IGCSE Biology Chapter 14 Homeostasis 2024 PDF

CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS by dr. MOATAZ BEDEWEY 0564559225 CELL :01110983031 00201110983031 [email protected] CHAPTER 14 HOMEOSTASIS...

CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS by dr. MOATAZ BEDEWEY 0564559225 CELL :01110983031 00201110983031 [email protected] CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS 1.Hormones organic substances which produced in small amount and work in another part which is called target Organ. 2.Insulin hormone is important for decreasing the blood glucose level and this is produced from the pancreas 3.Adrenaline is very important hormone which is called the fight or flight 4.Hormone works in the opposite way off insulin hormone 5.There are two types of diabetes type one which is inherited the pancreas cannot produce enough insulin. 6.Homeostasis homeostasis is to maintain the Internet environment of the organism’s body constant. 7.vasodilation is a process which is responsible for decreasing temperature in case of hot weather. 8.vasoconstriction is a process responsible for increasing and keeping temperature in a cold weather. CELL :01110983031 00201110983031 [email protected] CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS Hormones 1. Hormones Hormones Are organic substances secreted in small amounts by endocrine glands into the blood stream directly to reach and affect certain organs or tissues (known as target organs or tissues) its function is to alter the activity of the target organs and then destroyed in liver. NOTICE Hormones are also called chemical messengers because they can carry the messages from one part of the body to another to respond in a particular way. ICE Examples of hormones 1-Insulin. 2-Adrenaline 3-glucagon. CELL :01110983031 00201110983031 [email protected]  CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS 1. Insulin 1.A hormone secreted by certain cells in the pancreas called Islets of Langerhans 2.It is a protein 3.Its function is to lower the blood glucose level. How insulin can lower blood glucose level when its level becomes normal (a)Stimulates the liver cells to store excess glucose in the form of glycogen (b)Stimulates the muscle cells to store excess glucose in the form of glycogen (c)Stimulates the conversion of excess carbohydrates to fats (d)Stimulates the body cells to use glucose 2. Adrenaline is a hormone secreted by the adrenal glands which are found above the kidneys- It is known as fight, and flight hormone as it prepares the body for action in the following ways: a) Increases the rate of heat beats b) Increases the blood pressure. c)increases the rate of breathing. d) Causes constriction of the blood vessels in skin and digestive system to increase flow of blood to muscles. e) Converts glycogen stored in liver to glucose and fats to fatty acids (The above actions to provide the muscles with enough food and oxygen to produce the CELL :01110983031 00201110983031 [email protected]  CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS energy required for rapid and efficient response and also to allow blood to carry away the waste products of this metabolism. 3. Glucagon hormone  It is also secreted by Islets of Langerhans in pancreas-It is secreted when blood glucose level drops below normal.  It stimulates liver to break down amount of stored glycogen into glucose until glucose level becomes normal. DIABETES Type 1 diabetes 'insulin-dependent' diabetes: Pancreas unable to produce enough insulin so that blood glucose level may rise to such a high level that it is excreted in the urine, or fall so low that the brain cells cannot work properly and the person goes into a coma It is an autoimmune disease which means that immune system attacks all the produce insulin and destroy them CELL :01110983031 00201110983031 [email protected]  CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS EXPLAIN Why insulin cannot be taken through mouth? Insulin cannot be taken through mouth but as an injection because insulin being protein will be digested by the effect of proteases if taken through mouth Symptoms of diabetes 1.Feeling tired. 2.feeling very thirsty. 3.frequent urination and weight loss, because the body starts to break down muscle and fat. 4.It is dangerous as it damages tissues especially in brain and heart as it decreases water potential in blood as a result of this water moves from body cells to blood causing the cells.to shrink and die. Treatment of diabetes 1.carefully regulated diet to keep the blood sugar within reasonable limits 2.They should have regular blood tests to monitor the blood sugar levels and take regular exercise. 3.Insulin injection according to the need. CELL :01110983031 00201110983031 [email protected]  CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS How hormones improve sporting performance Anabolic steroids Steroid hormones include the reproductive hormones such as estrogen, progesterone and testosterone. Are known as anabolic as they stimulate building of large molecules from smaller ones such a building of proteins from amino acids. Ex: Testosterone Causes more proteins to be made in muscles causing muscles to be larger and stronger. Explain the importance of the anabolic test before competitions? 1. It gives someone an unfair advantage..2. Can lead to health risk such as decreasing efficiency of the immune system and liver damage. CELL :01110983031 00201110983031 [email protected]  CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS Homeostasis It is to maintain the internal environment of an organism's body constant Organs responsible for homeostasis 1-Lungs: keep the conc. of CO2 and O2 constant. 2-Skin : Regulates body temperature. 3-Kidneys : Regulate the conc. of water and urea. 4-Liver : Regulates the blood sugar level 1-Evaporation of sweat. 2-Excretion of warm feces. 3-Excretion of warm urine. 4-Expiration of warm air. CELL :01110983031 00201110983031 [email protected]  CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS Regulating body temperature  Part in the brain called hypothalamus act as sensor.  If the temperature rises above the normal, it sends messages along nerves to the parts of the body to reduce temperature.  If the temperature becomes lower than normal, the opposite takes place. Role of skin regulating body temperature 1. In case of over-cooling:  It means that the blood vessels of skin constrict, this reduces excretion of sweat and heat loss from warm blood when it comes near the body surface CELL :01110983031 00201110983031 [email protected]  CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS  The hair erector muscles contract to erect hair  Hair traps air  (Air is a bad conductor of heat therefore they reduce the rate of heat loss) (Fats are bad conductors of heat therefore they reduce the rate of the heat loss) 2. In case of over-heating  Means to keep the blood vessels in the skin wider This helps in getting rid of the excessive heat from the warm blood to the surrounding.  This helps in getting rid of the excessive heat by reducing the amount of trapped air that acts as an insulator.  Evaporation of sweat requires heat energy, an amount of this energy is gained from the body decreasing its temperature. CELL :01110983031 00201110983031 [email protected]  CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS Negative feedback It is the process by which the different internal conditions of the body such as level of circulating hormones is controlled, to maintain homeostasis. This process includes sequence of steps 1. A sense organ, detects a change. 2. A control center sends a message to the responding organ to decrease or increase its production. 3. The information form the responding organ is detected by the sense organ. Example A. When blood glucose level increases Pancreas secretes the hormone insulin to stimulate the body cells to use glucose and the liver cells to store it as glycogen. When the blood glucose returns to its normal level secretion of insulin is switched off. B. When glucose level decreases Pancreas secretes the hormone glucagon which stimulates the conversion glycogen to glucose to be added to the blood stream. When the blood glucose returns to the normal level, secretion of glucagon is inhibited. CELL :01110983031 00201110983031 [email protected]  CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS Describe adrenaline as the hormone secreted in ‘fight or flight’ situations and its effects, limited to increased breathing and pulse rate and widened pupils. 1. There are two adrenal glands, one above each kidney, They make a hormone called adrenaline. 2. When you are frightened, excited, your brain sends impulses along a nerve to your adrenal glands which secretes adrenaline into your blood. 3. Adrenaline cause your heart beat faster, supplying oxygen to your brain and muscles more quickly. 4. This provides them more energy for fighting or running away. 5. Adrenaline also increases breathing rate, so that more oxygen can enter the blood in the lungs. 6. Adrenaline also causes the pupils in the eye to widen (allows more light enter the eye so can see danger clearly). Give examples of situations in which adrenaline secretion increases? 1. Examination. 2. You see something scary. State the functions of insulin, oestrogen and testosterone INSULIN: Reduces the concentration of glucose in the blood OESTROGEN: Causes development of female secondary sexual characteristics, helps in the control of the menstrual cycle. Testosterone Causes development of male secondary sexual characteristics CELL :01110983031 00201110983031 [email protected] CHAPTER 14 HOMEOSTASIS IGCSE BIOLOGY GARDENS Discuss the role of the hormone adrenaline in the chemical control of metabolic activity, including 1. increasing the blood glucose concentration and pulse rate. 2. Adrenaline is secreted by adrenal glands located one above each kidney. 3. Adrenaline helps us to deal with danger by increasing the heart rate. 4. Thus, supplying oxygen to brain and muscles more quickly, this increase the rate of metabolic activity and gives more energy for fighting or running away. 5. The blood vessels in skin and digestive system contract and more blood goes to brain and muscles. 6. Adrenaline also causes the liver to release glucose into the blood. 7. This provides extra glucose to the muscles, thus more respiration and more energy is released for contraction. CELL :01110983031 00201110983031 [email protected]