Daily questions for Session 3

  1. What is meant by the term homeostasis and why does it matter?

  2. Design a basic system that allows you to regulate a function in the body. What components are needed and why?

  3. What is a negative feedback system?

  4. When you stand up after lying down gravity very quickly pulls blood towards your feet and away from your head. As a result, blood delivery to the brain decreases momentarily and you may feel dizzy. What type of feedback system would be best to manage these changes in blood pressure? Where should the sensors be located? What would happen if the system failed to work properly? Ageing and medications can adversely affect the function of this homeostatic system.

  5. When we have a fever, our body temperature has increased it in response to chemicals known as pyrogens. Pyrogens are produced by bacteria that infect the body and by the immune cells that combat the infection. The pyrogens act on the hypothalamus, which is the controller for body temperature, and increase the body temperature set point. Explain the process by which fever develops, and the symptoms that we associate with fever.

  6. Think about this question-the answer isn't obvious but common sense should help you work it out. Is fever always bad, and should we always treated using drugs? What are the adverse effects of fever and why do they occur?

  7. Fever is an increase in body temperature in response to an increase in set point. Hyperthermia is an increase in body temperature to a level that is higher than the setpoint. Would you expect homeostatic systems to respond differently to fever and hyperthermia?

  8. What is a second messenger and why is it important?

  9. Compare these 2 scenarios. A person has a fever in their body temperature is 40.5°C. Another person has been locked in a hot car and also has a body temperature of 40.5°C. They have hyperthermia. What is the difference between these cases?

  10. In a previous module you looked at the role of the cell membrane. One of its functions is to control the movement of molecules between the intracellular and extracellular fluid, and its chemical structure helps it to perform that function. Because of its lipid core, molecules that are polar do not pass easily through the cell membrane. Insulin is an important molecule that affects cell function. The exterior of the molecule is mainly polar, whereas the interior is mainly non-polar. Will insulin be able to pass freely through the cell membrane and if not, how does it influence cell function?

  11. Adrenaline is a protein (polar) hormone that increases blood pressure. Excessively high blood pressure damages the cardiovascular system and other body systems. Elevated blood pressure is an important cause of renal disease and cognitive dysfunction. How could we use our knowledge of adrenaline in the way that it interacts with cells in the treatment of high blood pressure?

  12. Cortisol is a lipid soluble molecule that plays an important role in many homeostatic processes. Do you think that cortisol will be able to pass through the cell membrane? Where are the receptors for cortisol likely to be found in the cell? Formulate a general rule for the location of receptors.

  13. Below is a flow chart showing how the secretion of cortisol is controlled. This is a classic negative feedback system. Both the hypothalamus and anterior pituitary gland measure the amount of cortisol in the blood. To increase cortisol production in the adrenal gland, the hypothalamus releases the hormone GnRH. GnRH acts on the anterior pituitary to increase the release of the hormone ACTH. ACTH acts on the adrenal gland to increase the production of cortisol.
    Failure to produce adequate amounts of cortisol causes Addison's disease which is a life-threatening condition. Addison's disease could be the result of problems in the hypothalamus, anterior pituitary or adrenal gland. Use the flowchart to explain how you would identify the likely site of dysfunction in a patient with Addison's disease. Pasted image 20220403214604.png

  14. Drugs that mimic the effects of cortisol are commonly prescribed to treat inflammatory, autoimmune and allergic conditions. These drugs are commonly called corticosteroids or glucocorticoids and include prednisolone, prednisone, dexamethasone and betamethasone. Although each of these drugs has a different molecular structure they all work in the same general way and mimic the effects of cortisol. What do you think is common between each of these drugs and cortisol that enables them to function in this way?

  15. The name ACTH is an abbreviation for adrenocorticotrophic hormone. A trophic hormone is a hormone that stimulates growth in another gland-in this case the adrenal cortex which is the site of cortisol production.Corticosteroids for a period of time, it is dangerous to suddenly stop treatment. Why do you think it is dangerous, and what strategy could you use to minimise the risk?

  16. Explain the role of oxytocin in childbirth. What sort of feedback system is operating in this example and why?

  17. What do we mean when we talk about the osmolarity of the blood and why does it matter?

  18. Severe head injury can result in swelling of the brain. This is a very serious condition because the brain is entirely contained within the bony skull-it has nowhere to go when it swells so the intracranial pressure increases. Mannitol is a simple sugar that can be administered in  intravenous fluids to reduce intracranial pressure. Using your knowledge of osmolarity, try to describe how mannitol exerts its effect.

  19. Diuretics are drugs that increase urine production. Many diuretics exert their effect by decreasing sodium reabsorption in the kidney tubules. In other words the concentration of sodium ions in the urine is increased. Usual knowledge of osmolality to explain why diuresis occurs.

  20. There is a common perception that we should drink as much water as we can while we are exercising. However, excessive water can Adversely affect exercise performance and cause problems like headache, altered levels of consciousness, and swelling of the hands legs and feet. Why would these changes occur in what could be done to prevent them?

  21. In previous questions you have looked at the way in which insulin interacts with receptors on the surface of the cell to change cellular function. Glucose homeostasis is dependent on having adequate amounts of insulin available, and adequate receptors to interact with the insulin. How does the cell know when insulin has combined with its receptor, and how is that information used to change cell function?

  22. In previous modules you have looked at the role of the cell membrane, cell membrane channels, membrane pumps, and differences between the concentrations of sodium and potassium ions in the intracellular and extracellular fluid. Can you unify these ideas to explain how the cell action potentials occur?

  23. Why do we need a homeostatic system to regulate blood glucose concentration?

  24. Glucose is a water soluble molecule and in previous questions you have looked at the fact that water soluble molecules do not passed directly through the cell membrane because of lipid core. How can we enable glucose absorption from the gut, glucose entry into the cells and glucose reabsorption in the kidneys?

  25. Use your answer to the previous question to explain how we could we apply our knowledge of glucose transport in the kidneys in the management of diabetes mellitus.

  26. How can we store glucose in cells?

  27. How does glucose storage in the cells contribute to glucose homeostasis?

  28. Diabetic ketoacidosis is a potentially fatal complication of diabetes mellitus. Why does diabetic ketoacidosis occur and what effects would it have on the body?

  29. The ketogenic diet is currently popular. How would the ketogenic diet work? Look at the chemical reaction below. This is the carbonic anhydrase reaction that occurs in many cells in the body. It is very useful reaction to remember.
    \(\(H^+ + HCO_3^- \leftarrow\rightarrow H_2O + CO_2\)\) A homeostatic mechanism in our body keeps the carbon dioxide levels in the blood stable by increasing ventilation (i.e. respiratory efforts) when carbon dioxide levels increase. Why is this necessary? What effect would diabetic ketoacidosis have on respiration?

  30. Why can we compare the glomerulus to a soaker hose?

  31. Why do we need the tubule system in our kidneys?

  32. Imagine you are a potter trying to turn a lump of clay into a delicate, precise shape. What would you do first, and what would you do subsequently? Applied the same thinking to explain what happens to filtrate as it passes through the renal tubules.

  33. In order to control the amount of glomerular filtration that is occurring the pressure inside the glomerular capillary must be regulated. Blood flows into the glomerular capillaries through the afferent arteriole and flows from the glomerular capillary into the efferent arteriole. We are able to change the diameter of the arterioles. How would this help us to regulate glomerular filtration?

  34. One action of the Loop of Henle is to make the renal medulla hyperosmotic. Why is this important in renal function (there is no active transport mechanism for water in the body)? We need to regulate water reabsorption to maintain homeostasis. How could we do this and how is this example analogous to another example that you have looked at?

  35. Diuretics are drugs that increase water excretion in the kidneys. They are useful for the treatment of conditions like heart failure. In heart failure the volume of blood in the body is often increased. This occurs to maintain blood pressure in the face of decreasing cardiac function, but it can have adverse effects in various tissues. There are a number of different diuretics that are available. For each of the following examples explain why they have their diuretic effect.

    1. Loop diuretics decrease the reabsorption of sodium in the loop of Henle.
    2. Spironolactone blocks the effect of aldosterone in the collecting duct.
    3. 3.35. Canvas solutions

  36. Diabetes insipidus is a condition where people excretes excessive amounts of very dilute urine. It is caused by an endocrine abnormality. What abnormality would cause diabetes insipidus? How does this relate to the increased urination that occurs when people drink large amounts of alcohol?

  37. In previous modules you have looked at the role of the cell membrane, cell membrane channels, membrane pumps, and differences between the concentrations of sodium and potassium ions in the intracellular and extracellular fluid. Can you unify these ideas to explain how the cell membrane potential is generated?

    • 3.37.