Homeostasis Flashcards
High blood glucose concentration
If blood glucose concentration is too high, the water potential of blood is reduced to a point where water molecules diffuse out of cells into the blood by osmosis. This causes cells to shrivel
Problem with low blood glucose levels
Not enough glucose available for respiration so energy isn’t released
Negative feedback
Receptors detect when a level is too high or too low. Effectors respond to counteract the change bringing the level back to normal via the negative feedback mechanism.
Positive feedback
Receptors detect change in normal level and effectors respond. Activates positive feedback mechanism and the normal level is amplified further
E.g. Platelets are activated and released a chemical which causes a positive feedback so more platelets are activated
Hypothermia positive feedback
Body temperature drops below 35 degrees Celsius. Positive feedback causes temperature to keep dropping unless action is taken
Is positive feedback involved in homeostasis
No because it doesn’t keep you internal environment stable
How does insulin lower blood glucose concentration when it’s too high
Insulin binds to specific receptors on the cell membranes of liver cells and muscle cells. It increases the permeability of muscle cell membrane to glucose so the cells take up more glucose. This involves increase the number of channel proteins in the cell membranes. Insulin also activates enzymes in liver and muscle cells that convert glucose into glycogen. The cells are able to store glycogen from glucose is called glycogenesis. Insulin also increases the rate of respiration of glucose
How does glucagon raise blood glucose concentration when it’s too low
Glucagon binds to specific receptors on the cell membranes of liver cells. Glucagon activates enzymes in the liver cells that break down glycogen into glucose during glycogenolysis. Glucagon also activates enzymes that are involved in the formation of glucose from glycerol and amino acids. Glucagon decreases the rate of respiration of glucose cells
Glycogenisis
Glucose converted to glycogen
Glycogenolysis
Glycogen converted to glucose
Gluconeogeneis
Glucose formed from glycerol and amino acids
Negative feedback of too high glucose levels
Pancreas detects blood glucose concentration is too high
Beta cells secret insulin and alpha cells stop secreting glucagon
Insulin binds to receptors on liver and muscle cells
Cells take up more glucose
Glycogenesis is activated
Cells respire more glucose
Less glucose is in the blood
Negative feedback when glucose levels are low
Pancreas detects blood glucose concentration is too low Alpha cells secrete glucagon Beta cells stop secreting insulin Glucagon binds to receptors on liver cells Glycogenolysis is activated Glucongeneosis is activated Cells repaire less glucose Cells release glucose into the blood
How do adrenaline and glucagon active glycogenolysis
Adrenaline and glucagon bind to their specific receptors and activate adenylate Cyclase. Adenylate cyclase convert ATP into a chemical signal called cyclic AMP. Cyclic AMP activated protein kinase A which causes a chain reaction of glycogenolysis reactions
What happens to the body in diabetes 1
The immune system attacks the beta cells in the islets of Langerhamd so they can’t produce insulin. This causes glucose levels to remain high after eating (hyperglycaemia) as the kidneys can’t reabsorb all the glucose
What happens to the body in type 2 diabetes
The beta cells don’t produce enough insulin or the insulin receptors on the membranes don’t work properly so the cells don’t take up enough glucose. Increase blood glucose levels.
How do the kidneys filter blood
Blood from the renal after enter smaller arteriolar in the cortex of the kidney. Each arteriolar splits into a structure called a glomerulus. This is where ultrafiltration occurs. The arteriole that takes the blood into each glomerulus is called the afferent arteriole and the arteriole that takes the filtered blood away from the glomerulus is called the efferent arteriole. The high pressure in the glomerulus forces liquid and small molecules in the blood out of the capillary and into the Bowman’s capsule. The liquid and small molecules pass through three layers to get into the Bowman’s capsule and entered the nephron tubules. Larger molecules like proteins can’t pass through so stay in the blood. The first rate flows through the collecting duct and passes out of the Kinsey along the ureter
Different between quantitative Benedict’s reagent and normal Benedict’s reagent
Quantitative Benedict’s reagent loses its initial blue colour when heated with glucose but a brick red precipitate is not formed
Second messenger model
Adrenaline binds to receptors. Activates adenylate Cyclades which converts ATP into cyclic AMP. This activates protein kinase A which causes glycogenlysis
Insulin activates
Glucogenesis
Glucagon causes
Glycogenolysis and gluconeogenesis
