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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