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Hormones 5076 2015

Hormones for Science (Biology) 5076/5077 syllabus.

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Hormones 5076 2015

  1. 1. CHAPTER 15 Hormones In this chapter, you need to learn •define a hormone as a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver. •explain what is meant by an endocrine gland, with reference to the islets of Langerhans in the pancreas.
  2. 2. Lesson recap : • Animal possess 2 coordinated systems to response to external stimuli and internal changes. Nervous SystemNervous System Endocrine (Hormone) System Endocrine (Hormone) System
  3. 3. 2 Types of Glands (a) Exocrine glands (b) Endocrine glands. • Both glands secrete chemical substances. However the secretions of exocrine glands are carried away in a duct. (e.g sweat glands, salivary glands) • Endocrine glands have no ducts. The secretions are released directly into the bloodstream & carried throughout the body. 15.1
  4. 4. Types of glands • Ductless glands that transport their secretions via the bloodstream • Examples: adrenal glands, pituitary gland, and pancreas • Ducts present to transport secretions to target organs • Examples: sweat glands, salivary glands and pancreas Endocrine glands Exocrine glands Two Types of glands
  5. 5. Glands and the hormones they secrete Thyroid gland Secretes thyroxine. Thyroxine controls the rate of metabolism and influences physical development. Adrenal gland (medulla) Secretes adrenaline. Adrenaline has wide-ranging effects that prepare the body for ‘fight or flight’ situations. Pancreas Islets of Langerhans in the pancreas secrete insulin and glucagon that regulate the blood glucose concentration. kidney Hypothalamus An endocrine gland that regulates the secretion of some pituitary hormones. Ovaries (in females) Secretes oestrogen and progesterone. Testes (in males) Secretes testosterone. Pituitary gland Plays an important role as a ‘controller’. It secretes a number of hormones, which control the functions of several other endocrine glands. This is why the pituitary gland is often referred to as the ‘master gland’.
  6. 6. What is a hormone? • A hormone is a chemical substance that is produced in minute quantities by an endocrine gland. • It is carried by the blood and it changes the activity of one or more specific target organs. • A hormone is then destroyed by the liver. 15.1
  7. 7. Hormone Insulin & Glucagon • Insulin and glucagon are hormones that regulate the concentration of glucose in the blood. • Both are produced by the islets of Langerhans in the pancreas. • Insulin is released when blood glucose conc. is high. • It causes the liver to convert excess glucose to glycogen, hence reducing the blood glucose concentration. • Glucagon is released when blood glucose conc. is low. It causes the liver to breakdown glycogen to glucose hence increasing the blood glucose conc. 15.2
  8. 8. Effects: INSULIN GLUCAGON Effect: 15.2
  9. 9. Diabetes Mellitus • There are two types of diabetes : Type 1 & Type 2 15.3
  10. 10. Diabetes Mellitus • In both cases, body is unable to control blood glucose concentration . • As a result, blood glucose becomes too high for kidney to completely reabsorb all the glucose. • Glucose is not absorbed but excreted in urine. • Diabetics are at risk developing infections at face and feet, may affect eyes leading to blindness. 15.3
  11. 11. Diabetes Mellitus Sign of diabetic patients: • High concentration of glucose in blood and urine. • Body become weak because no reserve of glycogen. • Persistently high blood glucose level • Healing of wounds is slow or difficult 15.3
  12. 12. Treatment • Diet • Exercise • Insulin injection 15.3
  13. 13. Effects of insulin secreted Amount of insulin secreted Effects on the body Normal Decreases blood glucose concentration by : (a)Increasing the permeability of cell membranes to glucose, thereby increasing rate of glucose uptake by cells. (b)Stimulating the liver and muscle cells to convert excess glucose into glycogen for storage. (c)Increasing oxidation of glucose during tissue respiration.
  14. 14. Effects of insulin secreted Amount of insulin secreted Effects on the body Lack of secretion Glucose cannot be stored or utilized by cells, so blood glucose concentration rises. Some glucose is subsequently lost in the urine. This leads to a disease known as ‘diabetes mellitus’. Since muscle cells have no reserve of glycogen, the body grows weak and continuously loses weight. The body oxidizes fats increase of glucose to release energy.
  15. 15. Effects of insulin secreted Amount of insulin secreted Effects on the body Over-secretion of insulin • Abnormal decrease in blood glucose concentration. • Low blood glucose concentration results in a condition known as ‘shock’. • Coma and death may follow.
  16. 16. A diabetic mum gave birth to the heaviest baby (8.7 kg) in world record in Indonesia. According to the doctor, the baby's extreme weight was the result of excessive glucose from his mother during pregnancy.
  17. 17.  1. What is an effect of insulin? A   decreased cell respiration B   decreased absorption of glucose by cells C   increased absorption of glucose D   increased synthesis of glycogen                       Answer :   D
  18. 18. 2. The graphs show the concentrations of glucose and insulin in  the blood of a healthy person. Which graph shows the changes  expected after a meal containing starch?                        Answer :  A 
  19. 19. 3. What of the effects below is not due to  insulin  secretion on the body? A.  Conversion of glucose to glycogen for storage. B.Oxidation of glucose during tissue respiration        increases. C.  Oxidation of fats to produce energy. D.  Permeability of cell membranes to glucose increases.                     Answer : C
  20. 20. Nervous System Nervous System Endocrine System Endocrine System
  21. 21. Comparing Hormonal & Nervous System • Both required stimulus and serve as means of coordination and response. • What are the differences between how they work in the aspects of: a. Form of messages b. Response time c. Effectors 15.5
  22. 22. Hormone System Nervous System Involves chemical  substances (hormones) Involves electrical signals  (nerve impulses) Hormones carried by  blood Impulses carried by  neurones Usually slow responses Fast responses Responses can be short- lived or long-lived Responses are short-lived Involuntary May be voluntary or  involuntary Can affect more than one organ. Effects are usually localised Differences 15.5