For scientists understanding the human brain took exceptionally longer time as it is the most complex organ in the human body. The chief objective of this organ is to control the central nervous system (CNS), which it achieves by way of the cranial nerves and spinal cord, the peripheral nervous system (PNS) and regulates virtually all human activity. Apart from that the brain also unconsciously governs many involuntary actions such as heart rate, respiration, and digestion. The brain achieves this through the autonomic nervous system. On the other hand, the brain consciously controls complex mental activities such as thought, reason, and notion.
The brain contains some one hundred billion neurons, which are capable of electrical and chemical communication with hundreds of thousands of other nerve cells. Nerve cells in turn rely on some quadrillion (1015) synaptic connections for their communications. On an average the normal adult human brain weighs between 1 and 1.5 kg and has an average volume of 1.6 litres. Anatomically, the brain can be divided into three parts, which are the forebrain, midbrain, and hindbrain. These three parts are responsible for controlling and governing different activities.
