maintenance of a constant internal environment independent of external conditions

examples of homeostasis

• control of blood glucose levels

• control of body temperature

• osmoregulation

• control of water and salt content of body fluids

• control of ph of body fluids

feedback system

• a sequence of events in which information about the status of a situation is continually reported to a central control system and corrective mechanism applied as a response

• negative feedback

• negative feedback maintains levels

• positive feedback

• example of positive feedback

  • secretion of the hormone oxytocin at the end of pregnancy

Hormones

• chemical messengers

• released directly into the blood from endocrine glands (no duct)

• travel to target cells or organs

• only target cells or organs have the receptor specific to the hormone

Endocrine and Exocrine glands

• endocrine glands produce hormones that are directly secreted into the blood

• exocrine glands produce substances that are secreted into ducts that are used to transport the secretions to their point of use eg sweat glands

• some organs are both endocrine and exocrine eg the pancreas different areas producing different substances

• research on glands ⭐

  • hypothalamus - TRH,GnRH,GHRH and CRH are secreted to maintain the body’s internal balance aka homeostasis

  • pituitary gland - is known as the master gland because it signals other glands to release hormones . It produces TSH,ACTH,FSH and LH

  • parathyroid - it regulates the calcium levels in the blood and it triggers the bones to produce calcium

  • thymus - produces white blood cells called T lymphocytes and it only produces these T cells until we become teenagers and it produces thymosin a hormone necessary for T cells

  • adrenal glands - they produce a lot of hormones but the main ones are epinephrine(adrenaline) and norepinephrine (noradrenaline) and it regulates the metabolism,immune system,blood pressure,response to stress and other essential functions

  • testis - primary male sex hormone essential for producing sperm and they produce testosterone

  • ovaries - they contain the egg cells needed for reproduction and they produce progesterone and estrogen

  • pancreas - produces insulin and glucagon and it helps the body to regulate the blood sugar levels and appetite

  • thyroid - produces hormones that help regulate the body’s metabolism and it produces thyroxine

  • pineal gland - revive and convey information about the current light-dark cycle from the environment and it produces melatonin,vasopressin,gastrin and histamine