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    Can someone explain how breathing and heart rate is controlled for me? Many thanks.

    Breathing: inspiratory system in the medulla causes the intercostal & diaphragm muscles to contract, this is detected by stretch receptors, which sends a message to the medulla to inhibit the inspiratory system, causing the muscles to relax... exhailation. The rate is increases when a rise in CO2 level in the blood is detected by chemoreceptops (in carotid & aortic bodies & medulla).. impulses are sent to the medulla to increase the rate.

    Heart rate: The sionatrial node (SAN) is myogenic and initiates contraction in the heart in the right atrium, the impulses then pass to the atrioventricular node, down the bundle of His (in the septum) and to the purkinji fibres in the apex, causing an upward contraction from the ventricles. There is a slight delay during spreading of impulses to allow the atrium to fully empty before the ventricles contract so the blood doesnt squish everywhere! The rate is increased in the same way as breathing.

    Hope this helps
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Updated: June 19, 2005
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