Sensory Aspects of Respiratory Disease

Question 1

What is a cough

Answer 1

Complex defence mechanism that protects the respiratory tract from inhaled foreign material or excessive mucous secretion
Usually secondary to mucociliary clearance
Vagus nerve most important

Question 2

Where are the nerve terminals for cough found

Answer 2

Next to mucous goblet cells

Allows recognition of mucous secretion to induce a cough

Question 3

What are the three types of sensory receptors for cough

Answer 3

C-fibre receptors
Rapidly adapting stretch receptors
Slowly adapting stretch receptors

Question 4

Describe the C-fibre receptors and where are they found

Answer 4

Free nerve endings
Unmyelinated

Larynx, trachea, bronchi, lungs

Question 5

What are the c-fibre receptors irritated by and what do they release

Answer 5

Chemicals and inflammatory mediators e.g. histamine, leukotrienes, capsaicin

Releases neuropeptide inflammatory mediators e.g. substance P, neurokinin A to stimulate RARs

Question 6

Describe the rapidly adapting stretch receptors and where are they found

Answer 6

Small, myelinated nerve fibres

Pharynx, larynx, trachea, bronchi

Question 7

What are the rapidly adapting stretch receptors stimulated by

Answer 7

Mechanical and chemical irritants and inflammatory mediators

Question 8

What can the vagal afferent nerve be activated by

Answer 8

Acid-sensing ion channels
Bradykinin receptor B2
Transient receptor potential vanniloid-1 receptor

Question 9

What are the mechanical and chemical stimulants of the afferent neural pathway for cough

Answer 9

Mechanical - dust, mucous, food/drink, citric acid (mechanosensor)

Chemical - noxious, intrinsic inflammatory agent, bradykinin, capsaicin, citric acid (nociceptor)

Question 10

Outline the neural pathway for cough (afferent and efferent)

Answer 10

1. Cough/irritant receptors are stimulated chemically or mechanically
2. Vagus nerve
3. Superior laryngeal nerve
4. Impulses integrated in the cough centre in the medulla
5. Activated suppression from the medial prefrontal cortex
6. Cough centre in the medulla
7. Glottis, diaphragm, expiratory muscles

Question 11

What happens to the airways during cough

Answer 11

Airways narrow to increase pressure and increase airflow out (trachea forms crescent)

Question 12

Give some common causes of cough

Answer 12

Asthma + eosinophilic related
Gastro-oesophageal reflux
Rhinosinusitis 
Chronic bronchitis
Drugs

Question 13

What is cough hypersensitivity syndrome

Answer 13

Increased expression of TRPV-1 (Calcium-permeable channel)
Activated by capsaicin, endocannabinoid, noxious heat and metabolites
Expressed in sensory neurones of dorsal root and trigeminal ganglia

Question 14

What are the symptomatic antitussives

Answer 14

Central - opiates e.g. codeine, morphine

peripheral e.g. moguistine, levodopropizine

Question 15

What are the disease-specific antitussives

Answer 15

Corticosteroids
Histamine H2 antagonists
Proton pump inhibitors
Post nasal drip

Question 16

What is the sensory input for the following:
nose
pharynx
larynx
lungs
chest wall

Answer 16

nose - trigeminal
pharynx - glossopharyngeal, vagus
larynx - vagus
lungs - vagus
chest wall - spinal nerves

Question 17

What is the neural pathway for touch

Answer 17

1. A𝛼 and Aβ via the dorsal horn which travel up to the medulla on the same side
2. Switches onto the other side of the spinal cord at the medulla
3. Link in the mid-brain in the primary somato-sensory cortex

Question 18

What is the neural pathway for pain

Answer 18

1. Aẟ and C-fibres recognise pain via the dorsal horn
2. Aẟ and C-fibres will cross at the same level of entry
3. Travels up the spinothalamic tract
4. Thalamus
5. Primary somato-sensory cortex

Question 19

What are the types of pain

Answer 19

Visceral - visceral organs, chronic-feeling, grumbling pain (lower number of afferents)
Somatic - pain from the skin, deep structures, bone (herpes zoster)
Referred - shoulder-tip pain of diaphragmatic irritation

Question 20

Give some respiratory causes of chest pain

Answer 20

Pneumonia
Malignancy
pneumothorax
Pulmonary embolism

Question 21

Give some non-respiratory causes of chest pain

Answer 21

MI
Pericarditis
GORD - heart burn
Costochondritis - patient can localise the pain

Question 22

What is dyspnoea

Answer 22

Shortness of breath reported by a patient

Occurs at inappropriately low levels of exertion, and limits exercise tolerance

Question 23

Describe the assessment of dyspnoea

Answer 23

Subjective rating scales

Questionnaires e.g. baseline dyspnoea test index, shortness of breath questionnaire

Exercise testing e.g. 6-minute walk test, shuttle test

Clinical dyspnoea scale (grade 0-4)

Modified Borg scale

Question 24

What can cause dypsnoea

Answer 24

Asthma
COPD 
MI 
Hypoxia 
Metabolic acidosis 
Anaemia 
Pregnancy

Question 25

What are some treatments for dyspnoea

Answer 25

Bronchodilators e.g. anticholinergics
Drugs that affect the brain e.g morphine, diazepam
Lung resection e.g. long volume reduction
Pulmonary rehabilitation (improve general fitness)

Question 26

What are some drugs used to treat dyspnoea

Answer 26

Amitryptiline
Gabapentin
Opiates

Question 27

Describe the slowly adapting stretch receptors (where they are found and what they are sensitive to)

Answer 27

Myelinated nerve fibres
Mechanoreceptors

Airways smooth muscle: trachea and main bronchi

Mechanical stimuli only (inflation)

Question 28

What are the effects of the cerebral cortex and cough centre on coughing

Answer 28

cerebral cortex - negative effect

Cough centre - Positive effect

Question 29

Explain the concept of sensitised cough reflex in disease

Answer 29

Irritation in the throat or upper chest
Cough difficult to control
Triggered by deep breath, laughing, smells, smoke, crumbly food, cold air etc.

Question 30

Describe the motor response of cough

Answer 30

Diaphragm, intercostals and laryngeal muscles involved

1. Inspiration
2. Compression as the laryngeal muscles close the glottis
3. Expulsion as the laryngeal muscles relax and air is expelled