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 ADHAnti 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 sexual development
Controls release of Ca from bones into blood plasma
Differences between endocrine & nervous systems
NERVOUS SYSTEM 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
1. Growth hormone can be used as a body building supplement
2. Oestrogen can be used to regulate the menstrual cycle
3. Insulin in the treatment of diabetes4. HRT hormone replacement therapy
to reduce the effects of the menopause
Negative feedback control of thyroxine levels – HIGHER LEVEL ONLY
1. When the level of thyroxine is LOW, thyroid releasing hormone TRH is produced by the hypothalmus
2. This causes the release of thyroid stimulating hormone TSH in the pituitary
3. TSH stimulates the secretion of thyroxine
4. When the amount of thyroxine reaches a certain level, the hypothalmus stops secreting TRH
5. When the level of thyroxine falls again the cycle repeats
6. This is an example of a negative feedback mechanism
THYROXINE control – Feedback
