Respiratory responses to irritation and invasion Flashcards
What are the adaptations present in the URT to protect against irritation and invasion?
Hair/ ciliated epithelium?
Goblet cells producing mucous
Diameter of passageways limits what can pass through
What is the adaptation present in the conducting airways (trachea to terminal bronchioles) to prevent irritation and invasion?
Mucociliary escalator
Cilia beat cranially to move mucus towards pharynx
Causes swallowing
What adaptation is there in the respiratory zone (lung parenchyma) to prevent irritation and invasion? Where do these drain into?
Alveolar macrophages
Drain into pulmonary lymphatic system
What are the 3 classes of sensory airway receptors?
Rapidly adapting receptors (RARs)
Slowly adapting receptors (SARs)
C fibres
Where are rapidly adapting receptors (RAR) found? What do they respond to?
Intrapulmonary airways Mechanical stimuli (ones in URT more mechanical, ones in LRT more chemical)
When are rapidly adapting receptors more active?
When rate and volume of lung inflation increases (during normal respiration)
What do rapidly adapting receptors cause if they detect mechanical or chemical stimuli? What NS pathway is responsible for this?
Reflex bronchoconstriction
Mucous secretion
Parasympathetic pathway
Where are slowly adapting receptors found and what do they detect?
Around bronchioles and alveoli
Mechanical stimulation
When does the activity of slowly adapting receptors increase? When does their activity decrease?
Increase during inspiration Decrease during expiration
What are the afferent fibres of the slowly adapting receptors responsible for?
Hering-Breur reflex
What do C-fibres detect? What directly activities them?
Noxious chemical/mechanical stimuli
Bradykinin and capsaicin
Are C-fibres involved in normal respiration?
No - only during irritation or invasion
What efferent effects do C-fibres cause after stimulation?
Bronchoconstriction
Mucous secretion
Apnoea and shallow breathing
Coughing
Name 3 reflexes caused by irritation or invasion
Sneeze reflex
Cough reflex
Nasopulmonary reflex
What is the purpose of the cough reflex? Which receptor types are involved?
To remove excess mucus or agents from the respiratory types All 3 (RARs, SARs, C-fibres)
Where are all three receptors concentrated?
Tracheal bifurcation
Is the coughing reflex under conscious control?
Automatic
Degree of concious control = psychogenic coughing
Where is the cough centre found?
Medulla oblongata and pons
What afferent nerve supplies the coughing reflex? Where does the efferent nerve go to and which nerve?
Afferent: vagus nerve
Efferent:
Diaphragm (phrenic nerve)
Abdominal and respiratory muscles (somatic spinal nerves)
Larynx ( vagus and recurrent laryngeal nerve)
What are the 3 phases to coughing?
Inspiratory phase
Compression phase
Expiratory phase
Where are the receptors for the sneeze reflex and what stimuli do they detect?
Nasal mucosa
Mechanical and chemical
What afferent nerve supplies the sneezing reflex?
Trigeminal nerve
Where is the sneezing centre located?
Medulla oblongata
Describe the process that takes place during sneezing
Eyes shut Inspiration Glottis closes Increased thoracic pressure Expiration through nose and mouth
What is the efferent pathway for sneezing?
Poorly understood but similar to coughing
Phrenic nerve - diaphragm
Somatic spinal nerve - abdominal and thoracic muscles
Vagus and recurrent laryngeal - larynx
What stimulates sneezing?
Irritation Invsaion Bright light Full stomach Any stimulation of trigeminal (plucking eyebrows) Psychogenic (for attention) Arousal
What is the nasopulmonary reflex? Give an example
Reflex bronchoconstriction due to irritant/invasion
Breathing through nose on a cold day
What happens if the nasopulmonary reflex results in longterm bronchoconstriction?
Hypoxia and hypercapnia
What afferent nerve and efferent nerve supply the naeopulmonary reflex?
Afferent - trigeminal
Efferent - vagus
