Hormones

• Hormones are produced in endocrine glands.
• Hormones have a general role in the body.
• Hormones are transported around the body by the blood.
• The production and release of some common hormones can be described from their endocrine glands such as the pituitary gland, thyroid gland, pancreas, adrenal glands, ovaries and testes.
• The target organs of some common hormones can be identified.
• The nervous system enables us to quickly respond to changes in our surroundings.
• The hormonal system uses chemical messengers called hormones, which are carried in the blood.
• Hormones target cells in other parts of the body and cause them to change the way they work.
• The hormonal system is slower compared to the nervous system.
• The response of the hormonal system is longer lasting.
• Hormones are released by special organs called glands.
• A gland is an organ that contains cells which produce particular substances.
• An exocrine gland releases what it produces on to a surface, often through a tube or duct.
• Examples of exocrine glands include sweat glands in the skin, and the parts of the pancreas that release digestive enzymes and other substances into the gut.
• An endocrine gland releases what it produces into the blood.
• Endocrine glands produce hormones.
• The pituitary gland releases many hormones, including ACTH, FSH, LH and growth hormone.
• During exercise, when the heart beats faster, the blood concentration of adrenalin increases by about 10 times.
• The blood concentration of adrenalin during exercise can be calculated in micrograms per dm3.
• After a shock, heart rate is much faster because the blood concentration of adrenalin may be more than 0.5 μg/dm3.
• The blood concentration of adrenalin after a shock may be more than 0.5 μg/dm3, which is at least 50 times larger than the resting concentration.
• Unless more hormone is released from the endocrine gland, its concentration in the blood will fall due to excretion in urine from the kidneys, some hormones being taken into cells and broken down into other substances there, and some hormones being broken down in the blood.
• Adrenalin released during exercise or a shock may be cleared from the blood in a few minutes, while it may take a week for the blood concentration of thyroxine to reduce by a half.
• The nervous system is much faster, and is directed to a particular effector (e.g. a muscle).
• The hormonal system is slower and one hormone may affect many different target cells.
• Insulin is produced by the pancreas.
• The pituitary gland produces ACTH and growth hormone.
• Adrenaline is produced by the adrenal gland.
• Sex hormones such as oestrogen and testosterone are released by reproductive organs but they stimulate the release of growth hormone.
• The sex hormones oestrogen and testosterone are released by reproductive organs but they stimulate the release of growth hormone.
• The release of these sex hormones will increase when there are changes in testosterone levels with age.
• The thyroid gland produces several hormones, including thyroxine.
• The pancreas contains cells that produce insulin and others that produce glucagon.
• The ovaries produce the sex hormones oestrogen and progesterone.
• The testes release the sex hormone testosterone.
• The adrenal glands release several hormones, including adrenalin.
• The target organs of hormones can be identified.
• The nervous system enables us to quickly respond to changes in our surroundings.
• The hormonal system uses chemical messengers called hormones, which are carried in the blood.
• Hormones target cells in other parts of the body and cause them to change the way they work.