FPA- Cardiorespiratory Flashcards
At what level do the IVC, oesophagus and descending aorta pierce the diaphragm, where do they pierce and why is the location relevant?
IVC T8, pierces central tendon, tension holds it open to aid venous return
Oesophagus T10, below muscle part, tension causes blockage so no acid goes upward due to the change in pressure
Descending aorta T12, behind diaphragm as blood flow cannot be interrupted
Name the heart valves and their cusp number
3- Tricuspid between RA/V,
Pulmonary between RV and lungs
Aortic between LV and circulation
2- Mitral valve between LA/V
The the three structures that help shut the valves in the RV, LA/V. What is different in the RA?
Chordae tendinae
Papillary muscles
Trabeculae carnae
Pectinate muscles, Crista terminalis is the border
What are the layers of the pericardium?
Fibrous
Serous (Parietal and Visceral)
What are the three intercostal muscles, their function and orientation?
External intercostal- inspiration inferomedially
Internal intercostal- expiration inferolaterally
Innermost intercostal- expiration discontinuous
What are some differences in the right and left lung?
Left- 2 lobes, heart descending aorta indents
Right- 3 lobes, azygous SVC indents
What nerves supply the lungs?
Sympathetic T1-4 bronchodilate
Vagus Parasympathetic bronchoconstrict
What is the difference between intercalated discs, desmosomes and gap junctions
Intercalated discs contain gap junctions and desmosomes
GJ- tunnels allowing signal to transduct
D- hold myocytes together during contraction
How is skeletal and cardiac muscle contraction different?
Skeletal, voltage sensor
Cardiac, Ca influx by voltage gated channel
How fast does depolarization spread in the heart?
0.5m/s
Generally what does PQRST represent?
PQR- Atrial systole SA AV
QRS- Ventricular systole
ST- Ventricular plateau
What are the phases of conduction?
0- Rapid rising phase, Na+
1- Early repolarization, Na+ close K+ open
2- Plateau, sustained depolarization, open Ca2+
3- Repolarization, Ca2+ close K+ stay open
4- Resting membrane phase
What are If (funny) channels?
Opened by hyperpolarization, allowing Na+ to leak in.
Describe vessels and their different physiology
Veins- highly compliant, little recoil, large lumen, less smooth muscle
Muscular artery- high smooth muscle
Elastic artery- more elastin, near heart, compliant
Arterioles- resistance vessels
Capillaries- small lumen, thin walled
Venules- b/n veins and capillaries
What are the three types of capillaries?
Continuous- endothelial cells joined by leaky gap junctions
Fenestrated- gaps in endothelial membrane e.g. kidney
Sinusoid- large fenestrations and intracellular clefts e.g. liver
What are intercellular clefts?
Gaps in the membrane of vessels
How does a large change in volume affect vein pressure?
Only small change as they are compliant
Which vessels has the highest fall in hydrostatic pressure and which has the slowest rate of blood flow?
Arterioles as they are resistance vessels
Capillaries as they have the smallest lumen
What are the largest vessels with the smallest cross-sectional area?
Elastic arteries and vena cava
What is the relationship between blood pressure and vessels?
Further from the heart, lower the blood pressure
Arteries > Capillaries > Veins
What factors increase and decrease blood flow?
I- Diameter of Vessel (most effect), Pressure,
D- Distance, Fluid Viscosity
What is laminar and turbulent flow?
Straight, unidirectional and jumbled, hitting wall
Laminar is low pressure, turbulent increases pressure
What do capillaries exchange?
Water, gases, nutrients and waste
What is transcytosis and pinocytosis?
Pino- fluid endocytosis
Transcytosis is both ways
What are the pressures involved in filtration and reabsorption?
F- hydrostatic pressure
R- oncotic pressure
As you go towards the venular end, how does capillary hydrostatic and oncotic pressure change?
Hydrostatic decreases, oncotic is constant.
Hydrostatic pressure in capillary is high so it goes to low interstitial pressure
Due to proteins in vessel known as albumin, this draws water back in. This occurs when hydrostatic pressure falls below oncotic pressure.
How does the autonomic nervous system affect vessels?
Sympathetic directly, PS indirectly through heart
What are endothelin?
Strong vasoconstrictors that begin as initially cause vasodilation by nitrate production
What is pulse pressure?
Difference between systolic and diastolic BP
What is systolic pressure?
Pressure measured in arteries
What is end-diastolic volume?
Amount of blood in the ventricle on the onset of ventricular systole
What is the Frank-Starling Mechanism?
Increase stretch on cardiac muscle increases stroke volume
What makes the lub-dub sound?
Lub, mitral/tricuspid valve closing
Dub, semilunar valves closing
What is isovolumetric contraction and relaxation?
C- Both valves closed before ventricular pressure can exceed aortic pressure
R- Both valves closed before ventricular pressure can fall under atrial pressure
How to calculate stroke volume?
Subtract end systolic volume from end diastolic volume
When does Korotkoff sounds occur?
As pump pressure equals systolic blood pressure
What two things does inspiration have to overcome and what is energy expended to overcome called?
Resistive- friction of airflow in bronchi
Elastic- expansion of lungs and chest wall
WOB
What does surfactant do?
Prevents collapse of alveoli and thus increases lung compliance
What is TLC, VC, RV, TV, FEV1 and FRC?
Total lung capacity- air in lungs at maximum inhalation
Residual volume - air in lungs at maximum exhalation
Vital Capacity- air exhaled from TLC to RV
Tidal Volume- volume of any breath
Forced expiratory volume in 1 second
Functional residual capacity, volume remaining after passive exhalation
What is the relationship between intrapleural and intra-alveolar pressure?
Intrapleural always less than intra-alveolar because of elastic recoil of lungs and chest wall
What are consequences to increased WOB?
Recruitment of accessory muscles scalene and SCM
Increased O2 consumption by muscles
Risk of respiratory fatigue
What factors increases and decreases diffusion of gas?
I- surface area, difference in partial pressure
D- thickness of membrane
What is ventilation and perfusion and what ratio are they most optimal for gas exchange?
P- blood flow V- O2 transfer
V/Q = 1
Analogy too many buses with no passengers
too many passengers with not enough buses to take them all
What happens when V/Q is low and its compensation?
Not all hemoglobin filled with O2, some of blood returning to left atrium will not be fully oxygenated.
Vasoconstriction occurs in areas of low ventilation to reduce hypoxaemia
When is PaO2 low?
Low PiO2, low ventilation, abnormal gas exchange (low V/Q, shunt, diffusion impairment)
When is PaCO2 high
Low ventilation
What is a shunt?
Shunt is extreme low V/Q, V/Q =0.
Doesn’t respond to supplemental oxygen
What ensures ventilation and perfusion is equal?
Fractal structure, tree
What is the difference between hypoxaemia and hypoxia?
Hypoxaemia- reduced PaO2 and SaO2 in systemic arterial blood
Hypoxia- reduced oxygen supply to tissues
Where is the steep curve of O2?
60 mmHg
What are the 4 causes of Hypoxia?
Hypoxia- gas exchange abnormality, altitude or hypoventialtion
Anaemic- low or abnormal Hb
Stagnant- insufficient cardiac output
Histotoxic- substance blocking the use of O2 in tissues e.g. CN
Where are the baroreceptors?
Aortic bodies and carotid bodies
What causes hypoventilation?
Reduced drive (low CO2), suppression (drug), paralysis
What is hypercapnoea?
Too much CO2
What is normal pH, PaCO2 and HCO3?
pH- 7.38-7.42
PaCO2- 35-45
HCO3- 22-28
Respiratory acidosis will see low pH and high PaCO2, compensation is to increase HCO3
What are the layers of the pleura?
Parietal and visceral
What are the innervations of the diaphragm, lungs and pleura?
Phrenic
Sympathetic
Sympathetic for visceral pleura, intercostal and phrenic for parietal
What factors increase and decrease resistance
I- viscosity and distance
D- Diameter of vessel (most effect)
What does Ventilation (Ve) = ?
Ventilation = Tidal Volume x frequency
How does breathing change from rest to exercise?
Initial, rapid rise than slow rise to steady-state
How does ventilation and VO2 change during incremental exercise?
Ventilation linear and then exponential rise, coincides with CO2 production which is major driver of ventilation
VO2 linear then plateaus
Why does plasma lactate increase ventilation?
Lactic acid production by anaerobic glycolysis, produces H+ which can produce CO2 through buffer, both are drivers of ventilation
What are the three phases after exercise and describe what happens in them?
Fast phase- replenish O2, ATP/CP
Slow phase- lactate removal, glycogen resynthesis, increase temp
Ultra slow phase- protein turnover
