Physiology

Question 1

What is internal respiration?

Answer 1

The intracellular mechanisms which consume oxygen and produce carbon dioxide

Question 2

What is external respiration?

Answer 2

The sequence of events that lead to the exchange of oxygen and carbon dioxide between the external environment and the cells of the body

Question 3

What are the four steps of external respiration?

Answer 3

Ventilation, gas exchange between alveolar air and blood, transport of gases between lungs and tissues, gas exchange between blood and tissues

Question 4

What are the three body systems involved in external respiration?

Answer 4

Resp, CV, Haemotology

Question 5

How does air move (in regards to pressure)?

Answer 5

Air moves from an area of high pressure to an area of low pressure

Question 6

What muscles contract during inspiration?

Answer 6

Diaphragm and external IC muscles?

Question 7

What are the accessory muscles of inspiration?

Answer 7

Scalene and sternocleidomastoid

Question 8

Explain intrapleural fluid cohesiveness

Answer 8

Water molecules in the intrapleural fluid are attracted to eachother and resist being pulled apart - pleural membranes tend to stick together

Question 9

Explain negative intrapleural pressure

Answer 9

sub-atmospheric intrapleural pressure creates a transmural pressure gradient across the lung wall and across the chest wall. So the lungs are forced to expand outwards while the chest is forced to squeeze inwards

Question 10

How does diaphragmatic contraction cause inspiration?

Answer 10

Diaphragm contracts and flattens - increases vol of thorax - decreases pressure in lungs ( controlled by phrenic nerve from C3,4 & 5

Question 11

How does external IC contraction cause inspiration?

Answer 11

external IC contraction lifts the ribs and moves out the sternum - increases thoracic vol - decreases pressure in lungs

Question 12

What is passive expiration caused by?

Answer 12

Elastic recoil of the lungs

Question 13

How does a pneumothorax affect pressure in lungs?

Answer 13

Abolishes transmural pressure gradient

Question 14

What causes the lungs to recoil during expiration?

Answer 14

Elastic connective tissue in the lungs and alveolar surface tension (more important)

Question 15

What is alveolar surface tension?

Answer 15

Attraction between water molecules at liquid air interface. In the alveoli this produces a force which resists the stretching of the lungs. If the alveoli were lined with water alone, the surface tension would be too strong - the alveoli would collapse

Question 16

According to the law of Laplace:

Answer 16

the smaller alveoli have a higher tendency to collapse

Question 17

What is pulmonary surfactant and what does it do?

Answer 17

PS is a complex mixture of lipids and proteins secreted by type II alveoli. It lowers alveolar surface tension by interspersing between the water molecules lining the alveoli. Prevents smaller alveoli from collapsing and emptying their contents into the larger alveoli

Question 18

What is respiratory distress syndrome of a new born?

Answer 18

Developing fetal lungs are unable to synthesise surfactant until late in pregnancy (means prem babies don’t have enough pulmonary surfactant) - causes resp distress syndrome of the newborn. Baby makes v. strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs

Question 19

What is alveolar interdependence?

Answer 19

If an alveolus starts to collapse then the surrounding alveoli are stretched. They then recoil - exerting expanding forces in the collapsing alveolus to open it.

Question 20

What are the forces keeping the alveoli open?

Answer 20

Transmural pressure gradient, pulmonary surfactant and alveolar interdependence

Question 21

What are the forces promoting alveolar collapse?

Answer 21

Elasticity of stretched pulmonary connective tissue fibres and alveolar surface tension.

Question 22

What are the four factors which influence gas transfer across membranes?

Answer 22

partial pressure gradient, diffusion coefficient, SA, membrane thickness

Question 23

What is the following description describing?

The processes that exchange oxygen and carbon dioxide between the external environment and the cells of the body

Answer 23

External respiration

Question 24

What is the following description describing?

Comprises ventilation, gas exchange between the alveoli and blood, gas transport and gas exchange at the tissues

Answer 24

External respiration

Question 25

Which receptors influence the pons?

Answer 25

Peripheral chemoreceptors

Question 26

What changes does the pons respond to?

Answer 26

Decreased pH
Increased H+
Increased PCO2
Decreased PO2

Question 27

What effect does the pons cause on the resp rate?

Answer 27

It increases

Question 28

Does smoking affect idiopathic fibrosis?

Answer 28

It increases the risk two-fold

Question 29

What’s the cure for IPF?

Answer 29

There isn’t one