Water homeostasis

• Define homeostasis

  The maintenance of a constant internal environment
• What are the components of a homeostatic system

  1. Receptor detects changes
  2. Control centre determines the response
  3. Effector produces the response
• Define osmosis

  The movement of water through a selectively permeable membrane along the concentration gradient.
• What are the functions of the urinary system

  Kidneys. Ureters. Bladder. Urethra.
• What is the outer layer of the kidney called

  The cortex
• What is the innder layer of the kidney called

  Medulla
• Label this structure and state what it is

  A nephron.

  A) Bowmans capsule

  B) Glomulerus

  C) Distal convoluted tubule

  D) Collecting duct

  E) Cortex

  F) Medulla

  G) Proximinal convoluted tubule

  H) Loop of henle

  
• What are the components of the renal corpuscle

  Glomerulus and bowman's capsule.
• Describe blood flow through the glomerulus

  Blood enters through the afferent and exits through the efferent.
• Which blood vessel in the kidney has the wider diameter and why

  The afferent this increases the pressure for filtration.
• Describe filtration in Bowman's capsule

  No proteins or red blood cells.

  All the plasma exits.
• Describe the structure of the filtration membrane

  The glomerular endothelium allows all the plasma to pass.

  The basal lamina prevents large proteins.

  The slit membrane prevents medium proteins.
• What extends from pedicels

  Podocytes
• Describe reabsorption in the PCT

  All amino acids and glucose.

  Some salts and water pass.

  H+, NH4+, Urea and HCO3- are variable.
• How does water get reabsorbed

  by osmosis.
• How is sodium reabsorbed

  By active transport.
• What are the adaptations of the PCT

  Microvilli on the apical surface increase surface area.

  Mitochondria produce ATP for active transport.
• What are symporters

  They transport 2 things in the same direction.
• How are symporters used ni the nephron

  In the proximal convoluted tubule for the reabsorption of water and salts.
• Which limb of the Loop of Henle does water move out of

  Descending
• Which limb of the Loop of Henle do salts move out

  Ascending
• Which limp of the LOH is impermeable to water

  Ascending
• Which limp of the LOH is impermeable to water

  Descending
• What part is the loop of Henle most concentrated

  At the hairpin
• Describe the loop of henle action

  Water exits the descending limb via osmosis. This is due to the low osmolarity of the medulla.

  Salts exit the ascending limb by active transport and diffusion. This is due to the high osmolarity of the medulla.
• What does a high osmolarity indicate

  There is a lot of water present
• Which parts of the nephron are in the medulla

  The collecting duct and loop of Henle.
• Where is the PCT found in a kidney

  The cortex
• where is the DCT in a kidney

  The cortex
• Where is the renal corpuscle found in a kidney

  the cortex
• where is the collecting duct in a kidney

  The medulla f
• Where is the loop of henle in a kidney

  The medulla
• Describe DCT action

  Aldosterone causes salt reabsorption.

  Water is reabsorbed by osmosis.
• Which substances are secreted into the tubular fluid in the DCT [Write as the ions].

  H+. K+ NH4+. Urea.
• Describe the action of the collecting duct

  ADH causes water reabsorption.

  Sodium ions are reabsorbed.

  Urea enters the base of the loop of Henle to increase the solute concentration.
• Which ions are secreted from the blood to the collecting duct

  K+ and H+.
• How does ADH work

  Causes insertion of aquaporin 2 water channels into the principal cells of the collecting duct.
• What are the types of nephrons

  Cortical and juxtamedullary.
• Describe the key features of juxtamedullary nephrons

  The loop of Henle extends deep into the medulla.
• Which type of nephron has a short loop of henle

  Cortical