Consciousness is perceived to be a state of awareness. It is a state in which you are aware of your surroundings and in control of the sensory nerve stimulations being conveyed by your immediate environment. So how do these nerve impulses culminate to a higher state of consciousness? The nervous system of a living thing is a masterpiece that has evolved over time under the watch of selective evolution. A cell being the basic building block of life knows fairly well how to go about its daily chores by controlling its chemical composition. This is achieved through the offset of triggered event to maintain an overall atmosphere of hospitability. As the hand of evolution never ceased working there was an inclination to form bigger and better systems that could protect the spark of life and aid in its survival through processes of replication and reproduction. Individual cellular systems would fail in these larger colonies as each cell would strive to maintain favourable conditions for its own well being compromising on the overall health of the colony. There was a need for cells to transmit information to ensure that the individual subsets of the colony would be aware of other neighbouring cells. This would evolve into a collective state of well being for the colony that is monitored by the chemical transmissions between individual cells. As even bigger colonies of cells started to form a messaging protocol was required that was faster and could take evasive actions. This triggered the formation of nerve cells that relayed information between the different parts of a system and monitored its health. The nervous system could also create motor responses that would collectively result in the locomotion of the organism. The formation of the nervous system was completely controlled by the underlying cells for their needs to serve a bigger purpose.
Although this neural network would coup perfectly well with smaller systems it required more intensive number crunching for bigger systems. As these bigger systems have sensory stimulus coming from a larger number of cells there was a need for an exterior control hub where all this information could be processed before devising a valid response. This gave rise to the formation of brain. In the human species this organ has developed far more superior analytical skills than any of its predecessors. All the information arising from our senses is raced towards the central nervous system to be analyzed and processed after which motor responses are initialized. These responses are further classified into conscious, subconscious and reflex actions based on the nature of the stimuli and the transpired reaction.
Most of these nerve impulses are transported between cells based on differences in action potential, caused by changes in the flow of certain ions at the cell boundaries. So an impulse can be classified as an electrical pulse flowing between different cells. These pulses have varying frequencies based on the nature of the stimulant. As you read this your brain is constantly getting millions of these impulses from sensory neurons spread all over your body, constantly monitory your internal and external environment. Some of these pulses make their way to the central nervous system and other don’t. The ones that don’t are considered to cause reflex responses and the ones that do further result in conscious or subconscious responses based on the nature of the request.