Various endocrine glands are stimulated to manufacture and release their hormones by three main types of stimuli -Hormonal, Humoral and Neural.
Hormonal is the most common it releases hormones in response to hormones produced by other endocrine organs. For example: the hypothalamic secrete hormones that stimulate the anterior pituitary, which stimulate glands to secret hormones (thyroid gland, adrenal cortex and gonads).
Humoral secret hormones in direct response to changing blood levels of ions and nutrients. Declining blood Ca2+ concentration stimulates the parathyroid glands to secrete PTH (parathyroid hormone) PTH causes Ca2+ concentrations to rise and the stimulus is removed. Other hormones releases due to humoral are calcitonin and insulin.
Neural, in some cases, nerve fibers stimulate hormone release. For example, catecholamine (epinephrine and norepinephrine) is released during times of stress by stimulation of the adrenal medulla by the sympathetic nervous system. Also, the hypothalamus stimulates the release of oxytocin and anti-diuretic hormone by neural stimulation.
No comments:
Post a Comment