We've examined the endocrine system and some of the hormones that will allow the athlete to adapt to training, maintain homeostasis and stay healthy. The nervous system is the other important player involved in adaption homeostasis and health. And one component of the nervous system that is particularly important is the autonomic nervous system that is located in the peripheral nervous system that's designated as PNS here. The autonomic nervous system, or ANS, works in concert with the endocrine system and the central nervous system to keep the physiology of the athlete's body in proper balance. Chronic fatigue in athletes is linked to over training. And both chronic fatigue and overtraining are linked to the inability of the brain to restore the body's homeostasis. So how does the hypothalamus know what hormones to tell the pituitary to release to keep the body functioning properly? A part of the answer to this question is found in the autonomic nervous system. The endocrine and the autonomic nervous systems work together to help keep the body functioning appropriately. The autonomic nervous system is preprogrammed to perform two important roles. One is to manage stress. And when the individual is in a stressful situation, the autonomic nervous system will stimulate a very primitive phenomenon called fight or flight response. And this is also known as the acute stress response. In this situation, the autonomic nervous system stimulates the endocrine system, to flood the body with hormones in order to activate it into high alert. Now, early in human evolution, this innate acute stress response served to quickly mobilize energy resources and prepare the body to do one of two things. To stay and fight the threat or to decide that fleeing to safety was the better option. Training and competition stimulates the same acute stress response our early ancestors used to deal with a dangerous situation in the environment, such as a big, scary animal that was looking for an easy source of food. In the case of training, the stress is artificially imposed, with the goal of outperforming a competitor. The autonomic nervous system also has a rest and digest component, they calms the activity of the body down. So on one end, the autonomic nervous system puts the body on higher route and on the other end, it puts it to sleep. In essence, the ANS allows the athlete into a turbo charged activity mode when needed. Such as during training and competition. And into an idle mode during recovery. And you'll see shortly why this see-saw effect of fast and slow aspect of the autonomic nervous system is important to understanding chronic fatigue. Now, we're going to talk a lot about the vagus nerve in this lesson and then in the next couple of lessons. It is the major nerve of the autonomic nervous system and holds potential key to explaining chronic fatigue. The name vagus means wandering in Latin. And here's an illustration of where this nerve goes in the body, it's basically everywhere. The vagus nerve connects to the brain at the brain stem and about 80% of the fibers in the vagus nerve carry information from the body back to the brain. And the remaining 20% shuttle instructions from the brain back to the organ systems. The vagus nerve has profound control over heart rate and blood pressure. And this is why this nerve is so important to athletes. So in this lesson, we're going to overview the difference between the two branches of the autonomic nervous system. The sympathetic branch or the fight or flight branch that puts the body on very high alert and the parasympathetic branch that is the rest and digest branch that allows the body to shift into a slow idle mode while it's digesting food and resting and recovering. We will also discuss the influence each branch has on the heart and other organs. And we will discuss the meaning of respiratory sinus arrhythmia, and what this tells us about the fatigue stages of the athlete. And finally, I'll introduce you to a really interesting theory about how the vagus nerve works to keep the body from destroying itself when it is under stress. The theory is called polyvagal theory. So this lesson's going to provide you with the insights you need to understanding training induced chronic fatigue and how heart rate monitoring Will help you track how well the autonomic nervous system is managing training stress. So let's get started.
