Physiology

Question 1

What is external respiration?

Answer 1

Exchange of oxygen and carbon dioxide between body cells and the external environment

Question 2

What is internal respiration?

Answer 2

The intracellular mechanisms that consume oxygen and produce carbon dioxide

Question 3

Which 4 body systems are involved in external respiration?

Answer 3

1. Respiratory system
2. Cardiovascular system
3. Haematology system
4. Nervous system

Question 4

In terms of respiration what does the term “ventilation” refer to?

Answer 4

The mechanical process of moving air between the alveoli and the atmosphere

Question 5

What is Boyle’s law?

Answer 5

At a constant temperature, the pressure exerted by a gas varies inversely with the volume the gas is continued within (as volume increases, excepted pressure decreases)

Question 6

Using the Boyle’s Law, describe why the lungs must expand to allow air to enter them during inhalation.

Answer 6

As the volume of the lungs (and the thoracic cavity) increase, the pressure decreases. This means atmospheric pressure is higher than intrathoratic pressure. Gas (air) flows down the pressure gradient into the lungs.

Question 7

Which two forces hold the thoracic walls and the lungs in close contact?

Answer 7

1. The intrapleural fluid cohesiveness (fluid tension)

2. The negative intrapleural pressure

Question 8

A transmural pressure gradient exists between lung walls. What is this?

Answer 8

A difference in pressure between any separation

Question 9

What causes the increase in thoracic volume during inspiration? (2)

Answer 9

1. Contraction of the diaphragm

2. External intercostal muscle contraction

Question 10

During expiration, which two factors contribute to the recoil of the lungs?

Answer 10

1. Elastic properties of the involved muscles

2. Alveolar surface tension

Question 11

What sort of situation would result in a lung collapse?

Answer 11

Any situation involving pleural pressure equalising with or exceeding atmospheric pressure e.g. a puncture wound

Question 12

What is alveolar surface tension?

Answer 12

The attraction between water molecules at the liquid air interference of the alveoli- water molecules pull towards each other

Question 13

What does alveolar surface tension allow for?

Answer 13

A resistance to lung stretching- the water molecules are attracted together so oppose stretching forces

Question 14

What does the law of LaPlace state?

Answer 14

Smaller alveoli have a higher tendency to collapse due to the increased proximity of the water molecules

Question 15

What is the pulmonary surfactant and where is it produced?

Answer 15

Pulmonary surfactant is a complex mixture of lipids and proteins. It is produced by type II alveoli

Question 16

What is the effect of pulmonary surfactant?

Answer 16

It reduces surface tension by “diluting” the effect the water molecules have by interspacing them

Question 17

Why do some infants suffer from respiratory distress syndrome?

Answer 17

Foetal lungs cannot synthesise surfactant meaning premature babies do not have enough surfactant in their lungs. Breathing will then become strenuous as the babies must overcome the high surface tension (of the water droplets) to inflate the lungs

Question 18

Describe alveolar interdependence?

Answer 18

Alveolar interdependence describes the fact the adjacent alveoli protect each other from collapse. If one alveoli begins to collapse, others around it will compensate and stretch. As volume increases the surrounding alveoli, pressure decreases meaning air flows to the collapsed alveoli to reinflate it. This is due to the pressure gradient

Question 19

What are the three types of muscles involved in respiration?

Answer 19

1. Accessory muscles (scalenus, sternocleidomastoid)
2. Major muscles ( diaphragm, external intercostal muscles)
3. Muscles of active expiration (abdominal muscles, internal intercostal muscles)

Question 20

What is the tidal volume?

Answer 20

The volume of air entering or leaving the lungs in a normal breath (around 500ml)

Question 21

What is the inspiratory reserve volume?

Answer 21

This is the extra volume of air that can be breathed in over and above the tidal volume (around 3000ml)

Question 22

What is the inspiratory capacity?

Answer 22

The maximal volume of air that can be breathed in ( inspiratory reserve volume + tidal volume)

Question 23

What is the expiratory reserve volume?

Answer 23

This is the extra volume of air that can be breathed out over and above the tidal volume (around 100ml)

Question 24

What is the residual volume?

Answer 24

This is the minimum volume of air remaining in the lungs even after a maximal expiration - it is always present

Question 25

What is functional residual capacity and how is it calculated ?

Answer 25

Resting lung volume (expiratory reserve volume + residual volume)

Question 26

What is vital capacity and how is it calculated?

Answer 26

This is the total volume of air available to be expired in the lungs (inspiratory reserve volume +tidal volume + expiratory reserve volume)

Question 27

What is total capacity and how is it calculated ?

Answer 27

This is the total volume of air the lungs can hold (vital capacity +residual volume) around 5.7 L

Question 28

Why is total lung capacity hard to measure in real life?

Answer 28

Residual volume must be known and this cannot be measured

Question 29

What could lead to the residual volume to increase?

Answer 29

Reduction in elastic recoil of the lungs- as in emphysema

Question 30

Which two measurements can be plotted on volume/ time curve, and what are they?

Answer 30

FVC- forced vital capacity - maximum volume of air inspired, the maximum volume of air that can be forcibly expelled FEV1- Volume of air that can be expelled (after full inspiration) in one second

Question 31

For normal healthy patients, FEV1/ FVC x 100 should equal what?

Answer 31

80%

Question 32

What does a low FEV1/FVC ratio indicate?

Answer 32

Obstructive lung disease

Question 33

What type of results do individuals with restrictive lung disease give for a FEV1/ FVC ratio test?

Answer 33

Normal, if not slightly elevated. They can instead be diagnosed by an initially low FVC

Question 34

What is the primary determinant of airway resistance?

Answer 34

The radius of the conducting airway

Question 35

How does the autonomic nervous system affect the resistance to airflow?

Answer 35

Sympathetic - decreases resistance (bronchodilation) | Parasympathetic - increase resistance (bronchoconstriction)

Question 36

Why are sufferers from obstructive lung conditions likely to suffer from collapsing airways?

Answer 36

Driving pressure (during exhalation) upwards from obstruction cannot occur. Relative airway pressure falls onwards from obstruction leading to airway compression due to rising pleural and lung pressure. The problem is exacerbated if elastic recoil of airways is also lost as in emphysema

Question 37

How is peak flow rate measured?

Answer 37

Using a peak flow meter

Question 38

Describe how to use a peak flow meter

Answer 38

A short sharp blow is given into the meter. The score on the scale at the side is taken, 3 attempts are given to allow for poor initial technique. The best value is recorded this test an highlight obstructive lung disease

Question 39

What is pulmonary compliance?

Answer 39

This is a measure of the effort required to stretch or distend the lungs

Question 40

What are the two methods to measure pulmonary compliance clinically?

Answer 40

1. Static- the change in volume for any given pressure is measured (measures elastic resistance only) 2. Dynamic - change in volume for any given pressure during the movement of air (measure both elastic resistance and airway resistance)

Question 41

The less compliant the lungs are the ____ work must be done to inflate them

Answer 41

more

Question 42

List 3 factors that decrease pulmonary compliance

Answer 42

``` Pulmonary fibrosis Pulmonary oedema Lung collapse Pneumonia Absence of surfactant ```

Question 43

How may a patient present clinically if they have less compliant lungs?

Answer 43

Breathless low exercise tolerance

Question 44

When would pulmonary compliance increase?

Answer 44

When elastic recoil is lost

Question 45

Describe a condition in which pulmonary compliance is increased

Answer 45

Emphysema hyperinflation occurs causing increased difficulty during exhalation. Age also increases compliance

Question 46

List 3 factors which will increase the required work done by the lungs

Answer 46

- Decreased pulmonary compliance - increased pulmonary compliance - increased airway resistance (potentially when bronchoconstricted) - decreased elastic recoil - increased elastic recoil - need for increased ventilation (low O2)

Question 47

What is airway physiological "dead space"?

Answer 47

This is the area within the airways (anatomical) and alveoli that is unsuitable for diffusion to occur

Question 48

How is alveolar ventilation calculated?

Answer 48

Dead space volume must be subtracted from the tidal volume

Question 49

What is the difference between pulmonary and alveolar ventilation?

Answer 49

Pulmonary -volume of air breathed in and out per minute (includes dead space) Alveolar- volume of air exchanged between atmosphere and alveoli (exclude dead space)

Question 50

How can pulmonary ventilation be increased ?

Answer 50

Increasing depth and rate of breathing

Question 51

Why is pulmonary ventilation increase advantageous?

Answer 51

About of inhaled air increases but dead space does not- this causes relative increases in alveolar ventilation

Question 52

What is ventilation?

Answer 52

Rate at which gas passes through the lungs

Question 53

What is perfusion?

Answer 53

Rate at which blood passes through the lungs

Question 54

What is the ventilation perfusion match?

Answer 54

This ensures ventilation of gas can match the blood flow for optimised gas transfer- local controls can ensure this can happen

Question 55

What will happen when perfusion is greater than ventilation?

Answer 55

CO2 build up in the alveoli airway resistance is reduced in these situations as well as contraction of arteriolar smooth muscle to reduce blood flow to match the airflow