Section 3

Question 1

How is resistance to flow determined?

Answer 1

Poiseuille’s law:

Flow rate (Q) = (πΔPr⁴)/8ηL

Question 2

Flow rate (Q) = (πΔPr⁴)/8ηL

Looking at this formula, can you predict what would be the primary determinant of resistance?

a) the length of the airway
b) the change in pressure across the airway
c) the radius of the airway
d) the volume of air

Answer 2

c)

Question 3

What are the two main types of inputs that innervate the airways, influencing airway resistance?

Answer 3

The airways are highly innervated with both sympathetic and parasympathetic inputs.

Question 4

what is the dominant activity at rest in the airways, promoting bronchoconstriction?

Answer 4

At rest, parasympathetic activity is dominant and promotes bronchoconstriction.

Question 5

Why does smooth muscle contraction occur in the bronchioles during rest?

Answer 5

Smooth muscle contraction occurs because ventilator demand is low, and these fibers have tonic activity to maintain a resting level of contraction or “tone.”

Question 6

What local chemical control influences bronchoconstriction by causing constriction to decrease ventilation?

Answer 6

Specifically, decreased CO2 causes constriction to decrease ventilation and maintain a physiological level of CO2.

Question 7

Name some pathological factors that contribute to bronchoconstriction.

Answer 7

Histamine release, excess mucus, airway collapse, edema of the airway walls, and allergy-induced spasm of the airways caused by slow-reactive substance of anaphylaxis.

Question 8

Provide the definition of bronchoconstriction.

Answer 8

Bronchoconstriction is when airway radii become smaller, causing an increase in airway resistance.

Question 9

When does sympathetic activity cause bronchodilation, and why?

Answer 9

Sympathetic activity causes bronchodilation during periods of increased body O2 demands, allowing maximum flow rates with minimum resistance.

Question 10

How is sympathetic activity two-fold in inducing bronchodilation? (How it innervate)

Answer 10

Sympathetic activity is mediated by both direct innervation, where nerve terminals release norepinephrine activating β2-receptors, and indirect innervation, where circulating epinephrine from the adrenal medulla affects the airway smooth muscle.

Question 11

What is the role of increased CO2 concentrations in bronchodilation?

Answer 11

Increased CO2 concentrations can also cause bronchodilation as an effort to increase ventilation and remove excess CO2.

Question 12

Is bronchodilation associated with any pathological conditions?

Answer 12

No, bronchodilation is not associated with any pathological conditions.

Question 13

provide the definition of bronchodilation.

Answer 13

Bronchodilation refers to the increased radius of the bronchioles.

Question 14

T or F: Oedema of the airway walls leads to bronchodilation of airways.

Answer 14

False

Question 15

T or F: Norepinephrine release activates β2-receptors on the bronchial smooth muscle cells.

Answer 15

True

Question 16

T or F: Bronchodilation primarily occurs under the influence of local chemical control.

Answer 16

False

Question 17

T or F: There are no pathological conditions that cause bronchodilation.

Answer 17

True

Question 18

T or F: When body O2 demands are increased, sympathetic activity causes bronchodilation.

Answer 18

True

Question 19

How are chronic lung diseases often characterized in terms of airway resistance?

Answer 19

Chronic lung diseases are often characterized by a narrowing of the lower airways, leading to an increased resistance.

Question 20

What are the three ways in which the airways may be impaired in individuals with asthma?

Answer 20

1. The airway walls are thickened due to histamine-induced edema.
2. Thick mucus secretion physically blocks the airways.
3. Airway hyper-responsiveness causes spasms of smooth muscles in smaller airways, resulting in their constriction.

Question 21

What are some triggers for the impairments in asthmatic airways, often involving repeated exposure?

Answer 21

The triggers for these impairments in asthmatic airways are varied but frequently involve repeated exposure to allergens, irritants, or infection.

Question 22

What is chronic obstructive pulmonary disease (COPD) and what are the two main conditions it covers?

Answer 22

COPD is a term used to cover both emphysema and chronic bronchitis.

Question 23

What is chronic bronchitis, and what are its main causes?

Answer 23

Chronic bronchitis is a long-term inflammatory condition of the lower airways, usually caused by chronic exposure to cigarette smoke, allergens, or air pollution. The airways become narrowed due to edema of the airway walls and the secretion of thick mucus.

Question 24

What characterizes emphysema, and what is its cause?

Answer 24

Emphysema is an irreversible condition characterized by the collapse of smaller airways and the breakdown of alveolar tissues. It is caused by chronic exposure to cigarette smoke, where alveolar macrophages release substances like trypsin as a defensive mechanism, leading to the destruction of lung tissue.

Question 25

___________: Long-term inflammatory disease of the airways, characterized by variable/recurring symptoms.

Answer 25

Asthma

Question 26

___________: Inflammation of the lining of your lower airways (bronchioles), which carry air to and from your lungs.

Answer 26

Bronchitis

Question 27

___________: An umbrella term used to describe progressive pulmonary diseases.

Answer 27

COPD

Question 28

__________: A progressive disease of the lungs that primarily causes shortness of breath due to breakdown of alveolar tissue.

Answer 28

Emphysema

Question 29

When pulmonary disease increases airway resistance, expiration is more difficult than inspiration.
During inspiration, the larger airways are kept open by cartilaginous rings whereas the smaller airways are held open by the positive transpulmonary pressure gradient (negative pleural pressure).

During expiration, the increased intrathoracic pressure places additional pressure on the already constricted airways, decreasing flow of air out of the lungs.

Considering what you just learned, you might find it surprising that COPD patients often complain that
they cannot get enough air in!
Why do you think patients experience this sensation?

Answer 29

The initial symptom pulmonary disease patients experience is often obstructive breathing (“can’t
breathe out”), however, this symptom can quickly become restrictive (“can’t breathe in”). When a patient has problem breathing out, they do not return to the usual end-expiratory lung volume.

Consequently, their next inhalation starts at a higher lung volume. This is good because higher lung volumes have lower resistance. But at this elevated lung volume, the person cannot breathe out completely, so any future breaths will only be able to draw a limited amount of air in.

This breath stacking can continue until their lungs hyperinflate (dynamic hyperinflation) to the point that it becomes very difficult to breathe either in or out. At this point, patients will complain of
dyspnea, a discomfort during inhalation.