This subject serves as an introduction to the biological bases of behaviour. Nerve cells are the basic building blocks of the brain. Therefore their functioning and methods of communicating form the basic principles of brain and nervous system functioning. Hence this subject includes introductory lectures on the elements of the nervous system that contribute to the conscious and unconscious aspects of behaviour. There is an emphasis on understanding how the cells of the nervous system function and communicate with each other, thus allowing us to explain how sensory information, drugs, and hormonal changes influence behaviour, as well as how behaviour influences the brain.