Biology 12 - The Hormones of the Excretory System: ADH & Aldosterone
ADH - Antidiuretic Hormone – makes you “pee less”!
• ADH is a hormone that makes
humans produce less urine.
• It is made by the hypothalamus
(part of the brain), and sent to the
pituitary gland, which is attached to
the hypothalamus by a stalk. It is
the pituitary gland that releases
ADH.
• ADH, when released, travels in the
ADH and the
blood to the kidney, where it acts on
hormone oxytocin are
the distal convoluted tubule and
released by the
posterior pituitary.
the collecting duct. In response to (FSH, LH, MSH, ACTH,
TSH, Prolactin)
ADH, the distal convoluted tubule
and the collecting duct will reabsorb
more water from the filtrate inside the nephron tube. This water is reabsorbed into
the peritubular capillary network -- i.e. more H2O goes back into the blood. This
will increase the amount of liquid in the blood, and therefore increase blood
volume.
Control of ADH is by a classic "Negative Feedback Loop"
1. blood volume drops if not enough water is being consumed
2. this is detected by receptors in the hypothalamus.
3. This stimulates hypothalamus to produce ADH and send it to pituitary gland
4. Pituitary gland releases ADH into blood
5. ADH acts on the collecting duct and distal convoluted tubule, causing them to
reabsorb more water from the kidney filtrate back into the blood
6. as there is less water in the filtrate, less urine is produced.
7. Blood volume rises. This is detected by the hypothalamus, which will then
shut off the release of ADH (negative feedback)
ALDOSTERONE: regulates Na+ and K+ ion concentrations, increases blood volume
• aldosterone is a steroid hormone produced by the adrenal cortex of the adrenal
glands. The adrenal glands sit on top of the kidneys.
• aldosterone causes the distal convoluted tubule to reabsorb more sodium ions
(Na+) back into the blood and excrete more potassium ions (K+) into the urine.
• the control of the release of aldosterone also operates on a negative feedback
cycle based on blood pressure and sodium ion concentrations.
• The increase of Na+ in the blood makes the blood more hypertonic compared to
surrounding tissue fluid. Therefore, more water will move into the blood via
osmosis. This will increase blood pressure and blood volume.
• The rising levels of sodium in the blood are detected by the adrenal cortex,
which then shuts off its release of aldosterone (negative feedback).
Raycroft
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Raycroft
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