Week 7 - Respiratory System

Question 1

Describe the function of the respiratory system

Answer 1

The primary purpose is to maintain arterial blood-gas homeostasis

Accomplished via a 4-step process:
1. Pulmonary ventilation
2. Alveolar gas exchange
3. Gas transport
4. Systemic gas exchange

Question 2

What separates the upper and lower respiratory tracts

Answer 2

The epiglottis

Question 3

Describe the structure of the airways

Answer 3

23 airway generations
Main bronchi is Z1-Z16 (conducting zone)
Gas exchange occurs between Z17-Z23 (respiratory zone)
The human lung contains 300-500 million alveoli (1/3mm in diameter)

Question 4

How and where does alveolar gas exchange occur

Answer 4

Pulmonary gas exchange takes place across pulmonary capillary
Oxygen and carbon dioxide move between air and blood by simple diffusion
There are 2 types of alveolar cells: Type I (critical for gas exchange) and Type II (release surfactant)

Question 5

What factors affect the volume of gas passing through a sheet

Answer 5

Surface area
Thickness
Diffusion coefficient
Pressure gradient

Question 6

What are the mechanics of breathing

Answer 6

The mechanics of breathing is concerned with the movement of air into and out of the lungs by the changes in pressure, flow, and volume

Bucket handle motion increases transverse, whilst pump handle motion increases anteroposterior diameter of thorax

Question 7

What muscles assist during inspiration

Answer 7

Rest: diaphragm
Exercise: diaphragm, intercostal muscles, scalenes, sternocleidomastoid

There are >60 respiratory muscles

Question 8

What is a technique to measure diaphragmatic fatigue

Answer 8

Bilateral phrenic nerve stimulation is a non-volitional measure of diaphragmatic fatigue

Question 9

Define Ohm’s and Posiseuille’s law

Answer 9

Ohm’s law: Current = voltage/resistance applied in breathing
Airflow is dependent upon a pressure gradient and airway resistance
Poiseuille’s law: Resistance is dependent upon length and radius of a tube

Question 10

What is the volume of air not participating in gas exchanged called

Answer 10

Dead space

Question 11

What can be used to diagnose pulmonary diseases

Answer 11

Spirometry can be used to diagnoses diseases such as COPD

Question 12

What difference is there between a normal and person with COPD during exercise

Answer 12

Dynamic hyperinflation in COPD
Increase end-expiratory lung volume
Increase work of breathing
Increase breathing discomfort

Question 13

Describe the ventilatory response to constant load steady-state exercise

Answer 13

Split into 3 phases.
1. Immediate increase in Ve
2. Exponential increases in Ve
3. Plateau

Question 14

Define Hyperpnoea

Answer 14

Hyperpnoea is defined as PaCO2 regulation due to proportional changes in alveolar ventilation and metabolic rate

Question 15

Describe the ventilatory response to incremental exercise

Answer 15

Ventilation increases linearly with exercise intensity until the ventilatory threshold (50-75% of peak workload)

After Tvent, Ve increases exponentially, resulting in hyperventilation

Question 16

What are some changes in breathing patterns during exercise

Answer 16

At exercise onset, changes in Ve are largely achieved by increased Vt During heavy exercise,
Vt plateaus and further increases in Ve are achieved by increased Fb
Vt does not exceed 60% of vital capacity
Arterial PO2, PCO2 and pH are well maintained during exercise

Question 17

What are the 3 main groups of neurons for controlling ventilation

Answer 17

Ventral respiratory group (inspiratory & expiratory)
Dorsal respiratory group (inspiratory)
Pontine respiratory group (modulatory)

Question 18

Describe the function of peripheral chemoreceptors

Answer 18

Located at the aortic arch and carotid body, it relays sensory information to medulla (decrease PaO2 concentration, increases Ve)
Temperature, adrenaline and CO2 also stimulate peripheral chemoreceptors

Question 19

Describe the function of central chemoreceptors

Answer 19

Located in the RTN, it is sensitive to changes in PaCO2/H (increase in PaCO2 concentration, increases Ve)

Relayed to medulla

Question 20

Describe the process in which these chemoreceptors provide feedback

Answer 20

1. Chemoreceptors detect error signals
2. Central and peripheral chemoreceptors increase afferent input to the brainstem in response to increasing PaCO2 or decreasing PaO2 or pH
3. Premotor neurons in the dorsal respiratory group are activated
4. Inspiratory muscle contract, increasing Ve
5. Changes in Ve elicit changes in PaO2, PaCO2, and pH, thus restoring blood-gas balance

Question 21

How does the pulmonary system limit exercise performance

Answer 21

1. Exercise-induced arterial hypoxaemia
2. Exercise-induced laryngeal obstruction
3. Expiratory flow limitation
4. Respiratory muscle fatigue
5. Intrathoracic pressure effects on cardiac output

Question 22

Do the lungs adapt to exercise training?

Answer 22

No they do not besides from some exceptions.
Respiratory muscles become stronger and more fatigue resistant, or be maladaptive as they become air hyper-responsiveness.

Question 23

Describe Dalton’s law

Answer 23

The total pressure of a gas mixture is equal to the sum of the pressure that each gas would exert independently
760mmHg at sea level (O2, CO2, N2)
PaO2 = 159mmHg, PaCO2 = 0.3mmHg, N2 = 600.7 mmHg

Question 24

Describe the process of pulmonary circulation

Answer 24

1. Pulmonary artery carries deoxygenated blood from right ventricle to lungs
2. Gas exchange between alveoli and pulmonary capillaries occurs
3. Oxygenated blood is returned to the left atrium via pulmonary vein
4. Oxygenated blood is pumped around the systemic circulation to systemic cells

Question 25

What are some aspects of pulmonary circulation

Answer 25

Low pressure, low resistance circuit
Thin walled, little smooth muscle
Accepts entire cardiac output
Does not redistribute blood flow

Question 26

How is oxygen transported in the blood

Answer 26

O2 is carried in the blood in two forms.
1. Combined with haemoglobin
2. Dissolved

Question 27

What effect does exercise have on the O2Hb dissociation curve

Answer 27

Exercise causes an increase in H+, CO2, and core body temperature, causing a rightward shift in the ODC known as the Bohr effect

Question 28

What is myoglobin

Answer 28

Myoglobin is an O2 binding protein found in skeletal muscle.
1. High O2 affinity
2. Shuttles O2 from muscle cell membrane to mitochondria
3. Provides intramuscular O2 storage

Question 29

How is carbon dioxide transported in the blood

Answer 29

CO2 is carried in 3 forms.
1. Dissolved (10%)
2. Bound to haemoglobin (20%)
3. Bicarbonate (70%)

Question 30

What adaptations occur with chronic endurance training on aerobic capacity

Answer 30

Decreased metabolite accumulation
Decreased afferent feedback
Decreased ventilatory drive

Question 31

Ventilatory control during moderate intensity exercise

Answer 31

No change in PaCO2 therefore primary stimulus is feedforward

Both central and peripheral neurogenic stimuli play a major role in the exercise hyperpnoea
Peripheral chemoreceptors ‘fine-tune’ breathing

Question 32

Ventilatory control during heavy or severe exercise

Answer 32

During exercise above Tvent, metabolites accumulate, including H+ and K+ which can stimulate breathing

Additional sources of ventilatory stimulus come from increased body temperature and augmented muscle afferent input

Question 33

Define Exercise-Induced Arterial Hypoxaemia

Answer 33

EIAH is defined as a reduction in PaO2 of > 10mmHg from rest

Occurs in highly trained males during heavy exercise and the majority of females regardless of fitness or exercise intensity

Originally theorised to occur because ventilatory demand exceeds capacity

Causes are not fully understood but generally believed to be due to:
1. Diffusion limitation
2. V/Q mismatch
3. Relative hypoventilation

Question 34

Why does alveoli not collapse

Answer 34

Lungs are enclosed with membranes called pleura
Atmospheric pressure is greater than intrapleural pressure which prevents alveoli to collapse

Question 35

What is the difference between O2 and CO2 ventilatory responses to exercise

Answer 35

O2 is curvilinear
CO2 is linear
Changes in CO2 has much greater effect on Ve than changes in O2

Question 36

Why does V/Q increase upon exercise

Answer 36

Increased tidal volume
Increased pulmonary artery pressures