Final answer:
A hormone is a signaling molecule produced by cells that travels through the bloodstream to target cells with specific receptors, initiating various physiological responses crucial for homeostasis.
Step-by-step explanation:
The chemical produced by cells in the body, which circulates in the bloodstream and affects a wide range of functions by acting on one or more target cells, is called a hormone. The targets of hormones are specific cells with receptors meant for these signaling molecules. Non-steroid hormones, a type of endocrine hormone made of amino acids, typically bind with a receptor on the plasma membrane of a target cell and initiate a sequence of events within the cell to produce a response.
Hormones are crucial for regulating physiological processes, including human reproduction, growth and development, metabolism, and fluid balance. Different hormones have specific targets and contribute to the regulation of water levels by signaling the kidneys, or control metabolism by affecting glucose and lipid metabolism in various cells. This intricate hormonal signaling is vital for maintaining homeostasis within the body.