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Homeostasis and excretion Typeit
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The maintenance of a constant environment in mammals is called . Animals detect stimuli using sensory receptors, and a response is brought about by effectors after signals travel throughout the body, either via hormones over long distances or by travelling down and across synapses between cells. Some animals, called , are unable to control their internal body temperature in this way, and instead rely on behavioural responses such as sunbathing.
It is important for organisms to control their blood sugar concentration not only to maintain a good level of glucose for respiration, but also because it affects the of the blood by changing the amount of dissolved respiratory substrates. Osmoreceptors in the of the brain detect these changes, and bring about changes in the - the main organ involved in controlling how much water is reabsorbed by the body to replace that which is lost through processes such as exhaling and sweating. The nephron, its functional unit, consists of:
If this organ fails to function correctly, it could be life-threatening. However, there are two main treatments available. In , a type of renal dialysis, blood passes through a machine across a partially permeable membrane and is filtered 2-3 times a week. Alternatively, an organ can be used to place a fully functioning organ from a donor into the recipient, but the recipient must take immunosuppressant drugs to ensure that the transplanted organ is not rejected.
The liver is another organ essential for excretion. It has four main connected vessels, three of which transport blood - the fourth is the , which carries excretory products to the gall bladder. One of the main functions of the liver is the of amino acids to produce ammonia and a keto acid. The ammonia enters the ornithine cycle to produce the less toxic nitrogen-containing molecule , which is concentrated in urine and removed via the bladder.