Respiratory System Flashcards
(345 cards)
1
Q
Define external respiration
A
the exchange of CO2 and O2 between the external environment and the cells of the body
2
Q
where does external respiration take place?
A
in the lungs
3
Q
what is atmospheric pressure value at sea level?
A
760 mmHg
4
Q
what is partial pressure?
A
the amount an individual gas contributes to overall air pressure
5
Q
how can partial pressure of a gas be calculated?
A
fraction of air that the gas you are considering equates to x total air pressure
6
Q
what do partial pressures define?
A
amount of o2 or other gas present in the lungs, blood or veins
7
Q
What to PA, Pa and Pv stand for?
A
PA: Partial pressure in lungs/alveoli
Pa: Partial pressure in blood (arteries)
Pv: Partial pressure in veins
8
Q
what factor must be considered when calculating partial pressures within the lungs?
A
water vapour is a gas so contributes to total atmospheric pressure
9
Q
what is the partial pressure of water within the lungs?
A
47mmHg
10
Q
what sort of muscle is the diaphragm formed from?
A
sheet of skeletal muscle
11
Q
what two body cavities are separated by the diaphragm?
A
thoracic and abdominal
12
Q
what nerve innervates the diaphragm?
A
phrenic nerve
13
Q
when does the diaphragm contract (flatten)?
A
during inspiration
14
Q
what is the chest wall formed from?
A
muscle and ribs
15
Q
what do accessory muscles in the chest wall do?
A
lift ribs and sternum
16
Q
name two accessory muscles in the chest wall
A
sternomastoid
scalene
17
Q
what muscles contract during quiet inspiration?
A
diaphragm
external intercostals
18
Q
what muscles contract during forceful inspiration?
A
diaphragm
external intercostals
accessory muscles
19
Q
what muscles relax during quiet expiration?
A
diaphragm
external intercostals
20
Q
what muscles are involved during forceful expiration?
A
diaphragm relaxes
internal intercoastals contract
abdominal muscles contract
21
Q
what do change do chest movements lead to?
A
volume change
22
Q
what happens to the chest volume during inspiration?
A
increases, leads to reduced pressure so air floods in
23
Q
what happens to the chest volume during expiration?
A
reduced chest volume, increased pressure
24
Q
what is the name of the membranes that covers the chest wall?
A
pleural membranes
25
what are the 2 types of pleural membranes?
parietal (chest wall)
| visceral (lungs)
26
what fluid do membranes secrete?
intrapleural fluid to provide lubricaition
27
what are the 2 airway zones?
conducting zone
| respiratory zone
28
what happens in the conducting zone?
movement of air into and out of lungs, no gas exchange
29
what happens in the respiratory zone?
gas exchange
30
what muscle is the airway made from?
smooth muscle
31
what changes resistance to airflow in the lungs?
changes in diameter of the conducting airways
32
what happens if the airway diameter dilates?
resistance to airflow will be reduced
33
what does contraction of airway smooth muscle cause?
narrowing (constriction) of airways
34
what body system is contraction and relaxation of airway smooth muscle influenced by?
autonomic nervous system
35
where within the lungs is most of the resistance to airflow?
upper airway (50-70%)
36
what are lungs held open by?
elasticity of lung tissue
37
what are the functional units of the lung?
alveoli
38
what are alveoli surrounded by?
sheet like capillaries
39
what type of cells is the alveolar wall formed of?
type 1 pneumocytes
40
what cells produce surfactant?
type 2 pneumocytes
41
what is the role of surfactant in lungs?
helps to stop the lung from collapsing and reduce the surface tension of fluid in the lungs
42
what is the driving force for the flow of air into and out of the lungs?
the difference between atmospheric pressure at the mouth and pressure within the alveoli
43
changes in which pressure determines the direction of airflow?
alveolar pressure
44
why does alveolar pressure determine the direction of airflow in and out of the lungs?
as atmospheric pressure is usually constant
45
in inspiration is the pressure greater in the lungs or the atmosphere?
greater in atmosphere
46
in expiration is the pressure greater in the lungs or the atmosphere?
greater in the lungs
47
what effect does movement of the ribs and diaphragm during inspiration have on the volume of the thoracic cavity?
increases
48
what effect does movement of the ribs and diaphragm during inspiration have on the intra-alveolar pressure?
decreases
49
why is inspiration phase active?
it requires muscles to achieve
50
what point must be reached to stop air flowing into the lungs
alveolar pressure reaches atmospheric pressure (PB)
51
what effect does movement of the ribs and diaphragm during expiration have on the volume of the thoracic cavity?
decreases
52
what effect does movement of the ribs and diaphragm during expiration have on the intra-alveolar pressure?
increases it
53
during quiet ventilation is the expiration phase passive or active?
passive
54
what does passive expiration depend on?
elastic recoil of lungs
55
when does air flowing out of lungs during expiration cease?
when alveolar pressure equals atmospheric pressure(PB)
56
is forceful ventilation active or passive?
active as it involves contraction of accessory expiratory muscles
57
what causes volume changes during respiration?
chest movements
58
what are the muscles of inspiration?
external intercostals
| diaphragm
59
what is the diaphragm shaped like?
a parachute/dome
60
what shape does the diaphragm become on contraction?
flat
61
when the diaphragm flattens on inspiration what effect does this have on the thoracic and abdominal (visceral) cavity?
increases thoracic volume
| displaces viscera caudally (downwards)
62
what are the 2 types of intercostal muscle?
external and internal
63
what are the two major accessory muscles of breathing?
```
scalene (within the neck)
abdominal muscles (pressurize abdomen)
```
64
what are the 4 pressures that need to be considered during the breathing cycle?
atmospheric
intra-alveolar
intrapleural
transmural
65
what is intra-alveolar pressure?
pressure in lungs
66
what is intrapleural pressure?
pressure between lungs and chest wall
67
what is transmural pressure?
the difference between intra-alveolar and intrapleural pressure
68
when is lung tissue stretched?
at all times even after full expiration
69
is the chest wall compressed or stretched at resting lung volumes?
compressed
70
what are the opposing forces which contribute to intrapleural pressure?
outward recoil of chest
| inward recoil of 'elastic' lungs
71
why do outward recoil of chest and inward recoil of 'elastic' lungs oppose each other?
because lungs and chest wall are attached
72
how is negative pressure in the pleural space produced?
force of elastic recoil of lung and chest wall oppose creating negative pressure in intrapleural spacethat exerts force on both.
73
define vital capacity
amount of air that can be expelled from lungs after full inhalation
74
what is functional residual capacity?
volume in lung remaining at the end of normal expiration
75
what are capacities the sum of?
two or more volumes
76
how is the work of breathing minimised?
when the lung volume at the end of expiration equals functional residual capacity
77
why is the lung volume at the end of expiration equal to functional residual capacity?
at FRC the inward force of lungs equals the outward force of chest
78
what quality aids the expansion of lungs during stretching?
high compliance (easy to distend)
79
what is the 'collapse' of lungs aided by when the stretching force is removed?
elasticity
80
for what 2 reasons does inspiration require energy?
stretch the lungs and chest wall
| overcome the resistance of airways
81
what process recovers some of the energy stored as elastic recoil?
expiration
82
what can an increase in lung compliance be caused by?
emphysema (loss of elastic tissue so easier to stretch)
| ageing
83
what can a decrease in lung compliance be caused by?
fibrosis (lung becomes stiffer)
pulmonary oedema
deficiency of surfactant
84
what does lung stretching (inspiration) increase within the lung?
tension
85
what does tension in the lung pull on and increase the size of?
airways and blood vessels
86
what effect does increasing the diameter of airways and blood vessels have?
reduces pulmonary vascular resistance
| reduces airway resistance
87
what must breathing overcome within the fluid lining alveoli?
surface tension
88
what creates surface tension in the alveoli?
fluid lining
89
is pressure caused by surface tension greater in smaller or larger alveoli?
smaller
90
where do surfactent molecules sit in the lung?
between water molecules in alveoli
91
what effect does the presence of surfactant molecules in the alveoli have?
reduces surface tension
92
what is pressure in the small and large alveoli equalised by?
presence of surfactant
93
what effect does surfactant have on pulmonary compliance?
increases it and so reduces the work of inflating the lungs
94
what effect does surfactant have on the tendency of lungs to recoil?
reduces it so they do not collapse so readily
95
what is the name of the pulmonary surfactant?
dipalmitoyl phosphotidyl choline
96
what is the pulmonary surfactant formed from?
phospholipids
97
where does the pulmonary surfactant originate from?
type II alveolar cells (pneumocytes)
98
what is the function of pulmonary surfactant?
reduces surface tension
99
what is the release of pulmonary surfactant stimulated by?
during inspiration (stimulated by stretch)
100
what must airway resistance be overcome by?
the action of inspiratory muscles that create the air to alveolar pressure gradient
101
how can airflow be calculated?
pressure gradient (air -alveolar pressure) divided by resistance of airway
102
what diseases increase resistance of airways?
COPD (encompasses bronchitis and emphysema
oedema (fluid restricts airflow)
asthma (increased constriction of smooth muscle and increased mucus secretion and inflammation)
103
what is anatomical deadspace within the lungs?
volume in airways that does not support gas exchange
104
how many ml per kg is there of dead space within the average human?
2.2 ml per kg
105
where is anatomical deadspace found?
conducting zone (permits movement of air in and out of the lungs
106
what is alveolar dead space?
where the alveoli is ventilated but not perfused, so not involved in gas exchange
107
is there alveolar dead space in a healthy adult human?
no
108
what is physiological dead space?
anatomical dead space + alveolar dead space
109
in a healthy lung what is physiological dead space?
anatomical dead space only as there should not be any alveolar dead space
110
where is there most and least resistance to airflow in the lungs?
most: trachea and primary bronchi
least: terminal bronchiole and alveoli
111
what are the 3 influences on airway diameter and resistance?
physical factors affecting airflow
chemical influences on airways
autonomic control of airways
112
how are lung tissues connected to bronchioles?
by lung parenchyma
113
how does increased airway diameter affect resistance to airflow?
reduces resistance to airflow
114
what are the 4 types of chemical influences on airways?
nervous
hormonal
chemical
physical
115
give an example of a nervous bronchoconstrictor and bronchodilator
constrictor: cholinergenic
dilator: adregenic
116
what receptor to adrenogenic bronchodilators act on?
alpha and beta adrenoreceptors
117
give an example of a hormonal bronchoconstrictor and bronchodilator
constrictor: acetylcholine
dilator: norepinephrine
118
what receptor do norepinepherine bronchodilators act on?
alpha and beta adrenoreceptors
119
give an example of 3 chemical bronchoconstrictors and 2 bronchodilator
bronchoconstrictors: histemine, SRS-A, prostaglandin F-2alpha
bronchodilator: CO2
120
give an example of 3 physical bronchoconstrictors
smoke
dust
SO2
121
what does the diameter of the conducting airways determine?
resistance to airflow
122
how can ANS influence resistance and airflow?
constricting/dilating airways
123
what effect do beta-receptor agonists have on airways?
act to dilate airways
124
what system is airway resistance (bronchomotor tone) increased by?
parasympathetic nervous system
125
what nerve processes causes bronchoconstriction?
parasympathetic neurons release acetylcholine that activate muscarinic receptors which causes contraction of muscle and bronchoconstriction
126
How does the nervous system cause bronchodilation?
sympathetic nervous system release of adrenaline acts on beta 2 receptors and causes bronchodilation
127
describe the process of the cough reflex
irritant receptors - sensory receptors - vagal afferents - medulla oblongata respiratory centres - vagal efferent - effector/target organs (bronchioles leading to vasoconstriction)
128
describe the process of the hering-breuer reflex
lung stretch receptors - sensory receptors - vagal afferents - medulla oblongata respiratory centres - vagal efferent - effector/target organs (bronchioles leading to vasodilation also termination of inspiration)
129
what is the energy in respiration used to overcome?
to stretch the lung
| overcome the resistance of the airways
130
how can disease alter compliance and resistance?
compliance increase: emphysema
compliance decrease: pulmonary fibrosis/oedema
resistance increase: asthma
131
what are the 3 ways the lung function can be measured?
```
static volumes (breathing cycle)
dynamic volumes (change with time)
CO2 in expired air (over time)
```
132
what equipment is used to measure static volumes?
spirometry
133
what equipment is used to measure dynamic volumes?
vitalograph
134
what equipment is used to measure CO2 in expired air?
capnography
135
what are static volumes a measure of?
capacity and volume
136
what is forced vital capacity (FVC)?
total volume of air expired from lungs
137
what is FEV1?
forced expiratory volume in 1 second
138
how do lung volumes change with reduced compliance?
air leaves faster but less is expelled
139
how do lung volumes change with increased airway resistance?
it is harder to move air into and out of the lungs so volume is reduced
140
what principle is capnography based on?
inspired air contains zero CO2 and expired air contains lots
141
where is capnography often used?
anesthesia
142
what is the usual mean BP in the pulmonary circulation?
15 mmHg
143
what is the usual mean BP in the systemic circulation?
100 mmHg
144
what are the two types of circulation in the lungs?
pulmonary and bronchial
145
what does the bronchial circulation in the lungs provide?
arterial blood to the lung tissue
146
what is the right to left anatomical shunt?
inclusion of some deoxygentated blood in the left atrium
147
by how much does the venous blood from the bronchial and coronary systems reduce the partial pressure of oxygen in the aorta?
5-15 mmHg
148
what can the measure of the A-a gradient be useful for?
in determining causes of hypoxaemia (low blood O2)
149
what is the A-a gradient?
difference between partial pressure of O2 in the alveoli (PAO2) and the arteries (PaO2)
150
what is the alveolar air equation?
PAO2 = PIO2 - (PaCO2/respiratory ratio)
151
what is the respiratory ratio?
ratio of CO2 to O2
152
what effect does hypoventilation have on PaO2?
reduces
153
what effect does hyperventilation have on PaCO2?
reduces
154
when does a physiological shunt occur in the lungs
when perfusion continues but alveoli is not ventilated
155
what is an effect of a physiological shunt?
increased venous admixture (more deoxygenated/poorly oxygenated blood in the left atrium)
156
what effect does a physiological shunt have on oxygenation?
reduced - similar to anatomical but larger
157
what medical conditions can cause a physiological shunt to be observed?
pulmonary oedema
pneumonia
foreign body entry
obstructions
158
what is the result of physiological shunt?
less oxygen in the blood
159
what is PaO2 determined by?
average PO2 of all blood leaving the left side of the heart (including the venous blood from lungs and heart)
160
what does pulmonary pressure prevent?
oedema
161
what happens to pulmonary resistance at high arterial pressure?
distention of opened capillaries and recruitment of closed ones to reduce resistance
162
what effect does the greater compression of alveolar capillaries at larger lung volumes have?
increases resistance
163
what effect does greater tension in tissue at larger lung volumes have?
dilates extra-alveolar vessels and so reduces resistance
164
does alveolar pressure rise or fall with increased lung volume?
rise
165
does extra alveolar pressure rise or fall with increased lung volume?
fall
166
what happens to pulmonary artery resistance while PAO2 falls?
rises which diverts blood away from the poorly ventilated regions of the lung
167
what conditions in the body cause vasoconstriction?
hypoxia
hypercapnia
decreased pH
angiotensin II
168
what substances can cause vasodilation?
adenosine
bradykinin
histamine
vasopressin
169
what are vasodilators of the lung dependant on?
receptors in the endothelium and nitric oxide enzymes
170
what is pulmonary hypertension caused by?
reduced perfusion, leading to less nitric oxide produced which leads to vasoconstriction
171
what is the dominant effect of the sympathetic nervous system on the lungs?
vasoconstriction
172
what receptor is sympathetic vasoconstriction in the lungs managed by?
alpha 1 adrenoreceptor (reduces pulmonary blood flow by 30%)
173
what receptor is sympathetic vasodilation in the lungs managed by and stimulated by?
alpha 2 and beta 2 receptors on endothelium stimulated by adrenaline
174
what effect does the PNS have on the lungs?
vasodilation
175
what effect does VIP and CGRP have on the lungs?
dilate
176
is pulmonary vascular resistance lower or higher than systemic?
lower
177
what are the main deternimants of PVR?
capillaries
178
what influences PVR (pulmonary vascular resistance)?
control by sympathetic and parasympathetic nervous systems
hypoxia
lung volume and alveolar pressure
179
is the perfusion in lungs uniform and why?
no - increases down the lung due to the effect of gravity
180
is the blood flow in lungs uniform and why?
no - blood vessels are more open lower down the lung and resistance is lower
181
is ventilation of the lungs uniform and where does most take place?
no - in the base of the lung
182
what ratio is PaO2 determined by?
ratio of ventilation to perfusion
183
what must happen to ventilation and perfusion for optimal gas exchange?
must be matched (~5 litres/min at rest)
184
what should VA/Q be equal to?
1
185
what is happening in the lungs when V greater than 1?
ventilation is normal or elevated, perfusion is reduced
186
what is happening in the lungs when V is equal to 1?
ventilation and perfusion are normal
187
what happens when V is less than one?
ventilation is reduced, perfusion is reduced
188
what are the consequences of V-Q mismatch?
hypoxia (low blood O2)
| hypercapnia (high blood CO2)
189
why may hypercapnia not be seen in mild to moderate V-Q mismatch?
hypoxia drives increased ventilation. so functioning alveoli are able to blow off more CO2 keeping PaCO2 normal
190
what can areas with low VQ (shunt effect due to poor ventilation)|be caused by?
blocked airways
191
what can areas with high VQ (poor perfusion dead space effect) be caused by?
loss of capillaries
192
is the effect of gravity more pronounced in?
ventilation
193
what is diffusion dependent on?
distance
surface area
permeability
194
what Law is diffusion determined by?
Fick's Law
195
what is diffusion in alveoli driven by?
partial pressures
196
how many alveoli are there approximately in the human?
~300 million
197
what is the formula used to calculate the diffusion of volume of a gas?
lung area x diffusion constant x pressure gradient divided by thickness of alveolar membrane
198
how thick are the alveolar membranes?
0.5 micrometres
199
why is it so crucial that alveolar membranes are so thin?
to reduce the thickness and so distance gas must travel by diffusion
200
what is the diffusion gradient in the lungs created by?
partial pressure of gases
201
is the difference in partial pressure greater in oxygen or carbon dioxide?
oxygen
202
what is the diffusion constant determined by?
solubility and molecular weight
203
what does the diffusion constant measure?
how quickly gases diffuse
204
how many more times more soluble in the blood is CO2 than O2?
up to 25 times
205
What is transit time/
the time blood takes to move along capillary
206
what is rate of gas uptake across the alveolar membrane limited by?
gas diffusion and blood perfusion
207
which gases cross the alveolar membrane quickly?
nitrus oxide
208
what is gas uptake limited by in gases which cross the alveolar membrane quickly?
perfusion - there is not enough blood in the capillaries to meet gas uptake
209
why does CO appear to cross the membrane slowly even when it diffuses quickly?
is bound to haemoglobin so that partial pressure remains low
210
what is diffusion limited gas exchange limited by?
rate of diffusion
211
how is oxygen transfer normally limited?
by perfusion
212
when can diffusion limited transfer happen in oxygen uptake?
if diffusion is impaired by thickening of alveolar wall
213
what is the effect of diffusion limited transfer on A-a gradient?
increases it
214
why does exercise in some species result in low PaO2 but high PAO2?
diffusion is limited as blood moves through the capillaries too quickly
215
what is right to left shunt the result of?
blood passing through lungs without respiratory gas exchange and venous blood draining from bronchial circulation
216
what level must PO2 in lungs remain at and why?
high to drive diffusion and match demand by tissues
217
what are the 2 ways oxygen is transported in the blood?
dissolved in solution
| bound to haemoglobin (Hb)
218
what does the solubility coefficient determine?
how much oxygen dissolves in plasma
219
how many ml of O2 per litre is present in the blood?
3ml/litre
220
when saturated how much oxygen can 1g of haemoglobin transport?
1.39ml
221
what is most of the O2 content of the blood bound to?
haemoglobin
222
does gas that is bound (not in free solution) contribute to the partial pressure of that gas?
no
223
what is blood PO2 a measure of?
the portion of O2 that is dissolved in the blood
224
what is gas dissolved in a liquid determined by?
pressure and solubility of the gas
225
what is the partial pressure of gas in liquid proportional to?
the partial pressure of the gas at the surface
226
what does the partial pressure gradient determine?
movement between gas (air) and liquid (blood)
227
does a bound gas exert partial pressure?
no
228
what is the role of haemoglobin?
binds O2 to increase partial pressure gradient
229
what does each alpha and beta polypeptide chain of haemoglobin contain?
a haem group
230
how many haem groups are there in a single RBC?
4
231
how is binding energy of oxygen to haem reduced?
allosteric effect of O2 binding
232
In what sort of environment does Hb have low affinity for O2?
acidic environement
233
why is oxygen released at tissues?
more CO2, lower pH, acidic
234
why is oxygen taken up at lungs?
less CO2, higher pH, alkaline
235
what is fully saturated oxygen known as?
oxyhaemoglobin
236
how many oxygen molecules is oxyhaemoglobin carrying?
4
237
what is haemoglobin with a single oxygen molecule known as?
deoxyhaemoglobin
238
what does the high affinity for O2 and high pH at the lungs encourage?
uptake of O2
239
what does the lower affinity for O2 and lower pH at the tissues encourage?
release of O2
240
what is the oxygen dissociation curve relationship known as?
sigmoidal relationship
241
what happens in anaemia?
Hb is reduced (can be up to by 50%)
242
what is the Bohr shift?
for a given PO2 more oxygen is given up at the tissues. Affinity of Hb for O2 is lower
243
how does increased temperature during skeletal muscle contractions affect oxygen dissociation?
causes reduced O2 affinity that aids unloading of oxygen
244
what are the 5 reasons we need erythrocytes?
holds a high concentration of Hb which decreases blood viscosity
Provides an environment for DPG
Encapsulates and concentrates carbonic anhydrase (CO2 transport)
Prevents Hb loss via filtration in the kidneys
Concave shape aids passage through tight spaces
245
how is carbon dioxide transported in the blood?
chemically in the form of HCO3-
combined with haemoglobin
dissolved in solution
246
what percentage of CO2 is directly dissolved into the blood?
~5% of total
247
what is the solubility coefficient of CO2?
0.3 mmol of CO2 per L blood per mmHg
248
in what form is CO2 bound to haemoglobin?
carbaminohaemaglobin
249
what percentage of CO2 is reversibly bound to Hb?
~30% of total
250
what percentage of CO2 is bicarbonate?
~65% of total
251
what is the chloride shift in red blood cells?
HCO3- is formed in RBC and diffuses into plasma via facilitated diffusion carrier in exchange for chloride (both negative, no charge difference)
252
what enzyme is needed to form HCO3- in RBC?
carbonic anhydrase
253
why is there no saturation of CO2 in blood as there is for oxygen?
Co2 is hugely soluble in plasma
254
what is the Haldane effect?
difference between venous and arterial blood. It enhances the unloading of CO2 from tissues into the blood
255
at low PO2 what does haemoglobin have a higher affinity for?
CO2
256
why is the curve for venous blood (on CO2 dissociation curve) to the left and above that for arterial blood?
venous blood contains more CO2 at any given value of PCO2 than does arterial blood
257
what does increased CO2 (due to ventilation) result in in terms of blood pH?
respiratory acidosis
258
what does decreased CO2 (due to ventilation) result in in terms of blood pH?
respiratory alkalosis
259
what is normal arterial blood pH?
~7.4
260
what is ventilation normally closely matched to?
metabolic requirements
261
what effect does increased ventilation have on PACO2?
reduced
262
what relationship is there between PACO2 and alveolar ventilation?
inverse
263
what effect can hyperventilation have on PaCO2?
<40mmHg
264
what effect can hypoventilation have on PaCO2?
>45mmHg
265
what causes hyperventilation?
inducible: high anxiety and pain
| altitude
266
what does hyperventilation lead to?
hypocapnia
| respiratory alkalosis
267
what are the effects on the body of hyperventilation?
```
cerebral vasoconstriction
muscle cramps (low calcium in muscles)
```
268
how can hyperventilation be compensated for?
hypoventilation or re breathing exhaled air
269
what causes hypoventilation?
chest injury
obstruction (COPD)
impaired respiratory drive
270
what does hypoventilation lead to?
hypercapnia
respiratory acidosis
hypoxia
271
what are the effects of hypoventilation?
peripheral vasodilation
confusion
drowsiness
coma
272
how can hypoventilation be compensated for?
hyperventilation
273
what are the 2 types of respiratory chemoreceptors?
peripheral
| central
274
where are peripheral chemo receptors located?
carotid sinus and aortic arch
275
where are central chemo receptors located?
within the medulla oblongata
276
define hypoxia
low O2 levels
277
define anoxia
no O2
278
define asphyxia
low O2 and high CO2
279
define hypercapnia
high CO2
280
define hypocapnia
low CO2
281
define hyperventilate
excessive breathing
282
define hypoventilate
shallow/inadequate breathing
283
define apnoea
no breathing
284
define dyspnoea
sensation of breathlessness
285
describe the reflex control system of breathing
CNS monitoring homeostasis of blood gases - motor efferent - effector/target organ: altered function of respiratory pump muscles (change in rate/depth of ventilation) - feedback - chemo (sensory) receptors - sensory afferent - CNS
286
what nerve is innervated by the carotid peripheral chemoreceptors?
sinus nerve
287
what nerve is innervated by the aortic peripheral chemoreceptors?
aortic nerve
288
which nerve does the sinus nerve join?
glossopharyngeal nerve
289
which nerve does the aortic nerve join?
vagus nerve
290
where do both the glossopharyngeal and vagus nerves terminate?
nucleus tractus solitarii (NTS) in the medulla oblongata
291
what is signalling from carotid body chemoreceptors stimulated by?
reduced PaO2
292
what does the CNS equate repeat firing of carotid body chemoreceptors with?
hypoxia
293
which cell releases the neurotransmitter to signal the chemoreceptor afferent ending
type 1 glomus cell
294
what stimulates peripheral chemoreceptors?
```
hypoxia
hypercapnia
haemmorrhage
acidosis
increased sympathetic activity
sodium cyanide (during experiments)
```
295
what is the most effective stimulant of peripheral chemoreceptors?
combination of hypoxia and hypercapnia
296
how quick is peripheral chemoreceptor response time?
fast! within 1 breath
297
what surface of the medulla oblongata are the chemo-sensitive regions located?
ventral
298
what is the CNS indirectly sensitive to?
PaCO2
299
what is the effect of increased H+?
increases ventilation, reduces PaCO2
300
what is the effect of reduced H+?
decreases ventilation
301
can H+ cross the blood brain barrier?
not well
302
does CO2 cross blood brain barrier?
yes
303
once in the CSF what happens to CO2?
converted to H+ and bicarbonate by carbonic anhydrase
304
why is the response of central chemoreceptors slow?
due to delay in creation of H+ and bicarb in CSF as H+ cannot pass blood brain barrier
305
describe the ventilatory response to hypoxia
as PaO2 reduces respiration rate increases until it reaches peak respiratory response. there is then depression of nervous activity of the brain which eventually leads to apnoea due to no driving of ventilation by brain
306
what percentage of the bodies receptors is the ventilatory response to hypercapnia mediated by?
80% central chemoreceptors
| 20% peripheral chemoreceptors
307
what is the synergistic effect of response to hypercapnia?
sensitivity to PACO2 is high when PAO2 is low
308
what effect do hypoxia and hypercapnia have on the nervous system?
increased sympathetic nerve activity
| increase in release of adrenaline from adrenal medulla
309
what is the hypocapnic braking response to hypoxia?
hypoxia drives ventilation increase less when PCO2 starts to fall. PaCO2 stimulates central chemoreceptors and a fall in PaCO2 will depress or 'brake' the response to low PO2
310
what is hyperventilation driven by peripheral hypoxia reduced by?
subsequent central hypocapnia
311
what is the advantage of a gas transport system based on haemoglobin?
blood O2 content can be relatively independent of the O2 content of inspired air due to the ability for saturation
312
why is th eclose regulation of blood CO2 necessary?
to regulate blood pH
313
why is the regulation of both blood CO2 and blood O2 not possible?
increased ventilation required to compensate for hypoxia would blow off blood CO2 and cause respiratory alkalosis
314
what areas of the brain command the patterns of breathing?
brainstem and spinal cord
315
what do afferent cranial nerves receive information from?
chemoreceptors and stretch receptors
316
what do efferent cranial nerves send information to
bronchial muscles which control resistance
317
where is the central control of ventilation located?
pons and medulla are only areas of the brain required to develop rhythm of ventilation (brainstem)
318
where is the rhythm of breathing generated?
pons
319
where is the pattern of breathing generated?
medulla
320
what are PaCO2, PaO2 and pH levels monitored by?
central chemoreceptors
peripheral chemorecptors
pulmonal mechanoreceptors
mechanosensors in joints, tendons and muscles
321
what are the types of sensory information which regulate breathing?
mechanoreceptors
| chemoreceptors
322
what nerve contains the afferent fibres of pulmonary mechanoreceptors?
vegus nerve
323
what type of receptors are pulmonary mechanoreceptors?
slowly adapting stretch receptors
324
wht are pulmonary mechanoreceptors stimulated by?
lung stretch and bronchoconstriction
325
what effect does stimulation of pulmonary mechanoreceptors have?
terminates inspiration
prolongs expiration
activates expiritory muscles
bronchodilation
326
what are 2 other vagal afferent receptors?
rapidly adapting stretch receptors (cough reflex)
| juxtapulmonary capillary receptors (leads by oedema)
327
what are 3 factors which drive breathing?
decrease in arterial PO2
increase in arterial PCO2
increase in H+ concentration
328
what type of receptors are the factors which drive breathing monitored by?
peripheral and central chemoreceptors
329
what is the venous partial pressure of oxygen?
40 mmHg
330
what is the arterial partial pressure of CO2?
40 mmHg
331
where are peripheral chemoreceptors located?
carotid bodies at carotid bifarcation
| aortic bodies
332
what are the carotid bodies activated by?
mainly decreased PaO2
increased PaCO2
decreased pH
333
what are the integrated responses to breathing regulation?
```
chemoreceptor feedback (interaction between CO2 and O2. Interaction between CO2 and H+)
feedforward regulation
```
334
what is the central response to CO2 via/
pH
335
what is CSF pH determined by?
arterial PCO2 and CSF concentration of H+
336
what do central chemoreceptors not detect?
hypoxia/PO2
337
in healthy breathing where does drive to breathe come from?
central chemoreceptors (PCO2 via H+), dependant on pH
338
if PCO2 is constant at what point will PO2 produce drive to breathe in the brain?
<60 mmHg
339
how can the pH set point change over time due to prolonged hypercapnia?
prolonged hypercapnia means CO2 removal is impaired leading to compensatory changes in HCO3- transport in CSF. The CSF pH is returned to normaleven though blood pH is still low due to elevated PCO2.
340
when central drive via CO2 is reduced by prolonged hypercapnia where must the chemoreceptive drive come from?
O2- hypoxic drive in peripheral chemoreceptors
341
what receptors does an increase in H+ stimulate?
peripheral chemo receptors
342
why are central chemo receptors not stimulated by an increase in H+?
H+ does not cross blood brain barrier
343
what is the effect of stimulation of peripheral chemo receptors but chemoreceptors not stimulated?
increase in ventilation reduced PaCO2 and reduces brain pH. This reduces the ability of both peripheral and central chemoreceptors
344
describe the route to increased ventilation in the respiratory system
PCO2 increased stimulates peripheral and central chemo receptors. Peripheral chemo receptor afferents stimulate the respiratory centre via NTS. Central chemo receptor cell bodies in medulla which increase the output of pre-motor neurons. Leads to increased ventilation
345
what factors can depress respiratory reflexes?
```
sleep
opiates
GA
Alcohol
Bacterial toxins
Stress/pain/fever
```
