Most of the functions of the brain are still unknown, and the ones we know about are very poorly understood. The brain is assumed to be the organ of higher mental function, of the mind and intellect, but there is surprisingly little evidence for this, and no one has any idea what physical structures or mechanisms perform these functions. The brain is known to control all bodily functions by means of motor and other nerves which carry impulses from the brain outwards to all parts of the body. Sometimes these are under our voluntary control; mostly, they are involuntary, reflexive or automatic. Reflexive actions are the result of impulses passed inwards from the body towards the brain by means of sensory nerves. Information arriving in the brain about various sensations like heat, pain, touch, position, the need for saliva or gastric juice or even the thought or smell of food are acted on in the various “centres” in the brain.