Higher centres (autonomic nervous system)

The main centres within the brain that regulates the autonomic nervous system is the hypothalamus. It receives multiple inputs from:

• other central nuclei e.g. those of the limbic system linked with emotion
• the external environment e.g. olofactory mucosa via the medial forebrain bundle
• the internal environment e.g. osmoreceptors, thermoreceptors within the hypothalamus

It integrates this information and then initiates an appropriate response via the:

• sympathetic nervous system:
  • neurones involved with sympathetic responses seem to congregate in the posterior hypothalamic nucleus
  • hence for example, stimulation of the posterior nucleus results in a positive chronotropic cardiac response
• parasympathetic nervous system:
  • neurones associated with the anterior nuclei of the hypothalamus
  • hence for example, stimulation of this area produces increased secretion within the gastrointestinal tract

Efferent fibres from these nuclei pass to the brainstem spinal lemniscus and on the intermediolateral column of the spinal cord.