Control of Blood Water Potential

Question 1

Define Osmoregulation

Answer 1

• maintaining water potential of the blood within restricted limits

Question 2

Which body parts are heavily involved in osmoregulation

Answer 2

• hypothalamus
• pituitary gland
• kidneys

Question 3

what is the functional unit of the kidney and how many are there in each kidney

Answer 3

• the nephron
• approximately 1 million nephrons in each kidney

Question 4

what are the two parts of the kidney

Answer 4

• the cortex (outer part) and the medulla (inner part)

Question 5

what does the cortex of each kidney contain

Answer 5

• the glomerulus
• renal capsule
• proximal convoluted tubule
• distal convoluted tubule

Question 6

what does the medulla of each kidney contain

Answer 6

• part of the loop of Henle
• the collecting duct of each nephron

Question 7

describe the process of ultrafiltration

Answer 7

• High hydrostatic pressure in
  glomerulus forces small molecules (glucose, amino acids, water, ions, urea) into the renal capsule through fenestrations and the basement membrane
• blood cells and large proteins stay in
  the blood

Question 8

how much of each substance is reabsorbed out of the glomerular filtrate and how

Answer 8

• most of the water via osmosis
• some small proteins via diffusion
• most of the ions via facilitated diffusion/active transport
• all of the glucose/amino acids via co transport

Question 9

where in the kidney are substances reabsorbed

Answer 9

• into the cells lining proximal convoluted tubule (PCT)

Question 10

describe and explain adaptations of the cells lining the PCT

Answer 10

• microvilli = large surface area
• numerous mitochondria = provide ATP for active transport
• continuous movement of blood = maintains concentration gradient for further reabsorption
• close to capillaries = short diffusion pathway

Question 11

how does the loop of Henle allow for the production of concentrated urine

Answer 11

• Na⁺ and Cl⁻ ions actively transported out of ascending limb = high ion conc in the medulla tissues
• water osmoses out of the descending limb as it has a higher water potential than surrounding medulla tissues
• filtrate then becomes more concentrated

Question 12

what feature of the loop of Henle allows it to function

Answer 12

• the descending limb is permeable to water and the ascending limb is impermeable to water