Vagus Nerve Function in Gut-Brain Communication

Abstract

The brain-intestinal axis plays an important role in maintaining the body's homeostasis. Nutrition can minimise and improve the undesirable negativities that can occur in the brain-intestinal axis. The gut microbiota is composed of the central nervous system, the hypothalamic-pituitary-adrenal (HPA) axis, the autonomic nervous system and the enteric nervous system. This feature of the enteric nervous system allows it to be described as the 'second brain'. Communication between the brain and the gut (second brain) creates a bidirectional system. The primary neuron that transmits gastrointestinal signals and contains sensory nerve fibres is the vagus nerve. The sensory neurons of the vagus nerve innervate the internal organs and the brain, perceiving and transmitting various sensory signals. This function enables communication between the gut and the brain. Although the vagus nerve is a nerve of broad physiological importance in maintaining homeostasis in the body, it also has important functions in the control of the intestinal, cardiovascular, immune, endocrine and respiratory systems. Before food is eaten, the vagal nerves in the gastrointestinal tract send detailed information about the food to the brain, which receives and processes the information. The brain receives and processes the information, initiating intestinal peristalsis for the digestion and absorption of the ingested food, and the secretion of hormones necessary for the end of the meal and the feeling of satiety. The vagal nerves in the gastrointestinal tract therefore play an important role in the control of food intake.