Control of Breathing Flashcards
What is the feedback loop of breathing?
Efferent output: Ventilation, glandular and smooth muscle control–> Feeback:gas exchange–> Afferent input: Hiher CNS centre (behaviour), lung receptors (mechanics), chemoreceptors (arterial blood)–> Central integration: pons and medulla–> efferent output
Describe how rhythmogenesis works in the medulla/pons
A central rhythm generator is influenced by suprapontine modulators, neuromodulators and sensory modulators. These combine to make a central pattern generator. The pattern consists of a frequency, a depth and inspiratory/expiratory ratio for timing
What is ordines curse?
A point mutation in the rhythm generator, dampening of response to new threshold for PCO2 and she will not breath at night
How is hypoxia sensed?
Chemoreceptors, unsure exactly how, but peripherally aortic bodies and carotid bodies.
Aortic bodies- sense O2, CO2 and pH. Transmit via vagus and are weak chemoreceptors.
Carotid: Sit at bifurcation of carotid arch. Account for all hypoxic drive, not necesarily hypocapnic. Feed via glossopharyngeal nerve to brainstem.
What will cause a increase in ventilation? Sensed from carotid receptors?
Low O2, High CO2 thus high pH
What are the carotid bodies more sensitive to?
PO2, not PCO2 unless the Po2 is supressed.
Describe the integreated response to hypoxia
Lower PO2 increases ventilation. This lowers PCO2 thus slowing the response as the receptors are engaged.
What happes during hypercapnia?
Increased PCO2 drives CO2 into the CSF, increasing H+ concentration, which stimulates the medulla to increase ventilation.
Why in a patient with damaged lungs (pneumonia/ COPD) when he is hypercapnic and hpoxic, when given oxygen does his CO2 rise?
The O2 releases hypoxic pumonary vasoconstriction, thus CO2 that is in better ventilated areas of the lung doesnt blow off. Removing hypoxia removes drive to breathe.
What are the 3 kinds of lung receptors?
Irritant (RAR); Stretch (SAR); J and C receptors
irritant receptors
Rapid acting, respond to irritants like noxious gases and particles. Found in the carina and large bronchi. Does cough reflex, bronchospasms and increase mucus. Also mechanoreceptors stiff lung)
Stretch receptors
Are slow adapting response, in smooth muscle of bronchi and posterior trachea. They inhibit further inflation, relaxes the muscle and decreases breathing frequency.
J and C receptors
Found in bronchial interstitium and next to capillaries.
Respond to histamine, serotonin, bradykinin, increased fluid.
Stimulation results in rapid shallow breathing, bronchoconstriction and mucus production. Tell us when to slow down.
