The Limbic System

The limbic system is a complex set of structures that lies on both sides and underneath the thalamus, just under the cerebrum.  It includes the hypothalamus, the hippocampus, the amygdala, and several other nearby areas.  It appears to be primarily responsible for our emotional life, and has a lot to do with the formation of memories. 

In this drawing, you are looking at the brain cut in half, but with the brain stem intact.  The part of the limbic system shown is that which is along the left side of the thalamus (hippocampus and amygdala) and just under the front of the thalamus (hypothalamus):

 

The Limbic System is comprised of a number of different parts of the brain and is largely responsible for how we interpret sensory input; how we code and remember this input; and how we emotionally respond to it.  It is also responsible for regulating hormones and our sense of smell.

The Limbic System mediates and controls all aspects of emotion and motivational functioning including sexual behaviour, the desire for food, feelings of anger, rage and even the most sublime of emotions ranging from love to religious ecstasy.

The hypothalamus is responsible for regulating your hunger, thirst, response to pain, levels of pleasure, sexual satisfaction, anger and aggressive behaviour, and more.  It also regulates the functioning of the parasympathetic and sympathetic nervous systems, which in turn means it regulates things like pulse, blood pressure, breathing, and arousal in response to emotional circumstances.

The hippocampus appears to be very important in converting things that are “in your mind” at the moment (in short-term memory) into things that you will remember for the long run (long-term memory).

The amygdala (one portion of the limbic system) assigns emotional significance to everything you see, hear, feel, smell, and taste.

It is the seat of social and emotional intelligence and it is the brain’s anxiety “switch”.

Accumulated and chronic stress has the ability to alter limbic system function and can damage any number of neurons along this cascading system.

Chronic and acute stress can cause the amygdala to get stuck on the “on” position.  Under normal circumstances, it remains in the 'off' position, only becoming activated when appropriate anxiety is required, in times of appropriate danger or threat for example.

Repeated activation of this 'switch', during times of stress, sadness, grief,  anger or as a direct result of damage to the brain can cause the amygdala to become 'stuck' in the 'on' position. This can result in impaired neuronal sensory input.

An impaired limbic system may manifest as wide mood swings, or quick temper outbursts. A person may also be "over-aroused," quick to startle, and hyper-vigilant. Lack of energy, sex drive, inability to focus or process information, inability to cope with stress, and an abnormal ability to detect chemicals through smell and taste are all symptoms of abnormal limbic system function.

This impaired response and resulting operant conditioning is at the root of Multiple Chemical Sensitivities, Chronic Fatigue Syndrome, Electro-Magnetic Sensitivities, Fibromyalgia and a number of anxiety disorders.