BRAINCAKEThe Cardiovascular Centre in the Medulla
Heart muscle is myogenic: the sinoatrial node (SAN) generates impulses without any nervous stimulation. However, the rate at which the SAN fires is adjusted by the cardiovascular centre in the medulla oblongata of the brain, so that heart rate matches the body's needs.
The cardiovascular centre is part of the autonomic nervous system, so it works without conscious thought. It has one part that increases heart rate and one that decreases it, and both connect to the SAN.
• To increase heart rate, impulses are sent along a sympathetic neurone, the accelerator nerve. Its endings release the neurotransmitter noradrenaline at the SAN, which increases the frequency of excitation.
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