Hormone (amines and peptide or protein hormones) are water-soluble and act on the surface of target cells via second messengers; steroid hormones, being lipid-soluble, move through the plasma membranes of target cells (both cytoplasmic and nuclear) to act within their nuclei. Hormone secretion may occur in many tissues. Endocrine glands are the cardinal example, but specialized cells in various other organs also secrete hormones. Hormone secretion occurs in response to specific biochemical signals from a wide range of regulatory systems. For instance, serum calcium concentration affects parathyroid hormone synthesis; blood sugar (serum glucose concentration) affects insulin synthesis; and because the outputs
Stress in early childhood the skin and gut. This allows a sufficient amount of blood to access the brain and muscles. Also, epinephrine initiates the breakdown of glycogen in the liver, in turn increasing blood glucose levels. This energy source allows humans to enact defensive responses due to stress. In the human body, the steps that lead to the release of glucocorticoids such as cortisol begin with the release of corticotropin releasing hormone (CRH) and arginine vasopressin (AVP). These hormones travel through the blood vessels to the anterior pituitary gland of the brain. At this location, adrenocorticotropic hormone (ACTH) is released. ACTH binds to