The physiology of the human examines the particular characteristics and mechanisms of the human body that make it a living organism. The fact that we remain alive almost surpasses our control, as our hunger forces us to seek food and fear drives us to seek shelter. Our sense of cold prompts us to take care to warm ourselves, and other forces compel us to seek companionship and reproduce. Therefore, humans are essentially automatic, and the fact that we have sensations, emotions, and knowledge is part of this automated sequence of life. These special abilities allow us to exist under very different conditions, which would otherwise make life impossible.