9.3 Maintaining the Excretory System

• What are osmoreceptors?

  Cells that are sensitive to osmotic pressure
• What part of the brain regulates hunger, thirst, blood pressure, fluid and salt balance are most osmoreceptors located?

  Hypothalamus
• What does the hypothalamus regulate?

  Mechanisms that enable the body to maintain homeostasis
• What happens to the blood plasma when it becomes too concentrated?

  Osmotic pressure increases
• What hormone is release when osmoreceptors in the hypothalamus send impulses to the adjacent pituitary gland in the brain?

  ADH (antidiuretic hormone)
• What does antidiuresis mean?

  Decreased excretion of urine
• What happens when ADH travels through the blood to the kidneys

  It decreases the permeability of the distal tubule and collecting duct, allowing more water to be reabsorbed into the blood.
• What happens when the blood plasma is too diluted?

  Osmoreceptors stop or prevent the release of ADH
• What happens when osmoreceptors stop the release of ADH?

  The distal tubule and collecting duct become less permeable to water.
• What condition does ADH activity is insufficient?

  Diabetes Insipidus
• How and where do kidneys regulate salt balance?

  In the blood by controlling the excretion and reabsorption of various ions.
• What hormone controls a drop in blood Na+ concentration and is normally compensated by the kidneys?

  Aldosterone
• What does aldosterone do?

  Stimulates the distal tubules and collecting ducts to reabsorb Na+ is followed passively by Cl- ions and water, and the secretion of K+ if the concentration is too high.
• What is the pH of body fluids?

  7.4
• What are the three ways of maintaining blood pH?

  1. The acid-base buffer system
  2. Breathing rate
  3. Renal control
• How does the acid-base buffer system work?

  Buffers the blood to prevent changes in pH by adding or removing H+ ions
• How does changes of breathing rate maintain blood pH?

  An increased breathing rate pulls the reaction to the right to generate CO2 more quickly
• What is renal insufficiency?

  A term used to describe the state in which the kidneys cannot maintain homeostasis due to damage to their nephrons.
• What is dialysate?

  A dialysis solution of where substances more concentrated in blood diffuse
• What are the two main types of renal dialysis?

  Hemodialysis and peritoneal dialysis
• How does hemodialysis work?

  Utilizes an artificial membrane in an external device
• How does peritoneal dialysis work?

  Utilizes the lining of intestines, called the peritoneum, as the dialysis membrane.