Lecture 1 - Respiratory system into

Question 1

What is respiration?

And how can it be subdivided

Answer 1

It’s the exchange of O2 and CO2 between the environment and tissues

dived into:

External: Exchange of O2 and CO2 between the atmosphere and the blood flowing through the lungs

Internal: Transport of O2 and CO2 between te tissues and lungs by circulating blood. And is also the O2 consumption and CO2 production in tissues.

Question 2

What are the 5 steps of respiration?

Answer 2

1. Ventilation: This is the process of moving air into and out of the lungs in order to supply O2 and remove CO2 from the alveoli. This is a process of BULK FLOW.
2. Gas Exchange: This describes how O2 and CO2 move across the alveoli membrane down their partial pressure gradients. This is a process of DIFFUSION.
3. Gas transport: The blood leaves the lungs high in O2 and low in CO2. It is pumped around the body to the cells by a process of BULK FLOW.
4. Gas exchange: At the interface between the capillaries and the cells there is exchange of O2 and CO2 down their partial pressure gradients by a process of DIFFUSION.
5. Cellular respiration: The cells use the O2 and produce CO2.

Question 3

What is the partial pressure of O2, CO2, N2 and what is the absolute pressure at sea level?

Answer 3

O2 = 20.93%

CO2: 0.03%

N2 = 79.04%

Absolute pressure at sea level is 760mmHg.

Times this by the % conc. of each gas in atmosphere to get partial pressures.

Question 4

How do you calculate the PO2 of inspired air once it has entered the trachea?

Answer 4

Water vapour reduces the PO2 in the trachea by ~10mmHg to 149mmHg.

The water vapour pressure is 47mmHg, so P_IO₂=F_IO₂ x (barometric pressure - 47) = 0.2093 x (760 - 47) = 149 mmHg

So P_iO₂ in the trachea is about 149mmHg.

Question 5

What is the PIO2 at summit of Mt everest?

P_B=253mmHg

Answer 5

Question 6

Wha are these values

Answer 6

Question 7

How do you calculate Alveolar ventilation?

Answer 7

V_A=f x (V_T-D)

It measures the flow of fresh gases into and out of the alveoli during a particular time

Question 8

What is the dead space normally?

Answer 8

150mls (0.15L)

Question 9

What breathing pattern is most effective in terms of ventilating the alveoli?

Answer 9

Slow deep breaths increase V_A

Whereas rapid, shallow breathing decreases V_A

Question 10

How is air inspired and expired

Answer 10

By changing the pressure in the lungs relative to atmospheric pressure. Since air moves from an area of high pressure to an area of low pressure, and then the gas flow and pressure equilises

Question 11

What does Fick’s Law of diffusion explain?

How is it affected by pulmonary fibrosis, or by emphysema?

Answer 11

Explains gas exchange through membranes.

Pulmonary fibrosis causing thickening of membrane = reduced gas exchange

Emphysema = Causes reduction of surface area

Question 12

What are the five mechanisms of arterial hypoxemia?

Answer 12

1. Reduced P_B of F_IO2
2. Hypoventillation
3. Impaired diffusion
4. Shunt
5. Ventilation-perfusion mismatching

Question 13

What is the O2 capacity of blood?

Answer 13

The maximum amount of O2 that can be combined with Hb is the O2 capacity. One gram of Hb combines with 1.34 ml of O2. Normal blood has about 150g of Hb per litre.

Question 14

What are the three forms that CO2 is transported as?

Answer 14

• 10% transported as CO2 dissolved in plasma
• 20% Transported as HbCO2
• 70% transported as HCO3-

Question 15

Describe the feed back loop for respiration

Answer 15