen saturation
44
What is the P50 value?
The P50 value is the partial pressure of oxygen (PO2) required to saturate 50% of the haemoglobin
45
What is the Bohr effect?
The Bohr effect describes the relationship between pH and haemoglobin affinity for oxygen. When the pH decreases, the haemoglobin affinity for oxygen also decreases
46
How does temperature influence haemoglobin affinity for oxygen?
Increased temperature decreases the haemoglobin affinity for oxygen
47
What is the influence of 2,3 BiPglycerate (2,3-BPG) on haemoglobin?
2,3 BiPglycerate (2,3-BPG) is a negative allosteric effector which binds to the haemoglobin, lowering the haemoglobin affinity for O2, increasing O2 release to the tissues
48
Why does the pH decrease when the carbon dioxide partial pressure (PCO2) increases?
Carbon dioxide is a gaseous acid and thus increased PCO2 will decrease pH
49
What are the three methods of carbon dioxide transport within the blood?
Dissolved in plasma
Carbaminohaemoglobin
As bicarbonate ions
50
What is carbaminohaemoglobin?
Carbaminohaemoglobin is the structure formed when carbon dioxide binds to the amino group of haemoglobin
51
How is carbon dioxide transported within the blood as bicarbonate ions?
CO2 diffuses into red blood cells where the carbonic anhydrase enzyme will catalyse the reactions between CO2 and H2O to form carbonic acid (H2CO3) which readily dissociates into bicarbonate ions (HCO3-) and H+. The HCO3- will move out of the red blood cell into the plasma in exchange for chloride ions (Cl-), a process known as chloride shift
52
What is a carbon dioxide dissociation curve?
An carbon dioxide dissociation curve plots the relationship between the partial pressure of carbon dioxide (PCO2) and the concentration of carbon dioxide in the blood
53
What is the Haldane effect?
The Haldane effect describes how the oxygenation of haemoglobin promotes displacement of the carbon dioxide from the haemoglobin and the deoxygenation of haemoglobin promotes the binding of carbon dioxide to the haemoglobin
54
Which device can be used to measure the concentration of carbon dioxide in exhaled air?
Capnogram
55
Describe the phases of capnography
Phase 1: No CO2 is going out as the patient is inhaling and thus the baseline is usually zero
Phase 2: The beginning of exhalation where CO2 begins to travel from the alveoli through the anatomical dead space causing a rapid rise in the graph. The graph continues to rise as the more concentrated CO2 gases from lower in the lungs moves past the sensor
Phase 3: The sensor is receiving the CO2 rich gas from the alveoli. Because this is a fairly stable amount of CO2, the graph levels off into a plateau. At the end of phase 3, a peak of CO2 is reached (known as the end tidal CO2 reading (EtCO2))
The patient will then inhale again, bringing clear air past the sensor, dropping the graph back down to baseline
56
Describe briefly the pulmonary circulation
Pulmonary artery transports deoxygenated blood from the heart to the lungs for gaseous exchange and the pulmonary vein transports oxygenated blood from the lungs to the heart where the blood will be transported into the systemic circulation via the aorta
57
Describe briefly the bronchial circulation (including the bronchial anatomic shunt).
Bronchial arteries transport oxygenated blood to the lung tissue and bronchial veins drain deoxygenated blood from the lung tissue into the pulmonary vein, forming an anatomic shunt as the deoxygenated blood in the bronchial vein is bypassing the alveoli and entering the systemic circulation
58
What is the ventilation perfusion (V/Q) ratio?
Ventilation perfusion (V/Q) ratio is the ratio between the volume of air inhaled and the volume of blood reaching the alveoli per minute
59
What is the ideal ventilation perfusion (V/Q) ratio for maximally efficient pulmonary function?
1:1
60
What causes a high ventilation perfusion (V/Q) ratio (>1)?
A high ventilation perfusion (V/Q) ratio is usually caused by a decrease in blood flow leading to high ventilation relative to perfusion
61
How will the partial pressure values for O2 and CO2 change when there is a high ventilation perfusion (V/Q) ratio?
There will be high PO2 and low PCO2 in the blood
62
What causes a low ventilation perfusion (V/Q) ratio (<1)?
A low ventilation perfusion (V/Q) ratio is usually caused by a decrease in ventilation, leading to high perfusion relative to ventilation
63
How will the partial pressure values for O2 and CO2 change when there is a low ventilation perfusion (V/Q) ratio?
There will low PO2 and high PCO2 in the blood
64
What are the three elements of the ventilatory control system?
Sensory receptors
Central respiratory control system
Respiratory muscles
65
What are the two types of sensory receptors involved in the control of pulmonary ventilation?
Chemoreceptors
Mechanoreceptors
66
What is the function of chemoreceptors in the respiratory system?
In the respiratory system, chemoreceptors detect changes in PO2, PCO2 and pH
67
Where are central chemoreceptors located?
Central chemoreceptors are located in the medulla oblongata and the pons
68
What is the function of central chemoreceptors?
Central chemoreceptors detect changes in the H+ concentration in the cerebrospinal fluid (CSF) and consequently detects the PCO2
69
Where are peripheral chemoreceptors located?
Peripheral chemoreceptors are located at the aortic arch and carotid sinuses
70
What is the function of peripheral chemoreceptors?
Peripheral chemoreceptors detect changes in the arterial PO2, PCO2 and H+ concentration
71
Which two cranial nerves transmit sensory information from the peripheral chemoreceptors to the central respiratory control centre?
Glossopharyngeal nerve (CN IX)
Vagus nerve (CN X)
72
What is the function of mechanoreceptors in the respiratory system?
Mechanoreceptors detect changes in the movement of the lungs and thoracic wall
73
Where is the central respiratory control centre located?
The central respiratory control centre is located in the medulla oblongata and the pons
74
What are the three main components of the central respiratory control centre?
Pre-botzinger complex
Dorsal respiratory group (DRG)
Ventral respiratory group (VRG)
75
What is the function of the pre-botzinger complex?
The pre-botzinger complex is a group of pacemaker neurones which regulate respiratory rhythm
76
What is the primary function of the dorsal respiratory group (DRG)?
The dorsal respiratory group (DRG) primarily regulates inspiration during quiet breathing through the innervation of the external intercostal muscles and the diaphragm
77
What is the function of the ventral respiratory group (VRG)?
The ventral respiratory group (VRG) receives information from the dorsal respiratory group during exercise, activating the ventral respiratory group to regulate inspiration and expiration through innervation of the intercostal, serrates ventralis and external abdominal oblique muscles
78
What is the function of the Hering-Breuer reflex?
Hering-Breuer reflex prevents excessive distension of the lungs during inspiration
79
What is hypoxaemia?
Hypoxaemia is low oxygen in the arterial blood
80
How does high altitude affect pulmonary ventilation?
When altitude increases, the atmospheric pressure decreases and thus the PO2 will decrease leading to acute hypoxaemia, stimulating the peripheral chemoreceptors which stimulate hyperventilation
81
Name a disease caused by high altitude
Brisket disease
82
How is pH measured?
pH is measured based on the free H+ concentration in arterial blood
83
What is the normal pH value of arterial blood?
pH = 7.4
84
What are pH buffers?
pH buffers are substances within the blood which can reversibly bind to H+ ions
85
What are the two main pH buffers found in the blood?
Bicarbonate ions (HCO3-)
Haemoglobin
86
What is acidaemia?
Acidaemia is the increase in free H+ in arterial blood
87
What is alkalaemia?
Alkalaemia is the decrease in free H+ in arterial blood
88
What is acidosis and alkalosis?
Acidosis and alkalosis refer to the processes which cause acidaemia and alkalaemia
89
How does hypoventilation alter blood pH?
Hypoventilation decreases how much CO2 is eliminated from the body, leading to an increase in the partial pressure of CO2 (PCO2) in arterial blood, leading to hypercapnia and acidosis
90
How does hyperventilation alter blood pH?
Hyperventilation increases how much CO2 is eliminated from the body, leading to a decrease in the partial pressure of CO2 (PCO2) in arterial blood, leading to hypocapnia and alkalosis
91
What is the only route in which H+ ions can be eliminated from the body?
H+ ions can only be eliminated in the proximal convoluted tubule of the kidneys
92
What are the two primary causes of acid-base disturbances?
Excessive accumulation or elimination of CO2
Excessive accumulation or elimination of H+ or pH buffers
93
What causes excessive accumulation or elimination of CO2?
Respiratory abnormalities
94
What causes excessive accumulation or elimination of H+ or pH buffers?
Metabolic abnormalities
95
What is the ratio between H2CO3 and HCO3- in the blood at a normal pH?
1:20 (H2CO3:HCO3-)
96
How does the renal system compensate for respiratory acidosis to maintain blood pH?
When there is respiratory acidosis, there is increased arterial PCO2, leading to a decreased pH. To compensate, the renal system resorbs bicarbonate ions into the blood and excretes H+ ions into the urine, aiming to increase the pH value
97
How does the renal system compensate for respiratory alkalosis to maintain blood pH?
When there is respiratory alkalosis, there is decreased arterial PCO2, leading to an increased pH. To compensate, the renal system excretes bicarbonate ions into the urine and conserves H+ ions in the blood, aiming to decrease the pH value
98
How do the renal and respiratory system compensate for metabolic acidosis to maintain blood pH?
When there is metabolic acidosis, there is increased arterial PCO2, leading to a decreased pH. To compensate, the renal system resorbs bicarbonate ions into the blood and excretes H+ ions into the urine, and, the respiratory system will stimulate hyperventilation to eliminate more CO2 , aiming to increase the pH value.
99
How do the renal and respiratory system compensate for metabolic alkalosis to maintain blood pH?
When there is metabolic alkalosis, the is decrease arterial PCO2, leading to an increased pH. To compensate, the renal system will excrete bicarbonate ions in the urine and conserve H+ in the blood, and, the respiratory system will stimulate hypoventilation to conserve CO2, aiming to decrease the pH value
100
What is the risk of respiratory compensation of metabolic alkalosis?
Hypoventilation to conserve CO2 could lead to hypoxia
101
In clinical therapy, what can be used to treat respiratory and metabolic acidosis?
Lactate solution fluid therapy as lactate will be converted into bicarbonate ions by the liver
102
In clinical therapy, what can be used to treat respiratory and metabolic alkalosis?
Chloride containing solution fluid therapy as chloride will replace bicarbonate ions with chloride (Cl-)
103
How does acidosis affect the distribution of potassium (K+) throughout the body?
Acidosis causes K+ to move into the blood stream in exchange for H+ ions moving into the cells, causing hyperkalaemia
104
How does alkalosis affect the distribution of potassium (K+) throughout the body?
Alkalosis causes K+ to move into cells in exchange for H+ ions moving into the blood stream, causing hypokalaemia
105
How can chloride (Cl-) depletion maintain metabolic alkalosis?
A chloride (Cl-) depletion stimulates the kidneys to resorb bicarbonate ions (HCO3-) to maintain electroneutrality. The HCO3- ions would bind to H+ in the blood, further increasing the pH and maintaining the alkalosis
