lisämunuaisydin

Lisämunuaisydin, also known as the adrenal medulla, is the inner part of the adrenal gland, one of the endocrine glands located on top of each kidney. It is a key component of the sympathetic nervous system's "fight-or-flight" response. Unlike the adrenal cortex, which produces steroid hormones, the adrenal medulla is composed of chromaffin cells.

These chromaffin cells synthesize and secrete catecholamines, primarily epinephrine (adrenaline) and norepinephrine (noradrenaline), directly into the bloodstream. These hormones play crucial roles in regulating the body's response to stress, physical activity, and emergencies. When the body perceives a threat, the sympathetic nervous system stimulates the adrenal medulla to release catecholamines.

The effects of epinephrine and norepinephrine are widespread. They increase heart rate and blood pressure, divert blood flow to muscles and the brain, elevate blood glucose levels by stimulating glycogenolysis and gluconeogenesis, and dilate airways. This coordinated physiological response prepares the body for immediate action.

While the adrenal medulla is primarily under neural control from the sympathetic nervous system, it also has some intrinsic regulatory mechanisms. Disorders affecting the adrenal medulla can lead to conditions such as pheochromocytoma, a tumor that causes excessive secretion of catecholamines, resulting in symptoms like severe hypertension, headaches, and palpitations. The adrenal medulla's function is vital for short-term survival and adaptation to challenging situations.