Control of breathing Flashcards
What controls respiration?
-autonomic control
-unconcious
-negative feedback system to maintain blood gases and acid base balance within normal ranges for optimal cellular function
-can be manually overidden
-odines curse- congenital central hypoventilation syndrome
Whats involved with the voluntary regulation- manual override of breathing?
-coritcal influences:
-breath holding, coughing, speaking, laughing
-limbic influences:
-fear,anger, pain, anxiety
Describe the feedback control of respiration
sensors-chemoreceptors, lungs and others
-central controller- pons, medulla, other brain parts
-effectors- respiratory muscles
What is the general role of the respiratory centre?
-central controller
-located in several regions in medulla and pons of brainstem
-generates respiratory rythm
-controls rate, depth and resp pattern
Where is the respiratory centre located?
-medullary centre- below 4th ventricle in medulla
-apneustic area- lower pons
-Pneumotaxic area- upper pons
Function of the medullary centre
-setting of basic respiratory rhythm
-dorsal respiratory group-inspiration
-ventral respiratory group-inspiration and expiration ( dormant during quiet breathing)
What is the function of the apneustic area?
excitatory effect on inspiratory area of the medulla and causes prolonged inspiration
-stimulates dorsal resp group and increases resp
-gets feedback from vagal nerves and other resp centres
What is the function of the pneumotaxic area?
-controls the transition of inspiration to expiration by inhibiting inspiration
-regulate inspiratory volume and rate
-element of fine tuning
-signals to inspiratory area and controls the switch off point for the insp ramp- controls filling phase of lung cycle
-strong signal from here reduces the ramp time to 0.5s and also reduces the duration of expiration, increasing RR
-a weak signal will increase duration of both insp and exp and reduces RR
Whats the function of the dorsal respiratory group?
-control of respiration, generates the basic rythum of respiration
located- dorsal medulla, close to sensory termination of both vagal and glossopharyngeal nerves which transmit sensory signals into the resp centre
What is the inspiratory ramp signal?
-nervous signal to inspiratory muscles is a steadily increasing signal, increasing over a period of 2 secs
-results in inspiratory muscle contraction and air enters the lungs
-singal stops for 3 secs, stops excitation of inspiratory muscles
-lungs passively recoil during expiration
-cycle repeats
Describe the ventral respiratory groups 4 nuclei and their functions
1- botzinger complex- controls expiration
2-pre-botzinger complex- sets respiration pace
3-nucleus ambiguous-inspiratory neurosn
4-nucleus retro ambiguous- has inspiratory and expiratory neurons
-particulary active during forced respiration- excersise
What are the effectors involved with breathing control?
-coordinated by the central controller
-diaphragm
-intercostal muscles
-abdominal muscles
-accessory muscles
Name some respiratory receptors
chemoreceptors- central and peripheral
lung receptors- J receptors, irritant receptors , stretch receptors
-receptors in muscles and joints
Where are central chemoreceptors located?
ventral surface of medulla in brainstem
What is the function of central chemoreceptors?
-Respond to H+ conc in CSF
-raised H+= increased ventilation
-Lowered H+ = decreased ventilation
CO2 can diffuse across the blood brain barrier- an increase in co2 in CSF will increase the H+ conc and stimulate the central chemoreceptors
-not sensitive to changes in PaO2, responsible for 80% of the response to CO2 , relatively slow response
Where are peripheral chemoreceptors located?
-cartoid bodies at bifurcation of common carotoid arteries
-aortic bodies above and below aortic arch
-carotid bodies most important
What is the function of peripheral chemoreceptors?
-respond to changes in blood PCO2, H+ and PO2
-20% of ventilatory response to CO2, much more rapid response than central chemoreceptors
Where are stretch receptors located?
smooth muscle of bronchial walls
What is the function of stretch receptors?
stimulation leads to
-shortening of inspiration
-shallow inspiration
-delay before next breath
-Hering-breuer inspiratory reflex
What is the Hering- Breuer reflex?
-volume reflex where lung inflation inhibits inspiratory muscle activity and prevents overinflation of lungs
-when airways are stretched, receptors stimulated, sends impulses to dorsal respiratory group
-switches of inspiratory ramp, stops inspiration, results in expiration
-reflex is weak in normal breathing, important when tidal volume increases- excersise
Where are J receptors located?
on alveolar and bronchial walls close to cappilaries
Wjhat are J receptors also known as?
juxtaposition receptors or c-fibres receptors
What is the function of J receptors?
-stimulated by pulmonary oedema, microembolisms, inflammatory mediators
-activation results in apnoea, decreased HR, reduced BP and larynx constriction
Where are irritant receptors located?
throughour airway in between epithelial cells
