Physiology 1

Question 1

What is internal respiration?

Answer 1

Relates to respiration within the cells

Uses O2 and produces CO2 as waste

Question 2

What is external respiration?

Answer 2

Relates to respiration from atmosphere into the tissues
The exchange of O2 and CO2 between external environment and cells of the body
Involves 4 steps

Question 3

What are the 4 steps of external respiration?

Answer 3

1. Ventilaiton/gas exchange between the atmosphere and alveolar air sacs
2. Exchange of O2 and CO2 between the air sacs and the blood
3. Transport of O2 and CO2 to the tissues and lungs
4. Exchange of O2 and CO2 between tissues and the blood

Question 4

What is boyles law? Proper and Basic?

Answer 4

P. At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas

B. As the volume of a gas increase the pressure exerted by the gas decreases

Question 5

Describe ventilation in more detail?

Answer 5

Air flows from a higher pressure to a lower pressure
Before inspiration - Intra-aleolar pressure is the same as atmospheric pressure
During inspiration - Intra-alveolar pressure has to be less than atmospheric pressure, the thorax and the lungs expand due to muscle expansion to cause this

Question 6

What are the 2 faces that hold the thoracic wall and lungs in close opposition?

Answer 6

Intrapleural fluid cohesiveness

Negative intrapleural pressure

Question 7

Describe Intrapleural fluid cohesiveness?

Answer 7

The water molecules that are in the intraplerual fluid stick together and resist being pulled apart, meaning the plural membranes stick together

Question 8

Describe negative intraplerual pressure?

Answer 8

The sub atmospheric gradient that is made across the lung wall. IT creates a transmural pressure gradient so that the lungs are forced to expand out when the chest is forced inwards.

Question 9

Is inspiration an active or passive process?

Answer 9

An active process depending on muscle contraction

Question 10

Describe contraction of the diaphragm?

Answer 10

Increases the volume of the thorax vertically.
Controlled by phrenic nerve from C3-5
When it contracts it flattens out

Question 11

What do the external intercostal muscles do?

Answer 11

When they contract they lift the ribs and move the sternum out… the bucket handle mechanism.

Question 12

Describe inspiration in terms of air movement?

Answer 12

The chest and lungs expand/stretch.
Which increases the size of the lungs (larger volume) which deceases the intra-alveolar pressure (Boyles law)
Air can travel down the pressure gradient, until the intra-alveolar pressure and atmospheric pressure are equal again.

Question 13

Is inspiration an active or passive process?

Answer 13

Inspiration is an active process brought about by contraction of inspiratory muscles

Question 14

Describe expiration?

Answer 14

The chest wall and lungs recoil due to their elastic properties
This recoil increases the intra-alveolar pressure due to boyles law as there is now a smaller volume
Air then moves out into the atmosphere until the 2 pressures are once again equal.

Question 15

What happens generally in a pneumothorax?

Answer 15

A hole in the lung or chest walls causes the pressure in there pleural space to equal the pressure outside the body. This means thyme vacuum is lost and the lung collapses

Question 16

Describe a traumatic pneomthorax?

Answer 16

A hole in the chest wall allows air fro the atmosphere to travel down its pressure gradient into the plural cavity, abolishing the transmural gradient. Can lead to a collapsed lung.

Question 17

What is a collapsed lung?

Answer 17

When the transmural pressure gradient is abolished, the lung collapses to its unstretched size and the chest wall springs outwards.

Question 18

Describe a tension pneumothorax?

Answer 18

A hole in the lung wall permits air to move down its pressure gradient and enter the pleural cavity from the lungs, abolishing the transmural pressure gradient. Can lead to a collapsed lung.

Question 19

What 2 reasons allows the lungs to recoil?

Answer 19

The elastic connective tissue of the lung

The alveolar surface tension

Question 20

What is alveolar surface tension?

Answer 20

The attraction between water molecules on the liquid air interface - produces a force which resists stretching of the lungs

Question 21

What is Surfactant?

Answer 21

A mixture of lipids and proteins secreted by type 2 alveoli.
It lowers alveolar surface tension by interspersing between water molecules lining the alveoli

Question 22

Does surfactant lower the surface tension of small or large alveoli more?

Answer 22

Small - which prevents the smaller alveoli from collapsing and emptying their air contents into the larger

Question 23

What happens in babies in terms of surfactant?

Answer 23

Often babies dont develop enough surfactant
Premature babies especially dont have enough
Causing resp distress syndrome of the new born

Question 24

What is alveolar interdependence?

Answer 24

If an alveolus start to collapse the surrounding alveoli are
stretched and then recoil exerting expanding forces in the collapsing alveolus to open it

Question 25

What are the opposing forces acting on the lung?

Forces keeping alveoli open:
Foces promoting alveolar closure:

Answer 25

Forces keeping alveoli open:

• transmural pressure gradient
• pulmonary surfactant (opposes alveolar surface tensions)
• alveolar interdependence

Foces promoting alveolar closure:

• elasticity of stretched pulmonary connective tissue fibers
• alveolar surface tension