Kidney

• What is negative feedback in biological systems?

  Mechanism to restore normal conditions
• How does the body respond if temperature exceeds 37 degrees C?

  Mechanisms are activated to lower temperature
• What does osmoregulation control in the blood?

  Water potential to keep it constant
• What are the two conditions of blood water potential?

  Hypertonic and hypotonic
• What does hypertonic blood indicate?

  Low water potential with high ions
• What happens to cells in hypertonic blood?

  Cells shrivel due to water loss
• What does hypotonic blood indicate?

  High water potential with low ions
• What happens to cells in hypotonic blood?

  Cells burst due to excess water
• What could cause hypertonic blood?

  Excessive sweating or high salt intake
• What could cause hypotonic blood?

  Drinking too much water or low salt
• What is the corrective mechanism for hypertonic blood?

  More water reabsorbed into the blood
• What is the corrective mechanism for hypotonic blood?

  Less water reabsorbed into the blood
• What is the role of the hypothalamus in osmoregulation?

  Detects changes in water potential
• What are osmoreceptors?

  Cells that detect water potential changes
• What happens when blood water potential is too low?

  Osmoreceptors shrink and stimulate ADH production
• What happens when blood water potential is too high?

  Osmoreceptors swell and reduce ADH production
• Where is ADH released from?

  Posterior pituitary gland
• What is the effect of ADH on the kidneys?

  Increases permeability of collecting ducts
• What are aquaporins?

  Channel proteins that allow water movement
• How does ADH increase water reabsorption?

  By embedding aquaporins in cell membranes
• What is the process when ADH binds to its receptors?

  Activates phosphorylase to embed aquaporins
• What happens when ADH levels decrease?

  Less water is reabsorbed, urine is dilute
• What is the overall purpose of osmoregulation?

  To maintain normal water potential in blood
• What are the key components involved in osmoregulation?

  • Hypothalamus
  • Posterior pituitary gland
  • Antidiuretic hormone (ADH)
  • Osmoreceptors
  • Aquaporins
• What is the negative feedback cycle in osmoregulation?

  1. Blood water potential changes
  2. Osmoreceptors detect changes
  3. Hypothalamus adjusts ADH production
  4. Kidney adjusts water reabsorption
  5. Blood water potential returns to normal
• What are the consequences of improper osmoregulation?

  • Hypertonic blood: cells shrivel, dehydration
  • Hypotonic blood: cells burst, lysis
• What are the main components of the nephron?

  • Renal capsule
  • Proximal convoluted tubule (PCT)
  • Loop of Henle
  • Distal convoluted tubule (DCT)
  • Collecting ducts
• Where does ultra filtration occur in the nephron?

  In the renal capsule
• What is selective reabsorption?

  Reabsorption of useful substances back into blood
• What surrounds the nephron?

  Capillaries
• What is the name of the arteriole leading into the nephron?

  Afferent arteriole
• What is the glomerulus?

  A network of capillaries in the nephron
• What is the renal capsule also known as?

  Bowman's capsule
• What is the overall function of the nephron?

  To create urine by filtering blood
• What substances are typically found in urine?

  Water, urea, dissolved salts, and minerals
• Why are proteins and blood cells not found in urine?

  They are too big to be filtered out
• How is glucose reabsorbed in the nephron?

  By active transport in the PCT
• What is the role of the proximal convoluted tubule (PCT)?

  To reabsorb 85% of the filtrate
• What adaptations do PCT cells have for reabsorption?

  Microvilli and many mitochondria
• How do sodium ions move into the PCT cells?

  By active transport from the filtrate