Osmoregulation & The Kidney - Anti-Diuretic Hormone (GCSE Biology)
Anti-Diuretic Hormone
Anti-Diuretic Hormone (ADH)
Function of ADH
- ADH is released by the pituitary gland. ADH is released by the pituitary gland, and its target organ is the kidneys. ADH also has another name, vasopressin. This is related to another of its uses in affecting blood pressure (but we do not need to cover this.
- ADH is important in water control. ADH has a very important effect in the body. It is a key factor in deciding the water content of the blood. When we are overly hydrated, it so to make sure that we urinate frequently. When we are dehydrated, it makes sure we urinate less and conserve water.
- Water content of the blood is controlled via a negative feedback mechanism. When an increase/ decrease in water content is detected, the body responds to bring water content back to normal.
- Water levels are detected the brain. Water content in the blood is detected by the brain, which controls how much anti-diuretic hormone (ADH) is released by the pituitary gland.
- ADH affects the permeability of the kidney tubules. ADH increases the permeability of the collecting duct of the kidney nephron. This means that more water is reabsorbed, so less water is excreted.
ADH in Dehydration
- More ADH is released during dehydration.
- A person is dehydrated
- The plasma is very concentrated with salt (low water potential)
- The pituitary gland releases more ADH
- The kidney tubules are more permeable to water, so more water is reabsorbed
- Urine is less dilute
ADH in Over-Hydration
- Less ADH is released during over-hydration.
- A person drinks lots of water
- The plasma is less concentrated with salt (high water potential)
- The pituitary gland releases less ADH
- The kidney tubules are less permeable to water, so less water is reabsorbed
- Urine is more dilute
ADH in Special States
- Alcohol – alcohol decreases ADH production, leading to more dilute urine and hence dehydration.
- Urea concentration – Urea is normally constant in urine during changes in water content.
Bodily Changes Cause Urine Composition to Change
As previously discussed, the concentration and volume of urine produced is dependent on the water content of the blood. When there are osmotic challenges or temperature changes, urine composition and/or concentration can change:
- Sweating – this causes dehydration as you lose water. Hence, more ADH is released to increase water reabsorption so you excrete more concentrated urine. When dehydrated, the brain also triggers a response so you feel thirsty and want to drink more water.
- Over-drinking – as discussed earlier, this causes over-hydration so less ADH is released so more urine which is diluted, is excreted.
- High salt intake– fewer salts are reabsorbed so more salts are excreted. This produces concentrated urine.
Osmoregulation is the process by which organisms regulate the balance of water and solutes in their bodies to maintain a stable internal environment.
The Kidney plays a key role in Osmoregulation by filtering waste and excess fluids from the blood and regulating the balance of water and electrolytes in the body.
Anti-Diuretic Hormone (ADH) is a hormone produced by the pituitary gland that regulates the amount of water reabsorbed by the Kidney.
ADH affects Osmoregulation by increasing the reabsorption of water by the Kidney, which helps to regulate the balance of water and electrolytes in the body.
When there is too much ADH in the body, it can lead to water retention and swelling. When there is too little ADH, it can result in excessive urination and dehydration.
ADH is regulated by the body’s thirst and water balance mechanisms. It is released in response to changes in the concentration of water and electrolytes in the blood.
Yes, ADH levels can be affected by factors such as stress, illness, and certain medications.
Yes, imbalances in ADH levels can lead to health problems such as diabetes insipidus or edema. It is important to have ADH levels regularly monitored and treated if necessary.
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