AP BIOLOGY

Detailed explanation-1: -A humoral stimulus refers to the control of hormone release in response to changes in extracellular fluids such as blood or the ion concentration in the blood. For example, a rise in blood glucose levels triggers the pancreatic release of insulin.

Detailed explanation-2: -Hormonal stimuli refers to the release of a hormone in response to another hormone. A number of endocrine glands release hormones when stimulated by hormones released by other endocrine glands. For example, the hypothalamus produces hormones that stimulate the anterior portion of the pituitary gland.

Detailed explanation-3: -When the release of a hormone is regulated by the variation in the concentration of extracellular fluids, such as blood or the ions in the blood, it is called a humoral stimulus. The release of parathyroid hormone (PTH) is stimulated by the low levels of calcium ions in the blood. This is an example of humoral stimuli.

Detailed explanation-4: -Hormone production and release are primarily controlled by negative-feedback. In negative feedback systems, a stimulus elicits the release of a substance; once the substance reaches a certain level, it sends a signal that stops further release of the substance.

Detailed explanation-5: -Chemical Nature of Hormones Chemically, hormones may be classified as either proteins or steroids. All of the hormones in the human body, except the sex hormones and those from the adrenal cortex, are proteins or protein derivatives.