protective reflexes Flashcards
Describe the nasal receptors
ie what are they sensitive to, what does stimulation cause
- nasal receptors are sensitive to irritating stimuli - both mechanical and chemical
- stimulation causes sneezing, apnoea, bradycardia, selective vasoconstriction and hypertension
Describe the laryngeal receptors
ie what are they sensitive to, what does stimulation cause?
- sensitive to irritating stimuli both mechanical and chemical
- stimulation of these receptors causes coughing, slow deep breathing / apnoea, laryngospasm, brady cardia etc
what is laryngospasm?
when the vocal cords in the larynx close over to prevent what ever is in the larynx getting deeper into the trachea
Describe trachea receptors
ie what they are sensitive to and what does stimulation cause
- sensitive to irritating stimuli - both mechanical and chemical
- stimulation causes coughing, slow deep breathing, bradycardia etc
what is the medical importance of the upper airway receptors?
- prevention of aspiration
- diving reflex - reflex that occurs when submersed in water - bradycardia
- important during intubation (insertion of tube into part of body eg trachea)
Give examples of CVS responses to stimulation of the upper airway receptors
- bradycardia
- vasoconstriction - via the pressor response - stimulation of sympathetic system
- hypertension - pressor response
what are the 3 intrapulmonary receptors?
- irritant receptors (analogous to upper airway receptors)
- J receptors
- pulmonary stretch receptors
Desceibe irritant receptors
location, sensitivity, stimulation
- located in airway epithelium
- sensory information travels via myelinated vagal afferent nerves
- sensitive to mechanical (particle) and chemical stimuli eg histamine
- stimulation causes hyperpnoea (leading to increased tidal volume) and bronchoconstriction
Describe J receptors
location, sensitivity, stimulation
- location in **alveolar walls beside pulmonary capillaries **(ie juxta-capillary)
- information travels via nonmyelinated vagal afferent nerves
- stimulation causes** rapid shallow breathibg, apnoea, hypotension & bradycardia**
Describe pulmonary stretch receptors
- receptors lie in airway smooth muscle
- info travels via** myelinated vagal afferents**
- sensitive to lung distension
- slowly adapting receptors - they are still active during lung inflation
- stimulation causes** inhibition of inspiration** (ie the hering breuer reflex). bronchodilatation, tachycardia
Describe the cholinergic innervation of the lung
- cholinergic nerves travel via CN X - vagus nerve to parasympathetic ganglia within the airway walls
- post ganglionic fibres run to airway smooth muscle, epithelium and submucosal glands
what do muscarinic antagonists prevent?
bronchoconstriction
compare the vagal tone in normal vs diseased patients
- normal - low vagal tone
- diseased - high vagal tone due to the increase of inflammatory mediators in the resp system eg histamine
what are examples of multiple irritant stimuli (chemicals)?
- histamine
- postaglandins
- bradykinin
- NH4
- dilute acids
Decribe the sympathetic innervation of the airways
- sparse sympathetic innervation in airways
- beta 2 adrenergic receptors expressed in airway smooth muscle
- adrenaline and NA cause bronchodilation
