Structural adaptations<span> are physical features of an organism like the bill on a bird or the fur on a bear. Other </span>adaptations<span> are behavioral. Behavioral</span>adaptations<span> are the things organisms do to survive. For example, bird calls and migration are behavioral</span>adaptations<span>.</span>
Heart rate. <span>From this site, the two channels of the autonomic nervous system originate the sympathetic and parasympathetic components. The sympathetic components increase heart rate by releasing the neural hormone catecholamines - epinephrine and norepinephrine. These hormones are cardio accelerators. Acceleration of the heart rate is called tachycardia.</span>
Apparently it is ATP as deduced from the last line of text and no model to refer to.
I'm not sure what you're asking, but if you're looking for a word to describe this change its "mutation"