Sensory Aspects of Respiratory Disease Flashcards
Physiologic or Pathological stimulus leading to conscious sensation
Sensory stimulation (e.g. pain from a cut in the skin) activates a sensory …………….. which transmits the signal via excitation of sensory ………….. which lead onto afferent nerves going to the …………
The CNS creates a sensory ………………….. -NEUROPHYSIOLOGY
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 ‘sensation’ - this is ……………………….. PSYCHOLOGY
People react differently to different sensations
Physiologic or Pathological stimulus leading to conscious sensation
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
The CNS creates a sensory impression -NEUROPHYSIOLOGY
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 ‘sensation’ - this is BEHAVIOURAL PSYCHOLOGY
People react differently to different sensations
Cough
A CRUCIAL ……………… MECHANISM protecting the lower respiratory tract from:
Inhaled foreign material
Excessive mucous secretion
Usually secondary to ………………. clearance
Particularly important in lung disease where mucociliary function is impaired and mucous production is increased
Expulsive phase of cough
Once the mucus gets to the large airways it ……………… the cough mechanism
Generates …………… velocity airflow
Expels the mucus or ………………. material
This is facilitated by mucus secretion and ……………………………
Cough
A CRUCIAL DEFENCE MECHANISM protecting the lower respiratory tract from:
Inhaled foreign material
Excessive mucous secretion
Usually secondary to mucociliary clearance
Particularly important in lung disease where mucociliary function is impaired and mucous production is increased
Expulsive phase of cough
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
Nerve Profiles in Airways
Image on the left shows a nerve terminal on the surface of the epithelium
It is well placed to sense the external environment (e.g. by mechanical stimulation of the nerve terminal by dust)
This nerve terminal could respond by triggering a cough
Localisation of Cough Receptors
Rapidly adapting irritant receptors found within the …………………. epithelium
They are MOST NUMEROUS on the ……………… WALL of the trachea
They are also found at the main ………………..
Less numerous in more ………….. airways
ABSENT beyond the ………………….
Cough receptors are found MAINLY IN THE ………………. AIRWAYS
Commonly found at ……………… points of large airways
Cough receptors are also found in the larynx, pharynx and the external auditory meatus
Can also be found in the diaphragm, pleura, pericardium and stomach
Localisation of Cough Receptors
Rapidly adapting irritant receptors found within the airway epithelium
They are MOST NUMEROUS on the POSTERIOR WALL of the trachea
They are also found at the main carina
Less numerous in more distal airways
ABSENT beyond the bronchioles
Cough receptors are found MAINLY IN THE PROXIMAL AIRWAYS
Commonly found at branching points of large airways
Cough receptors are also found in the larynx, pharynx and the external auditory meatus
Can also be found in the diaphragm, pleura, pericardium and stomach
Sensory Receptors in the Lungs and Airways
Can be divided into THREE main types:
list them
Sensory Receptors in the Lungs and Airways
Can be divided into THREE main types:
SLOW adapting stretch receptors
RAPIDLY adapting stretch receptors
C-fibre receptors
C-fibre receptors
Name 4 places where they are located?
Are they myelinated or unmyelinated?
What do they respond to?
List 3 things they release?
C-fibre receptors
Free nerve endings
Present in the upper airways - larynx, trachea, bronchi and lungs
They are small UNMYELINATED fibres - so conduction is SLOW
Responds to chemical irritant stimuli and inflammatory mediators - C FOR CHEMICAL
Release neuropeptide inflammatory mediators:
Substance P
Neurokinin A
Calcitonin Gene Related Peptide
Rapidly adapting stretch receptors
Are they myelinated or unmyelinated?
List 4 Places where they are found?
List 3 thing that stimulate these receptors?
Rapidly adapting stretch receptors
MYELINATED - so conduct very quickly
Present in the naso-pharynx, larynx, trachea and bronchi
Mechanical, chemical irritant stimuli, inflammatory mediators
If you stimulate them with hyperinflation there is a rapid response (rapid silencing of the receptor)
Slowly adapting stretch receptors
Where are they located?
Are they myelinated?
Predominantly in the ………….. and …………. ……………….
Slowly and rapidly adapting stretch receptors are ………………………………….
They respond to lung ………………………..
Slowly adapting stretch receptors
Located in airway smooth muscle
Also MYELINATED - so conduct very quickly
Predominantly in the trachea and main bronchi
Slowly and rapidly adapting stretch receptors are mechanoreceptors
They respond to lung inflation
Sensory Receptors in the Lungs and Airways
This is a recording from airway vagal afferent nerves in an experiment using anaesthetised rats
The vagus is the 10th Cranial Nerve through which ALL sensory nerves from the airways pass through to the brain
The above image shows measurements of the action potential, tracheal pressure (P) and arterial blood pressure (ABP)
Caspaicin has been given which is a stimulus to the sensory nerves
C-fibres are stimulated by CHEMICALS
The C-fibre is stimulated when the caspaicin is injected intravenously
The caspaicin has NO EFFECT on the rapidly and slow adapting stretch receptors
The MAIN STIMULUS for the rapidly and slow adapting stretch receptors is INFLATION
INCREASE in tracheal pressure = rapidly adapting stretch receptors STOP firing + slow adapting stretch receptors are STIMULATED to fire
These receptors are most likely to be involved in coughing
Sensory Receptors in the Lungs and Airways
This is a recording from airway vagal afferent nerves in an experiment using anaesthetised rats
The vagus is the 10th Cranial Nerve through which ALL sensory nerves from the airways pass through to the brain
The above image shows measurements of the action potential, tracheal pressure (P) and arterial blood pressure (ABP)
Caspaicin has been given which is a stimulus to the sensory nerves
C-fibres are stimulated by CHEMICALS
The C-fibre is stimulated when the caspaicin is injected intravenously
The caspaicin has NO EFFECT on the rapidly and slow adapting stretch receptors
The MAIN STIMULUS for the rapidly and slow adapting stretch receptors is INFLATION
INCREASE in tracheal pressure = rapidly adapting stretch receptors STOP firing + slow adapting stretch receptors are STIMULATED to fire
These receptors are most likely to be involved in coughing
There are TWO types of sensors that will lead to cough: name them
Vagal Afferent Innervation of Guinea Pig Trachea
There are TWO types of sensors that will lead to cough: Mechanoreceptors and Nociceptors
MECHANOSENSORS are activated by:
Mechanical Displacement
CITRIC ACID
NOCICEPTORS are activated by:
Caspaicin
Bradykinin
Citric Acid
Cinnamaldehyde
Mechanosensors look a bit like a tree
TRPV1, TRPA1 and B2 are present on nociceptors
Afferent Neural Pathways for Cough
Stimulation of mechanical or chemical receptors leads to impulses going up the …………… nerve, through the ………………….. to the ……………….. centre
Some signal goes to the ………………… ……………………
Afferent Neural Pathways for Cough
Stimulation of mechanical or chemical receptors leads to impulses going up the vagus nerve, through the brainstem to the cough centre
Some signal goes to the cerebral cortex
Efferent Neural Pathways for Cough
The efferent pathways involve the stimulation of various muscles leading to the closure of the ………….. and the production of sound
Efferent Neural Pathways for Cough
The efferent pathways involve the stimulation of various muscles leading to the closure of the glottis and the production of sound
Mechanics of Cough
There are THREE main phases:
List them
The …………….. phase opens up the trachea
During the act of coughing there is an ……………… in intrapulmonary pressure that compresses the ………………… membrane of the trachea which pushes through and narrows the trachea into a ……………….. shape
This increases flow and contributes to the sound produced
Mechanics of Cough
There are THREE main phases:
Inspiratory Phase
Glottic Closure
Expiratory Phase
The inspiratory phase opens up the trachea
The inspiratory phase opens up the trachea
During the act of coughing there is an increase in intrapulmonary pressure that compresses the posterior membrane of the trachea which pushes through and narrows the trachea into a crescent shape
This increases flow and contributes to the sound produced
The Complete Cough Pathway
Sensory information goes via the …………… nerve and through the ……………….. to the …………… centre
The ………………. centre consists of the ……………… ………………. …………….. - a collection of neurons that are connected to the ……………….. ………………….. ………………. …………………….
The reflex is probably a …………………. reflex
From the ………………. …………….. ………………… ……………….. you get stimulation of various muscles needed to produce the cough
The complete cough pathways also includes the ……………… ………………….
When you go to SLEEP, this reflex is ………………….. so you need to be awake to a certain extent to be able to cough
Under general anaesthetic this is also suppressed
The Complete Cough Pathway
Sensory information goes via the vagus nerve and through the brainstem to the cough centre
The cough centre consists of the nucleus tractus solitarius - a collection of neurons that are connected to the medullary cough pattern generator
The reflex is probably a brainstem reflex
From the medullary cough pattern generator you get stimulation of various muscles needed to produce the cough
The complete cough pathways also includes the cerebral cortex
When you go to SLEEP, this reflex is INHIBITED so you need to be awake to a certain extent to be able to cough
Under general anaesthetic this is also suppressed
Common Causes of Cough
ACUTE Cough (<3 weeks)
The most common cause of a cough is an acute cough caused by ……………..
By ……………. weeks most people would have lost their symptoms
ACUTE Cough (<3 weeks)
The most common cause of a cough is an acute cough caused by rhinovirus
By two weeks most people would have lost their symptoms
What makes a cough chronic?
CHRONIC Persistent Cough (>3 weeks)
Causes in order of frequency:
Asthma and eosinophilic-associated - 25%
Gastro-oesophageal reflux - 25%
Rhinosinusitis (post-nasal drip) - 20%
Chronic Bronchitis - 8%
Bronchiectasis - 5%
Drugs (e.g. ACE inhibitors) - 1%
Post-viral - 3%
Idiopathic - 10%
Other causes - 3%
When there is an infection, the mucus might change colour and become yellowish
Gastro-oesophageal reflux - the protons coming up from the stomach can activate the cough receptors which, in turn, activate brainstem cough receptors
Chronic Cough: Indication of Increased Cough Reflex
Also known as …………….. ………………. …………………….
Cough paroxysms that are difficult to control (not just throat clearing)
Triggers include: deep breath, laughing, talking too much, vigorous exercise, smells, cigarette smoke, eating crumbs, cold air, changing temperatures, lying flat
Sensitivity of the cough reflex can be measured using ……………….
………………… is the thing in chilies that give them their hotness
You initially give a dilute solution of caspaicin and then increase the concentration until the participant coughs
Chronic coughers are particularly sensitive to caspaicin
Caspaicin an activate ……………………. through ………………… receptors
Chronic Cough: Indication of Increased Cough Reflex
Also known as Cough Hypersensitivity Syndrome
Cough paroxysms that are difficult to control (not just throat clearing)
Triggers include: deep breath, laughing, talking too much, vigorous exercise, smells, cigarette smoke, eating crumbs, cold air, changing temperatures, lying flat
Sensitivity of the cough reflex can be measured using caspaicin
Caspaicin is the thing in chilies that give them their hotness
You initially give a dilute solution of caspaicin and then increase the concentration until the participant coughs
Chronic coughers are particularly sensitive to caspaicin
Caspaicin an activate nociceptors through TRPV1 receptors
Plasticity of neural mechanisms
This is the mechanism by which you get hypersensitivity
List 4 mechanisms
Plasticity of neural mechanisms
This is the mechanism by which you get hypersensitivity
Increased excitability of the afferent nerves by chemical mediators e.g. prostaglandin E2
Increase in receptor numbers e.g. TRPV1
Increase in neurotransmitter in the brainstem e.g. neurokinins
There may also be an increase in inflammatory mediators, which damage or change the reactivity of the nerves to various stimuli like caspaicin
this diagram shows that smooth muscle hypertrophy in asthma could affect the slowly adapting receptors that could contribute to enhanced hypersensitivity
Current Antitussives
If you are coughing excessively then you might want to suppress it but not completely eliminate the cough response because then you’d be getting rid of its defensive capabilities
Opiates can act as an antitussive but they are not particularly effective as they work at doses where there are a lot of side-effects (e.g. morphine and codeine)
Which of the following is insensitive to pain: parietal or visceral plueral?
Visceral pluera
The patient would not feel pain from inflammation of the visceral pleura because it is insensitive to pain – its afferent fibers relay stretch sensations only. However, the parietal pleura is very sensitive to pain due to the somatic afferent fibers that innervate it.
What nerve supplies the Nose, Pharynx, larync, Lungs, Chest wall?
Anatomical Pathways of Touch and Pain
We need to distinguish between touch and pain because the anatomical pathways are slightly different, as are the sensory receptors
Touch travels via ……………. and …………… fibres via the …………….. …………..
The MAIN DIFFERENCE between the two pathways is really at ……………………………………………………………………………………………………………
TOUCH - goes to the …………………. …………….. at the level of the ……………….. ………………… (……………..)
EXAMPLE: the sensation of touch from the leg will run up along the same side as the leg it is coming from and then cross onto the other side at the brainstem
PAIN - goes to the ………………. ……………… at the ………… anatomical level (it crosses right away)
Both touch and pain information goes to the ………….. ………………. ………………
CLINICAL IMPORTANCE: …………………-……………….. Syndrome (hemisection of the spinal cord)
If you have hemisection on the LEFT SIDE of the spinal cord, the …………. sensation will be fine on the opposite side but the …………… sensation on the other side will be affected
Anatomical Pathways of Touch and Pain
We need to distinguish between touch and pain because the anatomical pathways are slightly different, as are the sensory receptors
Touch travels via Aalpha and Abeta fibres via the dorsal horn
The MAIN DIFFERENCE between the two pathways is really at the level at which the pathways cross through to the contralateral side
TOUCH - goes to the contralateral side at the level of the caudal medulla (brainstem)
EXAMPLE: the sensation of touch from the leg will run up along the same side as the leg it is coming from and then cross onto the other side at the brainstem
PAIN - goes to the contralateral side at the same anatomical level (it crosses right away)
Both touch and pain information goes to the primary somatosensory cortex
CLINICAL IMPORTANCE: Brown-Sequard Syndrome (hemisection of the spinal cord)
If you have hemisection on the LEFT SIDE of the spinal cord, the touch sensation will be fine on the opposite side but the pain sensation on the other side will be affected
Different types of pain: somatic vs visceral
–Visceral pain (from visceral organs eg heart, gi tract, bronchial wall) is not the same as somatic pain (from skin).
–Visceral pain is difficult to localise( patients find it hard to distinguish pain from left lung or right lung), diffuse in character and is referred to somatic structures.
–Number of visceral afferents is ……….. than number of somatic afferents
–Pain arising from various viscera in the thoracic cavity and from the chest wall is often qualitatively similar and exhibits overlapping patterns of referral, localisation and quality, leading to difficulties in diagnosis.
Different types of pain: somatic vs visceral
–Visceral pain (from visceral organs eg heart, gi tract, bronchial wall) is not the same as somatic pain (from skin).
–Visceral pain is difficult to localise( patients find it hard to distinguish pain from left lung or right lung), diffuse in character and is referred to somatic structures.
–Number of visceral afferents is less than number of somatic afferents
–Pain arising from various viscera in the thoracic cavity and from the chest wall is often qualitatively similar and exhibits overlapping patterns of referral, localisation and quality, leading to difficulties in diagnosis.
Different Types of Pain: Somatic and Visceral
NOTE: there is also a third type of pain called ……………….
Visceral pain comes from the ……………. (internal organs)
This is NOT the same as somatic (which comes from the skin and subcutaneous tissue)
Somatic is VERY ……………. - we know exactly where the pain is coming from
Visceral is ……………. to localise, diffuse in character and is referred to somatic structures
The number of visceral afferents is FEWER than the number of somatic afferents
Pain arising from various viscera in the thoracic cavity and from the chest wall is often qualitatively similar and exhibits overlapping patterns of referral, localisation and quality leading to difficulties in diagnosis
Different Types of Pain: Somatic and Visceral
NOTE: there is also a third type of pain called neuropathic
Visceral pain comes from the viscera (internal organs)
This is NOT the same as somatic (which comes from the skin and subcutaneous tissue)
Somatic is VERY localised - we know exactly where the pain is coming from
Visceral is DIFFICULT to localise, diffuse in character and is referred to somatic structures
The number of visceral afferents is FEWER than the number of somatic afferents
Pain arising from various viscera in the thoracic cavity and from the chest wall is often qualitatively similar and exhibits overlapping patterns of referral, localisation and quality leading to difficulties in diagnosis
Chest pain from non-respiratory disorders
Cardiovascular Disorders:
Myocardial ischaemia/infarction
Pericarditis
Dissecting aneurysm
Aortic valve disease
Gastrointestinal Disorders:
Oesophageal rupture
Gastro-oesophageal reflux
Cholecystitis
Pancreatitis
Psychiatric Disorders:
Panic disorder
Self-inflicted
What is dyspnea or shortness of breath?
- Troublesome shortness of breath reported by a patient
- Occurs at inappropriately low levels of exertion, and limits exercise tolerance
- Unpleasant and frightening experience. Can be associated with feelings of impending suffocation
- Poor perception of respiratory symptoms and dyspnea may be life-threatening
Clinical Dyspnoea Scale (American Thoracic Society)
