Control of Breathing Flashcards
What respiratory control centres of the brainstem control breathing?
- Inspiratory centre (medulla)
- Expiratory centre (medulla)
- Pneumotaxic centre (pons)
- Apneuristic centre (pons)
What (3) factors control breathing?
- Cerebral cortex: can exert voluntary control over breathing as well as centres involved in emotion and pain
- Peripheral chemoreceptors (in vascular system) & central chemoreceptors (in brain): detect changes to O2 and CO2
- Stretch receptors (in lungs) & activity receptors (in muscles and joints)
What are (4) airway characteristics?
- Rich blood supply
- Large surface area
- Tissues have intrinsic elastic properties
- Fluid lubrication (ensure rapid diffusion + counteract physical forces like surface tension)
Pontine Centres.
influence output from the medullary respiratory centres
Medullary Respiration Centres.
provide output to respiratory muscles
How does high levels of CO2 affect the body?
changes the body’s pH = toxic
What are (3) factors affecting gas solubility?
- Partial pressure of gas
- Partial pressure of gas in liquid phase
- Solubility of a gas
What (3) key factors will influence gaseous exchange?
- Gas partial pressure and gas solubility
- Matching of alveolar ventilation with pulmonary blood perfusion
- Structural characteristics of the respiratory membrane
Where (in a healthy adult) is self-ventilating lung ventilation optimal?
lower 1/3 of lung (dependent region)
Which regions of the lung have a greater initial volume?
non-dependent (upper) lung
Which regions of the lung are partially expanded?
dependent (lower) lung
Why are the dependent (lower) lung regions partially expanded?
so they still have the capacity of further expansion + volume change
What (2) ways can Oxygen be carried in?
- Bound to haemoglobin (Hb) in red blood cells (RBCs) (98.5%)
- Dissolved in plasma (1.5% … this is how we measure PaO₂)
What does oxygen bind to in the blood?
Haem molecules in haemoglobin
How much O2 is reversible bound or released is determined by what?
- Partial pressure of oxygen in blood (PO2)
- Temperature
- Blood pH
- The partial pressure of carbon dioxide (PCO2) + therefore concentration of H+ ions
- Blood concentration of BPG (2,3-Biophosglycerate) produced by RBC
How much CO2 do respiring cells produce per minute?
200ml
What (3) ways does blood carry CO2 in the lungs?
- Dissolved as CO2 in blood plasma (7-10%)
- Chemically bound to Hb in RBC’s as carbaminohaemoglobin (20%)
- Bicarbonate ions in plasma (~70%)
What is carbaminohaemoglobin?
CO2 binds to globin portion of molecule
What happens when CO2 diffuses into red blood cells?
It combines with water to form carbonic acid.
Which enzyme speeds up the reaction between CO2 and water in RBCs?
carbonic anhydrase
Why is carbonic acid in red blood cells considered unstable?
It quickly dissociates into hydrogen ions and bicarbonate ions
What role do hydrogen ions play after being released from carbonic acid in RBCs?
They bind to haemoglobin and facilitate the release of oxygen
How does blood become more acidic?
increased CO2 = increased H+ = decreased pH
How does blood become more alkali?
decreased CO2 = decreased H+ = increased pH
Tidal Volume (Vt)
Volume of air inhaled or exhaled during a single normal breath
What is Tidal Volume (Vt) in men vs women?
Men: 500ml
Women: 50ml
Inspiratory reserve Volume (IRV)
Maximum amount of air that can be inspired on top of a normal tidal inspiration
What is Inspiratory Reserve Volume (IRV) in men vs women?
Men: 3000ml
Women: 1900ml
What is Expiratory reserve volume (ERV) in men vs women?
Men: 1100ml
Women: 700ml
Expiratory reserve volume (ERV)
Maximum amount of air that can be exhaled following a normal tidal expiration
Residual volume (RV)
Volume of air remaining in the lung after a maximal expiration
What is Residual volume (RV) in men vs women?
Men: 1200ml
Women: 1100ml
What is Minimal Volume (MV) in men vs women?
Men & Women: 30-120ml
Minimal volume (MV)
Amount of air that would remain if the lungs collapsed
Total Lung Capacity (TLC)?
Total volume of the lungs at the end of a max inspiration
TLC=VT+IRV+ERV+RV
Vital Capacity (VC)
Maximum amount of air that can be inspired and expired in a single breath
VC=VT+IRV+ERV
Inspiratory Capacity (IC)
Maximum volume of air that can be inspired after a normal tidal expiration
IC=VT+IRV
Functional Residual capacity (FRC)
Volume of air remaining in the lungs at the end of normal tidal expiration
FRC=ERV+RV
What is total lung capacity (TLC) in men vs women?
Men: 5800ml
Women: 4200ml
What is vital capacity (VC) in men vs women?
Men: 4600ml
Women: 3100ml
What is inspiratory capacity (IC) in men vs women?
Men: 3500ml
Women: 2400ml
What is functional residual capacity (FRC) in men vs women?
Men: 2300ml
Women: 1800ml
What are the main (2) determining factors of PaO2 & PaCO2?
- The amount of air reaching the alveoli (V)
- The amount of blood reaching the alveoli (Q)
What is a ‘shunt’?
An area with no ventilation
What is ‘dead space’?
An area with no perfusion
