The Endocrine System Chapter 36

ENDOCRINE GLANDS

ENDOCRINE SYSTEM: Set of hormone secreting glands within an animal’s body ENDOCRINE GLAND: Is a ductless gland that makes & secretes specific chemical messengers (hormones) into the blood

EXOCRINE GLAND: Secretes their chemicals into ducts that carry them to their destination eg sweat gland, salivary gland, gastric gland HORMONE: Is a chemical messenger secreted by an endocrine gland into the blood which distributes it through out the body altering the activity of specific target tissues

GLAND HORMONE FUNCTION pituitary ADH Anti diuretic hormone Growth hormone Thyroid stimulation hormone TSH Increases H2O absorption in the kidney Speeds up growth Causes thyroid gland to secrete thyroxine increasing cell metabolism

GLAND HORMONE FUNCTION Pituitary Thyroid Gonad stimulating hormone GSH Thyroxine Stimulates gonads (ovaries & testes) to secrete sex hormones Regulates metabolism, growth & development

GLAND HORMONE FUNCTION Adrenal Pineal Pancreas Adrenaline Melatonin insulin Prepares the body for emergency responses Controls body rhythms Regulates the amount of sugar in the blood

GLAND HORMONE FUNCTION Thymus Ovaries Testes Parathroids Thymosine Oestrogen & progesterone Testosterone Parathorome Matures WBC Controls sexual development Controls release of Ca from bones into blood plasma

Differences between endocrine & nervous systems ENDOCRINE SYSTEM Electrical – chemical message Chemical message Carried by nerves Carried by blood Impulses target specific sites Messages can be sent to many regions in the body Response is fast acting Response is slow acting Effects are short term Effects are long term

Growth Hormone Deficiency Symptoms: Lower than normal height, immature face Excess symptoms: Over enlargement of body tissue including bones in hands, feet, face & skull Corrective measures: (for deficiency) Injections of growth hormone

Hormone Supplements– know 2 Growth hormone can be used as a body building supplement Oestrogen can be used to regulate the menstrual cycle Insulin in the treatment of diabetes HRT hormone replacement therapy to reduce the effects of the menopause

Negative feedback control of thyroxine levels – HIGHER LEVEL ONLY When the level of thyroxine is LOW, thyroid releasing hormone TRH is produced by the hypothalmus This causes the release of thyroid stimulating hormone TSH in the pituitary TSH stimulates the secretion of thyroxine

4. When the amount of thyroxine reaches a certain level, the hypothalmus stops secreting TRH When the level of thyroxine falls again the cycle repeats This is an example of a negative feedback mechanism

THYROXINE control – Feedback