Asthma physiology and breathing control (physiology)

Question 1

What is asthma

Answer 1

A comyraction of the airway smooth muscle

Question 2

What causes asthma

Answer 2

Exposure to allergens: 
Pollen 
Dust mites : poo, cast skins and secretions
Mould spores
Respiratory infections
Pollutants (smoke)

Question 3

What happens when q person with asthma breathes in dust

Answer 3

An allergic reaction, the production of IgE antibody and inflammation. This is followed by constriction of the airways

Question 4

How do we treat asthma

Answer 4

1. Bronchodilation

2. Decrease inflammation

Question 5

Give an example of a type of bronchodilator and explain how it works
(Acute)

Answer 5

B²-adrenergic receptor agonists
- mimic the actions of epinephrine (adrenaline)
- activate adenylate cyclase
- this increases cyclic AMP (cAMP) in the cell
- leading to smooth muscle relaxation
Example: salbutamol

Question 6

Give another example of a type of bronchodilator and explain how it works

(Longer term)

Answer 6

Phosphodiesterase inhibitors (eg xanthines - theophylline)
Inhinbit the breakdown of cAMP
Helps to maintain smooth muscle relaxation

Question 7

Which asthma drugs decrease inflammation

Answer 7

Corticosteroids (eg beclometasone)

Question 8

Which cytokines lead to inflammation in the airway epithelium

Answer 8

Interleukin 1 beta and tumor necrosis factor alpha

Question 9

Explain the location of glucocorticoid receptors

Answer 9

In the cell cytoplasm bound by heat shock proteins

Question 10

Explain the mechanism of beclometasone

Answer 10

It binds to the glucocorticoid receptor leading to the heat shock proteins dissociating. The drug receptors complex will then move to the nucleus. In the nucleus, the complex binds to the cytokine genes preventing transcription, reducing vytokine production and hence inflammation

Question 11

What is omalizumab (Xoliar)

Answer 11

A specialist asthma treatment. Its a monoclonal antibody that binds to the Fč region of IgE. This prevents IgE from binding to the receptors of mast cells, basophils and dendritic cells reducing the production of inflammatory compounds

Question 12

Which 3 chemicals cause inflammation in asthma

Which one chemical causes muscle contraction

Answer 12

Histamines, cytokines, prostaglandins

Leukotrienes

Question 13

Which region of the brain controls breathing

Answer 13

The brain stem

Question 14

How do we control our breathing

Answer 14

Neurones within the pons and medulla of the brain stem control breathing. They extend from the brain to the diaphragm and muscles of the diaphragm.

Question 15

What happens if the brain stem is damaged

Answer 15

A ventilator is required for life support. In extreme cases, this damage can cause death

Question 16

What are chemoreceptors

Answer 16

Are cells found throughout the body which sense levels of pH, CO2 and O2

Question 17

What are the two types of chemoreceptors (give examples)

Answer 17

Central chemoreceptors - found in the brain stem medulla. They sense pH H+ and PCO2 through the cerebrospinal fluid in the CNS. Most important ones

Peripheral chemoreceptors - found in carotid bodies of the common carotid arteries and the aortic bodies at the arch of the aorta. They sense pH H+ and PCO2 and PO2 in arterial blood

PCO2 (partial CO2 levels)

Question 18

How do chemoreceptors control breathing

Answer 18

They signal to neurones in the brainstem to adjust breathing via contraction of diaphragm/intercostal muscles. This helps regulate O2, CO2 and pH