Temporary increase in motivation
Yes,staying awake all night will result in a temporary increase in motivational, positive characteristics due to the secretion of an hormone called 'Dopamine'.There will be a strong simulation of the mesolimbic pathway.This pathway controls the pleasure & reward feelings of your brain.So what happens now ? You will be confidently committing a lot of errors in your exams or in day today activities.
Lack of Planning & Evaluation
Staying awake all night shuts down your ability to plan properly.Combining the effects from the dopamine secretion.You will be overly optimistic.And staying awake all night for a very long period of time will result in loss of 'neural plasticity'.Simply put,Your neural system won't be able to adapt to new situations instantaneously.
Reduction in memory capacity
Memory.One of the vital necessity for smooth performance in the examinations will be affected.So what happens when you sleep? Imagine your brain as a lake,the memories ( formulas , essays , 8m questions , short answers etc.) are like particles in the water.When you sleep,they settle down smoothly in the water bed.The memories consolidate and settle in an organized manner only when you sleep.So sleeping increase your brain's Hard drive capacity.
So let us see what happens to the brain's processing power.The lack of sleep destroys the ability to form episodic memories.That means a sure problem.You wouldn't be able to retrieve the information with good speed.There will be no connection formed inside the memories.You may remember only the introduction or the first formula.The rest will be forgotten due to broken links in your memory structure.
The long term effect.Scientists say that the chances of heart diseases are equivalent to that of SMOKERS if your sleep is deprived terribly.Young professionals die around at the age of 30 due to heart diseases.
A sleep of 6.5 - 7.5 hours is recommended for a healthy happy life.Hope you get the sleep.Sleep well.Take care of your head. :)