IGCSE Biology glossary
ADH
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Definition
Antidiuretic hormone, produced by the pituitary gland, that controls water reabsorption in the kidneys. When blood water concentration is low, more ADH is released, making the collecting duct walls more permeable so more water is reabsorbed, producing less and more concentrated urine.
What to include in an exam answer
ADH is a key example of negative feedback and homeostasis. More ADH means more water reabsorbed. Less ADH means less water reabsorbed and more dilute urine. Remember: ADH is produced by the pituitary gland, not the kidneys.
Example in context
Explain the role of ADH when a person is dehydrated (3 marks): The pituitary gland releases more ADH into the blood. ADH increases the permeability of the collecting duct walls in the kidneys. More water is reabsorbed from the filtrate back into the blood, producing a smaller volume of more concentrated urine.
Related syllabus topic
Coordination & responseRelated terms
- Homeostasis
- Negative feedback
- Tropism
- Reflex arc
- Insulin
- Glucagon
- Adrenaline
- Synapse
- Neurone
- Sensory neurone
- Motor neurone
- Relay neurone
- Receptor
- Effector
- Cornea
- Iris
- Lens
- Retina
- Optic nerve
- Accommodation
- Type 1 diabetes
- Type 2 diabetes
- Hormones
- Endocrine gland
- Auxin
- Thermoregulation
- Vasoconstriction
- Vasodilation
- Sweating