Respiratory system

Question 1

What are the three components of the respiratory system?

Answer 1

1. Specialised gas exchange surface
2. Ventilation mechanism
3. Perfusion mechanism

Question 2

What equation describes the rate of diffusion in gas exchange?

Answer 2

Fick’s Law: Q ∝ (D × A × (PE - PI)) / L

Question 3

Why are gills suited for life in water?

Answer 3

They are thin, branched evaginations with high surface area and constant water flow

Question 4

What is ‘dead space’ in the respiratory system?

Answer 4

Regions like the trachea where no gas exchange occurs: it warms, moistens and filters air

Question 5

How is avian ventilation more efficient than mammalian ventilation?

Answer 5

Birds have unidirectional airflow, preventing mixing of rest and stale air

Question 6

What is the alveolar ventilation formula?

Answer 6

VA = (Tidal volume - (Dead Space) x Breathing Rate

Question 7

What are the three main requirements for an effective respiratory surface?

Answer 7

Thin surface, moist environment, large surface area

Question 8

Why is diffusion alone not sufficient for large animals?

Answer 8

Diffusion is too slow over large distances: metabolic needs are too high

Question 9

How do fish maintain gas exchange across their gills?

Answer 9

By continuous water flow and countercurrent exchange

Question 10

What are the functions of Type I and Type II alveolar cells?

Answer 10

Type I: gas exchange
Type II: produce surfactant to reduce surface tension

Question 11

What is anatomical dead space and its volume in humans?

Answer 11

Conducting airways with no gas exchange; ~150ml

Question 12

What are the advantages of having dead space?

Answer 12

Air is warmed, humidified, and filtered before reaching alveoli

Question 13

Why is unidirectional flow more efficient than tidal breathing?

Answer 13

Because fresh air doesn’t mix with stale air, keeping O2 levels high

Question 14

What structures make up the lower respiratory tract?

Answer 14

Trachea, bronchi, bronchioles, alveoli

Question 15

Why must respiratory surfaces be moist?

Answer 15

Gases must dissolve in water before diffusing across membranes

Question 16

How can alveolar ventilation be increased?

Answer 16

By increasing tidal volume or respiratory rate

Question 17

What law describes the inverse relationship between pressure and volume in lungs?

Answer 17

Boyle’s Law
P1V1 = P2V2

Question 18

What causes respiration in mammals?

Answer 18

Diaphragm and external intercostals contract, increasing thoracic volume and reducing pressure

Question 19

Is inspiration active or passive?

Answer 19

Active

Question 20

What causes air to leave the lungs during expiration?

Answer 20

Elastic recoil of lungs increases alveolar pressure, pushing air out

Question 21

What muscle group are used in forced expiration?

Answer 21

Internal intercostals and abdominal muscles

Question 22

What maintains lung inflation at rest?

Answer 22

Negative intrapleural pressure

Question 23

What is lung compliance and how is it calculated?

Answer 23

It measures how easily the lungs expand
Compliance = ΔV / ΔP

Question 24

What opposes airflow into lungs?

Answer 24

Airway resistance, tissue friction, inertia

Question 25

What assists airflow during expiration?

Answer 25

Elastic recoil and alveolar surface tension

Question 26

What is the main gas exchange site in birds?

Answer 26

Parabronchi in the lungs

Question 27

How do frogs ventilate their lungs?

Answer 27

Buccal pumping - air pushed in by the throat movements

Question 28

How does air move in and out of insect tracheae?

Answer 28

By contraction of abdominal muscles

Question 29

Describe the water flow system in fish gills

Answer 29

Mouth opens --> water flows in Mouth closes and opercular flaps open --> water exits over gills

Question 30

What are the two main mechanisms of air movement?

Answer 30

Bulk flow (convection) and diffusion

Question 31

What type of flow is most efficient and least resistant?

Answer 31

Laminar flow

Question 32

what does Poiseuille's Law tell us about airway resistance?

Answer 32

Resistance is inversely proportional to radius⁴

Question 33

Where is airway resistance the highest?

Answer 33

In the trachea and bronchi (70%), followed by upper airways (30%)

Question 34

What is radial traction and why is it important?

Answer 34

It's the outward pull on small airways during lung expansion. It helps keep airways open

Question 35

What is dynamic compression and when does it occur?

Answer 35

Collapse of small airways during forced expiration when intrathoracic pressure exceeds alveolar pressure

Question 36

How does inflammation affect RAW?

Answer 36

It increases RAW by narrowing airways and producing mucus

Question 37

Which nervous system causes bronchoconstriction?

Answer 37

The parasympathetic (vagal) system

Question 38

What causes bronchiodilation?

Answer 38

Sympathetic stimulation (e.g. adrenaline, beta2 agonists)

Question 39

What is the function of surfactant?

Answer 39

Reduces surface tension, prevents alveolar collapse, improves compliance

Question 40

What cells produce surfactant?

Answer 40

Type II alveolar cells

Question 41

What happens to compliance if surfactant is low?

Answer 41

Compliance decreases; lungs become stiff

Question 42

What two factors determine lung elastic recoil?

Answer 42

Elastic tissue properties and surface tension

Question 43

What is compliance a measure of?

Answer 43

The ease with which the lung expand

Question 44

What carries deoxygenated blood to the lungs?

Answer 44

The pulmonary arteries

Question 45

why is pulmonary circulation low pressure?

Answer 45

To protect alveoli and optimise gas exchange

Question 46

What is V̇A:Q̇?

Answer 46

The ratio of ventilation (V̇A) to perfusion (Q̇)

Question 47

What happens when V̇A:Q̇ = 0?

Answer 47

Shunt - blood passes lungs without gas exchange.

Question 48

What causes pulmonary vasoconstriction?

Answer 48

Low O2 (hypoxia) - direct blood away from poorly ventilated areas

Question 49

How is O2 mostly transported in the blood?

Answer 49

Bound to haemoglobin (Hb)

Question 50

What is cooperative binding?

Answer 50

Binding one O2 molecule to haemoglobin increases its affinity for more O2

Question 51

What causes the Bohr shift?

Answer 51

↑ CO₂, ↑ H⁺, ↑ temperature, ↑ 2,3-BPG → ↓ Hb’s O₂ affinity

Question 52

What is P50 in the Hb dissociation curve?

Answer 52

The pO₂ where Hb is 50% saturated

Question 53

What pigment stores O2 in muscle?

Answer 53

Myoglobin

Question 54

What are the three ways CO2 is transported in blood?

Answer 54

Dissolved, carbamino compound, bicarbonate ions

Question 55

What enzyme concerts CO₂ to HCO₃⁻ in RBCs?

Answer 55

Carbonic anhydrase

Question 56

How does CO2 affect blood pH?

Answer 56

↑ CO₂ = ↑ H⁺ = ↓ pH (respiratory acidosis)

Question 57

Where is the basic breathing rhythm generated?

Answer 57

In the medullary respiratory centre of the brainstem

Question 58

What does the pons do in breathing?

Answer 58

It modifies and smooths the breathing rhythm

Question 59

What do stretch receptors in the lungs prevent? What is this reflex called?

Answer 59

Over-inflation of the lungs (Hering-Breuer reflex)

Question 60

What do irritant receptors trigger?

Answer 60

Coughing or changes in ventilation when harmful substances are inhaled

Question 61

What are J receptors and what do they detect?

Answer 61

Juxtacapillary receptors --> detects fluid or inflammation in lungs

Question 62

What chemical does the central chemoreceptor respond to?

Answer 62

pH of CSF, which reflects pCO₂ levels

Question 63

There are peripheral chemoreceptors located?

Answer 63

In the carotid bodies and aortic bodies

Question 64

What do peripheral chemoreceptors detect?

Answer 64

↑ CO₂, ↑ H⁺ (↓ pH), ↓ O₂

Question 65

What is the main chemical driver of breathing?

Answer 65

CO2 (via central chemoreceptors)

Question 66

What triggers the diving reflex?

Answer 66

Cold water on the face

Question 67

What are the effects of the diving reflex?

Answer 67

↓ Heart rate, ↑ vasoconstriction, ↑ O₂ conservation

Question 68

What happens to ventilation when pH decreases (acidosis)?

Answer 68

Ventilation increases to blow off CO2

Question 69

What is the equation for compliance?

Answer 69

C = change in volume / change in pressure

Question 70

What would a flatter compliance curve suggest?

Answer 70

More pressure is required to change the volume

Question 71

In which direction does the compliance curve deviate during inspiration and why?

Answer 71

The right Due to resistive forces opposing airflow

Question 72

In which direction does the compliance curve deviate during expiration and why?

Answer 72

The left Due to resistive forces assisting airflow

Question 73

Describe laminar flow

Answer 73

Slow flow rate Parallel stream lines

Question 74

Describe turbulent flow

Answer 74

High flow rate Disorganised stream lines

Question 75

Describe transitional flow

Answer 75

Intermediate flow rate Eddy currents

Question 76

What does PEFR stand for?

Answer 76

Peak expiratory flow rate

Question 77

What is pulmonary surfactant made of and where is it secreted from?

Answer 77

Phospholipoprotein secreted from Type II alveolar cells

Question 78

What is the equation for vascular resistance?

Answer 78

Vascular resistance = (input pressure - output pressure)/blood flow

Question 79

What does the Bohr shift describe?

Answer 79

Haemoglobin's affinity for oxygen decreases when carbon dioxide levels in the blood increase

Question 80

Why do guard cells open?

Answer 80

Open in direct response to K+ influx and increased turgor pressure

Question 81

Where in the brain does the breathing pattern arise?

Answer 81

Medulla

Question 82

Where are the central chemoreceptors located?

Answer 82

The brainstem