The Endocrine System
Exocrine glands Endocrine glands Hormone Pituitary gland Hypothalamus Thyroid Thyroxine Pancreas KEYWORDS Insulin Islets of Langerhans Goitre Thymus Thymosin
What are glands? Exocrine glands release their product into ducts or tubes. Examples: salivary glands, sweat glands, mammary glands Endocrine glands are ductless glands that produce hormones which are released directly into the bloodstream. Example: Pituitary gland, adrenal gland NOTE: pancreas are both endocrine and exocrine glands.
What are hormones? A chemical messenger produced by an endocrine gland. Most hormones are made from protein. Hormones are slow acting. NOTE: some hormones are also produced by other organs: stomach and placenta.
Comparison of nervous system and endocrine system NOTE: This question is asked a number of times in past exams. Nervous system: fast acting, messages mostly electrical, short lived. Endocrine system: Slower acting, messages are mostly chemical, long lasting.
Location of the endocrine gland system
Pituitary gland Known as the master gland. Controls other glands by releasing hormones. Produces the hormone: i) FSH: Follicle stimulating hormone ii) LH: Luteinising hormone. iii) GH: Growth hormone (causes bones to elongate and grow longer. The Endocrine System - YouTube
Robert Wadlow Over active pituitary gland:world's Tallest Man [Guinness Primetime] - YouTube
Hypothalamus This gland links the nervous and endocrine system. Releases hormones that control the pituitary gland. Produces the hormone anti-diuretic hormone (ADH). Causes water to be reabsorbed in the kidneys.
Pineal Located within the brain. Produces the hormone melatonin.
Thyroid Located in the trachea. Produces the hormone thyroxine (amino acid combines with iodine). Controls the rate of body reactions (metabolism)
Symptoms: Thyroxine deficiency Under production in children: i) low metabolic rates ii) Retarded mental and physical development (cretinism) Under production in adults: i) Reduced metabolic rate(tiredness, lack of energy, weight gain) ---- myxoedema ii) Thyroid gland swells (goitre)
Goitre
Corrective Measures New born babies are tested for low thyroxine levels. In adults, thyroxine tablets or iodine can be taken to prevent myxoedema. Thyroid Surgery (Thyroidectomy) - YouTube
Thyroxine excess Over production of thyroxine: i) Increased metabolic rate (bulging eyes, hunger, weight loss, anxiety) ii) Known as Graves disease
Parathyroids Make parathormone which causes the release of calcium from bones into the blood plasma.
Thymus Located behind the breastbone. Produces the hormone thymosin which causes lymphocytes (white blood cells) to mature. Thymus degenerates around puberty.
Adrenals Located at the top of kidneys. Produce hormones to cope with stress. Produce adrenaline (fright, fight, flight hormone) Adrenal Glands Animation - YouTube
Pancreas Are both exocrine and endocrine glands. YouTube What is the Pancreas? -
Pancreas Exocrine function: Produce enzymes that enter the duodenum through the duct. Endocrine function: Contain the Islet of Langerhans (group of cells) They produce insulin Insulin stimulates cells to absorb glucose from the blood, and store it as glycogen in the liver.
Hormone Supplements Insulin: Low insulin levels cause diabetes (failure of the islet of langerhans) Low insulin levels cause high glucose levels in the blood. Symptoms: thirst, loss of weight, tiredness Controlled: injections of insulin Why can t insulin be taken into the digestive system?
Hormone Supplements Anabolic steroids Drugs that build up protein (muscle) Increase size and strength of muscle Risks: liver damage infertility, inpotence Used to increase animal mass
Control of thyroxine level Negative feedback method: Correct level of one hormone has a negative effect on the previous step to produce that hormone.
Normal concentrations of throxine It inhibits the pituitary gland from releasing thyroid stimulating hormone (TSH). This means no further thyroxine is made. IF Thyroxine level drop, the pituitary glands produce TSH which causes more thyroxine to be made in the thyroid gland until it returns to normal.
Goitre Goitre is the enlargement of the thyroid gland. Occurs due to underproduction of thyroid (lack of iodine in diet) Usually TSH combines with iodine in thyroid to produce thyroxine. If there is lack of iodine TSH is stored in the thyroid.
Exam paper 2013 Question 10a, b:
Exam Paper 2011 Question 11c
Exam Paper 2010 Question 11c
Exam paper 2007 Question 15b: