Biology GCSE (Combined)

• The five kingdoms of life are animals, plants, fungi, protists, and bacteria.
• The main job of the kidneys is to filter the blood and remove all of the waste that we don't want, with urea being the main waste product.
• The kidneys also regulate the levels of useful things like ions and water which we need to keep at the right levels.
• We gain ions like sodium and potassium ions from our diet and we need them for all sorts of things in the body.
• If the levels of ions or water get too high or too low it can start to damage our cells and cause problems.
• Sweat is a natural way to lose ions, but the main way we regulate our ions is through our kidneys.
• Water regulation is a bit more complex as we gain water from the foods and drinks that we consume and lose it partly from our skin when we sweat and our lungs when we breathe.
• Most of the water has to be lost from the kidneys in the form of urine.
• The kidneys remove waste products like urea and regulate other substances like ions and water.
• Each of our two kidneys contain around a million structures called nephrons which perform the filtration and selective reabsorption process.
• Inside the brain, there's a structure called the hypothalamus which detects the concentration of water in the bloodstream and sends a signal to the pituitary gland when the water levels in the body are too low.
• The pituitary gland releases a hormone called adh or antidiuretic hormone into the bloodstream when the water levels in the body are too low, and as the adh travels around the body it reaches the kidneys and tells the tubules to reabsorb more water into the blood, increasing the amount of water in the bloodstream and producing less urine.
• If the water levels in the body get too high, the hypothalamus will stop sending signals to the pituitary gland and the pituitary gland will release less adh, resulting in the kidneys reabsorbing less water and producing more urine.
• The process of water regulation is an example of a negative feedback loop as the body is constantly monitoring our water levels and adjusting them to make them balance.