21.16: Hormones of the Adrenal Glands
Adrenal hormones play a pivotal role in maintaining the body's electrolyte balance and orchestrating responses to stress, showcasing the intricate functions of the adrenal cortex and medulla.
The adrenal cortex, a powerhouse of hormone synthesis, generates over two dozen corticosteroid hormones. The zona glomerulosa produces mineralocorticoids, exemplified by aldosterone, influencing the electrolyte composition of body fluids. The synthesis of glucocorticoids such as cortisol and corticosterone occurs in the zona fasciculata. Aptly named for their impact on glucose metabolism, glucocorticoids accelerate glucose synthesis in the liver and promote glycogen formation in muscle and adipose tissue.
Additionally, the zona fasciculata produces small amounts of androgens, contributing to the development of pubic hair in adolescents and supporting muscle mass, blood cell formation, and the sex drive in adult women.
The adrenal medulla, on the other hand, houses chromaffin cells that secrete catecholamines in response to stress. Epinephrine and norepinephrine, continuously stored in vesicles and released at low levels through exocytosis, are crucial in promoting strength and endurance in skeletal muscles. Simultaneously, these hormones facilitate the breakdown of stored fat and glycogen in adipose tissue and the liver, providing the necessary energy for the body's heightened demands during stressful situations. The adrenal hormones finely tune the body's responses to ensure adaptability and survival.
