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Physiology Flashcards

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1
Q

Internal respiration

A

The intracellular mechanisms that consumes O2 and produces CO2

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2
Q

External respiration

A

The sequence of events that leads to the exchange of O2 and CO2 between the external environment and cells of the body

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3
Q

4 steps in external respiration

A

Ventilation - Mechanical process of moving air between the atmosphere and alveolar sacs
Gas exchange between alveoli & blood in pulmonary capillaries
Gas binding and transport in circulating blood
Gas exchange between blood in systemic capillaries & tissue

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4
Q

4 body systems involved in external respiration

A

Respiratory
Cardiovascular
Haematology
Nervous

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5
Q

Boyle’s Law

A

P1V1=P2V2 (When T is constant)

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6
Q

Must the intra-alveolar pressure be more/less than atmospheric pressure for air to flow into the lungs

A

LESS

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7
Q

Forces holding thoracic wall and lungs in opposition (2)

A

Intrapleural fluid cohesiveness

Negative intrapleural pressure (negative in comparison to atmosphere)

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8
Q

Intrapleural fluid cohesiveness (2)

A

Water molecules in intrapleural fluid are attracted to each other
So pleural membranes stick together

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9
Q

Negative intrapleural pressure (2)

A

Sub-atmospheric intrapleural pressure create a transmural pressure gradient across the lung and chest wall
So the lungs are forced to expand outwards while the chest is forced to squeeze inwards

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10
Q

Atmospheric pressure at sea level (2)

A

760mmHg

101kPa

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11
Q

Intra-alveolar (intrapulmonary) pressure

A

Same as atmospheric pressure when equilibriated

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12
Q

Intrapleural (intrathoracic) pressure

A

756mmHg

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13
Q

Inspiration mechanism (4)

A

Active process depending on muscle contraction
Thorax volume is increased vertically by diaphragm contraction
Involves phrenic nerve from cervical 3,4 & 5
External intercostal muscle contraction lifts ribs and moves out of sternum - ‘Bucket handle’ mechanism

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14
Q

Before inspiration

A

External intercostal muscle and diaphragm are relaxed

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15
Q

During inspiration (3)

A

External intercostal muscles contract to elevate ribs and increase side-to-side thoracic cavity dimensions
Diaphragm lowering on contraction increases vertical thoracic cavity dimension
Ribs elevation lifts sternum upwards and outwards that increases front to back thoracic cavity dimension

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16
Q

Inspiration pressure changes (2)

A

Increase in lung size makes intra-alveolar pressure to fall

Air then enters down pressure gradient until equilibrium is reached

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17
Q

Expiration (4)

A

Passive process caused by intercostal muscles relaxing and diaphragm moving upwards
Chest wall and lungs recoil to preinspiratory size due to elastic properties
The recoil increases intra-alveolar pressure
So air leaves lungs down pressure gradient until equilibrium is reached

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18
Q

Pneumothorax (7)

A

Air in pleural space
Can be spontaneous, traumatic or iatrogenic
Air enters the pleural space from outside or from the lungs
This can abolish transmural pressure gradient leading to lung collapse
Small pneumothorax can be a symptomatic
Symptoms of pneumothorax include shortness of breath and chest pain
Physical signs include hyper resonant percussion note and decreased/absent breath sounds

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19
Q

What causes lung recoil during expiration (2)

A

Elastic connective tissue

Alveolar surface tension

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20
Q

Alveolar surface tension (3)

A

Attraction between water molecules at liquid air interface
This produces a force which resists lung stretching
If the alveoli were lined with water alone the surface tension would be too strong so the alveoli would collapse

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21
Q

LaPlace’s Law

A

P (Inward directed collapsing pressure) =2(Surface tension)/(Radius of buble)

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22
Q

Pulmonary surfactant (3)

A

Complex mixture of lipids and proteins secreted by type 2 alveoli
Lowers alveolar surface tension by interspersing between water molecules lining the alveoli
More effective with smaller sized alveoli to prevent collapsing and emptying of air content to larger alveoli

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23
Q

Respiratory Distress Syndrome of the New Born (3)

A

Developing fetal lungs are unable to synthesize surfactant until late in pregnancy
Premature babies will lack pulmonary surfactant
So baby has to make hard inspiratory efforts to overcome high surface tension and inflate the lungs

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24
Q

Alveolar Interdependence

A

If an alveolus start to collapse the surrounding alveoli are stretched and then recoil exerting expanding forces in the collapsing alveolus to open it

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25
Forces keeping alveoli open (3)
Transmural pressure gradient Pulmonary surfactant Alveolar interdependence
26
Forces promoting alveolar collapse (2)
Elasticity of stretched lung connective tissue | Alveolar surface tension
27
Major inspiratory muscles
Diaphragm and external intercostal muscles
28
Accessory muscles of inspiration
Sternocleidomastoid, scalenus, pectoral
29
Muscles of active expiration
Abdominal muscles and internal intercostal muscles
30
Tidal Volume (TV) (2)
Volume of air entering or leaving lungs during a single breath Average value at 0.5 L
31
Inspiratory reserve volume (IRV) (2)
Extra volume of air that can be maximally inspired over and above the typical resting tidal volume Average value at 3.0 L
32
Expiratory reserve volume (ERV) (2)
Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume Average value at 1.0 L
33
Residual Volume (RV) (3)
Minimum volume of air remaining in the lungs even after a maximal expiration Average value at 1.2 L Increases when elastic recoil of lungs is lost
34
Inspiratory Capacity (IC) (3)
Maximum volume of air that can be inspired at the end of a normal quiet expiration (IC =IRV + TV) Average value at 3.5 L
35
Functional Residual Capacity (FRC) (3)
Volume of air in lungs at end of normal passive expiration (FRC = ERV + RV) Average value at 2.2 L
36
Vital Capacity (VC) (3)
Maximum volume of air that can be moved out during a single breath following a maximal inspiration (VC = IRV + TV + ERV) Average value at 4.5 L
37
Total Lung Capacity (TLC) (3)
Total volume of air the lungs can hold (TLC = VC + RV) Average value at 5.7 L
38
Can residual volume be measured by spirometry
NO so not possible to measure total lung volume by spirometry
39
Volume time curves determines (4)
Forced Vital Capacity (maximum volume that can be forcibly expelled from the lungs following a maximum inspiration) Forced Expiratory volume in one second (volume of air that can be expired during the first second of expiration in an FVC determination) FEV1/FVC ratio (the proportion of the Forced Vital Capacity that can be expired in the first second -normally more than 70%) Volumes useful in diagnosis of Obstructive and Restrictive Lung Disease
40
Flow formula
F = Change in Pressure/Resistance
41
Airway resistance (5)
Normally low and air moves with small pressure gradient Primary determinant is radius of conducting airway Parasympathetic stimulation causes bronchoconstriction Sympathetic stimulation causes bronchodilatation Diseases like COPD increases resistance than makes expiration harder than inspiration
42
Dynamic airway compression during active expiration (3)
Rising pleural pressure pushes air out of alveoli but compresses the airway In healthy people it is no issue for increased airway resistance increases airway pressure upstream which helps open airway by increasing driving pressure If obstruction present driving pressure is lost where a fall in airway pressure results in compression due to rising pleural pressure
43
Diseased airway more likely to collapse (True/False)
True
44
Peak flow Meter (4)
Assess airway function Useful in patients with obstructive lung disease Measured by patient giving short sharp blow into meter Best out of 3 attempts is taken
45
Pulmonary Compliance (3)
Measure of effort lungs has to go into stretching or expanding Volume change per unit of pressure change across the lungs The less compliant the lungs the more work is required to produce a degree of inflation
46
Decreased pulmonary compliance (3)
Caused by fibrosis, oedema, lung collapse, pneumonia, lack of surfactant Indicates greater pressure change needed to produce a given change in volume - causes SOB Causes restrictive pattern of lung volumes
47
Increased pulmonary compliance (3)
Caused by lost of elastic recoil Occurs in emphysema where patients work harder to force air out (hyperinflation) Increases with increasing age
48
Work of breathing is increased when (4)
Pulmonary compliance is decreased Airway resistance is increased Elastic recoil is decreased There is a need for increased ventilation
49
Pulmonary Ventilation (2)
Volume of air breathed in and out per minute | = Tidal Volume*Respiratory Rate
50
Alveolar Ventilation (4)
Volume of air exchanged between the atmosphere and alveoli per minute Less than pulmonary ventilation due to anatomical dead space = (Tidal Volume-Dead space Volume)*Respiratory Rate More vital as it determines new air available for gas exchange
51
Way to increase pulmonary ventilation
Increase depth and rate of breathing
52
Gas transfer between body and atmosphere depends on (2)
Ventilation - Rate of gas passing through lungs | Perfusion - Rate of blood passing through lungs
53
Ventilation Perfusion (3)
Both blood flow and ventilation vary from bottom to top of the lung Causes average arterial and alveolar partial pressure of O2 to be different Significant in disease
54
Alveolar Dead Space (4)
Match of alveoli air and blood is not perfect Ventilated alveoli which are not adequately perfused with blood are considered as alveolar dead space In healthy people space is tiny More significant in disease
55
Ventilation Perfusion Match in Lungs (3)
Local controls act on smooth muscles of airways and arterioles to match airflow to blood flow Accumulation of CO2 in alveoli due to increased perfusion decreases airway resistance causing increased airflow Increase in alveolar O2 concentration due to increased ventilation causes pulmonary vasodilation which increases blood flow to match larger airflow
56
Area that perfusion is greater than ventilation (Applies vice versa) (6)
``` CO2 increase in area Local airway dilation Airflow increases O2 decrease in area Local blood vessels constrict Blood flow decreases ```
57
Do systemic arterioles constrict/dilate under low O2 concentration
Dilate
58
4 factors affecting gas exchange rate across alveolar membrane
Partial Pressure Gradient of O2 and CO2 Diffusion Coefficient for O2 and CO2 Surface Area of Alveolar Membrane Thickness of Alveolar Membrane
59
Partial Pressure of Gas (2)
The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied by the mixture at a given temperature Determines pressure gradient of that gas
60
Dalton's Law of Partial Pressure
P(Total)=P1 + P2 + P3 (Sum of the partial pressures of each individual component in the gas mixture)
61
Alveolar Gas Equation
PAO2 = PiO2 – [PaCO2/0.8] PAO2 = Partial Pressure of O2 in alveolar air PiO2 = Partial pressure of O2 in inspired air PaCO2 = Partial pressure of CO2 in arterial blood 0.8 is the Respiratory Exchange Ratio (RER)
62
Partial Pressure of Oxygen in the Alveolar air (PAO2)
Water vapour in lungs has pressure of 47 mmHg So pressure of inspired air = 760(atm)-47=713 mmHg (at sea level) PiO2 = 713*0.21 = 150 mmHg Normal arterial PCO2 is 40 mmHg PAO2 = 150 - (40/0.8) = 100 mmHg at sea level
63
Why is Partial pressure gradient of CO2 smaller than O2 (3)
CO2 is more soluble than O2 Solubility of gases in membrane is the diffusion constant Diffusion constant of CO2 is 20 times more than O2
64
A big gradient between PAO2 and PaO2 indicates (2)
Gas exchange issues in lungs | Right/left shunt in heart
65
Lung Adaptations to increase SA (3)
Airways divide repeatedly Small airways form outpockets Extensive capillary network
66
Lung Adaptations to decrease diffusion path (3)
Thin walled alveoli consist of single layer of type 1 alveolar cells Capillaries encircle each alveolus Narrow interstitial space
67
Non respiratory functions of respiratory systems (5)
``` Route of heat elimination by water loss Enhances venous return Maintain acid-base balance Enables speech Defends against inhaled foreign matter ```
68
Henry's Law
``` The amount of a given gas dissolve in a given type and volume of liquid at constant temperature is proportional to the partial pressure of the gas in equilibrium with the liquid ```
69
Dissolved oxygen volume and partial pressure
3 ml per L | 13.3 kPa
70
Normal O2 concentration is arterial blood
200 ml per L
71
O2 is present in the blood in 2 forms:
Bound to haemoglobin - 98.5% | Physically dissolved - 1.5%
72
Haemoglobin and oxygen (4)
Each Hb molecule has 4 haem group Each haem group reversibly binds to one O2 molecule Haemoglobin is fully saturated when all Hb present is carrying its maximum O2 load Partial pressure of O2 is primary factor of percent saturation of haemoglobin with O2
73
Oxygen Delivery Index formula
``` DO2I = CaO2 x CI DO2I = Oxygen Delivery Index (ml/min/metre2) CaO2 = Oxygen content of arterial blood (ml/L) CI = Cardiac index (L/min/metre2) ```
74
Cardiac Index (2)
Relates to cardiac output to body surface area | Normal range is 2.4 - 4.2
75
Oxygen Content of Arterial Blood Formula
``` CaO2 = 1.34 x [Hb] x SaO2 One gram of Hb carry 1.34 ml of O2 when fully saturated [Hb] = haemoglobin concentration (gram/L) SaO2 = %Hb saturated with O2 ```
76
Oxygen delivery to tissues is impaired by (3)
Respiratory disease - Decreased partial pressure of inspired O2 affecting arterial PO2 Heart failure - Decreased cardiac output Anaemia - Decreased Hb concentration
77
Partial Pressure of inspired O2 depends on (2)
Total pressure | Proportion of O2 in gas mixture
78
Haemoglobin Oxygen binding (3)
Binding of 1 O2 to Hb increases affinity of Hb for O2 - Co-operativitty Causes sigmoid curve shape Flattens when all sites are occupied
79
Flat upper portion on sigmoid curve indicates
Moderate fall in alveolar PO2 will not much affect oxygen loading
80
Steep lower part on sigmoid curve indicates
Peripheral tissues get a lot of oxygen for a small drop in capillary PO2
81
Bohr Effect
When the curve shifts to the right
82
Conditions for Bohr Effect (4)
Increased PCO2 Decrease pH Increased temperature Increased 2,3 - Biphosphoglycerate
83
Foetal Haemoglobin (HbF) (4)
Has different Hb structure to adults (2 alpha, 2 gamma subunits) Causes less interaction with 2,3 - Biphosphoglycerate So HbF has higher affinity for O2 even at low PO2 Shifts Bohr effect to the left
84
Myoglobin (Mb) (7)
Present in skeletal and cardiac muscle Only 1 haem group per molecule No cooperative binding Hyperbolic dissociation curve Releases O2 at very low PO2 Short term storage of O2 during anaerobic conditions Presence in blood indicates muscle damage
85
3 types of CO2 transport in the blood
Solution - 10% Bicarbonate - 60% Carbamino compounds - 30%
86
CO2 in solution (2)
Based on Henry's Law | 20 times more soluble than O2
87
CO2 as bicarbonate (2)
Most CO2 is transported this way | Occurs in RBCs
88
Bicarbonate formation formula (2)
CO2 + H2O<=>H2CO3 <=>H+ + HCO-3 Involved enzyme carbonic anhydrase in the first equilibrium
89
Bicarbonate formation mechanisms (3)
CO2 diffuses from capillary into RBC CO2 reacts with H2O with carbonic anhydrase to form H2CO3 H2CO3 then dissociates to H+ which is buffered by haemoglobin and HCO3- that moves into the plasma due to the chloride shift
90
Carbamino Compounds (4)
Formed by combination of CO2 with terminal amine groups in blood proteins Especially globin to give carbamino- haemoglobin Rapid without enzyme Reduced Hb can bind more CO2 than oxidised Hb
91
Haldane Effect
Removing O2 from Hb increases the ability of Hb to pick-up CO2 and CO2 generated H+
92
Bohr and Haldane effect work in synchrony to
Facilitate O2 liberation, CO2 uptake & CO2 generated H+ at tissues
93
Oxygen shifts the CO2 Dissociation Curve to the Left/Right
Right
94
The Bohr Effect Facilitates the Removal of O2 from Haemoglobin at Tissue Level by
Shifting the O2-Hb Dissociation Curve to the Right
95
Neural control of respiration (2)
Mostly medulla oblongata and pons of brain stem are rhythm generators A network of neurons of the upper medulla called the Pre-Botzinger complex displays pacemaker activity
96
What gives rise to inspiration (5)
Rhythm generated by Pre-Botzinger complex Excites Dorsal respiratory group neurones Fire in bursts Firing leads to contraction of inspiratory muscles When firing stops, passive expiration occurs
97
What gives rise to active expiration (hyperventilation) (2)
Increased firing of dorsal neurones excites a second group | Ventral respiratory group neurones excite internal intercostals and abdominals for forceful expiration
98
Pneumotaxic centre (PC) (4)
Located in pons Terminates inspiration PC stimulated when dorsal respiratory neurons fire Without PC, breathing is prolonged inspiratory gasps with brief expiration - Apneusis
99
Apneustic centre (3)
Located in pons Prolongs inspiration Impulses from these neurones excite inspiratory area of medulla
100
Respiratory centre is influenced by stimuli from (6)
``` Higher brain centers Stretch receptors Juxtapulmonary (J) receptors Joint receptors Baroreceptors Central and Peripheral chemoreceptors ```
101
Higher brain centre examples (3)
Cerebral cortex Limbic system Hypothalamus
102
Stretch receptors (4)
Located in walls of bronchi and bronchioles Activated during inspiration Activated only at large (>>1 L) tidal volume Guards against hyperinflation The Hering-Breur reflex
103
Juxtapulmonary (J) receptors
Stimulated by pulmonary capillary congestion, oedema and emboli
104
Joint receptors (2)
Impulses from moving limbs reflexly increase breathing | Contribute to the increased ventilation during exercise
105
Baroreceptors
Increased ventilatory rate in response to decreased blood pressure
106
Involuntary modifications of breathing (4)
Pulmonary Stretch Receptors Hering-Breuer Reflex Joint Receptors Reflex in Exercise Stimulation of Respiratory Center by Temperature, Adrenaline, or Impulses from Cerebral Cortex Cough Reflex
107
Factors increasing ventilation during exercise (5)
``` Reflexes originating from body movement Adrenaline release Impulses from the cerebral cortex Increase in body temperature Accumulation of CO2 and H+ generated by active muscles ```
108
Cough Reflex (4)
Part of defense mechanism from foreign bodies Activated by irritated or tight airways Centre in the medulla Afferent discharge stimulates: short intake of breath, followed by closure of the larynx, then contraction of abdominal muscles (increases intra-alveolar pressure), and finally opening of the larynx and expulsion of air at a high speed
109
Chemical control of respiration (3)
Negative feedback control system Controlled variables are blood gas tensions Chemoreceptors sense gas tension values
110
Peripheral Chemoreceptors (2)
Located in aortic and carotid bodies Sense tension of oxygen and carbon dioxide and [H+] in the blood
111
Central Chemoreceptors (2)
Situated near surface of medulla | Respond to [H+] of cerebrospinal fluid (CSF)
112
Cerebrospinal fluid (4)
Separated from blood by blood brain barrier Impermeable to H+ and HCO3- CO2 diffuses readily Contains less protein than blood so is less buffered
113
Hypercapnia
Abnormal build up of CO2 levels in blood
114
Hypoxic drive of respiration (4)
Effect mediated via peripheral chemoreceptors Stimulated when arterial PO2 falls below 8 kPa Not vital in normal respiration Vital in high altitudes and patients with chronic CO2 retention
115
Hypoxia at high altitudes is caused by (2)
Decreased PiO2 | Acute response is hyperventilation & increased cardiac output
116
Chronic adaptation to high altitude hypoxia (5)
Increased RBC production - More O2 carrying capacity Increased 2,3 Biphosphateglycerate - O2 offloaded to tissue more easily Increased capillary number - More blood diffusion Increased mitochondria number - O2 used more efficiently Kidneys conserve acid- Arterial pH decrease
117
H+ drive of respiration (4)
Effect mediated by peripheral chemoreceptors Peripheral receptors play major role in adjusting acidosis caused by addition of non-carbonic acid H+ to blood Stimulation by H+ causes hyperventilation and increases elimination of CO2 from the body Vital in acid-base balance

Respiratory (8 decks)

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