How on Closing the eyes and gently pressing it you see the light when no light is entering?

Answer 1

Waw an interesting question. This is because recepor neurones (or primary afferent neurones) always fire their action potential to the same place and (so results in the same sensation within the brain) no matter what the stimulus is. So for example if a pain sensing peripheral neuron was stimulated electrically, even if no painfull stimulus was present the brain would still think that part of the body was in pain. No when cells are damages they release certain chemicals and neurons often release they neurotransmitters as one of these chemicals. And finally the eye ball is not empty but infat contains a liquid (called the humors). Put all these together: Puhing the eye inceases the pressure of the humors on the the retina which contains rods and cones, adapted neurones that detect light. As they are squashed by the humor they release chemicals that activate the normal nuerones and which carry the action potentiol back to the brain and intereperate the damge as light signal and so creating immages in the brain.