Now when we talk about the physiological systems and now we're going to start integrating everything we've learned from previous models about how physiological systems function normally and how stress can now impact them. The foundations of the stress response is primarily by the nervous system. So we're going to talk about how stress can affect all different systems, but the nervous system activation or the sympathetic nervous system activation is really the foundations of our stress response. Things that sympathetic nervous system activation does is increase glucose in the bloodstream. So stored glucose as glycogen will be mobilized from our liver and would actually be broken down. So we have more energy theoretically to escape from the dangerous situation. Pupil dilation. Decreased digestion. So we actually have a decrease of the activation of our digestive tract, absorption, breaking down of nutrients because we really want to make sure that the focus of our bodies is not undigested at that time. We have an increase in catecholamines which is a group of hormones or a group of cell signaling molecules that are released from the adrenals, and that includes epinephrine or adrenaline or epinephrine and dopamine as well as cortisol which is also relief released from the adrenals. Things like increased heart rate, increased blood pressure and increased respiratory rate are the main sympathetic nervous system response. So what happens is we have a flight or a fight response. But when this flight or fight response and activation of our sympathetic nervous system is chronic, we got a long-term drain on the body. So the sympathetic nervous system is great. There are cases where we want to have all of this sympathetic activation when we're under acute stress. But the problem we start to see is that a lot of us in modern life are affected with chronic stress and we start to carry around these stressful events, situations or memories that start to have a long-term drain on the body. So the main center of this stress response is what's called the HPA axis which includes the hypothalamus, the pituitary and the adrenals. The activation from the hypothalamic area to the adrenals is a combination of our nervous system and neurotransmitters down to hormones. So essentially what happens is the hypothalamus is going to activate the pituitary and the anterior pituitary is going to secrete ACTH which is adrenocorticotropic hormone. Adrenocorticotropic hormone is then going to affect and stimulate the production of and the release really of catecholamines like epinephrine, norepinephrine and dopamine as well as cortisol from the adrenal glands. Now, long-term effect is that if we constantly have these catecholamines and cortisol being activated, it starts to have stress on various physiological systems. In particular talking about the nervous system, we can still have a direct impact. So remember that these activations of catecholamines and cortisol are great but they become a problem when they're chronic. So things that the nervous system might start to experience, our memory and learning changes, because if we're constantly bombarded with essentially a hyper-vigilant aware stressed out physiological system, memory and learning will change. So many studies have shown structural changes to hippocampus, decrease in neurogenesis or decrease in the production of new dendrites and new connections between neurons which affects learning. Mood disorders start to come up. So things like anxiety, depression, PTSD, are all associated with many of the symptoms or many of the aspects of this constant stress. Then we have things like pain loops or chronic pain where we're thinking about the pain, we're stressed about the pain, and this becomes almost like an ingrained pain loop that we really can't get away from. Then sleep becomes really just regular. So this might not be as extreme as insomnia but a lot of studies show that of course stress and chronic stress especially can really affect sleep patterns. Last is heart rate variability. So this is really important. This concept of heart rate variability is one of the things that many of the studies and many other papers that you were reading for this module and for many modules where we see mindfulness, stress reduction, breathing and yoga really have an impact. So heart rate variability is a measure of literally the variability in our heart rate. Which means sometimes we'd want to have an increased heart rate due to stress and activation of the sympathetic nervous system or a decrease heart rate where the parasympathetic nervous system starts to kick in. What heart rate variability tells us is how easy and how constantly we're switching back and forth between these two. It really shows that we have optimized autonomic nervous system functioning and it can give us an indication of overall fitness and well-being. So as you can imagine you'd like to have, when you're running away from something very scary, you have activation of the sympathetic nervous system. But when that danger is gone, you would like to then drop back down into a meditative state. Unfortunately, a lot of us carry this stress around constantly and we have all of this research and data coming out showing that stress and stress reduction therefore can have a huge impact on heart rate variability. Okay. So now we're going to look at how this stress response and this HPA access is going to have effect on the other physiological systems that we've talked about. So looking at musculoskeletal system. One of the biggest things that we see is muscle tension. So if we're constantly stressed out, we maybe start to hold muscles in a particular position, neck pain, back pain, shoulder stiffen up by our ears often, and just overall stiffness is one of the first things. In addition, things like osteoporosis can be exacerbated by chronic stress, and this can be due to a number of things. Poor absorption, chronic breakdown of bones due to nutritional reasons but overall we have this unhealthy reaction of both bones and muscles. In terms of respiratory system, people who are already suffering from things like asthma and emphysema can have a huge impact when we start to have increase in blood pressure, increase in respiratory rate because of the stressful situation that's prolonged. In addition, hyperventilation but all of these irregular breathing patterns can start to accumulate and have an effect then on more tissues because we start to decrease oxygen availability to cells and tissues and we start to perhaps change pH levels in our blood because we're not exhaling as much carbon dioxide or as much as regularly as we need to. The cardiovascular system. Again, this has been shown many times in many papers the amount of or the way stress can have an impact on the cardiovascular system and cardiac health. One of the biggest things is that first, the stress hormones we keep talking about adrenaline, cortisol, they elevate blood pressure. As soon as you elevate blood pressure, your heart has to work harder and the vascular chair has additional pressure against it. So it causes many problems. Chronic increase in high blood pressure can have inflammation effects, long-term heart disease problems, blood pressure changes, vascular problems and then also vascular disease because we start to have this accumulative effects at these chronic conditions. The endocrine system is deeply rooted into the stress response. So again, we have the hypothalamus that's going to be activated to the pituitary. We got this release of stress hormones once the ACTH hormone is actually stimulating the adrenal glands to release cortisol and epinephrine and norepinephrine. This can have an extreme effect because we start to change feedback loops. So we might not turn off these stress responses. But then in long-term we start to have other endocrine glands that are affected. In particular, men will have a change in the testosterone production, change in sperm production and menstrual cycles for women also will start to change. So irregular cycles, changes in the levels. These are just some examples of how the endocrine system can really start to be impacted by this chronic stress. Liver in particular, we talked before during our gastrointestinal module, how important the liver is for a variety of reasons. One really important thing though is that when we have chronic stress, as I mentioned before, this fight or flight response forces an increase in glycogen breakdown so that we mobilize glucose so we can create more energy. However, if we don't really need the energy. So if we don't actually have to run long distances or escape or use this energy, we're just actually starting to have increasing glucose in our bloodstream. This can cause many other problems such as diabetes because we start to have too much glucose in the blood over long periods of time. Also we have decrease in overall proper functioning and this of course can affect things like its ability to filter properly. One of the biggest things that the gastrointestinal system gets affected with chronic stress is acid reflux because we have a huge diet change. This can mean that we have an increase in acid in our stomach. We also have things like nausea and pain or ulcers and pain and then a change in the microbiome. In addition, nutrient absorption will also change. We have the inability or a change in ability to reabsorb any of the nutrients they need, and excess removal of water to compensate for the high blood pressure that the increase in blood pressure was causing, and this can also cause dehydration which can have systemic effects over time. Immune system and the lymphatic system is also going to be impacted. So this stress response will likely increase infection due to a microbiome disruption, due to increase in inflammation. Autoimmune reactions might be exacerbated and this is the inability for our cells and our body to say what is self versus non-self. We can have an overactive where we start to have autoimmune reactions and an underactive immune system where our bodies might not be picking up as well what's actually a threat. We talked about genetics and we said that one of the really interesting things happening in research right now is this ability to study how epigenetic changes are happening all the time, they're ingrained due to environment, they are ingrained due to behavior, they are ingrained due to repetition, and they're actually passed down. We say that on a molecular level these ingrained patterns are called methylation patterns. One thing that stress does without question is that it actually changes these methylation patterns. So chronic stress starts to change gene expression because all of a sudden we're telling our bodies, we have to make more catecholamines, we have to make more cortisol. So the genes that are associated with creating these molecules are being over expressed and that changes the pattern. So constant creation of stress proteins and hormones for stressful events is going to change this methylation pattern, and this is actually something that can be passed down. The good news of course is that this is also something that can be changed. So through yoga, through meditation, through mindfulness and actually through decreasing the constant stress that we're bombarding our systems with, we can actually start to have a huge impact and it's really impressive. It's really amazing to see how much just a couple of minutes can have on the quality of your mind set and the amount of stress that you feel like you're constantly bombarding your system with. So chances are we're all at home and in life and at work carrying around extra stress with us. So hopefully, some of the exercises in the demo give you this ability to influence your stress levels, your HPA access, your stress response and start to decrease this response even if it's just for a couple of minutes a day.
