Final answer:
The adrenal medulla contains chromaffin cells, which secrete the hormones epinephrine and norepinephrine, key agents in the body's stress response, affecting heart rate, blood pressure, and energy metabolism.
Step-by-step explanation:
The adrenal medulla is composed of specialized neuroendocrine cells known as chromaffin cells. These cells originate from the autonomic nervous system and are responsible for the production and secretion of catecholamines, which include the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline). The adrenal medulla serves as a crucial part of the body's response to stress, significantly influencing various physiological processes such as heart rate, blood pressure, and glucose metabolism.
Epinephrine is the predominant hormone produced by the adrenal medulla, accounting for approximately 75 to 80 percent of its secretions. This hormone, along with norepinephrine, is released into the bloodstream in response to stress and works to prepare the body for 'fight or flight'. These hormones increase heart rate, enhance blood flow to muscles, raise blood glucose levels, and accelerate the breakdown of stored fat, thereby equipping the body with immediate energy and heightened awareness to react to the stressor.
The adrenal medulla is innervated by preganglionic autonomic nerve fibers from the central nervous system. Despite being called preganglionic, these fibers do not target a ganglion but directly connect with the chromaffin cells in the adrenal medulla, further illustrating its role as an extension of the sympathetic nervous system and reinforcing its importance in the body's stress response.