WEEK 1 Flashcards
Define compliance
stretchability NOT elasticity
- High = Large ↑ in volume –> Small ↓ in ip pressure
- Low = Small ↑ in volume –> Large ↓ in ip pressure
Define TIDAL VOLUME
the volume of air you breathe in and out at rest (~half capacity) (500mL)
Define INSPIRATORY RESERVE VOLUME
the maximum volume of air which can be drawn into the lungs at the end of a normal inspiration (3000mL)
Define VITAL CAPACITY
MAXIMUM amount of air that can be EXPIRED after a MAXIMUM INSPIRATION (4600mL)
Define EXPIRATORY RESERVE VOLUME
the MAXIMUM VOLUME of air which can be EXPELLED from the lungs at the end of NORMAL EXPIRATION (1100mL)
Define RESIDUAL VOLUME
the volume of gas in the lungs at the end of a maximal expiration (1200mL)
Define INSPIRATORY CAPACITY
tidal volume + inspiratory reserve volume (3500mL)
Define FRC - FUNCTIONAL RESIDUAL CAPACITY
expiratory reserve volume + residual volume (2300mL)
Alveolar gas pressure
PAO2 = 100mmHg or 13.3kPa
PACO2 = 40mmHg or 5.3kPa
Arterial blood gas pressure
PaO2 = 75-100mmHg or 10-13.3kPa
PaCO2 = 35-45mmHg or 4.7-6kPa
Factors favouring CO2 unloading to the alveoli at the lungs
- High partial pressure of CO2 in the blood (as a result of metabolic activity [exercise])
- Low partial pressure of CO2 in the alveoli (ventilation)
- The Haldane effect (binding of O2 to haemoglobin displaces CO2)
- Carbonic anhydrase action (catalyses conversion of CO2 and H2O into bicarbonate and H+ ions)
Forms CO2 is carried in the blood
When CO2 molecules diffuse from the tissues into the blood,
- 7% remains dissolved in plasma and erythrocytes,
- 23% combines in the erythrocytes with deoxyhemoglobin to form carbamino compounds,
- 70% combines in the erythrocytes with water to form carbonic acid, which then dissociates to yield bicarbonate and H+ ions.
Most of the bicarbonate then moves out of the erythrocytes into the plasma in exchange for Cl- ions & the excess H+ ions bind to deoxyhemoglobin.
The reverse occurs in the pulmonary capillaries and CO2 moves down its concentration gradient from blood to alveoli.
What is the the function of carbonic anhydrase?
Carbonic anhydrase is an enzyme found in red blood cells that transports CO2 from tissue to lungs
What are the steps of CO2 transport by carbonic anydrase i.e. the buffer system
- It catalyzes the reaction between CO2 and water (H2O), converting them into carbonic acid.
- This carbonic acid then spontaneously dissociates to form bicarbonate ions and H+
- In the tissues, this process helps to remove CO2. The bicarbonate ions are transported in the plasma of the blood to the lungs.
- In the lungs, the reaction is reversed.
- Bicarbonate ions and hydrogen ions recombine to form carbonic acid, which then splits to form CO2 and water under the action of carbonic anhydrase.
- The CO2 is then exhaled from the body.
This process is known as the bicarbonate buffer system, and it plays a vital role in maintaining the body’s pH balance.
Explain why the shape of the oxyhaemoglobin dissociation curve is important to O2 loading in the lungs and unloading in the tissues.
At the alveoli in the lungs, where the partial pressure of oxygen is high, the curve is flat. This means that even small changes in the partial pressure of oxygen result in large amounts of oxygen binding to haemoglobin (loading). This allows for efficient oxygen uptake in the lungs.
At the tissues, where the partial pressure of oxygen is lower, the curve is steep. This means that even small decreases in the partial pressure of oxygen cause haemoglobin to release a significant amount of its bound oxygen (unloading). This allows for efficient oxygen delivery to the tissues.
