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Anatomy and Physiology for Health and Social Care P5 Homeostasis Homeostasis Definition Homeostasis means “staying the same” It is the technical term for the process of maintaining a constant internal environment despite changes happening externally. Exercise In pairs think about: We are able to live in both hot and cold countries because our bodies have the ability to regulate temperature. What would happen if we could not regulate our temperature? What do we mean by our internal environment? • It is our tissue fluid (lymph) in which all of our cells are bathed. • Every substance must pass through the fluid to move to and from our cells. • Tissue fluid is derived from blood, so blood forms part of our internal environment. • Our enzymes operate in a narrow range of temperature and pH and can only work effectively if conditions are maintained. What do enzymes do? • deliver nutrients, • carry away toxic wastes, • digest food, • Clean and purify the blood, • deliver hormones by feeding the endocrine system, • balance cholesterol levels, • feed the brain and • cause no harm to the body. All of these factors contribute to the strengthening of the immune system The Negative Feedback System Detector Controller Effector Feedback Loop Reference Point What needs to be regulated • • • • Heart rate Breathing rate Body temperature Blood glucose Regulation of Heart Rate Controlled by the autonomic nervous system It has 2 branches: The Sympathetic - accelerates the heart The Parasympathetic – slows it down Like a brake and an accelerator in a car The effects of stimulating the sympathetic nervous system • Heart rate increases • Blood flow increases to muscles, lungs and brain but decreases to gut and kidney • Breathing rate increases • Sweat production increases • Muscles of hairs contract • Bladder and anal sphincters contract • Glycogen converted into glucose in the liver • Iris in the eyes dilate Control of Heartbeat during exercise • The cardiac centre is found in the medulla of the brain. • It receives signals from chemoreceptors which are receptors that detect chemicals Regulation of Breathing • Most of the time we do this on AUTOMATIC PILOT • Only when we take deep breaths, speaking, holding our breath do we control our breathing. • Controlled by the respiratory centre in the medulla of the brain. • The medulla controls nerves going into the intercostal muscles and the diaphragm muscles. • Normal breathing is a homeostatic mechanism What happens when we breathe • We breathe in when the respiratory centre sends impulses to the intercostal and diagphram muscles they contract and the lungs inflate. • This inflation sends impulses to the respiratory centre which stops sending impulses to the intercostal and diagphram muscles. • These muscles then relax • They are no longer stimulated by the impulses from the respiratory centre so it starts up again. Control of Temperature • Temperature of cells must be maintained at a certain level to stop the structure of enzymes being destroyed. • Normal body temperature is? 36.8˚c (36.5 – 37.2 ˚c) Exercise What would these lead to? • • • • • • Below 25 ˚c 32 ˚c 36.5 - 37.2 ˚c Above 37.2 ˚c Above 38 ˚c Above 43 ˚c • • • • • • Lead to death Hypothermia Normal Fever Heat exhaustion Death Temperature • Core body temperature is the one concerned with operating enzymes • Surface temperature can fluctuate rapidly Question: How do we gain heat How do we loose heat Heat Gain • Metabolism of food • Absorbing solar energy from objects, from the ground and connections with the ground Loss • Evaporation • Conduction • Convection • Radiation Regulation of Body temperature • Is the role of the hypothalmus • It sends nerve impulses to muscles, sweat glands and skin blood vessels to cause changes that counteract the external changes • The skin is the main organ of thermoregulation Body responses Cooling • Speeds up metabolism • Shivering to produce heat • Vascoconstrictions Heating • Slows down metabolism • Sweating • Vasodilation • insulation Control of blood glucose • Glucose in the blood is referred to as blood sugar level. • The cells use glucose for respiration • Carbohydrate levels fluctuate • Cells need a constant supply of glucose • Achieved by hormones interacting with glycogen stored in the liver. Hormones Insulin Glucagon Lowers blood glucose if the level goes too high. Excess glucose is converted to glucagon and stored in the liver Raises blood glucose if the level goes too low. Glycogen in the liver is broken to glucose and released into the blood Diabetes There are different types TYPE 1 • Occurs when the pancreas doesn’t function properly and doesn’t produce enough insulin to control blood glucose. • People with this type of diabetes need to have regular injections of insulin TYPE 2 • Insulin is produced by the pancreas but the receptors in the cells don’t recognise it as being there • People have to control the amount of sugar they eat in their diet. • Insulin injections wouldn’t work