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Physiology Flashcards

1
Q

Internal respiration

A

Intracellular mechanisms which consume O2 and produce CO2

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2
Q

External respiration

A

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

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3
Q

4 steps of external respiration

A
  1. Ventilation - the mechanical process of moving gas in and out of the lungs
  2. Exchange of O2 and CO2 between the air in the alveoli and the blood in the pulmonary capillaries
  3. Transport of O2 and CO2 in the circulating blood (between lungs and tissues)
  4. Exchange of O2 and CO2 between the blood and the tissues
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4
Q

4 body systems involved in external respiration

A

Respiratory
Cardiovascular
Haematology system
Nervous system

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5
Q

What is ventilation

A

Mechanical process of moving air between the atmosphere and alveolar sacs

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6
Q

What is Boyle’s law

A

At any constant temperature the pressure exerted by gas varies inversely with the volume of the gas

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7
Q

What is atmospheric pressure

A

Pressure caused by the weight of the gas in the atmosphere on the earths surface

760mmHg

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8
Q

What is intra-alveolar pressure

A

Pressure within the lung alveoli

760mmHg

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9
Q

What is intrapleural pressure

A

Pressure exerted outside the lungs within pleural cavity

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10
Q

Negative intrapleural pressure

A

The sub-atmospheric intrapleural pressure (intra-thoracic pressure) creates a transmural pressure gradient across the lung wall and across the chest wall

Means lungs expand outwards while chest squeezes inwards

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11
Q

Intrapleural cohesiveness

A

Water molecules in intrapleural fluid are attached to each other and resist being pulled apart

Pleural membranes stick together

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12
Q

How do you convert between mmHg and kilopascals

A

Divide by 7.5

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13
Q

4 steps of inspiration

A
  1. Diaphragm contracts and descends, increasing vertical chest dimension
  2. External intercostal muscle lifts the ribs and moves out the sternum → increased volume of thorax
    Bucket handle mechanism
  3. Lung size increases so intra-alveolar pressure decreases (Boyle’s Law)
  4. Air enters the lungs down its pressure gradient until the intra-alveolar pressure becomes equal to atmospheric pressure
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14
Q

What is the difference in force inspiration compared to normal inspiration

A

Forced has:
- greater outflow of action potentials of longer duration causing maximal descension and flattening
- intercostal muscles contract forcefully to raise ribs maximally
- accessory muscles

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15
Q

What are the accessory muscles of inspiration

A

Pectoralis major
Pectoralis minor
Sterocleidomastoid
Scalenus anterior, medius, and posterior

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16
Q

3 steps of expiration

A
  1. Diaphragm relaxes and rises, intercostal muscles contract
  2. Intra-alveolar pressure increases (Boyle’s Law)
    Caused by relaxation of inspiratory muscles → passive process
  3. Lungs recoil to expell air from the lungs down its pressure gradient until the intra-alveolar pressure becomes equal to atmospheric pressure
    Due to alveolar tension
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17
Q

Difference in forced expiration and normal respiration

A

In forced:
- right and left anterolateral abdominal wall muscles contract forcefully, increasing intra-abdominal pressure
- diaphragm forced superiorly by compressed abdominal contents
- Intrathoracic pressure increases, air moves from high to low pressure - out of lungs

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18
Q

What is alveolar surface tension

A

Attraction between water molecules at liquid air interface

Produces a force which resists stretching of the lungs in alveoli helping lungs to recoil during expiration

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19
Q

Law of LaPlace

A

Inward collapsing pressure is equal to 2x surface tension divided by radius

P = 2T / r

Means smaller alveoli are more likely to collapse

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20
Q

What is lung surfactant

A

Complex mixture of lipids and proteins secreted by type 2 alveoli

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21
Q

What does lung surfactant do

A

Intersperses water molecules lining alveoli reducing alveolar surface tension to prevent collapse

Lowers surface tension of smaller alveoli more than larger alveoli to prevent collapse at end of expiration

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22
Q

What is respiratory distress syndrome of the newborn

A

Developing fetal lungs are unable to synthesise surfactant until late pregnancy

There’re premature babies may not have enough pulmonary surfactant

At birth baby make strenuous inspiratory effects to overcome high surface tension and inflate lungs which can cause damage

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23
Q

What are the forces keeping the alveoli open

A

Transmural pressure gradient

Pulmonary surfactant

Alveolar interdependence

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24
Q

What is alveolar interdependence

A

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

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25
What forces promote alveolar collapse
Elastic recoil of lungs and chest wall Alveolar surface tension
26
What are the major inspiratory muscles
Diaphragm External intercostal muscles
27
Accessory muscles of inspiration
- Sternocleidomastoid - Scalenus - Pectoral
28
Muscles of active expiration
- Abdominal muscles - Internal intercostal muscles
29
4 lung volumes
Tidal volume - TV Inspiratory reserve volume - IRV Expiratory reserve volume - ERV Residual volume - RV
30
4 lung capacities
Vital capacity Inspiratory capacity - IC Functional residual capacity - FRC Total lung capacity - TLC
31
Tidal volume
Volume that enters and leave with each breath Normal quiet inspiration and expiration
32
Inspiratory reserve volume
Amount of air that can be forcibly inhaled after a normal tidal volume Relies on; muscle strength, lung compliance (elastic recoil) and normal starting point
33
Expiratory reserve volume
The volume of air that can be exhaled forcibly after exhalation of normal tidal volume Flies on muscle strength and low airway resistance
34
Residual volume
Volume of air remaining in lungs after maximal exhalation Increases when elastic recoil of lungs is lost Cannot be measured by spirometry
35
Vital capacity
Volume that can be exhaled after maximum inspiration VC = IRV + TV + ERV
36
Inspiratory capacity
Volume that can be inhaled after quiet exhalation IC = IRV + TV
37
Functional residual capacity
Volume of air in lungs at end of normal passive expiration FRC = ERV + RV
38
Total lung capacity
Volume of air in lungs after maximal inspiration Sum of all volumes
39
What do you call a graph that plots volume against time using data from spirometry test
Vitalograph
40
2 important spirometry volumes on Vitograph
Forced vital capacity (FVC) - maximum volume of air subject can expel in maximal expiration from maximal inspiration Forced expiratory volume in 1 second (FEV1) - the maximal volume of air that a subject can expel in one second from point of maximum inspiration
41
In obstructive lung diseases what happens FVC and FEV1
FVC is only reduced slightly FEV1 <80% of predicted
42
In restrictive lung diseases what happens FVC and FEV1
Both <80% of predicted
43
Airway resistance equation
F = ∆P / R ∆P = pressure gradient R = radius
44
Which type of stimulation normally causes bronchoconstriction
Parasympathetic
45
Which type of stimulation normally causes bronchodilation
Sympathetic
46
What is dynamic airway compression
In active expiration lungs are compressed so air is pushed out of alveoli and airway
47
What is pulmonary compliance
The measure of effort that goes into stretching lungs. Volume change per unit of pressure change across lungs
48
Lungs normally operate at 1/2 full. What causes work of breathing to increase (4)
Pulmonary compliance decreased Airway resistance increased Elastic recoil decreased Increased need for ventilation
49
Pulmonary ventilation
Volume of air breathed in and out per minute - tidal volume x respiratory rate
50
Alveolar respiration
Volume of air exchanged between the atmosphere and alveoli per minute - (tidal volume - dead space) x respiratory rate
51
Anatomical dead space
Airways that fill but cannot perform gas exchange
52
Definition of Ventilation
Rate at which gas is passing through the lungs
53
Perfusion
Rate at which blood is passing through the lungs
54
Ventilation and perfusion (Q) at apex (top) of lung
Good V but poor Q
55
Ventilation and perfusion at base of lung
Poor V but good Q
56
What is alveolar dead space
Ventilated alveoli which are not adequately perfused with blood
57
What happens when perfusion is greater than ventilation
CO2 increases - vasodilation of airways :. Airflow increases O2 decreases - Vasoconstriction of local blood vessels :. Blood flow decreases
58
What happens when ventilation is greater than perfusion
CO2 decreases - Vasoconstriciton of airways :. Airflow decreases O2 increases - Vasodilation of local blood vessels :. Blood flow increases
59
4 factors that affect rate of gas exchange
Partial pressure gradient of O2 and CO2 Diffusion coefficient for O2 and CO2 Surface area of alveolar membrane Thickness of alveolar membrane
60
What is the equation for partial pressure of oxygen in alveolar air
PAO2 = PiO2 - PaCO2 / 0.8
61
What is the difference between CO2 diffusion coefficient and O2 coefficient
CO2 coefficient is 20x O2 coefficient
62
What are the non-respiratory functions of the respiratory system
Water loss and heat elimination Enhances venous return Helps maintain normal acid-base balance Speech Smell Defence against inhaled foreign material
63
What is Henrys law of partial pressure
The amount of a given gas dissolved in a given type and volume of liquid (e.g. blood) at a constant temperature is proportional to the partial pressure of the gas in equilibrium with the liquid
64
What are the two ways oxygen is transported around the body
Dissolved in blood (1.5%) Attached to haemoglobin (98.5%)
65
How is Oxygen delivery index calculated
DO2I = CaO2 x Ci CaO2 - O2 consent of arterial blood Ci = function of cardiac output (cardiac index)
66
How is Oxygen content of arterial blood calculated
CaO2 = 1.34 x [Hb] x SaO2 1 gram of [Hb] can carry 1.34ml of O2 when fully saturated SaO2 = %[Hb] saturated with O2
67
How is foetal haemoglobin different to adult haemoglobin
Differs in structure - 2 alpha and 2 gamma haem groups Has higher affinity for O2 compared to adult haemoglobin so that O2 can transfer from mother to foetus
68
What is Myoglobin
Oxygen carrier present in skeletal and cardiac muscle Only has one haem group per molecule Releases oxygen at very low PO2 Short term storage of oxygen in anaerobic conditions
69
What causes oxygen delivery to tissue to be impaired
Decreased partial pressure - at altitude Respiratory diseases - decreased arterial PO2 Anaemia - decreased Hb conc Heart failure - decreased CO
70
What are the 3 ways CO2 is transported in the blood ?
In solution (10%) Carb amino compounds (30%) (Includes haemaglobin) Bicarbonate (60%)
71
What is the Haldane effect
Removing of O2 from [Hb] increases the ability of [Hb to pick up CO2 and CO2 generated H+
72
What is bicarbonate converted into in RBCs What enzyme converts this product to CO2
Carbonic acid Carbonic anhydrase
73
What is the network of neurones in the medulla that is believed to generate breathing rhythm
Pre-Botzinger complex
74
What are the 8 stimuli that influence respiratory centres
Higher brain centres Stretch receptors Juxtapulmonary receptors Joint receptors Exercise Baroreceptors Chemoreceptors Cough reflex

Respiratory (2 decks)

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