The limbic system is involved in some of the most challenging neurobehavioral disorders known to medicine, including disorders of mood and anxiety such as depression and posttraumatic stress disorder (PTSD), substance abuse and dependence, and disorders of cognition and memory such as Alzheimer disease.
Chronic stress and inflammation activates the limbic system in a way that damages the body. Long-term release of epinephrine and other hormones can cause:
Mood imbalances, often cranky/irritable or mentally exhausted
Impulsive decisions or acting erratically
Damage to blood vessels
High blood pressure
Poor digestion, upset stomach
Chronic stress and inflammation impairs cognitive function, namely on tasks that rely on the integrity of cortico-limbic networks.
Hippocampus: Emotion, Learning, Memory
The hippocampus receives input from neurotransmitter systems, including serotonin, norepinephrine, and dopamine systems.
If your nerves are sending constant stress signals to your brain from:
1) chronically inflamed organs
2) chronic stress
If our vagus nerve is sending positive signals and we're able to activate our PSNS the body will release ACh. If our system is under chronic inflammation and chronic stress from this our vagus nerve will be sending negative signals back to the brain and there will be a lack of ACh release.
With this comes an increased norepinephrine release which will throw off your hippocampal theta rhythms in turn directly affecting the regulation of your emotions, it will affect how you learn and take in information and will affect your memory. The hippocampus responds to the neurotransmitter acetylcholine from the medial septum, which regulates the hippocampal physiological state. The medial septum is involved in setting one of the critical oscillatory rhythms in the hippocampus, the theta rhythm.
Abolishing that region or the associated theta rhythm interferes with hippocampal function.
Because our hippocampus receives input dopamine and serotonin it’s no surprise why we easily become addicted to things that bring us an instant rush of dopamine or serotonin. The memory and emotion alone are enough to invoke our temptation. I think we truly reach an equilibrium when we are able to balance and regulate our emotions based on our memories and use them as fuel to our learning. Our emotions and memories can teach us a lot, we can either learn from them or repeat them.
Amygdala: Aggression, Eating, Drinking, Sexual Behaviors, Fear, Survival Instincts
The amygdala and hippocampus work together to regulate emotions, especially evolutionary “old” emotions that play a role in survival—love for one’s children, aggression, fear, and anxiety.
The amygdala assigns emotional meaning to memories and helps the brain in forming fear-based memories.
The hippocampus helps form sensory memories, which are memories associated with sensory input. When the smell of a crisp apple or warm beach air brings back memories of a long-ago summer, the hippocampus is responsible.
Together, these two organs help the brain interpret the emotional content of memories.
If chronic inflammation is left unchecked for extended periods of time without activation of the PSNS to reset, calm down and balance the system, you can easily see how mental health takes a huge hit.
Hypothalamus: Monitors blood glucose levels, salt, blood pressure and hormones
The hypothalamus releases hormones that play a role in a wide range of emotions, including pain, hunger, thirst, pleasure, sexual feelings, anger, and aggression. It also helps the body maintain a state of homeostasis by regulating the autonomic nervous system.
Receives information from the vagus nerve about blood pressure and how full the stomach is, using this information, it releases chemicals that regulate appetite and blood pressure.
Gathering information from the reticular formation of the brain stem about temperature and then using that to manage the body’s response to heat or cold.
Regulating the body’s internal clock, the circadian rhythm, based on light, darkness, and other sensory input.
Chronically inflamed organs are going to constantly be sending distress signals to the brain and limbic system that they are stressed and in the next part of the series I'm going to write about how new research shows how depression is directly linked to chronic inflammation.