Cram Deck Flashcards
Boyle’s Law
At a constant temperature, the pressure exerted by a gas is inversely proportionally to the volume the gas is in.
What 2 forces hold the thoracic wall and the lungs together?
Intrapleural fluid cohesiveness + Negative intrapleural pressure
What gives lungs their elastic behaviour?
Elastic connective tissue + alveolar surface tension (attraction between water molecules at liquid air interface)
LaPlace’s Law
The smaller the aveoli, the higher their tendency to collapse
P= 2T/r
What is respiratory distress syndrome in newborns?
Developing fatal lungs are unable to synthesise surfactant until very late in pregnancy -> premature babies may not have enough pulmonary surfactant -> restrictive lung disease
Forces keeping the alveoli open vs promoting alveolar collapse
Open: transmural pressure gradient, pulmonary surfactant, alveolar interdependence
collapse: elasticity of connective tissue, alveolar surface tension
accessory muscles of inspiration
sternocleidomastoid, scalenus, pectoral
active expiratory muscles
abdominal muscles, internal/innermost intercostal muscles
Explain dynamic airway compression
rising pleural pressure during ACTIVE expiration compresses alveoli and airways
What is pulmonary compliance decreased by?
E.g. pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, absence of surfactant
What is pulmonary compliance increased by?
Emphysema, old age
What is the work of breathing increased by?
low pulmonary compliance, high airway resistance, low elastic recoil, need for increased ventilation
Difference between pulmonary and alveolar ventilation?
Alveolar ventilation is pulmonary ventilation (tidal volume x RR) minus the anatomical dead space.
Gas transfer is dependent on…?
Ventilation + Perfusion
What is alveolar dead space?
Alveoli that are ventilated but not sufficiently perfused
Dalton’s Law
The sum of partial pressures makes up the total pressure exerted by a gas.
P= P1 + P2 + P3 + P4 + P5+…+Pn
What is the respiratory exchange ratio (CO2 produced/O2 consumed) for someone eating a normal diet?
0.8
Out of O2 and CO2, which has the higher diffusion coefficient, which one the higher pressure gradient
Diffusion coefficient: CO2
Pressure gradient: O2
Fick’s Law of Diffusion
Thin membranes are easier to diffuse through
What are the factors that influence gas transfer across the alveolar membrane?
Partial pressure gradient
Diffusion coefficient
Surface area of membrane - exercise increases this
Thickness of membrane - increases with pulmonary oedema, fibrosis
Henry’s Law
The amount of gas dissolved in a liquid is proportional to its partial pressure above the liquid.
How many oxygen molecules can 1 haemoglobin molecule carry?
What are the groups called in adults and feotuses?
4.
Adult: 2 alpha, 2 beta
Foetus: 2 alpha, 2 gamma -> increased affinity
Oxygen delivery depends on…?
Arterial oxygen content
Cardiac output
Arterial oxygen content depends on…?
Hb concentration
Saturation of Hb with O2
Bohr effect. what causes it?
Shifts oxygen curve to the right - decreases affinity and promotes oxygen release at the tissues.
increased pCO2, increased H+ conc, increased temperature, increased 2,3-BPG
How is myoglobin different to haemoglobin?
Sits in skeletal and cardiac muscle cells, much higher affinity for oxygen, stores O2 for anaerobic conditions
Presence of this in the blood indicates muscle damage.
How is CO2 transported in the blood and what are its percentages?
Dissolved - 10%
Bicarbonate - 60%
Carbamino compounds - 30%
What enzyme catalyses the formation of carbonic acid, and in turn the formation of bicarbonate and H+?
And where does it happen?
Carbonic anhydrase
In red blood cells
Haldane effect.
What causes it?
Oxygen shifts CO2 dissociation curve to the right - decreases affinity between Hb and CO2, replaces its, which increases oxygen uptake and CO2 removal.
What is the major rhythm generator of respiration and what does it excite?
- Dorsal respiratory neurones are excited by the Pre-Bötzinger complex in the medulla oblongata
- When excitation subsides -> passive expiration
- If dorsal neurones fire excessively, they activate adjacent ventral neurones which promote active expiration
- pneumotaxic centre terminates inspiration
- dorsal neurone firing can be increased by apneustic centre (IN THE PONS) -> prolonged inspiration
What stimuli influences the rest centre
Higher brain centre, stretch receptors in the airways, juxtapulmonary receptors, joint receptors, baroreceptors, chemoreceptors
Hering-Breuer-reflex
guard against hyperinflation, by pulmonary stretch receptors
What do peripheral chemoreceptors sense?
Where are they?
O2, CO2, H+ conc
Carotid+aortic
What do central chemoreceptors sense and where do they sit?
H+ conc in the cerebrospinal fluid, the more H+ the more CO2 due to bicarbonate reaction
What is hypoxic drive?
Lack of oxygen stimulates chemoreceptors which increase respiration
->only significant if it falls below 8 kPa
What causes hyperventilation at high altitudes?
Low PaO2 -> hypoxia -> stimulation of chemoreceptors
Chronic adaptations at high altitudes
Increase in: -RBC production -2,3 BPG produced within RBC -number of capillaries -number of mitochondria Decrease in: -pH
What part of the respiratory tract does the SNS innervate?
None, it acts on the adrenal gland to promote adrenaline release
What is the Gq protein associated with?
Calcium release
Gs
cAMP production
Gi
inhibits cAMP production
What does the phosphorylation of MLC through MLCK do?
Promotes the formation of myosin cross bridge -> contraction
What does the dephosphorylation of MLC through Myosin phosphatase do?
myosin cross bridge release -> relaxation
What two things does adrenaline do to airway smooth muscle?
- phosphorylation of myosin phosphatase -> induces relaxation
- phosphorylation of MLC - inhibits contraction
What type of hypersensitivity reaction Is asthma?
Type I - early
Type IV - late
What does PKA do in the airway smooth muscles?
Phosphorylation of MLCK and myosin phosphatase -> inhibition of contraction, stimulation of relaxation
What are the most common side effects?
Dysphonia (hoarse and weak voice) Oropharyngeal candidas (thrush)
What immune cells are involved in COPD
neutrophils, CD8+ T cells, macrophages
Why are LAMAs (e.g. tiotropium) superior to SAMAs (e.g. ipratropium) in bronchodilation?
Ipratropium is non-selective -> acts on M1, M2, M3 receptors -> decreases M2’s inhibitory effect
Tiotropium is selective for M3 effector cells
What do rhinitis and rhinorrhea do?
- Increased mucosal flow
- Increased blood vessel permeability
these cause swollen nasal mucosa -> difficulty breathing in
What is the moa of sodium cromoglicate?
Mast cell stabiliser - stops them from granulating (releasing inflammatory mediators)
What are the Gi tract’s layers from inside to outside and where are the nerve plexuses located?
Mucosa, submucosa, muscularis externa, serosa
Submucous (Meissner’s) plexus - submucosa
Myenteric (Auerbach’s) plexus - muscularis externa
What is the electrical rhythm of the stomach, small intestine, and colon?
Stomach - 3/min
Small intestine - 8-12/min
Colon - 8-16/min
What are the secretagogues that induce acid secretion from the parietal cells?
- ACh - can act both directly on ECL-cells as well as parietal cells
- Gastrin - can act both directly on ECL-cells as well as parietal cells
- Histamine - released from ECL-cells, acts on parietal cells
What is the migrating motor complex, and when does it happen?
Strong peristaltic movement cleaning out all the left-over shit, in between meals.
What does SGLT1 do?
Uses 2Na+ gradient to pump in a glucose ,molecule against its conc gradient.
Why is haustration important?
Non-propulsive segmentation allows time for fluid and electrolyte reabsorption
Cullen’s sign
bruising around the umbilicus
grey turner’s sign
bruising along the flanks
Courvoisier’s law
Jaundice + enlarged/palpable mass = highly suspicious of pancreatic malignancy
horner’s syndrome
miosis + ptosis + anhidrosis
Cushing’s syndrome
too much cortisol
Brugada syndrome
Inherited Na+ channel-patchy in the myocardium
tetralogy of fallot
- pulmonary stenosis
- RVH
- ventricular septal defect
- overriding aorta
->combination of congenital abnormalities
ALT
- Serum transaminase, transfer amino groups for mitochondrial energy production, predominantly glucose
- very sensitive
- look for 10-fold increase
- extremely high in cholelithiasis, >1-2000 U/L
AST
- Serum transaminase, transfer amino groups for mitochondrial energy production, predominantly glucose
- usually becomes deranged with ALT
- extra enzyme to show hepatocellular pathology
ALP
- catalyse the hydrolysis of esters on the epithelial cells of billiary ducts
- cholestasis raises ALP levels as it enhances synthesis and release
- look for 3-fold increase
GGT
- Enzyme involved in gluthionine metabolism in the liver
- GGT is inducible (drugs, alcohol, other diseases can increase it)
- can help determine whether raised ALP is of bone or liver origin
Bilirubin
- Breakdown product of heme
- conjugated in the liver
- bilirubin in the urine means that there is a post-hepatic obstruction (bile ducts)
