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Endocrine Glands The endocrine system coordinates the body’s response to changes in the environment using chemical messengers (hormones). Hormones are released by glands into the bloodstream, where they travel to target organs. There are lots of different endocrine glands: Testes • The testes produce testosterone, which controls puberty and sperm production. Pancreas • The pancreas produces insulin and glucagon, both of which are involved in regulating blood glucose levels. Thyroid gland • This gland is in our neck and releases thyroxine. • Thyroxine regulates our metabolism, heart rate and temperature. Ovaries (female only) • The ovaries produce oestrogen, which controls puberty and is one of the main hormones in the regulation of the menstrual cycle. Adrenal glands • The two adrenal glands are situated above each kidney. • They produce adrenaline, which triggers the ‘fight or flight response when an organism is presented with a dangerous situation. Pituitary gland • This is the main endocrine gland or "master gland". • It is found in the brain and is linked to the hypothalamus (part of the brain that receives signals from receptors). • The pituitary gland releases hormones in response to changes detected by the hypothalamus. • Lots of these hormones trigger other glands to release more hormones. The central nervous system (CNS) is different from the endocrine system in a few key ways: Central nervous system (CNS) • Triggers rapid response. • Uses electrical signals that are carried by neurones. • Response is very short. • Acts on a very precise part of the body. Endocrine (hormonal) system • Triggers a slower response. • Uses chemical messengers that are carried by the blood. • Response can be long-lasting. • Can act on large areas of the body. Controlling Blood Glucose Levels It is important for an organism to keep its blood glucose levels within a small range. Too little glucose • Glucose is important for respiration. • Respiration releases the energy needed by every living cell. • If there is not enough glucose, an organism cannot produce enough energy. • Glucose is fuel for respiration, which is the chemical reaction that releases energy in many living cells. • Why is it important to control blood glucose levels? • Glucose is fuel for respiration. This is the chemical reaction that releases energy in many living cells. • Therefore, if blood glucose levels are too low, then an organism cannot meet its energy demands. • But if there is too much glucose in the blood, this has an impact on osmosis by affecting concentration gradients. As blood flows through the pancreas, the body can detect if blood glucose levels are too high. If the concentration of blood glucose is too high, the pancreas release the hormone ‘ insulin’ into bloodstream. The liver and muscle tissue detect the presence of insulin. These convert the excess glucose into glycogen. This process continues until the pancreas detect a normal blood glucose concentration. Glycogen is a form of glucose that is insoluble and can be stored for later use. Diabetes Diabetes sufferers are not able to control their blood glucose levels. There are two types of diabetes: Type 1 diabetes • In type 1 diabetes, sufferers are unable to produce enough insulin. Type 2 diabetes • In type 2 diabetes, sufferers can still produce insulin, but their body no longer responds to it. Type 1 Diabetes In type 1 diabetes, the pancreas cells in the body either produce little or no insulin. Timeline • Type 1 diabetes develops during childhood. • We do not know what causes Type 1 diabetes, but we think that the body's immune system attacks the pancreas cells. Treatment • The main treatment is to inject insulin when blood glucose levels rise too high. • Sufferers can also manage their diet and exercise regularly to keep blood glucose levels as steady as possible. • • In type 2 diabetes, sufferers can still produce insulin, but their body no longer responds to it. Timeline • Type 2 diabetes usually develops later in life. • Old age and being overweight are recognised as two of the primary risk factors. Treatment Because the body no longer responds to insulin, injecting insulin will not help. injections are an ineffective method of treatment. • Instead, sufferers must manage their diet and exercise regularly to keep blood glucose levels steady. Water Balance Water levels in the body must be kept relatively constant to control the amount of water and ions diffusing in and out of cells. Many factors can disrupt this balance. Exhalation • Water in the lungs leaves the body in the person’s breath. Eating too much salt • This can make the blood ion concentration too high. Sweating • Water, ions and urea are all lost in sweat. Illness • Illnesses that cause fever, vomiting or diarrhoea can result in dehydration (the blood's water concentration is too low). Kidneys The kidneys are important for homeostasis. They control the water and ion levels in the blood. Ion levels • The body's ion levels must be kept relatively constant to control osmosis and diffusion between cells in the body. Excess water • The volume of water in the blood is monitored by the hypothalamus in the brain. Kidneys - Urine Production Each kidney contains millions of very small structures called nephrons. There are two stages in the process of urine production. These stages happen in every nephron. Ultrafiltration • The blood is filtered and all water, urea and salts move into the nephron tubule. • Blood cells and proteins remain in the blood as they are too big to move across the capillary walls. Puberty Males and females respond differently when their bodies reach puberty: Females • The amount of the hormone oestrogen rises and triggers the menstrual cycle. • Underarm and pubic hair grow. • Breasts enlarge. Males • The amount of the hormone testosterone rises. This stimulates sperm production. • Underarm, facial and pubic hair grow. • Voice deepens.