6: Physiology III

Question 1

Some inspired air remains in the airways where it is not available for gas exchange. What is this space called?

Answer 1

Anatomical dead space

Question 2

Give an equation for pulmonary ventilation.

Answer 2

Pulmonary ventilation = Tidal volume x Respiratory rate

Question 3

What is the average value for pulmonary ventilation (in L/min)?

Answer 3

6 L/min

Question 4

Why is alveolar ventilation less than pulmonary ventilation?

Answer 4

Because there is anatomical dead space in the airways

Question 5

Give an equation for alveolar ventilation (in L/min).

Answer 5

Alveolar ventilation = (Tidal volume - Anatomical dead space) x Respiratory rate

Question 6

What is the average value for alveolar ventilation, in L/min, under resting conditions?

Answer 6

4.2 L/min

Question 7

What is the definition of pulmonary ventilation?

Answer 7

The volume of air breathed in and out per minute

Question 8

What is the definition of alveolar ventilation?

Answer 8

The volume of air exchanged between the atmosphere and alveoli per minute

Question 9

To increase pulmonary ventilation during exercise, the respiratory rate and depth of breathing (tidal volume) increase.

Which increase is most beneficial? Why?

Answer 9

It’s more advantageous to increase the DEPTH of breathing (i.e the tidal volume)

because of anatomical dead space.

Question 10

The transfer of gases between the body depends on the matching of two factors - what are they?

Answer 10

Ventilation

Perfusion

Question 11

What is ventilation?

Answer 11

The rate at which gas passes through the lungs

Question 12

What is perfusion?

Answer 12

The rate at which blood passes through the lungs

Question 13

What is alveolar dead space?

Answer 13

Ventilated alveoli which are inadequately perfused with blood

Question 14

What name is given to ventilated alveoli which are inadequately perfused with blood?

Answer 14

Alveolar dead space

Question 15

Give an equation for physiological dead space.

Answer 15

Physiological dead space = anatomical dead space + alveolar dead space

Question 16

In disease, alveolar dead spaceis significantly(increased / decreased).

Answer 16

increased

Question 17

Accumulation of CO₂ in alveoli ___ airway resistance leading to ___ airflow.

Answer 17

decreases , increased

Question 18

What vascular change results from increased alveolar O₂ concentration?

Answer 18

Pulmonary vasodilation

Increases blood flow to match ventilation

Question 19

Why are the pulmonary vascular changes in response to O₂ concentration different to those of the systemic circulation?

Answer 19

Pulmonary vasculature aims to maintain V/Q match - alveoli which aren’t being perfused receive less blood flow

Question 20

What is Dalton’s Law of partial pressures?

Answer 20

The total pressure of a gaseous mixture is = to the sum of the partial pressures of each component gas

Question 21

What is the partial pressure of a gas?

Answer 21

The pressure that gas would exert if it were the only gas present in the whole volume

Question 22

Gases move from ___ to ___ partial pressures.

Answer 22

higher , lower

Question 23

How do you convert mmHg into kPa?

Answer 23

kPa = mmHg / 7.5

Question 24

Why can CO₂ diffuse easily across membranes although its partial pressure gradient is less than that of oxygen?

Answer 24

Diffusion coefficient for CO₂ is 20x that of O₂

Question 25

Why do the alveoli increase gas exchange in the lungs?

Answer 25

Thin walled

Large surface area

Question 26

The lungs have an extensive ___ network.

Answer 26

capillary

Question 27

Which kind of alveolar cells make up the alveolar walls?

Answer 27

Type 1 alveolar cells

Question 28

What are the four factors influence rate of gas exchange across the alveolar membrane?

Answer 28

Partial pressure gradient

Diffusion coefficient

Surface area of membrane

Thickness of membrane

Question 29

The respiratory system also enhances ___ return.

How?

Answer 29

venous

Increased intrathoracic pressure during compresses veins and increases venous return

Question 30

The respiratory system is also involved in maintaining normal ___-___ balance.

Answer 30

acid-base