Lecture 18

Question 1

Formula for calculating how much air we breath in and out?

Answer 1

VE (Respiratory Minute Volume) = VT (Tidal Volume/strength) x f (respiratory rate/speed)

Question 2

What is dead space?

Answer 2

Some of the initial air that never gets to the alveoli so cannot do gas exchange (Vo)
- Located in conducting airways

Question 3

What can decrease the amount of air going into the alveoli?

Answer 3

Short shallow breaths

Question 4

How do you work out Alveolar Ventilation?

Answer 4

VA = (VT - Vo) x f

Question 5

What is Dalton’s Law?

Answer 5

In a gas mixture 9air) gas exerts it’;s own individual pressure , called a partial pressure.

Question 6

What is Total gas?

Answer 6

Sum of individual gas pressures

Question 7

Purpose of moving gas across the membranes?

Answer 7

Move gas back and forth between the alveoli and capillaries
Transport inhaled oxygen into the capillaries.
Transport carbon dioxide into the alveoli to be exhaled

Question 8

What is Fick’s law of diffusion?

Answer 8

gases move across the membranes between the alveoli and the capillaries by diffusion.

Question 9

What determines the rate of diffusion?

Answer 9

• Surface area of the membranes
• thickness of the membranes
• pressure difference between the two sides

Question 10

formula for Fick’s law?

Answer 10

F = A/T D (P1-P2)

Question 11

What is diffusion dependent on?

Answer 11

Solubility (S) and it’s molecular weight

Question 12

Solubility of CO2 and O2

Answer 12

CO2 diffuses easily across the membrane because it is highly soluble. However, O2 is also relatively easy.

Question 13

What factors create surface area for gas exchange?

Answer 13

Bulbous structure of alveoli and high density of capillaries.

Question 14

What is Emphysema?

Answer 14

A disease characterized by dilation of the alveolar spaces and destruction of the alveolar walls.

Question 15

What is the consequence of less surface area?

Answer 15

Reduction in Surface area means less contact between the air and capillaries so oxygen exchange is greatly reduced.

Question 16

What is the membrane composed of?

Answer 16

Mostly alveolar and capillary walls.

Small distance between alveolar air and the blood.

Question 17

What is gas transfer by diffusion dependent on?

Answer 17

Alveolar area for diffusion
Thickness of alveolar membrane
Pressure differences

Question 18

What does partial pressure of oxygen (PA)2) depend on?

Answer 18

• Partial pressure of oxygen in inspired air
• Alveolar consumption - blood oxygen
• Alveolar ventilation

Question 19

Atmospheric pressure of Oxygen?

Answer 19

Usually constant, so it is the balance between oxygen consumption and alveolar ventilation that is most important.

Question 20

Effect of low activity on blood oxygen?

Answer 20

Reduced oxygen consumption therefore Higher levels of oxygen in the venous blood.

Question 21

Effect of exercise on blood oxygen?

Answer 21

Increased oxygen consumption and therefore lower levels of oxygen in the venous blood.

Question 22

What is partial pressure of CO2 dependent on?

Answer 22

Partial pressure of CO2i in inspired air
Alveolar ventilation
CO2 production

Question 23

Alveolar pressure of Carbon dioxide?

Answer 23

Usually determined only by the balance between CO2 production and alveolar ventilation, because atmospheric PCO2 is negligible.

Question 24

How does CO2 diffuse down a pressure gradient?

Answer 24

Moves from low pressure in capillaries to high pressure in alveoli