Central control of respiration Flashcards
Where in the brain is respiration controlled?
The pons and medulla oblongata of the brainstem
What is the function of the central pattern generator?
Rhythmically activates the neurones in the dorsal respiratory group in the medulla which stimulates the motor neurones innervating the external intercostal muscles and diaphragm
What is the function of the pulmonary stretch receptors?
Stimulate the pons as an ‘off switch’, this prevents over inflation of the lung
What is the function of irritant receptors?
- stimulated by contact with foreign material
- initiate mechanisms designed to protect the airways
e. g. cough, increased mucus secretion, bronchoconstriction and shallow breathing
What monitors the movements of the respiratory muscles to enable their strength of contraction to be modulated
Muscle spindle stretch receptors and Golgi tendon organs in the respiratory muscles
What is monitored by peripheral chemoreceptors?
PaO2, PaCO2 and arterial [H+]
What is monitored by Central chemoreceptors in the brain?
PaCO2 only as this is the most important factor affecting respiration
Why don’t increases in systemic arterial [H+] affect the central chemoreceptors?
It cant cross the blood:brain barrier into the cerebrospinal fluid
What is the pH of a substance determined by?
The concentration of hydrogen ions present
What is the normal blood pH in domestic animals?
7.4
What pH defines acidosis and alkalosis?
<7.35 = acidosis >7.45 = alkalosis
What causes respiratory acidosis?
Increases in blood [H+] which are due to increased PaCO2 cause a drop in blood pH
What are the 3 mechanisms to reduce free hydrogen ions in the ECF?
- buffering
- lungs
- kidneys
By which reaction is most H+ formed?
The reaction between CO2 and H2O, forming H2CO3 which dissociates
What causes metabolic acidosis?
H+ accumulates when fixed acids (e.g. phosphoric acid H3PO4 which is produced during phospholipid and protein breakdown) dissociate in water
