Respiratory strand: Lecture 9 - Control of Ventilation Flashcards
Why do we need to breath?
- to take in O2: requirement for generating ATP through oxidative phosphorylation
- to remove CO2
What is minute ventilation?
Ve= breathing frequency x tidal volume
What are the parts of the respiratory system that participate in gas exchange?
Only respiratory bronchi and alveoli
What happens to the air that isn’t used?
Contributes to “dead space” of upper airways
What factors cause breathing rate to vary?
- Activity vs rest
- Altitude - less O2 in air so need to work harder to maintain supply
- Disease
What diseases effect the amount of breathing?
- pulmonary diseases e.g emphysema
- cardiovascular diseases
- sleep apnoea: periodic cessation during sleep
- opioid depression of breathing
- conditions of chronic hypercapnia (abnormally high CO2 levels)- require oxygen sensing
Which 3 factors effect breathing?
Input, output and control
flow chart slide 4
What is in the respiratory centre?
Medulla and pons
image slide 5
What does input involve?
Receptors sending information to the respiratory centre e.g chemoreceptors detecting CO2, lung receptors, nasal and upper airway receptors etc
What does output involve?
Sending impulses from the respiratory centre to target muscles (effectors) controlling ventilation
effectors include diaphragm, intercostal muscles, abdominal muscles and accessory muscles
What do the medulla and pons do?
Medulla is the primary centre for respiration as it contains the dorsal respiratory group (DRG) which is all too need to breath
Pons regulates medulla
What is the ventral respiratory group (VRG) mostly responsible for?
Expiration
What is inside pons?
- pneuomotaxic centre (simulates inspiration)
- apneustic centre (opposite to apneustic - inhibits inspiration)
What occurs in the VRG (ventral respiratory group?)
Contains mixed neurones
some fire during inspiration,
some during expiration
What happens in the DRG? (dorsal respiratory group)
Contains neurones
which fire during inspiration
How is our reciprocal breathing pattern achieved?
DRG inhibits VRG
VRG inhibits DRG
How can inspiratory activity be depressed?
- hypoxia
- a wide variety of therapeutic drugs e.g opiates, barbiturates and anaesthetic agents
- inhibition of blood supply
What is hypocapnia?
Low CO2 - alkalosis
What might influence the higher brain centre?
voluntary hyperventilation, voluntary breath holding, emotions (anger, anxiety), sensory receptors (pain, cold)
What are pulmonary stretch receptors?
- mechanoreceptors
- afferent fibres from smooth muscle of bronchi and trachea
- run in vagus nerve to the respiratory centre (medulla)
- cause inspiration
What is the hering-breuer lung inflation reflex?
limits minute ventilation (breathing frequency x tidal volume)
prevents over inflation of lungs
What are irritant/ cough receptors?
- Receptors throughout the airways initiate an explosive expiration (a cough) when stimulated
- fibres from these receptors run in the vagus to the respiratory centre
What do local anaesthetics do to irritant/cough receptor reflexes?
Prevent them when passing tubes into patients
Which receptors relay information about activity induced motion which can influence ventilation?
Muscle/joint stretch receptors and proprioreceptors
