sensory aspects of resp disease Flashcards
what is a symptom?
- an abnormal or worrying sensation that leads a person to seek medical attention
what is the difference between sensory stimulation and sensory impression?
sensory stimulus –> transducer –> excitation of sensory nerve –> integration CNS –>sensory impression
( this is neurophysiology )
sensory impression –> perception –> evoked sensation
( this is behavioural psychology)
what is the function of a cough?
- crucial defense mechanism
- protecting the lower resp tract
- inhaled foreign material
- excessive mucus production
what does a cough come after?
- mucociliary clearance
what happens in the expulsive phase of a cough?
- once the mucus gets to the large airways it stimulates he cough
- it generates a high-velocity airflow
- expels the mucus or foreign material
- this is facilitated by mucus secretion
where are cough receptors normally found?
- they are most numerous on the posterior wall of the trachea
- they are found at the main carina
- they are less numerous in the more distal airways
- they are absent beyond the bronchioles
- normally found on the proximal airways
what are the three types of sensory receptor in the lungs and the airways?
- slow adapting stretch receptors
- rapidly adapting stretch receptors
- C- fibre receptors
what cranial nerve is the vagus nerve?
the 10th cranial nerve
through which all the sensory nerves from the airways pass through to the brain
what is caspaicin?
- this is a stimulus to the sensory nerve
what is the stimulus for C fibres?
- stimulated by chemicals
what is the stimulus for the rapidly and slow adapting stretch receptors?
- inflation
- caspaicin has no effect
what happens to the stretch receptors after an INCREASE in tracheal pressure?
- the rapidly adapting stretch receptors stop firing and he slows adapting stretch receptors are stimulated to fire
these receptors are involved in coughing
what are features of C fibre receptors
- they have free nerve endings
- they are present in the upper airways
- they are small and unmyelinated fibres
- the conduction is slow
- releases neuropeptide, inflammatory mediators
what are features of rapidly adapting stretch receptors?
- they are myelinated
- conduct very fast
- present in nasopharynx, larynx trachea and bronchi
- stimulated with hyperinflation causes a rapid response
features of the slowly adapting stretch receptors?
- located in smooth muscle airway
- myelinated
- therefore also conduct very quickly
- mechanoreceptors
they also respond to lung inflation
what types of receptors lead to coughing?
- mechanoreceptors
- nociceptors
what are the mechanoreceptors stimulated by?
- mechanical displacement
- citric acid
what are nociceptors activated by?
- caspaicin
- bradykinin
- citric acid
what is the complete cough pathway?
- sensory information goes via the vagus nerve and through the brainstem to the cough center
- this cough center consists of nucleus tractus solitarius
- the nucleus tractus solitarius is a collection of neurones that are connected to the medullary cough pattern generator
- from the medullary cough pattern generator, you can stimulation of various muscles to produce the cough
- the complete cough pathway also includes the cerebral cortex
what are the afferent neural pathways for a cough?
- stimulation of the mechanical or chemical receptors leading to impulses going up the vagus nerve
- travels through the brainstem to the cough center
- some of the signals goes to the cerebral cortex
what are the efferent neural pathways for a cough?
- involves the stimulation of various muscles
- which leads to the closure of the glottis and the production of the cough sound
what are the 3 phases of a cough?
- inspiratory phase (opens trachea)
- glottic closure
- expiratory phase
what happens to the intrapulmonary pressure during the act of coughing?
- increase in intrapulmonary pressure
- this compresses the posterior membrane of the trachea
- which pushes and narrows the trachea into a crescent shape
- this increases the flow and emphasizes the sound that is produced
what is an acute cough?
what is it normally caused by?
lasts less than 3 weeks
- caused by a rhinovirus
what is a chronic cough?
- lasts more than 3 weeks most common causes are : - asthma - gastroesophageal reflux (when protons coming up from stomach activate the cough receptors) - rhinosinusitis
what happens to the mucus when there is an infection?
- the mucus may change color and become yellow
what is an increased cough reflex?
- cough hypersensitivity syndrome
- this is like a cough that is hard to control
- triggers might be deep breath, laughing, talking ect. temp change, lying flat
how to identify an increased cough reflex?
- giving the patient a range of doses of caspaicin
- give diluted amounts and keep increasing the concentration
- chronic coughers are particularly sensitive to this
what is the mechanism of getting cough hypersensitivity?
- increased excitability of the afferent nerves
by chemical mediators - results in an increase in the number of receptors
- this also increases the neurotransmitter
- there might also be an increase in inflammatory mediators
what are current suppressants for coughing?
- using opiates
however they do come with side effects
what are the sensory nerves coming from each of these places? nose pharynx larynx lungs chest wall
nose = trigeminal pharynx = glossopharyngeal + vagus larynx = vagus lungs = vagus chest wall = spinal nerves
what is the difference between the anatomical pathways of touch and pain?
- the level at which the pathways cross over to the contralateral side
- touch goes to the contralateral side at level of CAUDAL MEDULLLA
- pain goes to the contralateral side at the level of the same anatomical level - direct
what are the two types of pain?
- somatic pain
- visceral pain
what is the nature of somatic pain?
very localised pain
- there are lots of somatic afferents
what is the nature of visceral pain?
very generalized pain difficult to identify
the number of visceral afferents are fewer
where might chest pain from respiratory disorders be coming from?
- pleuropulmonary disorder
- tracheobronchitus
- inflammation
- referred pain
where might the pain come from if not the resp system?
- cardiovascular disease
- gastrointestinal
- referred pain
what is dyspnoea?
- shortness of breath
- occurs at low levels of exertion
