D 3.3 Homeostasis PDF

D 3.3 Homeostasis “How are constant internal conditions maintained in humans?” “What are the benefits to organisms of maintaining constant internal conditions?” Learning Objectives Variables are kept within preset limits, despite fluctuations in extern...

D 3.3 Homeostasis “How are constant internal conditions maintained in humans?” “What are the benefits to organisms of maintaining constant internal conditions?” Learning Objectives Variables are kept within preset limits, despite fluctuations in external Homeostasis as maintenance environment. Include body temperature, blood pH, blood glucose D3.3.1 of the internal environment concentration and blood osmotic concentration as homeostatic variables in of an organism humans. Students should understand the reason for use of negative rather than Negative feedback loops in positive feedback control in homeostasis and also that negative feedback D3.3.2 homeostasis returns homeostatic variables to the set point from values above and below the set point. Regulation of blood glucose Include control of secretion of insulin and glucagon by pancreatic endocrine D3.3.3 as an example of the role of cells, transport in blood and the effects on target cells. hormones in homeostasis Physiological changes that Students should understand the physiological changes, together with risk D3.3.4 form the basis of type 1 and factors and methods of prevention and treatment. type 2 diabetes Thermoregulation as an Include the roles of peripheral thermoreceptors, the hypothalamus and D3.3.5 example of negative pituitary gland, thyroxin and also examples of muscle and adipose tissue feedback control that act as effectors of temperature change. Students should appreciate that birds and mammals regulate their body temperature by physiological and behavioural means. Students are only Thermoregulation D3.3.6 required to understand the details of thermoregulation for humans. mechanisms in humans Include vasodilation, vasoconstriction, shivering, sweating, uncoupled respiration in brown adipose tissue and hair erection. Homeostasis as maintenance of the internal environment Homeostasis is the ability to Which factors must stay “the maintain a constant internal environment at preset values same” inside the body to http://www.harborathletic.com/wp-content/uploads/2015/02/balance.jpg despite fluctuations from the maintain a steady state? external environment. It works by monitoring levels of variables and making corrections by negative feedback mechanisms. Homeostasis as maintenance of the internal environment Negative feedback loops in homeostasis All homeostatic functions of an organism are under control of a feedback loop, which uses information about the outcome of a process to make adjustments. https://www.albert.io/blog/positive-negative-feedback-loops-biology/ Positive Feedback Negative Feedback Positive feedback amplifies their initiating Negative feedback counteracts changes of stimuli - they move the system away from its various properties from their target value (set starting state. Only few examples exist in the points). They form the basis of homeostatic human body (e.g. During the menstrual cycle control systems used to keep internal release of FSH stimulates follicle growth conditions within narrow limits. They require which in turn stimulates FSH release) energy but keep the body at stable conditions. Negative feedback loops in homeostasis http://classroom.sdmesa.edu/eschmid/F01.02.L.150.jpg Homeostasis is controlled by negative feedback. This is the type of control in which conditions are brought back to a set value as soon as it is detected that they have deviated from it. Regulation of blood glucose http://www.drugs.com/health-guide/images/205333.jpg Transport of glucose to all cells is a key function of the blood circulation. In human blood a set value of around 90mg/100ml blood is normal. What situations cause the blood sugar level to drop above or below that value? Hyperglycemia increases the blood pressure. Why? http://tomdemenkoff.com/image/5531e5e3cede4.jpg Regulation of blood glucose Blood sugar levels are adjusted by two hormones: Insulin and Glucagon, which are produced in pancreatic cells (Langerhans islets), which are hormone-secreting glands (endocrine glands). The hormones are transported in the body by the blood to reach their target cells. The Langerhans islets contain two types of cell, α cells (releases glucagon) and β cells (releases insulin). http://philschatz.com/anatomy-book/resources/1820_The_Pancreas.jpg Regulation of blood glucose Insulin and glucagon are released by endocrine glands. Because the pancreas has multiple functions, it is important to distinguish between endocrine and exocrine glands. exocrine An exocrine gland is a gland which releases its products into endocrine a duct (e.g. digestive An endocrine gland is a enzymes from gland which secretes the pancreas or products (e.g. in the stomach hormones from wall, sweat ovaries/testes, glands, salivary hypothalamus, glands,…) pituitary gland) into the bloodstream. Regulation of blood glucose https://1drv.ms/v/s!Au8ZKE_EDcrQjowU0ol_KAUScQnY-A?e=MATXCA Regulation of blood glucose Annotate the diagram: In muscle and tissues… Release of… Detected by… In the liver… Blood glucose levels now… Start here Blood glucose levels now… In the liver… Detected by… Release of… Regulation of blood glucose Insulin and Glucagon reach different target cells. Describe the effects they have. Insulin causes migration of membrane Glucagon causes breakdown of proteins and absorption into the cell polymer storage products in the liver http://henryivespt.com/wp-content/uploads/2014/06/shutterstock_114645271.jpg http://dtc.ucsf.edu/images/charts/1.h.epi_rev1.jpg Physiological changes that form the basis of type 1 and type 2 diabetes Diabetes is the condition in which a person has consistently elevated blood https://mydr.com.au/diabetes/diabetes-in-seniors/ glucose levels even during prolonged fasting. This leads to the presence of glucose in the urine. There are two main types of diabetes: Type I diabetes Type II diabetes (early onset) (late onset)  Physiological changes that form the basis of type 1 and type 2 diabetes https://1drv.ms/v/s!Au8ZKE_EDcrQjowTbyHkQoJBA1TRLw?e=EHb5Jz https://1drv.ms/v/s!Au8ZKE_EDcrQjowS_WjSMHKmN_1h9Q?e=Y3kWfZ Watch these videos and note down causes, consequences and treatments for diabetes 1 and 2. https://1drv.ms/v/s!Au8ZKE_EDcrQjowVgxYp0TmCXlI0gA?e=Esc6Fh Type I & Type II diabetes: Causes & Risk factors A diabetic is a person whose body is failing to regulate blood glucose levels correctly. Type I diabetes (early-onset): Type II diabetes (late-onset): Results from a failure of insulin production by Is the inability to process or respond to the β cells due to an autoimmune disease insulin due to a deficiency of insulin receptors which destroys the beta cells in the pancreas. or glucose transporters on target cells. Caused by genetics, environmental, auto- Caused by lifestyle (sugary, fatty diet, obesity immune factors not well understood. and lack of exercise), genetics (affecting energy metabolism), aging. Symptoms are increased thirst & urination, kidney failure, constant hunger, weight loss, Symptoms are mild, fatigue, slow healing. blurred vision, nerve damage. Usually blood sugar levels are high, only receptors are defective. It affects children and young people. It affects older people. Type I & Type II diabetes: Treatment Type I diabetes (early-onset): Type II diabetes (late-onset): Treatment includes injections, oral Treatment includes diet and exercise, medicine, diet and exercise, blood blood glucose monitoring. Sometimes glucose monitoring. insulin injections and oral medicine. Injections are mostly done before a Sugar food should be avoided, starchy https://medicorx.com/wp-content/uploads/treatment-of-diabetes-type-1-and-type-2-diabetes.jpg meal to prevent a peak of blood food only with low glycemic index glucose when food is digested. (indicating that it is digested slowly). Thermoregulation – control of body temperature Thermoregulation is control of core body temperature to keep it close to a set point (which might differ at different times of the day, year, organism, etc.) Negative feedback is the basis of thermoregulation. https://studymind.co.uk/notes/thermoregulation-2/ Body temperature is monitored by peripheral thermoreceptors in the skin and by central thermoreceptors in the core of the body and hypothalamus. The hypothalamus is also the regulatory part, taking in information from thermoreceptors and initiating responses. Thermoregulation – control of body temperature Some organs are more Heat is generated by metabolically active (like the metabolism in cells. Heat heart and kidneys, lungs and is then distributed by the brain, from which over 70% blood circulation. of the body heat emerges) Thermoregulation – control of body temperature The metabolic rate can be decreased or lowered to adjust the amount of heat generated. To increase the metabolic rate, the hypothalamus secretes thyrotropin releasing hormone (TRH), which activates the pituitary gland to release thyroid stimulating hormone (TSH), which in turn stimulates thyroxin (T4) production by the thyroid gland. Thyroxin in the blood circulation stimulates oxygen consumption and increases the metabolic reactions that generate heat as a waste product.  Thermoregulation – control of body temperature The target cells for tyroxin are muscles, brain and liver https://www.frontiersin.org/articles/10.3389/fendo.2018.00447/full which respond accordingly. Adipose tissue also acts as an insulator and reduces heat loss. Brown adipose tissue can generate heat at a rapid rate – small mammals and newborn babies have larger quantities of this type of adipose tissue, as they are particularly prone to heat loss. Thermoregulation – control of body temperature In humans, body temperature is controlled by the thermoregulatory centre in the hypothalamus. Using the diagram, explain how body temperature is adjusted. Thermoregulation – control of body temperature What mechanisms has the body developed in order to respond to an increased core temperature? Sweating, dilation of blood vessels (vasodilation), Behavioral adaptations (taking off clothes), hydration (drinking) How does sweating allow for a decrease in temperature? Explain: Water molecules are held together by hydrogen bonds – When bonds are breaking in the process of evaporation, energy is required. Energy taken to break these bonds is removed from the body → temperature reduced. How does vasodilation (the widening of blood vessels) allow for lowering body temperature? Blood vessels become wider and move closer to the skin’s surface resulting in heat to be transported away easier (conduction & convection) How does vasoconstriction (the narrowing of blood vessels) allow for increasing body temperature? Blood vessels become more narrow and deeply burried inside the muscle tissue – this will remove the blood flow from the surface of the skin, and therefore reduce heat loss through the skin.