week 3 Flashcards
1
Q
factors that modulate breathing
A
physiological challenges - exercise, sleep emotional events - crying vocalisation - singing volitional control - breath hold reflexes - cough temperature, cardiovascular
2
Q
function of mechanoreceptors
A
sensory receptors that detects changes in pressure, movement, touch
in respiratory system - provide feedback to brain on mechanical status of lungs, chest wall and airways (detects movement of lung and chest wall)
different types with different reflexes
3
Q
function of chemoreceptors
A
detect chemical changes in surrounding environment
in respiratory system - provide feedback to brain on blood Po2, Pco2 and pH after detecting changes to these in blood
hypercapnia and hypoxia would trigger
4
Q
where does the brain send signals to in order to control breathing
A
respiratory muscles - to produce rhythmic breathing movements
upper airway muscles eg tongue
produces reflexes to keep airways patent eg cough
5
Q
two types of chemoreceptors
A
peripheral and central
6
Q
function of peripheral chemoreceptors
A
responds to decreases in Po2 (hypoxia)
information sent via glossopharyngeal and vagus nerves to the nucleus in brainstem called NTS
7
Q
NTS
A
nucleus tractus solitarus
8
Q
structure and location of peripheral chemoreceptors
A
small highly vascularised bodies in region of aortic arch and carotid sinus
9
Q
how chemoreceptors respond to hypoxia
A
reduction in arterial Po2
peripheral chemoreceptors stimulated
neural signals sent from carotid and aortic bodies to NTS
ventilation increases to restore Po2 levels
10
Q
when does hyperventilation take place in terms of Po2
A
progressive reductions in inspired O2 have little effect until about 60mmHg
below 60 there is hyperventilation
11
Q
location of central chemoreceptors
A
these are clusters of neurons located in the brainstem
12
Q
when are central chemoreceptors activated
A
when Pco2 is increased (hypercapnia) or pH is decreased
13
Q
mechanism of central chemoreceptors
A
increase in arterial Pco2
central chemoreceptors stimulated
signals processed and info passed to neuronal clusters in brainstem involved in generating breathing
signals sent to respiratory muscles
ventilation increases to restore Pco2 levels
14
Q
how does hypercapnia effect ventilation
A
small changes in Pco2 have very large effects on ventilation unlike O2
15
Q
mechanism of mechanoreceptors
A
inflation of lungs activates mechanoreceptors
neural signals sent via vagus nerve to NTS in brainstem
ventilation adjusted
mechanoreceptors located throughout respiratory tree
16
Q
role of brainstem in breathing control
A
NTS receives info from mechanoreceptors and peripheral chemoreceptors - processed by respiratory neurones
cluster of respiratory neurones in brainstem generate rhythm of breathing - rhythmic signal sent to respiratory muscles
17
Q
respiratory rhythm generating neurones
A
bilateral cluster of neurones with rhythm generating properties
continues to produce a respiratory-like rhythmic output when isolated
18
Q
output from brainstem to respiratory muscles
A
brainstem neurones produce rhythmic output
rhythmic neural signals sent to spinal cord
phrenic nerve innervates diaphragm
nerves exiting thoracic spinal cord innervate intercostal muscles
19
Q
pathway of respiratory rhythm generated in brainstem
A
pontine respiratory group ->
ventral respiratory group (pattern and rhythmic generating neurones) or dorsal respiratory group (NTS)
neural output to muscles
20
Q
how does volitional control of breathing work
A
upper motor neurones originate in the primary motor cortex
descend as corticospinal tract
synapse with lower motor neurones, either directly or indirectly via interneurones located in the anterior horn of C3-5
motor neurones projects as phrenic nerve to the diaphragm
21
Q
properties that the respiratory and circulatory systems have to facilitate gas diffusion
A
large surface area for gas exchange
large partial pressure for gradients
gases with advantageous diffusion properties
specialised mechanisms for transporting O2 and CO2 between lungs and tissues
22
Q
what is partial pressure
A
sum of the partial pressures or tensions of a gas must be equal to total pressure
barometric pressure = 760mmHg
23
Q
gas concentration gradients in pulmonary and systemic capillaries
A
O2 and CO2 move down their pressure gradients from high to low concs
similar volumes of both gases move each movement
CO2 is more diffusible
24
Q
what is between alveoli and a RBC
A
type 1 alveolar epithelial cell, capillary endothelial cell and basement membrane
25
how is O2 carried in blood
dissolved and bound to haemoglobin
26
how is dissolved O2 measured clinically
in an arterial blood sample Po2
| amount of dissolved O2 is proportional to its partial pressure
27
describe levels of dissolved O2
only a small percentage of O2 in blood is in the dissolved form
not adequate for body's requirements even at rest
28
structure of haemogloblin
four heme groups joined to globin protein
two alpha chains and two beta chains
each heme group contains iron in the reduced ferrous form (Fe+++) which is the site of O2 binding
29
how oxyhemoglobin dissociation curve can be altered
increase in temp shifts curve to the right
decrease in pH shifts curve to the right
high percent of saturation at low Po2 with low temp and high pH
drop in Po2 from 100 to 60 mmHg has little effect
30
describe the oxyhemoglobin dissociation curve
O2 to Hb is reversible
flat portion - drop in Po2 from 100 to 60 mmHg has little effect
steep portion - O2 released from Hb with a small change in PO2
31
O2 saturation
refers to the amount of O2 bound to Hb relative to maximal amount that can bind
100% sat = all heme groups of Hb fully saturated with O2
1g Hb combines with 1.39ml O2
32
how O2 saturation is measured
pulse oximeters used in clinic
| measures ratio of absorption of red and infrared light by oxyHb and deoxyHb
33
normal respiratory exchange ratio is 0.8
80 CO2 to 100 O2
34
how is CO2 transported in blood
7% dissolved
23% bound to haemoglobin
70% converted to bicarbonate
35
bicarbonate production equation
H2O + CO2 -> H2CO3 -> H+ + HCO-3
reversible
rightwards in systemic capillaries when CO2 produced b tissues and expelled into blood
leftwards in pulmonary capillaries when CO2 is expelled into alveoli
36
how is acidity regulated
using ventilation to adjust PCO2 or by using kidneys to regulate the bicarbonate concentration
37
V/Q ratio
ratio of ventilation to blood flow
| can be defined for a single alveolus, a group or an entire lung
38
V/Q ratio for a single alveolus or lung
alveolar ventilation divided by capillary flow
| total alveolar ventilation divided by CO
39
healthy V/Q ratio
for lung - 0.8-1.2
varies greatly for individual units
>1 when ventilation exceeds perfusion
40
possible triggers of asthma
```
cold air and scents
inflammation:
allergy
viral/bacterial infection
exercise
drugs:
beta-blockers
non steroidal anti-inflammatory drugs
```
41
presentation of asthma symptoms
bronchospasm - tightening of the smooth muscle mesh surrounding the airway - wheeze, dyspnoea, exercise intolerance
inflammation - cough
42
consequence of having a shared entrance and exit in airways
limits maximum ventilation as must utilise airways for both phases
43
normal adult peak flow rate
Normal adult peak flow scores range between around 400 and 700 litres per minute
higher in taller, younger people and men
44
function of airway resistance
maintains flow of air - in absence of airway wall tesnion, air would simply compress due to low viscosity
slows airway flow by r4 - small changed to airway calibre with result in a large drop in airflow
45
ways of narrowing an airway in asthma
dynamic (acute) - rapid muscle contraction and secretions
| fixed (chronic asthma) - smooth muscle bulk and thickened BM cause a stiff airway wall
46
pathology of asthma
weakened and denuded airway epithelium
thickened BM
increased SM
mast cells in smooth muscle
47
consequence of increased SM in asthma
increased force of contraction
48
consequence of mast cells in SM in asthma
twitchy SM variable airway calibre
| mast cells have bags of histamine
49
consequence of increased BM in asthma
loss of relaxation after contraction
50
symptoms from increased contraction in asthma
triggered breathlessness/wheeze eg. histamine
daily variation
cough
51
symptoms of variable airway calibre in asthma
bronchial hyper-reactivity - exaggerated response to usually constricting stimuli eg metacholine or histamine
52
clinical measurement for variable airway calibre in asthma
peak flow variability would show this
| keeping a peak flow diary and seeing day to day variability of FEV1 value - also diurnal variability (lower in morning)
53
clinical measurement for inflammatory secretions in asthma
exhaled nitric oxide
increased in eosinophilic inflammation
normal value is 30ppb
54
clinical measurement for reversible airflow contraction
spirometry
| narrowed constricted airway relaxes and dilates in response to salbutamol - narrowing would be irreversible in COPD
55
3 phases that contribute to asthma
smooth muscle only - triggered by direct mediator release eg histamine - rare wheezy episodes
chronic inflammation - irritates SM and causes regular wheezy episodes
acute inflammation - viral infection - clinical exacerbations
56
molecules associated with type 2 inflammation (asthma)
cells - lymphocytes (Th2), eosinophils and mast cells
cytokines - IL-4,5
prostanoids - PGE2, leukotriene D4
immunoglobulins - specific IgE
57
problem with immunity to infection in asthma
immunity drives inflammation
memory in IgE on mast cell surface - way it is remembered and retained is dependent on cytokine environment in which it happens
on second exposure - antigen binds to IgE on MCs and cross links MC receptors for IgE - activates signalling cascade and mast cell mediator release which promotes inflammation
58
mast cell mediators and their effect on airway
histamine - smooth muscle contraction - immediate
leukotrieneD4 - smooth muscle contraction and airway wall oedema - slightly longer response than histamine
prostaglandin - airway wall oedema and inflammation and increased secretions - slightly longer response than histamine
VEGF - blood vessel formation - reduces airway wall space by expanding bulk of airway wall - chronic change
59
result of SM contraction in asthma
bronchospasm and wheeze
60
result of alveolar wall oedema in asthma
airway narrowing
61
result of BV hypertrophy in asthma
airway wall thickening and lumen narrowing - chronic
62
chemical ways of triggering mast cells in asthma
IgE - allergen exposure
salicylates - aspirin
scents
63
how exercise triggers mast cells in asthma
exercise increases ventilation
exceeds humidifying capacity of upper airway
drying air causes osmotic rupture of mast cells
this can be mimicked by mannitol bronchial challenge testing
64
cells different infections use to stimulate inflammation
viral - neutrophils/lymphocytes
parasitic - eosinophils
bacterial - neutrophilic
65
asthma treatment
B2 agonists
corticosteroids
anti-leukotriene receptor drugs
66
corticosteroid action in asthma
mainstay of treatment prevents and treats inflammation non-selectively
reduces airway twitchiness and reduces exhaled NO
these are inhaled straight to lung
67
anti-leukotriene receptor drug action in asthma
add on treatment for resistant inflammation
targets only leukotriene D4 in the airway
direct effect on mast cells and smooth muscle
good in exercise asthma
68
emerging asthma treatment
anti-IgE biological therapy - blocks IgE peripherally and results in down regulation of IgE in MCs - leads to down regulation of twitchiness of asthma
69
bronchial thermoplasty
still unproven
reduces bulk of airway SM
reduction in twitchiness
70
upper respiratory tract
nasal cavity
pharynx
larynx
71
lower respiratory tract
trachea
bronchi
bronchioles
alveoli
72
distribution of SM in airway
SM becomes increasingly responsible for calibre of airways as you get into the smaller airways
73
activation of muscarinic receptors
activated by vagus parasympathetic nerve
ACh and methacholine used
causes smooth muscle to contract
bronchoconstriction - want to block this in asthma
PSNS also controls airway secretions
74
activation of adrenergic receptors in lung
circulating adrenaline stimulates not nerves
| B2 agonist for asthma - smooth muscle relaxation
75
mechanism of steroids
take hours to work
not acting on SM to relax
bind to an intracellular receptor and influence transcription
acting to produce proteins that will interact with interleukins
76
some of the side effects of steroids
```
easy bruising
poor wound healing
increased abdominal fat
thinning of skin
osteoporosis
increased appetite
obesity
```
77
describe asthma
recurrent reversible airflow obstruction
wheezing, cough, dyspnoea, hyperinflation
largely reversible airflow obstruction
inflammatory changes in airways
bronchospasm
bronchial hyper-reactivity
78
pathology of asthma
epithelial shedding exposes nerves
increased number of eosinophils
exposed nerves are sensitive to kinins (hyperstimulation)
mucous gland hypersecretion
smooth muscle constriction leads to hypertrophy
leaking blood vessels
79
drugs for asthma
bronchodilators
| anti-inflammatory drugs - corticosteroids and other agents
80
types of bronchodilators
B2 adrenoreceptor agonists
anticholinergic agents
leukotriene antagonists
xanthines
81
types and examples of B2 adrenoreceptor agonists
short acting - salbutamol, terbutaline
long acting (LABA) - salmeterol, formoterol - these are short acting molecules held by chemical arms so they repeatedly act on the receptor
main action - dilate bronchi
also stabilise mast cells, monocytes, cilia
82
problems with B2 adrenoreceptor agonists
tremor is a principle side effect
tolerance may occur
some concerns regarding excess mortality
83
types and examples of anticholinergic agents
short acting - ipratropium
long acting - tiotropium
they bronchodilate and are antisecretory
84
function and examples of leukotriene antagonists
montelukast, zafirlukast
mild bronchodilators by acting on interleukins
possibly weak anti-inflammatory agents
85
describe xanthines
```
oral or IV
bronchodilators
have weak anti-inflammatory action
throphylline, aminophlyline
many side effects
narrow therapeutic window
```
86
anti-inflammatory agents
glucocorticoids
cromoglycate/nedocromil
anti IgE antibodies
87
describe glucocorticoids
inhaled, tablet, IV
intracellular receptor and then intranuclear action
decreases Th2 cytokines
88
asthma therapy
regular inhaled corticosteroid with or without a LABA in the same inhaler
B2 agonist in blue inhaler - rescue treatment or used before exercise
89
bronchial thermoplasty
all visible airways are treated excepted RML
3 treatment sessions to treat all accessible airways
max 30 minutes, approx 45 activations per session
90
COPD
largely irreversible airflow obstruction
| often includes emphysema
91
differences between asthma and COPD
cause of COPD is cigarette smoke, cause of asthma is unknown
epithelial cells and mast cells involved in asthma, alveolar macrophages and epithelial cells involved in COPD
CD4+ cells and eosinophils increased in asthma, CD8+ cells and neutrophils involved in COPD
result is bronchoconstriction in asthma, small airway narrowing and alveolar destruction in COPD
92
treatment of COPD
```
smoking cessation
LABA/ICS combination
LAMA
LAMA/LABA
LAMA/LABA/ICS
```
93
where does the right lymphatic duct empty
at junction of right internal jugular and right subclavian veins
94
function of lymphatic ducts
carry lymph from abdomen to circulatory system
95
cisterna chyli
most inferior part of the thoracic duct
96
where does the thoracic duct empty
into junction of left internal jugular and left subclavian veins
97
chylothorax
lymphatic fluid in the pleural space
98
effect of ANS on SA node
rate increase with sympathetic system and decreases with parasympathetic
99
effect of ANS on AV node
conduction velocity is faster with SNS and slower with PSNS
100
effect of ANS on ventricles
contract harder and relax faster with SNS
101
autonomic innervation of the heart
vagus nerve is the PS innervation
| sympathetic ganglia from lower cervical and T1-4
102
how can the firing rate of the SA node be altered
changes in autonomic activity - sympathetic or vagal
circulating hormones - hyperthyroidism and hypothyroidism
serum ion concentration - hyperkalemia and hypokalemia (K ions)
cellular hypoxia - usually from ischemia
drugs
103
fainting caused by standing for a long period of time
blood pools in legs
less blood is being pumped
brain is insufficiently perfused
104
sick carotid sinus syndrome
overactive problem with carotid vagus nerve
with little trigger, vagus nerve is stimulated
pass out, heart doesnt beat properly
105
ductus venosus
allows blood to bypass the liver
106
ductus arteriosus
allows blood to bypass lungs
| connects arch of the aorta and pulmonary trunk
107
patent ductus arteriosus
medical condition in which the ductus arteriosus fails to close after birth
allows a portion of oxygenated blood from the left heart to flow back to the lungs
108
barium swallow
a test that shows the inside of your oesophagus
helps diagnose oesophageal cancer
white barium liquid is drunk, which shows up on x-rays
x-rays taken while liquid is swallowed
109
where does the pleural cavity extend to superiorly
2-3cm above medial clavicle
110
pneumothorax
air in pleural cavity
111
haemothorax
blood in pleural cavity
112
empysema
pus in pleural cavity
113
atelectasis
the collapse or closure of a lung resulting in reduced or absent gas exchange
can occur with obstruction of a bronchus
114
which bronchi is an inhaled object more likely to block
right as it is shorter, wider and more vertical
115
left vagus nerve and phrenic nerve in relation to the hilum of the lung
LVN passes posteriorly whereas the phrenic nerve passes anteriorly
116
pericardial effusion
excess fluid in pericardial cavity
117
pericardial tamponade
compression of heart due to excess fluid and fibrous pericardium
118
impressions on the left lung
arch of the aorta and descending thoracic aorta
119
impressions on the right lung
SVC and azygous azygos vein
120
effect of aortic stenosis on the heart
left ventricular hypertrophy
121
ligamentum arteriosum
remnant of ductus arteriosus
122
what forms the superior vena cava
left and right brachiocephalic vein
123
what vein drains into the SVC
azygous vein
124
blood in coronary sinus
deoxygenated blood from heart walls
125
crista terminalis
a boundary
smooth wall - sinus venarum posteriorly
rough wall - pectinate muscles anteriorly
126
fossa ovalis
remnant of opening between L and R atria
| allows blood to bypass lungs in embryonic development
127
explain foetal circulation
oxygenated blood enters through umbilical vein
some blood enters the liver and the rest enters the ductus venosus to bypass liver and enter IVC
IVC enters the RA and most of the blood passes through foramen ovale to LA, LV and aorta
blood entering RA from SVC is poorly oxygenated as is blood returning from the lungs
this passes through the ductus arteriosus and reduces the oxygenation of the blood in the aorta
128
where are the SA and AV nodes located
RA
129
function of tricuspid valve
prevents backflow of blood into RA during systole
130
cordae tendineae
attaches cusps to papillary muscles
131
papillary muscles function
contract to prevent cusps reverting into atria during systole
132
function of pulmonary valve
prevents backflow of blood into right ventricle during diastole
133
what are trabeculae carnea
muscular ridges in wall of ventricle
134
function of mitral valve
prevents backflow of blood into LA during systole
135
function of aortic valve
prevents backflow of blood into LV during diastole
136
components of the posterior mediastinum
oesophagus
descending thoracic aorta
azygos vein and hemi-azygous
thoracic duct
137
what are conchae/turbinates
shelves of bone in nasal cavity
surface of these are lined with collated respiratory epithelium - secrete mucous and fluid, warm, filter and humidify air and increase turbulence of inspired air to ensure greater contact with RE
138
turbulent air
airflow is turbulent higher in tract
this flow produces numerous collisions between molecules so the air quickly loses speed and a higher pressure gradient is require to maintain rate
more work required to move same volume of air
mixes better with surroundings
139
laminar flow
layers of air moving in same direction
resistance is lower
from bronchi downwards
140
role of diaphragm in breathing
contraction causes it to flatten - increases volume of the thoracic cavity lowering the pressure within it and allowing lungs to fill with air
relaxation of the muscle causes it to become dome shaped which decreases volume of thoracic cavity and raises pressure within the cavity - helps push air out of lungs
primary muscle involved in breathing
141
role of external intercostal muscles in breathing
fibres run downwards and forwards between ribs
contraction raises and rotates the ribs to increase thoracic cavity volume
involved in quiet and forced breathing
innervated by intercostal nerves
142
role of internal intercostal muscles in breathing
fibres run downwards and backwards between ribs
contraction pulls ribs down and in - decreases volume of thoracic cavity and assists forced expiration
intercostal nerves innervate
143
role of abdominal muscles in breathing
relax during inspiration
| contract during forced expiration and help decrease volume of thoracic cavity by pushing diaphragm up
144
role of accessory muscles in breathing
become active if respiration is more vigorous or in disease when breathing is difficult
145
interactions of gas particles depends on the following
dimensions of the airway
density of gas - high water vapour in humid air increases air density
flow type
146
inspiratory capacity (IC)
all air breathed in during a maximal inspiration at the end of a normal expiration
IRV +Vt
147
expiratory capacity (EC)
Vt + ERV
| all air breathed out during a maximal expiration at the end of a normal inspiration
148
functional residual capacity (FRC)
volume of air remaining in the lungs at the end of the normal expiration ERV + RV
149
vital capacity (VC)
all the air that can be expired from a maximal inspiration
| IRV + Vt + ERV
150
total lung capacity (TLC)
all the air that is possible for lungs to contain
| IRV + Vt + ERV + RV
151
inspiratory reserve volume (IRV)
maximum volume above tidal volume that we can inspire into our lungs (approx 3L)
152
tidal volume (Vt)
volume we inspire and expire during restful breathing
| approx 0.5L in restful breathing
153
expiratory reserve volume (ERV)
max volume below the tidal volume that we can expire
| approx 1.5L
154
residual volume (RV)
volume of air remaining in the lungs after a full expiration
can never empty lungs completely
approx 1.2L
155
causes of heart failure
```
common:
MI
dilated cardiomyopathy
excess alcohol
high BP
less common:
chemotherapy
genetics
nutritional
```
156
symptoms of heart failure
breathlessness
ankle swelling
fatigue
157
signs of heart failure
```
sinus tachycardia
raised JVP
murmurs
ankle/sacral oedema
pulmonary crackles
pleural effusion
etc
```
158
waves on a JVP graph
a wave - atrium contracting; tricuspid valve open
x descent - atrium filling; tricuspid closed
v wave - atria tense, full; tricuspid closed
y decent - atrium emptying; tricuspid open
159
diagnosis of heart failure
```
CXR - can be normal
blood tests
ECG
angiography
history
CMRI - dead/scarred heart is white
CMR
VO2
ECHO
examination
not in order
```
160
signs of heart failure on an ECHO
regional wall motion abnormality (eg post MI)
dilated chambers
valvular dysfunction
161
treatment of heart failure
beta blockers
ACE inhibitors
aldosterone antagonists
diuretics
162
SGLT2 inhibitors
inhibit proximal tubular glucose reabsorption
cause diuresis, natriuresis
lower BP
reduces weight
163
drugs which may precipitate/aggravate heart failure
```
NSAIDs
Ca2+ antagonists
anti-arrhythmics
tricyclic antidepressants
corticosteroids
```
164
implantable cardioverter defibrillator
```
if heart goes chaotic it will fire - returns heart to sinus rhythm
problems:
does not improve symptoms
expensive
inappropriate shocks
psychological burden
driving implications
```
165
intra-aortic balloon pump
```
1st line for cardiogenic shock
diastolic augmentation of aortic pressure
increased coronary perfusion
reduces afterload
improves cardiac output
```
166
heart transplantation for heart failure
```
last resort
mean survival of ~10 years
increased risk of:
opportunistic infection
malignancy
renal failure
hypertension
coronary artery disease
```
167
function of the azygous vein
drains posterior thoracic wall
back up if vena cava is blocked
hemiazygous vein is similar but on the left and is smaller
168
where does gas exchange take place in a foetus
placenta not lungs
169
what carries oxygenated blood in fetal circulation
IVC
170
function of autorhythmic cells
have the capacity to get excited
tell heart to contract and relax
grouped at SA and AV nodes
the AR cells at SA node are dominant - set pacing for rest of the heart - start electrical impulse causing RA to contract
