Homeostasis

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

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