Principles of Homeostasis Flashcards
What is homeostasis?
The ability to maintain a constant internal environment in response to environmental changes.
What is the importance of homeostasis?
Homeostasis enables organisms to remain balanced while living in constantly changing environment. Maintaining temperature allows enzymes to function properly, maintaining blood glucose levels ensure cells are not affected by osmotic effects.
What are the features of a control mechanism?
Stimulus - Receptor - Coordinator - Effector - Response
What is the difference between negative and positive feedback?
Negative feedback - Responses keep levels around the norm
Positive feedback - responses move levels further away from the norm
How do hormones work?
Only hormone’s target cell, with receptors necessary for that hormone will response to that signal. When the hormone binds to its receptor, it causes a biological response within the cell.
What is the role of the pancreas in regulating blood glucose?
Pancreas detects changes in blood glucose levels. Beta cells secrete insulin and alpha cells secrete glucagon.
What factors influence blood glucose concentration?
Diet, exercise, insulin levels, stress, menstrual cycle, temperature (excess sweating)
What is the role of insulin in regulating blood glucose?
High blood glucose levels stimulate the release of insulin. Insulin helps control blood glucose levels by signalling the liver and muscle and fat cells to take in glucose from the blood. Alters channel proteins or increases the number of glucose channel proteins. Increases rate of respiration in cells.
What is the role of glucagon in regulating blood glucose?
The alpha cells of the pancreas release glucagon when the concentration of glucose in the bloodstream falls too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream.
What is the role of adrenaline in regulating blood glucose?
Adrenaline acts via a second messenger by binding to the plasma membrane of cells and exert their influence from the outside by causing a cascade of enzymatic reaction events inside the cell which ultimately end up in their response.
How can each type of diabetes be controlled?
Type 1 cannot be controlled without taking insulin but diet and exercise is still important
Type 2 usually treated initially with controlled diet and exercise without medication or with tablets. Bariatric surgery may be used.
Describe ultrafiltration and the production of glomerular filtrate
Filtration under pressure due to a wider afferent arteriole and narrower efferent into and out of the glomerulus.
Smaller molecules are forced out of the blood into the nephron, such as ions, glucose, water.
Explain reabsorption of glucose and water by the proximal convoluted tubule.
Glucose - Reabsorbed by co-transport with sodium ions
Water moves via osmosis
Explain how a gradient of sodium ions in the medulla of the loop of Henle is maintained.
Sodium ions are actively transported out of the top of the ascending limb into the interstitial tissue. This creates a higher water potential in the cortex and a lower water potential further into the medulla.
Water moves out of the descending limb into the interstitial region via osmosis then passes into the blood capillaries.
Explain the role of the distal convoluted tubule and collecting duct in the reabsorption of water
DCT absorbs water and salts to balance the pH of the blood. The permeability of both the DCT and collecting duct are affected by ADH.
