In Stronger: Develop the Resilience You Need to Succeed there is a section on the Biological Bases of Human Resilience that is fascinating.
It turns out the key to developing resilience at the biological level is to interpret experience in a way that increases performance and facilitates homeostasis. Changing attitudes and developing resilience through training is key. Optimism is your friend.
In 1975, neurologist Paul MacLean coined the term triune brain to describe its three functional levels: The neocortex is the most sophisticated component of the human brain, representing its highest functioning level. Not only does the neocortex interpret sensory signals, communications, and gross proprioceptive-based control of motor (musculoskeletal) behaviors, but part of it—the ventromedial prefrontal cortex (vmPFC)—presides over imagination, logic, decision making, problem solving, planning, apprehension, and, most important, the interpretation of experience.
It is the vmPFC that labels an experience (real or imagined) as threatening, punishing, or rewarding. It finds solutions to problems, it sees the opportunity in danger, and it sees the glass as half full rather than half empty. Based on the nature of the interpretation of experience, the vmPFC then activates the second level of the triune brain: the limbic system.
The limbic system is relevant in any discussion of stress and resilience because of its role as the human brain's emotional control center. The limbic system is believed to be just that, a system, consisting of numerous highly connected neural structures, for example, the hypothalamus, hippocampus, septum, cingulate gyrus, and the amygdala. The amygdala is the primary anatomic center for fear, anger, trauma, and aggression. It's also the center of the fight-or-flight response, a term coined by psychologist Walter Cannon in 1915. The amygdala serves as the primary survival mechanism in the human body. Thus, it's a key anatomic component in the biology of resilience.
The brain stem and spinal cord represent the lowest level of the triune brain. The major functions of this level are the maintenance of so-called vegetative roles such as heartbeat, respiration, vasomotor activity, and the conduction of impulses to many higher levels of the brain. The spinal cord represents the central pathway for neurons as they conduct signals to and from the brain. The brain stem is the basic engine that drives the machinery of the human body.
Human resilience represents a most elegant and ongoing dance between the vmPFC and the amygdala. When faced with danger, the vmPFC activates the amygdala so as to prepare you to fight, flee, or otherwise resolve the threat. Highly resilient people appear to be able to effectively regulate the amygdala so as to benefit from its activation but then allow it to quickly recover its baseline activity. This process of recovery to a steady state is what Cannon called “the reestablishment of homeostasis.”
Consequently, the bodies of resilient people are supercharged with moderate increases in hormones such as adrenalin, noradrenalin, gamma-Aminobutyric acid, neuropeptide Y and Cortisol,which allow you to do “superhuman” things for short periods of time. When these hormones surge, your strength and perception
increase, your memory improves, your eyesight may get better, your tolerance for pain increases, and you react to stimuli faster. In other words, you're better prepared to meet any challenge success fully.
The person who is not resilient experiences homeostatic failure, during which the vmPFC interpretations either overstimulate or understimulate the limbic system. The result of overstimulation can be anxiety, panic attacks, confusion, reduced problem-solving capacity, irritability, anger, even violence (for example, road rage, airline rage), and seizures. The result of under stimulation may be hopelessness, depression, resentment, and a lack of motivation. With highly frequent or chronic overstimulation the amygdala can develop a state of chronic hypersensitivity at the cellular level. Amygdaloid nerve cells literally become highly irritable and will over-respond to experiences that would have not otherwise caused excitation. It's like having 10 cups of coffee.