3: Physiology I

Question 1

Which gas do cells require to produce energy and function?

Answer 1

Oxygen (O₂)

Question 2

Which gas, produced by cellular reactions, must be continuously removed from our bodies?

Answer 2

Carbon dioxide (CO₂)

Question 3

What is internal respiration?

Answer 3

The intracellular mechanisms which consume O₂ and produce CO₂

Question 4

What is external respiration?

Answer 4

The sequence of events involved in the exchange of O₂ and CO₂ between your cells and the external environment

Question 5

What is ventilation?

Answer 5

The mechanical process of moving air between the atmosphere and the alveolar sacs

Question 6

What is Boyle’s Law?

Answer 6

As the volume of a gas increases, the pressure exerted by the gas decreases

i.e a gas’s volume and the pressure exterted by it are inversely proportional

Question 7

Air flows from a region of ___ pressure to a region of ___ pressure.

Answer 7

high ⇒ low

Question 8

During inspiration, intra-alveolar pressure is ___ than atmospheric pressure.

Answer 8

less

Question 9

During inspiration, the thorax and lungs expand as a result of the ___ of inspiratory muscles.

Answer 9

contraction

Question 10

What minor force causes the pleural membranes to stick together during inspiration?

Answer 10

Intrapleural fluid cohesiveness

Question 11

The thorax, pleura and lungs stick together because the transmural pressure gradient across the lung wall is ___.

Answer 11

negative

i.e the lungs are pushed AGAINST everything superficial to them

Question 12

The fact that intra-alveolar pressure is ___ with atmospheric pressure means that the intrapleural pressure is (higher/lower), allowing the lungs to expand with the chest wall during inspiration.

Answer 12

equalized

lower

Question 13

Which major inspiratory muscle increases the vertical volume of the thorax when it contracts?

Answer 13

Diaphragm

Question 14

The contraction of the diaphragm increases the ___ volume of the thorax.

Answer 14

vertical

Question 15

Which nerves control the contraction of the diaphragm during inspiration?

Which spinal nerves innervate the diaphragm?

Answer 15

Phrenic nerves

C3, C4, C5 (C345 keep the diaphragm alive)

Question 16

The contraction of which muscles lift the ribs and move out the sternum?

Answer 16

External intercostal muscles

Question 17

Inspiration is an (active / passive) process.

Answer 17

active

Question 18

The increase in the size of the lungs during inspiration causes a ___ in intra-alveolar pressure.

By which law does this occur?

Answer 18

decrease

Boyle’s Law

Question 19

Expiration is an (active / passive) process.

Answer 19

passive

Question 20

Why do the thorax and lungs recoil to their preinspiratory size?

Answer 20

Relaxation of inspiratory muscles

Elastic recoil

Question 21

Recoil of the lungs causes the intra-alveolar pressure to ___.

By which law does this occur?

Answer 21

rise

Boyle’s Law

Question 22

In expiration, air leaves the lungs ___ the pressure gradient until intra-alveolar pressure becomes ___ to the atmospheric pressure.

Answer 22

down

equal

Question 23

Contraction of the diaphragm, during inspiration, causes it to move (up / down).

Answer 23

down

Question 24

During expiration, the relaxation of the diaphragm causes it to move (up / down).

Answer 24

up

Question 25

What is a pneumothorax?

Answer 25

Air in the pleural space

Question 26

Pneumothorax ___ the transmural pressure gradient.

Answer 26

abolishes

The alveolar air spaces and the pleural space become continuous, so there’s no force pushing the lungs outwards against the pleura and thorax

Question 27

Connective tissue found in the lungs is ___ and allows it to bounce back into shape during expiration.

Answer 27

elastic

Question 28

Which force resists the stretching of alveoli?

Answer 28

Alveolar surface tension

Question 29

If the alveoli were lined with water alone, the surface tension would be too ___ and the alveoli would ___.

Answer 29

high

collapse

Question 30

According to LaPlace’s Law, smaller alveoli have a ___ tendency to collapse.

Answer 30

higher

Question 31

What is pulmonary surfactant?

Answer 31

Fluid consisting of lipids and proteins which prevent the alveoli from collapsing

Produced by Type II pneumocytes

Question 32

Which type of alveoli secrete pulmonary surfactant?

Answer 32

Type II alveoli

Question 33

Pulmonary surfactant ___ alveolar surface tension.

Answer 33

decreases

Question 34

Pulmonary surfactant tends to have a greater reductive effect on the alveolar surface tension of (larger / smaller) alveoli.

Answer 34

smaller

by Law of LaPlace, smaller alveoli are more likely to collapse, so surfactant is more effective for them

Question 35

Why can premature newborns develop respiratory distress syndrome?

Answer 35

Premature newborns haven’t produced enough pulmonary surfactant to oppose alveolar surface tension

So their alveoli are more likely to collapse, reducing ventilation and causing respiratory distress

Question 36

If an alveolus starts to collapse, the surrounding alveoli stretch and recoil to open it - what is this called?

Answer 36

Alveolar interdependence

Question 37

What is alveolar interdependence?

Answer 37

When an alveolus collapses, it’s stretched and reopened by elastic fibres from surrounding alveoli

Question 38

What are three forces keeping alveoli open?

Answer 38

Intra-alveolar pressure (transmural pressure gradient)

Pulmonary surfactant opposing AST

Alveolar interdependence

Question 39

What are two forces which promote alveolar collapse?

Answer 39

ALVEOLAR SURFACE TENSION - resisted by pulmonary surfactant

ELASTIC RECOIL - elasticity of the connective tissue which is seen in expiration

Question 40

Arrange the following forces into forces keeping alveoli open and forces promoting alveolar collapse:

Alveolar surface tension

Alveolar interdependence

Transmural pressure gradient

Pulmonary surfactant

Elasticity of pulmonary connective tissue

Answer 40

Open:

Transmural pressure gradient

Pulmonary surfactant

Alveolar interdependence

Collapse:

Elasticity of pulmonary connective tissue

Alveolar surface tension