Hello and welcome to Module 4, stress and trauma-related disorders. This is Lecture 1. In this lecture, we will discuss stress and the brain and body's response to it. What is stress? This is a word that is used quite a bit. Some might even say overused. But what does this word actually refer to? Stress is broken down into two components. The first component is the stressor, which is a demand placed on a person by the environment that exerts pressure on the person to change, adapt, or respond in some way. The second component is the stress response, which is the person's unique response to the stressor. We experience a great many stressors as minor predictable aspects of everyday life such as juggling multiple responsibilities at work, or taking a very difficult class, or managing a household that includes a small child and pets. Sometimes stressors take the form of major life events, even positive ones such as moving, receiving a promotion at work, or getting married. Some stressors are both chronic and negative such as caring for a sick spouse or child, trying to financially support a family on a minimum wage job, or living in a high-crime community. Other stressors may meet the definition of trauma, which is an event in which a person is exposed to actual or threatened death, serious injury, or sexual violation. Examples of trauma include natural disasters such as hurricanes or tornadoes, a terrorist attack, or sexual assault. The way in which we respond to stressors is determined by two factors, the way in which we understand or interpret the stressor and the way in which we understand our own ability to cope effectively with it. This is true for both minor everyday stressors such as sitting in a traffic jam all the way up to an including major traumatic events. Research has demonstrated that people who have confidence in their ability to cope with stressors are the people who tend to respond well to them. When people struggle in their responses to extreme stress and traumatic events, they may go on to develop particular psychological disorders. Before we delve into this topic however, let's spend some time considering the normative predictable response of our brains and bodies to stress. The brain responds in a very specific way when faced with a stressor. A structure within the brain, known as the hypothalamus, initiates and directs the brain and body's response. When a person encounters something in their environment they perceived to be threatening or dangerous, the hypothalamus responds with a cascade of activity throughout the brain and body. Specifically, it activates two different systems, the autonomic nervous system or ANS and the endocrine system. Let's consider each system separately. The ANS is a network of nerve fibers that connects the brain and spinal cord to various organs within the body. These nerves control actions of the organs that are not within our voluntary control such as breathing, blood pressure, digestion, heart rate, and respiration rate. When a person is confronted with something in their surrounding environment that they perceive as being dangerous, the ANS activates what is known as the sympathetic nervous system or SNS. The sympathetic nervous system increases heart rate, blood pressure, and respirations while slowing other functions such as digestion and salivation. When the danger has passed, the ANS activates the parasympathetic nervous system or PNS. The parasympathetic nervous system counteracts the effects of the SNS in order to bring the body back to its normal state of relaxation. The PNS slows heart rate and breathing, lowers blood pressure, and restores digestion and salivation. What part does the endocrine system play? The endocrine system is made up of glands found throughout the body. Glands produce chemicals called hormones, which are released into the bloodstream and act in various ways throughout the body. At the same time that the hypothalamus activates the sympathetic nervous system in response to a perceived threat, it also activates the endocrine system. It influences the adrenal glands which are found on top of the kidneys to release the hormones epinephrine and norepinephrine. These hormones travel through the bloodstream and cause further arousal as the body's response to threat. The hypothalamus also activates the pituitary gland, a very small gland found in the brain to secrete adrenocorticotropic hormone or ACTH. ACTH is often referred to as the major stress hormone. It travels through the bloodstream to a particular part of the adrenal glands which then secrete a group of hormones called the corticosteroids. The best-known corticosteroid is cortisol. Like the other hormones we've already mentioned, the corticosteroids travel through the blood to various organs and muscle groups, influencing the body to heighten its readiness to respond to the environmental threat. Taken together, the autonomic and endocrine response to a perceived threat is known as the fight-or-flight response because it influences the body to respond to threat by either fleeing from it or attacking it. While everyone experiences the fight-or-flight response differently, some people are very sensitive and experience an intense response. While others feel it only mildly, it is a completely normal adaptive physiological response to the presence of something threatening in the environment. For most people, most of the time their bodies return to their typical state of relaxation after the danger has passed. Some people, however, continue to experience a high level of physiological arousal long after the threat is gone along with significant anxiety, depression, and other symptoms as well. At this point, the experience changes from being a normative and predictable response to a psychological disorder. In the next lecture, we will discuss acute stress disorder and post-traumatic stress disorder.