By the end of this chapter, you will:

• Outline three interacting biological systems and understand their primary role in the regulation of health and illness: the nervous system, endocrine system and immune system
• Gain an understanding of how each system works and the interactions between these systems
• Show awareness of the circadian clock in the regulation of behaviour and mood
• Understand the role of the microbiome
• Describe and discuss research on psychoneuroimmunology
• Define and describe the role played by homeostasis in the creation of stability and equilibrium