The Endocrine System, Overview, Animation

The endocrine system is one of the two systems  that are responsible for communication and   integration between various body tissues,  the other being the nervous system. Endocrine   communication is achieved by means of chemical  messengers called hormones. Hormones are produced   in endocrine glands and secreted into the  bloodstream to reach body tissues. A hormone   can travel wherever the blood goes, but it can  only affect cells that have receptors for it.   These are called target cells. There are 2 major  types of hormones: steroid hormones derived from   cholesterol and are lipid-soluble; and non-steroid  hormones derived from peptides or amino-acids   and are water-soluble. Lipid-soluble steroid  hormones can cross the cell membrane to bind   to their receptors inside the cell, either in the  cytoplasm or nucleus. Steroid hormone receptors   are typically transcription factors. Upon forming,  the hormone/receptor complex binds to specific DNA   sequences to regulate gene expression, and thus  mediating cellular response. On the other hand,   water-soluble non-steroid hormones are unable  to cross the lipid membrane and therefore must   bind to receptors located on the surface of the  cell. The binding triggers a cascade of events   that leads to production of cAMP, a second  messenger that is responsible for cellular   response to hormone. It does so by changing  enzyme activity or ion channel permeability.  Major endocrine glands include: the  hypothalamus, pituitary gland, pineal gland,   thyroid and parathyroid glands, thymus, adrenal  gland, islets of the pancreas, and testes in men   or ovaries in women. The endocrine system  also includes hormone-secreting cells from   other organs such as kidneys and intestine. Except for the hypothalamus and the pituitary,   different endocrine glands are involved in  different, more or less independent, processes.   For example, the pancreas produces insulin and  glucagon that keep blood sugar levels in check;   the parathyroid glands produce hormones that  regulate calcium and phosphorus; thyroid hormones   control metabolic rates; while the ovaries and  testes are involved in reproductive functions.   On the other hand, the hypothalamus and  pituitary gland play a more central,   integrative role. The hypothalamus is also part  of the brain. It secretes several hormones, called   neuro-hormones, which control the production  of other hormones by the pituitary. Thus,   the hypothalamus links the nervous system  to the endocrine system. The pituitary is   known as the master gland because it controls  the functions of many other endocrine glands.  A major role of the endocrine system is to  maintain the body’s stable internal conditions, or   homeostasis, such as blood sugar levels or serum  calcium levels. To do this, it utilizes negative   feedback mechanisms, which work very much like a  thermostat: the heater is on when the temperature   is low, off when it’s high. For example, when  blood glucose level is high, such as after a meal,   glucose induces insulin release from the pancreas.  Insulin helps body cells consume glucose, clearing   it from the blood. Low blood glucose can no longer  act on the pancreas, which now stops releasing   insulin. Another example is the regulation of  thyroid hormones levels which are induced by a   pituitary hormone called thyroid-stimulating  hormone, TSH. TSH, in turn, is under control   of thyrotropin-releasing hormone, TRH, from the  hypothalamus. When thyroid hormone levels are   too high, they suppress the secretion of TSH and  TRH, consequently inhibiting their own production.

Channel: Alila Medical Media

Views: 923,624

Keywords: yt:quality=high, steriod receptors, steroid hormones, mechanism of action, nonsteroid hormones, peptide, transcription factors, gene expression, cellular response, cyclic AMP, parathyroid glands, pancreas, overview, basics, insulin, blood sugar levels, master gland, anatomy, animated, biology, endocrine system, endocrinology, homeostasis, hypophysis, hypothalamic, medical, medicine, neuroendocrine, regulation of hormones, science, for patient education, negative feedback loop

Id: vLdNX5Te1Xo

Length: 4min 52sec (292 seconds)

Published: Mon Nov 05 2018