Signals from specialized heart tissue {sinoatrial node} {pacemaker} initiate and regulate heartbeat. Heart fibers beat by themselves. Blood carbon dioxide, blood thyroxin, blood epinephrine, vagus-nerve stimulation, body temperature, fever, and muscle stretching affect heart rate.
Biological Sciences>Zoology>Organ>Circulation>Parts>Heart>Node
4-Zoology-Organ-Circulation-Parts-Heart-Node
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Date Modified: 2022.0224