sensory aspects of respiratory disease

Question 1

purpose of cough

Answer 1

crucial defence mechanism protecting lower respiratory tract from inhaled foreign material or excessive mucous secretion

Question 2

cough and mucociliary clearance relationship

Answer 2

usually secondary to mucociliary clearance, but important in lung disease when mucociliary function impaired and increased mucous production

Question 3

expulsive phase of cough

Answer 3

generates high velocity of airflow; facilitated by bronchoconstriction and mucous secretion

Question 4

location of respiratory sensory receptors

Answer 4

upper airways, pharynx, many in larynx, large airways (most numerour on posterior wall of trachea; main bronchi); absent beyond respiratory bronchioles

Question 5

nerve important in coughing

Answer 5

vagus

Question 6

3 types of sensory receptors

Answer 6

C-fibre receptors (stimulated by chemicals); rapidly adapting stretch receptors; slowly adapting stretch receptors

Question 7

C-fibre receptors

Answer 7

free nerve endings; larynx, trachea, bronchi, lungs; small unmyelinated; chemical irritant stimuli (e.g. capsaicin), inflammatory mediators; release neuropeptide inflammatory mediators

Question 8

rapidly adapting stretch receptors

Answer 8

naso-pharynx, larynx, trachea, bronchi; small myelinated; activated by stretch on inspiration; mechanical, chemical and inflammatory stimuli

Question 9

vagal afferent innervation: physical and chemical

Answer 9

mechanosensors (physical), nociceptors (chemical)

Question 10

methods of activation of sensors: mechanosensor and nociceptor

Answer 10

ion channels (mechanosensor); transient receptor potential cation channels/transient receptor potential vanniloid-1 receptors (nociceptor)

Question 11

afferent neural pathway for cough from receptors in lungs and larynx

Answer 11

stimulation of irritant receptors or cough receptor (mechanical/chemical) → afferent vagus nerve from lungs (superior laryngeal nerve from larynx) → cough centre in medulla oblongata → (info sent to cerebral cortex for voluntary control) → efferent vagus nerve → effector muscles

Question 12

efferent neural pathway for cough

Answer 12

changes in breathing and expiratory airflow to expel mucous and foreign material; cerebral cortex → cough centre in medulla → glottis, (accessory muscles of inspiration, external intercostals), diaphragm, expiratory muscles

Question 13

mechanism of cough in glottis

Answer 13

inspiratory phase → glottic pressure in minimum flow phase, with glottis close to generate pressure → glottis opens → expiratory phase

Question 14

what is each cough followed by

Answer 14

short inspiration

Question 15

what does an increase in intrathoracic pressure cause in trachea and why

Answer 15

invagination and narrowing to form crest shape, increasing airflow

Question 16

common causes of cough

Answer 16

acute and chronic infections, airway diseases, parenchymal diseases, tumours, aspirated foreign bodies, middle ear pathology, cardiovascular disease, other diseases (e.g. obstructive sleep apnea), drugs (angiotensin-convertin enzyme inhibitor medications for hypertension)

Question 17

features of acute cough: duration, causes

Answer 17

< 3 weeks; common cold: cough, post nasal drip, throat clearing, nasal blockage and discharge

Question 18

chronic persistent cough: duration, causes

Answer 18

> 3 weeks; asthma and eosinophilic-associated; gastro-oesophagul reflux, post nasal drip, chronic bronchitis, bronchiecstasis, ACE inhibitors, post-viral

Question 19

what is sputum and what does it look like

Answer 19

frothy milky; turns greener on infection; huge amounts of protein

Question 20

cough hypersensitivity syndrome triggers

Answer 20

irritation in throat or upper chest; various triggers (smoking, smells, exercise, crumbs, cold air, lying flat, deep breath, laughing)

Question 21

plasticity of neural mechanisms causing cough hypersensitivity syndrome

Answer 21

excitability of afferent nerves increased by chemical mediators; increase in receptor numbers; neurotransmitter increased in brain stem; increased voltage-gates channel expression (TRPV-1) to easily stimulate cough

Question 22

cough hypersensitivity syndrome causing chronic cough: what does it increase

Answer 22

increase in acid present, inflammatory mechanism in airways, increase neurotransmitter in brain stem

Question 23

treatment of cough: pharmacological symptomatic suppressants

Answer 23

opiod-based (codeine) act centrally, blocking signals sent from brain; moguistine act peripherally

Question 24

treatment of cough: disease-specific

Answer 24

corticosteroids if eosinophil problem, steroids for post-nasal drip, proton pump inhibitor for gastro-oesophageal reflux disease

Question 25

other treatment of cough

Answer 25

speech pathology management to increase voluntary control

Question 26

what worsens cough effectiveness if trying to remove foreign material

Answer 26

asthma as bronchoconstriction and watery mucous

Question 27

what worsens cough effectiveness if excessive mucous secretion

Answer 27

smoking as thicker, increased volume mucous