Physiology Flashcards
(74 cards)
1
Q
what is lung compliance
A
- distensibility of lung
, ability to swell under pressure
2
Q
increased lung compliance
A
- less elastic fibres
- less recoil
- hard to expire
e. g. COPD
3
Q
decreased lung compliance
A
- fibrosis/ scarring
- more effort to expand
- breathless
- oedema, pneumothorax
4
Q
inspiration overview
A
active process
air into lungs
5
Q
Expiration overview
A
air out of lungs
passive/ active process
elastic recoil/ accessory muscles
6
Q
Control of breathing + nerve origination
A
phrenic nerve
C3 - C5
7
Q
Inspiration muscles
A
Diaphragm - contracts - inferiorly
External costal muscles
- out + up
bucket handle
8
Q
passive expiration muscles
A
relaxation of diaphragm + elastic recoil
9
Q
Active expiration muscles
A
abdominal wall + internal costal muscles
10
Q
Process of inspiration
A
- Phrenic nerve innervation
- Diaphragm contracts
- Decrease in pleural pressure
- Lungs expand
- Air in
11
Q
Keeps lungs inflated
A
Intra -pleuric cohesiveness - water in pleural space attracts each other Negative pressure - pleural space has -ve pressure pressure grad., keeps inflated
12
Q
Pneumothorax
A
Air into pleural cavity
- increases pressure
No pressure gradient
- lung collapses
13
Q
passive Expiration process
A
- decreased phrenic nerve innervation diaphragm relaxes increase in pleural pressure elastic recoil air out
14
Q
Active respiration
A
diaphragm relaxes + internal costal muscles contract + abdominal wall contracts
- increased pleural pressure (become +ve)
forces air out lungs
- dynamic collapse
15
Q
alveolar pressure = to
A
pleural pressure + elastic recoil pressure
16
Q
Elastic recoil
A
- elastic fibres in membrane
- decreases as less stretched
17
Q
Dynamic Collapse
A
Positive pressure from active respiration
- Transmural pressure = -ve
- inward pressure on airway
exacerbated if decreased airway pressure
Causes a collapse
- Increases pressure behind collapse
- Airway re opened - pressure grad.
18
Q
Emphysema + dynamic collapse
A
decreased elastic recoil (swollen alveoli)
- decreased transmural pressure
- airway more likely to collapse
19
Q
Alveolar collapse
A
inward pressure = 2x surface tension/ radius - more likely in smaller alveoli - surfactant = amphipathic reduces tension via repulsion Alveolar independence - one alveoli collapses rest = stretched, elastic recoil, open
20
Q
Tidal Volume
A
- normal expiration
0,5L
21
Q
Vital Capacity
A
- volume expired after max inspiration
4. 5 L
22
Q
Inspiratory reserve volume
A
- volume inspired after tidal volume
- 3L
23
Q
expiratory reserve volume
A
- volume exhaled after tidal volume
1L
24
Q
residual volume
A
- remaining air in lungs volume
1. 2L
25
Total lung capacity
Vital capacity + residual volume
| = 5.7L
26
Functional reserve capacity
total air left in lung after tidal volume
| - 2.2L
27
Forced Vital Capacity
- volume of air forcibly exhaled after maximum inhalation
28
Forced expiratory volume 1
- max air expired 1 second after max inhalation
29
FEV1/FVC ratio + features of abnormalities
```
70% = normal
<70% = obstructive airway disease
- can't expire (narrow lumen)
70% but low FVC + FEV1 = restrictive
(cant inflate)
```
30
Physiological dead space
anatomical + functional dead space
31
Anatomical dead space
- recycled air/ not used air
| e. g. airways
32
Functional dead space
- air not diffused
| e. g. no blood supply
33
alveolar resp.
(tidal volume - dead space) x resp. rate
34
Diffusion - air -> blood
```
ideal 1:1 ratio
- not likely, gravity
apex < base lung
- vasodilation
perfusion/ diffusion limited
```
35
perfusion limited O2 uptake
- sub optimal conditions due to inadequate blood supply
| determined by unbound gas (no partial pressure if bound)
36
diffusion limited O2 uptake
- dependent on a diffusion factor e.g. size of membrane
37
Dead Space
- air not available for perfusion
| - anatomical/ functional
38
anatomical dead space
- air in airways
| can't be perfused into blood
39
functional dead space
- insufficient blood supply
| perfusion limited
40
4 factors effecting gas perfusion
- partial pressure of gas
- Surface Area
- Thickness of Membrane
- Solubility in membrane
41
Features of O2 dissociation curve
- sigmoidal
high O2 uptake at slightly low O2 conc.
- keeps O2 sats high
42
Bohr effect
graph moves to right
- increased dissociation of O2 in tissue + uptake in lung
CO2, H+ conc., temp, 2,3 bisphosphoglycerate
43
Oxygen delivery index =
cardiac output x O2 arterial content
44
foetal haemoglobin
2 alpha, 2 gamma sub units
higher affinity for O2
- picks up O2 from mother
- less reactive to 2,3 bisphosphoglycerate
45
Myoglobin
in muscles
carries 1 O2
short term relief of anaerobic conditions
46
Haldane effect
No O2 bound
- globin has high affinity for CO2
O2 has greater affinity - displaces CO2
- CO2 removal, lungs
47
Reduce effects of dead space
Heavy deep breathing
48
Alveolar gas equation
Partial pressure O2 in air - (partial pressure CO2/0.8)
49
PO2 arterial + alveolar
small grad. = normal
| large grad. = circulatory problem
50
Henrys law
Gas dissolved in liquid = proportional to partial pressure of gas
51
O2 arterial blood content
1.34 x haemoglobin conc. x 5 saturation
52
Oxygen delivery Index
Arterial O2 content x Cardiac Output
53
3 methods of CO2 transport
- plasma
- bicarbonates
- Carbamino Compounds
54
CO2 transport in plasma
Henrys law
- proportional to partial pressure + solubility
only unbound gas
55
Bicarbonates
In RBC carbonic anhydrase catalyses:
CO2 + H2O H2CO3 H+ + HCO3-
- bicarbonate exchanged for Cl-
in RBC
56
Carbamino compounds
CO2 binds to globin
| - doesn't affect partial pressure, bound CO2
57
Control Of respiration - 2 forms
neural
| chemical
58
Neural control - rhythm
medulla
Pre botzinger complex
- innervates dorsal respiratory group neurones
59
Stimulation of inspiration
pre botzinger complex causes innervation of diaphragm via dorsal respiratory group neurones via phrenic nerve
60
Pneumotaxic centre function
- Inhibits dorsal respiratory group neurones, allows respiration
activated by dorsal neurones
- ve feedback
61
Apneustic centre function
Prolongs inspiration
| - excites dorsal respiratory group neurones
62
Expiration
Pre botzinger complex inhibits dorsal respiratory centre innervation of phrenic nerve
- relaxation
63
Active expiration
- ventral respiratory group neurones stimulated
| innervation of internal intercostals + abdomen
64
Apneusis
Respiration - no pneumotaxic centre
| long inspiration, short expiration
65
hering Breur reflex
Prevents hyper inflation
| - inhibits inspiration
66
Chemical control of respiration mechanisms
Negative feedback of central + peripheral chemoreceptors
67
Location of central chemoreceptors
- surface of medulla
68
Main mechanism of resp. control
- H+ ion conc. in CSF via central chemoreceptors
69
Process of resp. control via central chemoreceptors
```
- CSF = impermeable to H+ + HCO3- ions
very permeable to CO2
CO2 dissolves in H2O
produces increased H+ ions
low protein levels - low buffering
```
70
Peripheral control of respiration
senses PaO2, PaCO2 + Pa H+
71
Peripheral control - changes in Pa CO2
```
Hypercapnia
- High CO2
increase ventilation
expel more CO2
Hypocapnia - acidaemia
- decreases ventilation
decreases CO2 expelled
prevents alkalaemia
- process ineffective in severe chronic COPD
```
72
Peripheral chemoreceptor control of PaO2
Detects very low O2 levels
Hypoxaemia
very low PaO2
- increase ventilation
73
Mechanism of cough initiation signalling
Afferent signals
-cough receptors on posterior trachea + pharynx + carina
internal laryngeal nerve -> superior laryngeal nerve -> vagus nerve
74
Mechanism of cough signalling - efferent
```
Contraction of diaphragm + external intercostals
- short breath in
Closure of larynx
- rima glottis shut by vocal chords
- active expiration
contraction of abdomen + internal intercostal muscles
- larynx opens
- air expulsed
```
