11. Sensory aspects of respiratory disease Flashcards
Symptom
An abnormal sensation that leads someone to seek medical attention
e.g. Cough, Chest pain
Sign
An observable feature on physical examination e.g. Increased respiratory rate
Describe the pathway from stimulus to evoked sensation? What are the names for the 2 main parts of this?
Stimulus - transducer - excitation of sensory nerves - integration of CNS - sensory impression
= NEUROPHYSIOLOGY
Sensory impression - perception - evoked sensation
=BEHAVIOURAL PSYCHOLOGY
Cough
A crucial defence mechanism protecting the lower respiratory tract from:
inhaled foreign material
excessive mucous secretion
Expulsive phase of cough
generates a high velocity of airflow
facilitated by bronchoconstriction and mucous secretion
Describe the distribution of rapidly adapting irritant receptors within the airway epithelium.
Most on posterior wall of the trachea and in the main carina.
Decrease in number as you go down the airways and are absent in the bronchioles.
Commonly found at the branch points of large airways.
What is the most important nerve involved in cough?
Vagus nerve
Stimuli of cough receptors
Laryngeal and tracheobronchial receptors respond to chemical and mechanical stimuli
What are the 3 main types of sensory receptors in the lungs and airways?
C-fibre receptor
Slowly adapting stretch receptors
Rapidly adapting stretch receptors
Which nerve do all the sensory receptors in the lungs and airways pass through?
Vagus nerve
What is used as a stimulus for the C-fibres?
Caspaicin
What stimulates C-fibres?
Chemicals
Describe C-fibres structure, distribution and action
“Free” nerve endings
Larynx, trachea, bronchi, lungs
Small unmyelinated fibres
Release neuropeptide inflammatory mediators e.g. Neurokinin A
Describe rapidly adapting stretch receptors (RARs) structure and distribution
Naso-pharynx, larynx, trachea, bronchi
Small, myelinated nerve fibres (A-delta)
What stimulates RARs?
Mechanical, chemical irritant stimuli, inflammatory mediators
What do the rapidly and slowly adapting stretch receptors respond to?
Inflation (increase in tracheal pressure)
Describe the differences between the 3 types of sensory receptor.
C-fibres are unmyelinated whereas the others are myelinated.
C-fibres are found in the larynx, trachea, bronchi and lungs
Rapidly adapting stretch receptors are found in the naso-pharynx, larynx, trachea and bronchi
Slowly adapting stretch receptors are located on airway smooth muscle, mainly in the trachea and main bronchi
What are the 2 broad types of sensory receptor in the airways?
Mechanoreceptors
Nociceptors