Final answer:
The correct answer is b. An increased heart rate caused by the release of adrenaline from the adrenal glands is an example of endocrine signaling.
Step-by-step explanation:
An increased heart rate caused by the release of adrenaline from the adrenal glands, which are located just above the kidney, is an example of endocrine signaling.
Endocrine signaling involves signals from distant cells that originate from endocrine cells, such as the adrenal glands. These signals, called hormones, are produced in one part of the body but affect other body regions some distance away. In the case of increased heart rate, the adrenal glands release adrenaline into the bloodstream, which then binds to receptors in the heart to stimulate the signaling pathway and increase heart rate.
In contrast to endocrine signaling, autocrine signaling acts on the signaling cell itself, paracrine signaling acts on nearby cells, and contact-dependent signaling requires direct contact between cells.