Sensory aspects of respiratory disease Flashcards
what is a symptom?
An abnormal or worrying sensation that leads the person to seek medical attention
Describe the pathway from stimulus to evoked sensation? What are the names for the two main parts of this?
Stimulus - transducer - excitation of sensory nerves - integration of CNS - sensory impression
This is NEUROPHYSIOLOGY
Sensory impression - perception - evoked sensation
This is BEHAVIOURAL PSYCHOLOGY
- Neurophysiology
- Sensory stimulation (e.g. pain from a cut in the skin) activates a sensory transducer which transmits the signal via excitation of sensory nerves which lead onto afferent nerves going to the CNS - Behavioural psychology
- The CNS creates a sensory impression
- This sensory impression then leads to the perception of the information
- The brain interprets the information coming from the sensory nerves and this evokes a
why do we cough?
It is a crucial defence mechanism protecting lower respiratory tract from:
- inhaled foreign material
- excessive mucous secretion
what is usually the primary defence mechanism against lower respiratory infections?
-Mucociliary clearance
how does cough expel foreign material and what else is also involved?
- Once the mucus gets to the large airways it stimulates the cough mechanism
- Generates high-velocity airflow
- Expels the mucus or foreign material
- This is facilitated by mucus secretion and bronchoconstriction
Describe the distribution of rapidly adapting irritant receptors within the airway epithelium.
- Rapidly adapting irritant receptors which are located within airway
epithelium. - Most numerous on posterior wall of trachea, at main carina, and branching points of large airways, less numerous in more distal airways.
- Absent beyond the respiratory bronchioles.
- Possibly also in the external auditory meatus, eardrums, paranasal sinuses, pharynx, diaphragm, pleura, pericardium, and stomach
They are also found in the diaphragm, pleura, pericardium and stomach.
What are the three main types of sensory receptors in the lungs and airways?
C-fibre receptor
Slow adapting stretch receptors
Rapidly adapting stretch receptors
which cranial nerve does the vagus come from and what comes from this?
It is the 10th cranial nerve.
-all sensory nerves from the airways pass through to the brain.
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?
what is a stimulus to the sensory nerves?
Caspaicin
What stimulates C-fibres?
Chemicals
describe the process in which the c-fibre is stimulated?
C-fibre is stimulated when the caspaicin is injected intravenously.
what effect does caspaicin have on the rapidly and slow adapting stretch receptors
NO EFFECT
What do the rapidly and slowly adapting stretch receptors respond to?
Inflation (increase in tracheal pressure)
Describe the differences between the three types of sensory receptor.
C-fibre receptors:
-Unmyelinated fibres so conduction is slow
-responds to chemical irritant stimuli and inflammatory mediators
Sensitive to chemical irritant stimuli, inflammatory mediators and capsaicin
- Free nerve endings
-C-fibres are found in the larynx, trachea, bronchi and lungs
-release neuropeptide inflammatory mediators:
-Substance P
-Neurokinin A
-Calcitonin Gene Related Peptide
Rapidly adapting stretch receptors are found in the naso-pharynx, larynx, trachea and bronchi.
-if stimulate them with hyperinflation there is a rapid response (rapid silencing of the receptor)
Mechanical, chemical irritant stimuli, inflammatory mediators
*can respond to chemical stimuli but does not involve TRPV1 channels
Slowly adapting stretch receptors are located on airway smooth muscle, mainly in the trachea and main bronchi. Respond to lung inflation.
Slowly adapting stretch receptors are mechanoreceptors - respond to lung inflation
Both are myelinated.