Homeostasis (including non-communicable diseases)

With the topic of homeostasis students often fail to make the link between external changes (effect of drinking a lot of water, resulting in increased urine output) with the internal changes that bring about the external changes.

Students need to be able to explain the importance of maintaining a constant internal environment in response to internal and external change, this includes (but is not limited to!) an explanation of how insulin controls blood sugar levels in the body.  The level of detail required is important for the study of the topic at GCSE, in explaining how insulin controls blood sugar students should include how glucagon reacts with insulin. Students should also be able to compare type 1 and type 2 diabetes and explain how they can be treated.

Other homeostatic mechanisms and considerations also need to be explained these include, temperature regulation, effect on cells of osmotic changes in body fluids and functioning of the kidneys in maintaining water balance. In describing the function of the kidneys in maintaining water balance students should include the effect of ADH on permeability of kidney tubules. 

Students often have misconceptions in relation to homeostatic mechanisms, one such misconception is the role of the kidneys. Delivery of this topic should clearly explain the role of the kidneys in filtering substances from the blood in response to external and internal stimuli. Animations are useful teaching tools to help support learning in this area. Another misconception students have is that insulin raises blood sugar levels, when delivery this aspect of the topic ensure that key words are clearly defined and highlighted to students. Students could work in pairs to produce poster size flow diagrams which they must then display for other students to critique. 

Students often seem to get confused between vasoconstriction and vasodilation, using the terms the wrong way round, it would be worth spending some time going through the temperature regulation processes step by step- perhaps students could produce their own animation or provide a voice over to an animation. Ensure that students do not talk about blood vessels moving towards or way from the skin surface. 

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