Fainting due to dehydration. Power?

Yesterday night I returned to my hostel after class at night. I was feeling so much tired,so I had my food quickly and went to sleep. Unfortunately I forgot to switch on the fan. I was sweating profusely till whole night beacuse the average temperature in Rajasthan is about 45 degree centrigrade.I did not wake up to switch the fan. Whole night my body lost water in the heat and my bed was wet. When I tried to get up in the morning I feel difficult to get up may be because of the water loss by sweating. My head seemed to whirl and I feel like I was about to faint. My world in front of me became dark and I cried. Two of my friends hear my voice and they helped me. They washed my head with water. Now my question is am I all right now? Does fainting due to dehydration harms the brain.? I am a student .Did the fainting affected my brain and memory Power?