Homeostasis

• Glycogenisis- glucose is converted into glycogen this happened when glucose conc is too HIGH
• Glycogenolysis- glycogen being Brocken down into glucose this happens when conc of glucose in blood is too LOW
• Gluconeogenesis- amino acids are turned into glucose when all the glycogen has been hydrolysed
• negative feedback - when any deviation from the normal value are restored to their original value
• 
  

  1. Beta cells in the islets of langerhans dectect the high concentration
  2. beta cells release insulin
  3. cell surface of cells become more permeable to glucose and enzymes are released to turn glucose into glycogen
  4. glucose is removed from blood and stored as glycogen in cells
• 1. Blood glucose levels decrease
  2. the alpha cells in the islets of langerhangs detect this
  3. alpha cells release glucagon and adrenal glands release adrenaline
  4. enzymes are released to hydrolyse glycogen
• Cross section of a kidney

  A) Fibrous capsule

  B) Medulla

  C) Cortex

  D) Urteter

  E) Renal Vein

  F) Renal Artery

  G) Renal Pelvis

  
• Structure of a nephron

  A) Proximal convoluted tubule

  B) Distal Convoluted Tubule

  C) Cortex

  D) Medulla

  E) Collecting Duct

  F) Renal Pelvis

  G) Loop of Henle

  H) Glomerulus

  I) Bowmans capsule

  
• Glucose is stored in the liver and muscles as glycogen.
• A pancreas produces two types of cells from clusters of cells within it called the islets of Langerhans.
• One type of cell in the pancreas, the beta cells, produces human insulin which causes the blood glucose concentration to fall.
• The other type of cell in the pancreas, the alpha cells, produces the hormone glucagon which has the opposite effect of insulin.
• Another hormone, adrenaline, can also raise the blood glucose.
• Type 1 diabetes is when the pancreas is unable to produce insulin this can be caused by an auto immune response and the immune system attacks the beta cells of the islets of Langerhans in the pancreas
• Type two diabetes is when the glycoprotein receptor on body are lost or lose the responsiveness to insulin because the pancreas produces and in adequate supply of insulin
• How does insulin lower the concentration of glucose in the blood?

  • by binding to the receptors on target cells. this causes the tertiary structure of the channel protein to change causing more glucose to enter the cell by facilitated diffusion
  • more carrier proteins are incorporated into the CSM when vesicles fuse with the CSM so more glucose is absorbed
  • it activates enzymes that are involved in the conversion of glucose to glycogen
• what is the order of the parts of the nephron?

  1. Afferent arteriole
  2. glomerulus
  3. proximal convoluted tubule
  4. descending loop of henley
  5. ascending loop of Henley
  6. Distal convoluted tubule
  7. Collecting duct
• ULTRAFILTRATION: Blood enter through the the afferent arteriole and it splits up into tiny capillaries (glomerulus) causing a high hydrostatic pressure of blood. water and small molecules like glucose and mineral ions are forced out of the capillaries to form the glomerulus filtrate. Large proteins and blood cells are too big to fit through the gaps so they remain in the blood and leave through the efferent arteriol.
• Selective reabsorption occurs in the the proximal convoluted tubule (PCT)
• The cells that line the proximal convoluted tubule have microvilli to increase the surface area and maximise the reabsorption of glucose and lots of mitochondria to provide energy for active transport
• 1. The concentration of sodium ions in the PCT cell is low as they are actively transported out of the PCT cells into the blood in the capillaries
  2. sodium ions diffuse down their concentration gradient from the lumen of the PCT to the PCT cells
  3. As the sodium ions diffuse down their concentration gradient the also carry glucose (co-transport) into the PCT cell
  4. The glucose can then diffuse from the PCT cell into the bloodstream
• The function of the loop of Henley is to maintain a sodium ion gradient to enable the reabsorption of water
• 1. mitochondria in the walls of the cells in the ascending limb provide energy to actively transport sodium ions out of the ascending limb
  2. the accumulation of sodium ions outside the nephrons in the medulla lowers the water potential
  3. therefore at the descending limb water diffuses out by osmosis into the interstitial space.
• At the base of the ascending limb some sodium ions leave by diffusion due to all the water coming out the descending limb making a dilute solution do the ions can diffuse down the concentration gradient
• In the loop of Henley at the ascending limb sodium and chloride vongs are actively transported out into the interstitial space the walls of the ascending loop of Henley are thick as they contain the protein that enables the sodium potassium pump they also contain lots of mitochondria to provide energy for the active transport of the islands that are transported in Na+and Cl- into the interstitial space lowers the water potential this causes water to move out by osmosis at the descending limb water moves out only at the descending limb as it has been the walls which are permeable to water
• Glucose is reabsorbed in the proximal convoluted tubule when sodium ions are actively transported out of the PCT cells into the bloodstream this causes the concentration of Na+ in the PCT cell to decrease. Na+ down its concentration gradient by facilitated diffusion but also carrying glucose with it (co-transport) glucose is now in the PCT so we can be in we can diffuse into the bloodstream( facilitated diffusion)
• The re-absorption of water can be increased in the collecting duct when water moves out of the osmoreceptors in the hypothalamus.
• The shrinking of these osmoreceptors causes the hypothalamus to produce the hormone ADH.
• ADH is secreted by the posterior pituitary gland.
• ADH binds the receptors on the target cells which are the cells of the distal convoluted tubule and collecting duct changing their tertiary structure.
• This causes ATP to change into CAMP which activates the enzyme protein kinesis.
• The activation of protein kinesis releases the hormone phosphorylase which causes the vesicles containing aquaporins to fuse with the the internal cell surface membrane.
• More aquaporins are in the channel proteins for water to pass through out of the collecting tubule and into the bloodstream.
• • Adrenaline or glucagon bind to receptors on the cell membranes of liver cells.
  • Adrenaline and glucagon are primary messengers because they do not enter the cell.
  • Binding of adrenaline or glucagon activates an enzyme called adenylate cyclase.
  • Adenylate cyclase converts ATP to cyclic AMP (cAMP).
  • cAMP activates an enzyme called protein kinase A.
  • Protein kinase A triggers a cascade of reactions that result in glycogenolysis.
• • People with type I diabetes cannot produce insulin to counteract the increased levels of glucose so the blood glucose level remains high.
  • This is called hyperglycaemia.