walter Cannon was an American doctor in the early 1900s who spent a lot of his career expanding our understanding of homeostasis which is the tendency of our body to respond to the environment in a way that keeps the internal workings of our body stable so the body's ability to maintain the right temperature the body's ability to maintain the right pH etc so as a part of his study of homeostasis Dr canon was really interested in the homeostatic response of animals to threats or dangers so threats or dangers and and threats or dangers are what we've been referring to as stressors so uh so basically Dr canon was interested in our homeostatic response to stressors and he coined the response that he saw the fight orflight response because he basically saw that we were either going to prepare to fight against these threats or dangers or we were going to prepare to run away from these threats or dangers so the fight orflight response that Canon was so interested in it revolves around the inner workings of the nervous system and the endocrine system so on the nervous system side of things we have the sympathetic nervous system so we have our brain and our spinal cord that make up the central part of our nervous system and then nerves branch off um of the central core and we have the part of our nervous system that we don't always think about um or or aren't thinking about to control is the autonomic nervous system and a branch of that autonomic nervous system that's going on behind the scenes is the sympathetic nervous system and this is the the aspect of our of our nervous system that's going to transition our body into the get out of danger mode and so with that we'll see increased heart rate in order to pump blood with oxygen and nutrients all around our body so we have an increased heart rate that heart's just going to beat a lot faster and we're also going to see increased respirations so we have an increased respiratory rate and that gives us the ability to get more oxygen into our blood and and all the way to our tissues and it gives us the ability to expel more carbon dioxide as a as a waste product from our muscle work and then we're also going to see increased uh peripheral vasoc constriction so the the blood vessels in our peripheral parts of our body like our arms and our legs are going to clamp down and they're going to tighten in order to push more blood to our core area because our arms and legs are important but we could live without them it would be a lot harder to live without our brain or our vital organs so we need a lot of our blood forced into those really crucial areas so we're going to see um peripheral vasoc constriction happening in this fight or-flight response and then lastly we're going to turn off less important things like digestion and immune function and ovulation because these things are great if we're just hanging out but they're definitely less crucial in life or death situations so teaming up with the sympathetic nervous system we have the endocrine system and so the endocrine system is going to supply some of the hormones which remember are those chemical messages in order to rally the troops around the body and the two biggest hormone players actually come out of the same organ which sit on top of our kidneys the same organs um and those are your adrenal glands and so the inside of our adrenal glands this hash part um is called the medela and from the medala we get our catakolamine hormones and our catakolamine hormones excuse me include epinephrine and norepinephrine so sometimes those are more often called adrenaline and noradrenaline but these are the hormones that are major communicators for increasing the heart rate and blood pressure and otherwise communicating that sympathetic response that we just talked about so those are really supporting the sympathetic nervous system these uh these hormones coming out of the adrenal medala and then on the outside this boulder part of our adrenal glands uh that's called the cortex and out of the cortex comes some other major stress hormones uh and and the biggest one is a gluccocorticoid called cortisol and it helps me remember u that that cortisol comes from the cortex if I'm thinking about that court kind of root word uh or root part of the word but cort Cortisol is a steroid hormone which contributes to the stress response by redistributing glucose energy in the body and um and suppressing the immune system and so just to review real quick we have this fightor-flight response to stressors so we're preparing to either fight or to run away and that's being communicated by our sympathetic nervous system um which is being assisted by the the hormones of our endocrine system um and so we have this fightor-flight response that Dr canon um coined the the terminology of but we also have another response called tend and befriend we're calling this affiliative response the tend or befriend response because it turns out that sometimes a better response to stress is to huddle together and to form support systems and an important biological component to this response is the hormone oxytocin and oxytocin is associated with things like pair bonding and and so it can moderate this stress response um and it's really interesting if you know much about oxytocin it's majorly integrated with the hormone estrogen and so estrogen is a major sex hormone in women and so what follows is kind of a naturally greater disposition to this tend and befriend response in women uh much much more so than in men and so we have these two major kind of categories of response to stressors we have this fightor-flight response and this tendon befriend response and in the later part of the 20th century a guy named Hans Sally continued the stress research of Dr canon and he was able to classify distinct stages to the adaptive fight orflight and tendon or tendon befriend responses and he called this generalization the general adaptation syndrome so I'm going to I'm going to shorten that to GS for general adaptation syndrome and he saw this general adaptation syndrome as having three phases and in the first phase um he called it the alarm phase and in this alarm phase that stress reaction kicks in so your heart starts racing um and and your resources are mobilized and you're ready to fight or or to run for your life and that's the alarm phase and the second phase um which he called the resistance phase uh we're actually fighting or or fleeing or or huddling together our our temperature is elevated and our blood pressure and and rate of breathing remain high and we're also bathing our body in the stress hormones like like cortisol um and so our body has reserves to react to those acute stressors in this resistance phase but those reserves only go so far and that brings us to the third phase of the gas and that's exhaustion so if the resistance stage isn't followed by recovery the body's stress resources get depleted um and it leads to exhaustion and our tissue and muscles become damaged and our our dampened immunity can make us really susceptible to illness and and all around overexposure to stress can have some really damaging effects because like many animals our body is pretty well equipped to handle short-term stress but the problem is that when we apply those life-saving stress reactions um to our daily commutes and to our nine-to-five jobs and to other psychosocial kind of trivialities of life we end up spending way too much time experiencing the negative consequences of stress this exhaustion consequence and it has some pretty nasty consequences so next up we're going to explore what happens to our body's behaviors and emotions when we're exposed to chronic stress