explanation text example and generic structure

Explanation text about "how does the body react to heat?"

When the human body is exposed to very hot conditions one result can heatstroke. this is often the case for the athletes and people who have to work outside in summer. (part I)

heatstoke is a sudden, uncontrolled rise in body temperature. it is a reaction that result from the human body not being able to replace fluid lost through perpiration. if the lost fluids are not replaced the dehydration occurs and this leads to a decrease in blood. (part II)

in this situation the body must decide whether to give the blood to the main organs (liver, kidneys, brain and so on) or to the skin. because the main organs are mor important, they will receive the blood. also, as a consequence of the drop in fluids, the body loses its ability to sweat. the situation becomes critical. the body now cannot produce sweat; therefore it cannot cool itself. excess heat cannot be released through the skin as a result of the loss of blood supply to that part of the body. the lack of blood supply and the inability to sweat together cause the body to overhead. (part III)

heatstroke can cause permanent injury if not treated properly. it is one way of how the body can react to heat. (part IV)

note :
part I : general statement
part II, III : explanations
part IV : closing/concludes