Control of Lung function Flashcards
What are the different groups of neurones in the medulla?
Dorsal respiratory group
Ventral respiratory group
Apneustic centre
Pneumotaxic centre
What is the function of the dorsal respiratory group?
Inspiratory centre
Main ‘controller’ of inspiration
Set the ‘rate’
What is the function of the ventral respiratory group?
Expiratory centre
Inactive during quiet breathing
Inhibit apneustic centre
What is the function of the apneustic centre?
Stimulates activity in DRG
Inhibited by pulmonary afferents
What is the function of the pneumotaxic centre?
The ‘inspiratory off switch’
Regulates depth & frequency
What provides the main stimulus to breather
Proton concentration which is proportional to CO2 concentration
What are the main features of the irritant receptors?
Afferent receptors embedded within and beneath airway epithelium
Leads to cough: which involves forceful expiration against a closed glottis with sudden glottal opening & high velocity expulsion of air
What are the main features of stretch receptors?
Excessive inflation of lungs activates pulmonary stretch receptors
Afferent signals to respiratory centres inhibit DRG and apneustic centre and stimulate pneumotaxic VRG
Inspiration inhibited & expiration stimulated
What are the main features of J-receptors?
Sensitive to oedema and pulmonary capillary engorgement
Increases breathing frequency
What is an acid?
An acid is any molecule that has a loosely bound H+ ion that it can donate
H+ ions are also called protons (because an H atom with a +1 valency has no electrons or neutrons)
What is a base?
A base is an anionic (negatively charged ion) molecule capable of reversibly binding protons (to reduce the amount that are ‘free’)
Why might the acidity of the blood be tightly regulated?
Marked changes will alter the 3D structure of proteins
How does the blood regulate pH?
The blood has an enormous buffering capacity that can react almost immediately to imbalances
What is alkalaemia?
Refers to high-than-normal pH of blood
What is acidaemia?
Refers to lower-than-normal pH of blood
What is alkalosis?
Describes circumstances that will decrease [H+] and increase pH
What is acidosis?
Describes circumstances that will increase [H+] and decrease pH
What can changes in ventilation stimulate?
RAPID compensatory response to change CO2 elimination and therefore alter pH
What can stimulate a SLOW compensatory response to increase/decrease pH?
Changes in HCO3- and H+ retention/secretion in the kidneys
What does acidosis need to correct?
Alkalosis
What does alkalosis need to correct?
Acidosis
Where are the peripheral chemoreceptors
Near the carotid baroreceptors (sensitive to changes in blood pressure?
Describe what happens to breathing during exercise?
Efferents from primary motor cortex to gross skeletal musculature partly innervate medulla
Proprioceptive afferents from muscle spindles & golgi tendon organs innervate medulla on way to brain
Describe the effects of skin afferents on breathing
Immersion in cold water
Inspiratory gasp
Hyperventilation
