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KS4 Biology Hormones 1 of 31 © Boardworks Ltd 2004 Contents Hormones The endocrine system Endocrine glands Blood glucose regulation Summary quiz 2 of 31 © Boardworks Ltd 2004 Hormones and the endocrine system What exactly are hormones? What effect do hormones have on the body? To understand hormones you need to know about the endocrine system and how it works. 3 of 31 © Boardworks Ltd 2004 The endocrine system The endocrine system coordinates the body’s organs so that they work together. The endocrine system is based on the production of chemical messengers called hormones. Hormones are produced by glands (endocrine glands) in different parts of the body. These chemical messengers are produced in very small quantities and are transported in the blood. Hormones control body processes that require several organs of the body to interact for a combined effect. 4 of 31 © Boardworks Ltd 2004 What do hormones do? Hormones travel slower than nervous impulses but cause longer-lasting effects. They are delivered to all parts of the body but can have local effects. Hormones are used to stabilize the body’s internal environment through homeostasis and also coordinate longer-term processes such as growth and sexual development. Over- or under-activity of some endocrine glands can cause functional disorders such as diabetes. 5 of 31 © Boardworks Ltd 2004 Which body system? 6 of 31 © Boardworks Ltd 2004 Contents Hormones The endocrine system Endocrine glands Blood glucose regulation Summary quiz 7 of 31 © Boardworks Ltd 2004 Endocrine glands – thyroid Produces the hormone thyroxine: thyroid Regulates rate of metabolism. Excess causes hyperactivity. Deficiency causes weight gain and sluggishness. 8 of 31 © Boardworks Ltd 2004 Endocrine glands – adrenal glands Produce the hormone adrenalin. Adrenaline causes the ‘fight or flight’ response resulting in: Increased heart rate and breathing rate. adrenal glands 9 of 31 Blood diverted to the muscles. Increased respiration to increase the amount of glucose in the blood. © Boardworks Ltd 2004 Endocrine glands – reproductive organs In females, ovaries produce several hormones: oestrogen Controls the development of female secondary sexual characteristics. Regulates menstrual cycle. ovaries progesterone Thickens uterine wall. Prevents contractions until a baby is being born. 10 of 31 © Boardworks Ltd 2004 Endocrine glands – reproductive organs In males, testes produce the hormone testosterone: Promotes the development of male secondary sexual characteristics. testes 11 of 31 © Boardworks Ltd 2004 Endocrine glands – pancreas Produces the hormone insulin: Controls the conversion of blood glucose to insoluble glycogen, which is stored in the liver. Increases metabolic rate by stimulating cellular glucose uptake. pancreas Increases protein synthesis in some cells. Deficiency causes the condition “sugar diabetes”, where the blood sugar level is unregulated. 12 of 31 © Boardworks Ltd 2004 Endocrine glands – pancreas Produces the hormone glucagon: Controls the conversion of insoluble glycogen to glucose in the liver. pancreas 13 of 31 © Boardworks Ltd 2004 Endocrine glands – pituitary gland pituitary gland Produces several hormones: growth hormone Promotes bone and muscular growth. antidiuretic hormone (ADH) Controls reabsorption of water into the blood by kidneys. thyroid stimulating hormone (TSH) Controls the endocrine function of the thyroid gland. 14 of 31 © Boardworks Ltd 2004 Endocrine glands – pituitary gland pituitary gland Produces several specific hormones in females: follicle stimulating hormone (FSH) Causes the follicle in the ovary to develop and secrete oestrogen. luteinizing hormone (LH) With FSH and other hormones causes ovulation. 15 of 31 © Boardworks Ltd 2004 Name that gland 16 of 31 © Boardworks Ltd 2004 Match hormones to glands 17 of 31 © Boardworks Ltd 2004 Contents Hormones The endocrine system Endocrine glands Blood glucose regulation Summary quiz 18 of 31 © Boardworks Ltd 2004 Negative feedback Some hormones affect only one target organ, but most affect more than one. When the hormone has had the desired effect, further production of the hormone needs to be controlled. Hormone production is controlled by a process called negative feedback. The regulation of blood glucose level is an example of negative feedback. 19 of 31 © Boardworks Ltd 2004 Negative feedback – blood glucose Which of these parts of the body are involved in the negative feedback process that regulates blood glucose? The brain, the pancreas and the liver are all involved in regulating blood glucose. 20 of 31 © Boardworks Ltd 2004 Negative feedback – high blood glucose The brain detects the level of glucose in the blood. When the level of blood glucose increases above normal, what hormone does the pancreas release? increased blood glucose 21 of 31 © Boardworks Ltd 2004 Negative feedback – high blood glucose The pancreas is stimulated to release insulin. What effect does this have? The insulin stimulates the liver to take glucose from the blood and convert into glycogen, which is stored in the liver. increased blood glucose 22 of 31 insulin © Boardworks Ltd 2004 Negative feedback – high blood glucose The level of glucose in the blood decreases, causing the pancreas to stop producing insulin. What would happen if the pancreas kept on producing insulin? increased blood glucose insulin blood glucose returns to normal 23 of 31 © Boardworks Ltd 2004 Negative feedback – low blood glucose Negative feedback also occurs when the blood glucose level decreases below normal. This time the brain detects decreased blood glucose and so the pancreas is stimulated to release which hormone? decreased blood glucose 24 of 31 © Boardworks Ltd 2004 Negative feedback – low blood glucose The pancreas produces the hormone glucagon. Glucagon stimulates the liver to convert glycogen back to glucose and release this glucose into the bloodstream. decreased blood glucose 25 of 31 glucagon © Boardworks Ltd 2004 Negative feedback – low blood glucose The level of glucose in the blood increases, causing the pancreas to stop producing glucagon. What would happen if the pancreas kept on producing glucagon? decreased blood glucose glucagon blood glucose returns to normal 26 of 31 © Boardworks Ltd 2004 Blood glucose activity 27 of 31 © Boardworks Ltd 2004 When hormones go wrong – diabetes What happens if the pancreas is unable to produce the hormone insulin? Lack of insulin production means that the blood glucose level is unregulated and causes the condition known as “sugar diabetes”. After a person with diabetes has eaten, their blood glucose level increases. What happens to this glucose? The absence of insulin means that glucose is not converted to glycogen and stored in the liver, so the blood of a diabetic contains extra glucose. 28 of 31 © Boardworks Ltd 2004 When hormones go wrong – diabetes Glucose is essential for the body, so why is excess glucose a danger for people with diabetes? The ability of the kidneys to absorb glucose is also exceeded, so the excess is excreted in urine. When the glucose is used up, coma and convulsions may occur. So how is diabetes controlled? Regular insulin injections and a careful diet can control the condition. 29 of 31 © Boardworks Ltd 2004 Contents Hormones The endocrine system Endocrine glands Blood glucose regulation Summary quiz 30 of 31 © Boardworks Ltd 2004 Multiple-choice quiz 31 of 31 © Boardworks Ltd 2004