Water Balance

Balancing Act Water is vital to life. It is required for both chemical reactions and the excretion of waste. Water is vital to life. It is required for both chemical reactions and the excretion of waste. Your body adjusts the amount of urine your produce to coincide with the amount of water used by the body. Your body adjusts the amount of urine your produce to coincide with the amount of water used by the body. The hormone that regulates water balance is called antidiuretic hormone or ADH. The hormone that regulates water balance is called antidiuretic hormone or ADH.

Regulating ADH – Part I ADH acts in the kidneys causing them to increase the rate of water reabsorption. ADH acts in the kidneys causing them to increase the rate of water reabsorption. The osmoreceptors of the hypothalamus (brain) detects the osmotic pressure of the blood. The osmoreceptors of the hypothalamus (brain) detects the osmotic pressure of the blood. When water is lost – the solute concentration (dissolved stuff) in the blood increases and the osmotic pressure increases. It’s like the blood turning from water to concrete. When water is lost – the solute concentration (dissolved stuff) in the blood increases and the osmotic pressure increases. It’s like the blood turning from water to concrete. More water needs to move into the bloodstream in order to balance out the solutes – osmosis. More water needs to move into the bloodstream in order to balance out the solutes – osmosis.

Regulating ADH – Part II When water enters blood – cells of hypothalamus shrink and tell pituitary to release ADH. When water enters blood – cells of hypothalamus shrink and tell pituitary to release ADH. ADH travels to kidneys and signals the reabsorption of more water. More water back into blood and less into urine. ADH travels to kidneys and signals the reabsorption of more water. More water back into blood and less into urine. Shrinking hypothalamus cells also initiate the sensation of thirst. You drink and more water moves into the system to replenish the low concentration in the blood. Shrinking hypothalamus cells also initiate the sensation of thirst. You drink and more water moves into the system to replenish the low concentration in the blood. As hypothalamus cells swell again, the hypothalamus sends a message to the pituitary and the release of ADH is lessened. As hypothalamus cells swell again, the hypothalamus sends a message to the pituitary and the release of ADH is lessened.

Kidneys & Blood Pressure Kidneys also help balance blood pressure through the use of a hormone called aldosterone. Kidneys also help balance blood pressure through the use of a hormone called aldosterone. Aldosterone increases the reabsorption of sodium ions (Na + ) from the nephron, which in turn attracts more water to follow. Aldosterone increases the reabsorption of sodium ions (Na + ) from the nephron, which in turn attracts more water to follow. The water will follow the salt and try to balance it out. Put salt in blood and water comes after it and blood pressure goes back up. The water will follow the salt and try to balance it out. Put salt in blood and water comes after it and blood pressure goes back up.

Blood Pressure – Detailed Glomerulus has low blood pressure detector. When blood pressure is low – it releases renin. Glomerulus has low blood pressure detector. When blood pressure is low – it releases renin. Renin causes angiotensinogen to become angiotensin. Renin causes angiotensinogen to become angiotensin. Angiotensin causes release of ADH from adrenal gland which will act to bump up the blood pressure through reabsorption of water. Angiotensin causes release of ADH from adrenal gland which will act to bump up the blood pressure through reabsorption of water. Angiotensin also constricts (squeezes) blood vessels to help increase pressure. Angiotensin also constricts (squeezes) blood vessels to help increase pressure.

pH Balance The kidneys help maintain pH balance in the blood by using a buffer system that includes the following… The kidneys help maintain pH balance in the blood by using a buffer system that includes the following… H 2 O + CO 2  H 2 CO 3  HCO H + The carbonic acid (H 2 CO 3 ) can lower blood pH while the bicarbonate (HCO 3 - ) can raise blood pH. The carbonic acid (H 2 CO 3 ) can lower blood pH while the bicarbonate (HCO 3 - ) can raise blood pH.

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