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Flashcards in Physiology Deck (101):
1

What are the 4 stages of external respiration?

Ventilation
Gas exchange between alveoli and blood
Gas transport in blood
Gas exchange at tissue level

2

What is Boyle's law?

At any constant temperature the pressure exerted by s gas varies inversely with the volume of gas
(Gas volume increase = pressure exerted by gas decrease)

3

How are the lungs linked to the thorax?

Intrapleural fluid cohesiveness
Negative intrapleural pressure

4

What 3 pressures are important in ventilation?

Atmospheric pressure
Intra-alveolar pressure
Intrapleural pressure

5

How is lung volume increased physiologically?

Flattening of the diaphragm
External intercostal muscle (lifts ribs and moves out sternum)

6

What nerve innervates the diaphragm?

Phrenic nerve
(From C3,4,5)

7

What can abolish the transmuted pressure gradient?

Pneumothorax (air in the pleural space)

8

How to lungs recoil after inspiration?

Elastic connective tissue
Alveolar surface tension

9

What is alveolar surface tension?

Attraction between water molecules at liquid air interface
Produces a force which resists the stretching of the lungs

10

What is LaPlace's law?

Smaller alveoli have a higher tendency to collapse

11

What is pulmonary surfactant?

Mixture of lipids & proteins secreted by type II alveoli

Lowers the surface tension & stops collapse

12

What is respiratory distress of the newborn?

Not enough surfactant

13

What is alveolar interdependence?

When neighbouring alveoli collapse surrounding alveoli stretch then recoil pulling it open

14

What is tidal volume?

Volume of air entering or leaving the lungs during a single breath

15

What is inspiratory reserve volume?

Extra volume of air that can be maximally inspired over and above the typical resting tidal volume

16

What is the inspiratory capacity?

Max volume of air that can be inspired at the end of a normal quiet expiration

17

What is exploratory reserve volume?

Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume

18

What is functional residual capacity?

Volume of air in lungs at end of normal passive expiration

19

What is the vital capacity

Max volume of air that can be moved out during a single breath following a maximal inspiration

20

What is total lung capacity?

Max volume of air that the lungs can hold

21

What is FEV1?

Volume of air that can be expired during the first second of expiration in an FVC determination

22

What is FVC?

Maximum volume of air that can be forcibly expelled from the lung follows a maximum inspiration

23

What does a restrictive lung pattern look like?

Low FEV1
Low FVC
Normal ratio

24

What does an obstructive pattern look like?

FEV low
FVC low or normal
Ratio low

25

What does parasympathetic stimulation do to bronchioles?

Bronchoconstriction

26

What does sympathetic stimulation do to bronchioles?

Bronchodilation

27

What so dynamic airway compression?

In expiration pressure on alveoli and airway
Pressure on alveoli = good pushes air out of lungs
Pressure on airway = bad
(Causes no problem in normal people)

28

What patients is peak flow useful for?

Obstructive (COPD & asthma)

29

What is pulmonary compliance?

A measure of the effort that has to go into stretching or distendjng the lungs
Low compliance = stuff lungs = more work to breath

30

What decreases pulmonary compliance?

Pulmonary fibrosis
Pulmonary oedema
Lung collapse
Pneumonia
Absence of surfactant

31

What pattern does decreased pulmonary compliance have in spirometry?

Restrictive

32

When would pulmonary compliance become abnormally increased?

If elastic recoil of the lungs is lost
Emphysema - hyperinflation of lungs

33

Does compliance increase or decrease with age?

Increase

34

When is the work of breathing increased?

Pulmonary compliance Decreased
Airway resistance Increased
Elastic recoil Decreased
Need for increased ventilation

35

What is internal respiration?

The intracellular mechanisms which consume O2 & produce CO2

36

What is external respiration?

Exchange of O2 & CO2 between external environment and cells

36

What is anatomical dead space?

Air that remains in the airway where it is not available for gas exchange

37

Difference between pulmonary and alveolar ventilation?

Pulmonary = TV x RR
(Volume of air breathed in and out per minute)

Alveolar = (TV - dead space) x RR
(Volume of air exchanged between the atmosphere and the alveoli per minute)

38

What is the difference between ventilation and perfusion?

Ventilation - rate at which gas is passing through the lungs
Perfusion - rate at which blood is passing through the lungs

39

What is alveolar dead space?

Ventilated alveoli which are not adequately perfused
(Can significantly increase effect of disease)

40

How to V/Q stay matched in the lungs?

Increased perfusion --> increased CO2 --> decrease airway resistance --> increased airflow --> V/Q match

Increased ventilation --> increased O2 --> pulmonary vasodilation --> increased blood flow

41

Effect of local change in O2

Decreased O2 Increased O2

Pulmonary arterioles Vasoconstriction Vasodilation
Systemic arterioles Vasodilation Vasoconstriction

42

4 factors that influence the rate of gas exchange 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

43

What is the partial pressure of gas?

The pressure that one gas I 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

44

How do you calculate the partial pressure of oxygen in alveolar air?

PAO2 = PiO2 -[PaCO2/0.8]

PiO2 = partial pressure of oxygen in inspired air
0.8 = respiratory exchange ratio

45

Why is the partial pressure gradient for CO2 is much smaller than that of O2?

CO2 is more soluble in membranes than O2

46

What does a big gradient between PAO2 and PaO2 indicate?

Problems with gas exchange or a right to left shunt in the heart

47

What is Ficks law of diffusion?

The amount of gas that moves across a sheet of tissue in unit time is proportional to the area of the sheet but inversely proportional, to its thickness

48

What are alveoli?

Thin walled inflatable sacs
Function in gas exchange
Walls consist of a single layer of flattened Type I alveolar cells
Pulmonary capillaries encircle each alveolus
Narrow interstitial space

49

What are the non-respiratory functions of the respiratory system?

Route for water loss and heat elimination
Enhances venous return
Helps maintain normal acid-base balance
Enables speech and other vocalisations
Modifies materials that pass through the pulmonary circulation
Nose serves as organ of smell

50

What is Henry"s Law?

The amount of gas dissolved in blood is proportional to the gas' partial pressure

51

How is most oxygen transported in the blood?

Bound to haemoglobin

52

How else is oxygen transported in the blood (very little)?

Physically dissolved

53

How many groups does each haemoglobin molecule have?

4

54

What does the oxygen haemoglobin disassociation curve show?

Haemoglobin affinity for oxygen

55

How do you calculate the oxygen delivery index?

DO2I = CaO2 x CI

CaO2 = oxygen content of arterial blood
CI = cardiac index

56

How do you calculate the oxygen content of arterial blood?

CaO2 = 1.34 x [Hb] x SaO2

57

What can impair oxygen delivery to the tissues?

Respiratory disease
Heart failure
Anaemia

58

What is cooperativity?.

When the binds of 1 O2 to Hb increases the affinity of Hb for O2
(Flattens when all sites become occupied

59

What shape is the oxygen haemoglobin dissociation curve?

Sigmoid

61

What is the Bohr effect?

Shifting of oxygen haemoglobin curve to the right (less affinity)

62

What causes the Bohr effect?

Low pH
High temperature
Increased pCO2
Increased 2,3-BPG

63

What causes haemoglobin to have higher affinity for oxygen?

High pH
Low temperature
Low pCO2
Foetal haemoglobin.

64

Where is myoglobin found?

Skeletal & cardiac muscles

65

What does myoglobin do?

Provides short term storage for O2 under anaerobic conditions
Releases O2 at very low PO2

66

What does the presence of myoglobin in the blood indicate?

Muscle damage

67

3 means of CO2 transport in the blood?

Solutions
As bicarbonate
As carbamino compounds

68

How many times more soluble is CO2 than oxygen?

20

69

Where is bicarbonate formed?

Red blood cells

70

How are carbamino compounds formed?

Combination of CO2 with terminal amino groups in blood proteins

(Especially glob in of haemoglobin)

71

What is the haldane effect?

Removing O2 from Hb increases the ability of Hb to pick up CO2 and CO2 generated H+

72

What do the Bohr effect and the haldane effect with together to facilitate?

O2 liberation and uptake of CO2 & CO2 generated H+ at tissues

73

What complex in the brain controls the rhythm of breathing?

Pre-Botzinger complex

74

What is the neural control of inspiration?

Dorsal respiratory group neurones fire in bursts
Leads to inspiration
When firing stops, passive expiration

75

What is the neural control of hyperventilation?

Increased firing of dorsal neurones excites a second group:
Ventral respiratory group neurones
Excite internal intercostals, abdominals ect. --> forceful expiration

76

What can alter the rhythm generated in the medulla?

Neurones in the pons:
- pneumotaxic centre (PC) stimulation terminates inspiration
- stimulated when dorsal respiratory neurones fire
- inhibits inspiration

77

What is apeusis?

Breathing is prolonged inspiratory gasps with brief expiration
(What would happen if there was no PC)

78

What is the apneustic centre?

Impulses from these neurones excite inspiratory area of the medulla
Prolongs inspiration

79

Where do respiratory centres in the brain receive signals from?

Higher brain centresv(e.g. cerebral cortex)
Stretch receptors in the walls of bronchi/bronchioles
J receptors (stimulated left heart failure & pulmonary emboli)
Joint receptors (stimulated by joint movement)
Baroreceptors
Central chemoreceptors
Peripheral chemoreceptors

80

What does the Hering-Breur reflex do?

Stops hyperinflation of the lungs

81

Examples of involuntary modifications of breathing

Cough receptors
Joint receptors in exercise
Temperature, adrenaline changes

82

Factors that increase ventilation during exercise?

Reflexes originating from body movement
Adrenaline release
Impulses from cerebral cortex
Increase in body temp
Accumulation of CO2 and H+ generated by active muscles

83

What is the cough reflex for?

Helps clear airways of dust, dirt or excessive secretions
Activated by irritation of the airways or tight airways

84

Where in the brain is the cough reflex stimulated?

The medulla

85

What are the physiological aspects of the cough reflex?

Afferent discharge
Stimulates short intake of breath
Closure of the larynx
Contraction of abdominal muscles (increases intraalveolar pressure)
Opening of the larynx
Expulsion of air

86

What is the role of peripheral chemoreceptors in breathing?

Sense tension of O2, CO2 and [H+] in the blood

87

Where are the central chemoreceptors involved in respiration situated?

Near the surface of the medulla of the brain stem

88

What do the central chemoreceptors involved in respiration respond to?

[H+] of the cerebrospinal fluid (CSF)

89

Why is CSF less buffered than blood?

Contains less protein

90

What shape is the myoglobin dissociation curve?

Hyperbolic

91

What separates CSF from the blood?

Blood brain barrier

92

Does CO2 diffuse across the BBB?

Yes

93

What is hypercapnia?

Increased CO2

94

When is the hypoxia drive off respiratoration important?

Chronic CO2 retentive patients
At high altitudes

95

When is the hoodie drive stimulated?

When PO2

96

What causes hypoxia at high altitudes?

Decreased partial pressure of inspired oxen

97

What is the body's acute response to hypoxia?

Hyperventilation & increased cardiac output

98

Symptoms of acute mountain sickness

Headache
Fatigue
Nausea
Tachycardia
Dizziness
Sleep disturbance
Exhaustion
Dyspnoea
Unconsciousness

99

Chronic adaptations to high altitudes hypoxia?

Increased RBC (increases O2 carrying capacity of blood)
Increased 2,3 BPG produced within RBC (O2 offloaded more easy to tissues)
Increased number of capillaries (blood diffuses more easily)
Increased number of mitochondria (O2 can be used more efficiently)
Kidneys conserve acid (arterial pH drops)

100

Does H+ readily cross the BBB?

No

101

How does H+ excess affect respiration?

Peripheral chemoreceptors add non carbonic H+ to the blood
(e.g. lactic acid during exercise & diabetic ketoacidosis)
Causes hyoerventillation (blow off CO2)
IMPORTANT IN ACID BASE BALANCE