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Fight or Flight Physiology
The body has a whole range of internal control systems that consist of two opposing parts (a kind of yin and yang). The balance between these two halves allows the body to maintain a constant internal environment (so-called ‘homeostasis’) despite major changes in the outside world. For example, when it gets too hot outside, the body has its own thermostat (in the base of the brain) which stimulates the sweat glands and opens up the blood vessels in the skin to lose heat. If it gets too cold, these same blood vessels are shut down and the body hairs are made to stand up (goose bumps) to trap a layer of air next to the body for insulation. Using this kind of balanced control system, the internal environment of the body can be kept within tight constraints and thus the body can give optimal performance.
A classic example of this kind of control is the autonomic nervous system. This system automatically adjusts a whole range of bodily functions according to our needs. For example it allows us to suddenly run for a bus if we need to, but without keeping the heart pumping at top speed every minute of the day. Most of these adjustments are quite small and we don’t notice them – in fact the whole idea is that the system just gets on with it so we are free to think about the more important things in life – like when the next bus is due.
A game of two halves
The autonomic system has two parts: the parasympathetic nerves, which allow the body to rest and recuperate (you could think of this as the soft, female, yin side of the system); and the sympathetic nerves (the hard, male side), which prepare the body for action (in extreme circumstances this is known as the ‘fight or flight’ reaction). When the autonomic nerves fire they release different chemicals (known as neurotransmitters) from their endings into the various parts of the body that they supply. These chemicals have a direct effect on the different tissues – for example nor-adrenaline from the sympathetic nerves causes the heart to beat faster.
The various effects of the two systems on different parts of the body are shown in Table 1. Basically, the sympathetic system prepares the body for action by speeding up the heart and diverting blood away from non-essential duties (such as the gut) to more important areas such as the muscles. When the threat is passed, the balance swings back to the parasympathetic system which allows the body to recuperate and replace the energy stores etc that have been used up.
The slow side
As you know from experience, these changes can happen almost instantaneously when you are suddenly faced with a stressful situation (for example when a horror movie makes you jump). But as well as this fast ‘nervous’ reaction, the body also makes slower, longer term adjustments by releasing various chemicals into the blood, such as hormones. For example, glucagons (the opposite of insulin) release the stores of glucose (blood sugar) in the liver into the bloodstream so that extra energy is available for the brain and muscles. The composition of the blood is also altered to make it thicker and more likely to clot – so any cuts are sealed quickly and blood loss kept to a minimum. The brain also releases its own morphine-like pain killers (called endorphins – theses are thought to be involved in acupuncture mediated pain control) which block the brain’s pain receptors so you can continue to think clearly without being hampered by constant pain messages. The sympathetic nerves also supply the adrenal glands, which sit on top of the kidneys and release adrenaline and nor-adrenaline (among other things) into the blood. These transmitters have similar effects on the body as the sympathetic nerve endings themselves.
Today’s lifestyle
All these changes are meant to be temporary. Once the danger is passed, the parasympathetic takes over and the body ‘stands down’. The body isn’t built to be constantly ready for action. Obviously, these systems were developed to help us deal with physical threats when we had to fend for ourselves day-to-day, for example when hunting. Although most of us no longer hunt (Saturday nights excepted), the body still reacts to stress in the same way. These days the stress is different – it’s less physical and much more sustained. For example, knowing you have to hit a deadline by the end of the day can cause stress all day, or even for several days. This means that the body stays ‘hyped up’ for much longer than it is meant to – and this is potentially unhealthy. For example, sustained high levels of corticosteroids, such as cortisol, which are released by the adrenal glands, are thought to contribute to cancer risk and heart disease. And the increase in blood clotting can increase the risk of heart attacks occurring.
Can we beat the system?
Yes! The triggers (stresses) that change the balance between the sympathetic and parasympathetic systems come mainly from our senses. What we see, hear, feel, etc is fed into the brain, which then sifts the information and decides what level of alert we should be on (see Table 2). This isn’t an ‘all or nothing’ decision, but rather a question of what is the level of threat or likely need. In addition, the level of reaction to any given stress seems to be influenced by the mood we happen to be in at the time – for example, if you feel happy and in control to start with, you may react less extremely to a given stress than if you feel on edge. And, of course, we can get used to different stresses so that the sympathetic system is fired up less easily. For example the first time you take a class or give a lecture your heart beats faster and you get a dry mouth etc, but after teaching for several months or years the reaction no longer occurs – you might even find it relaxing. And, of course, different people react to different degrees to different stresses.
In short, the autonomic nervous system is influenced by the ‘higher’ brain functions. This means that it is possible to learn how to ‘artificially’ control the fight/flight reaction and even induce a ‘papa-sympathetic’ state. This is what many Eastern doctrines have achieved, for example with mediation.
Summary
This is just a brief overview of quite a complex system that has evolved over millions of years. However, I think it has many parallels with martial arts and Eastern philosophy in general. It accepts that most things are represented by a balance between two opposing forces, and that adaptability depends upon the maintenance of a dynamic system that is largely automatic but which can be influenced by conscious thought.
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Table 2: Influence of higher (brain) systems
on autonomic function
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Dr Nigel Lincoln