The limbic system is made of structures present underneath the cortex but above the brain stem. It consists of the following structures:
- Septum, the mid-line of the brain - inhibits aggression
- Mammillary bodies - involved in maternal behaviour
- Ventral tegmental area
- Nucleus accumbens - these are activated by viewing pictures or mental imagery whch the person perceives as being pleasant.
- Amygdala (almond) - plays important role in fear / anxiety, anger and sexual motivation. It mediates aggression. This structure gets bigger in people that have post-traumatic stress disorder. Periods of high stress cause neurons here to grow more dendritic processes.
- Hippocampus (sea horse) - measures blood levels of glucocorticoids, important in the "fight or flight" response. This brain area is smaller in people with long-term major depression.
- And, arguably, the prefrontal cortex which could be considered a cortical component of the limbic system as it is strongly interconnected with structures such as the amygdala.
The primary function of the limbic system can be considered as attempting to influence the hypothalamus. The hypothalamus plays a major role in the autonomic nervous system.