STRESS AND THE HUMAN BODY
In this module you will examine the effects of chronic stress and cortisol dysregulation on the cardiovascular and digestive systems. First you will examine the normal structure and function of these systems, and then investigate the mechanisms behind chronic diseases associated with high stress levels, such as high blood pressure and obesity.
Let’s begin by learning more about each system. As you may already know, the cardiovascular system is a closed loop circulatory system (unlike the lymphatic system, which is an open loop), with the main function of circulating blood carrying nutrients and oxygen to the tissues of the body and removing waste products and carbon dioxide from the body’s tissues.
The heart is the pump that drives this circulation. The hypothalamus in the CNS has control over heart rate and respiration. The hypothalamus sends signals directly to the heart and adrenal glands in response to signals collected from blood chemistry and pressure to adjust heart rate, keeping oxygen levels up and carbon dioxide levels down. In a crisis, the CNS and endocrine system respond to severe blood loss to return blood pressure back to normal. Complete this tutorial on the circulatory system in order to better visualize these processes.
Let’s look more closely at factors that affect blood pressure (BP). Click on this brief explanation of peripheral resistance for an illustration of its contribution to BP.
There are two mechanisms that the body uses to respond to stress that affect heart rate and BP:
Signals from the sympathetic nervous system override the normal “pacemaker” of the heart to increase HR and constrict the blood vessels. Higher heart rate accompanied by vasoconstriction causes blood pressure to increase.
The kidneys can also respond to a drop in BP by conserving water and returning it back to the blood stream to attempt to restore normal BP. A hormone, ACTH, is released from the adrenal medulla in response to hemorrhaging (uncontrollable bleeding) or dehydration. In summary, hormones signal water conservation to increase blood volume.
Both the CNS and endocrine systems also influence digestive system function. Complete the tutorial to learn about the anatomy and physiology of this system. Once the food that we ingest is broken down into its chemical components, the nutrients are absorbed by the small intestine. The small intestine is highly vascularized, and the nutrients enter the blood stream and the circulatory system here. As the blood vessels make their way back to the heart, they merge as the hepatic portal vein and travel to the liver.
The nutrient-rich blood makes a stop at the liver, where toxins are removed and blood sugar levels are detected and corrected with the help of the hormone insulin. The contents of the blood are now appropriate to travel to the heart and enter systemic circulation. You will learn more about how insulin regulates blood sugar levels, and the effects that the stress response have on insulin, blood sugar, and fat storage.
Now review the effects of positive and negative feedback from the neuroendocrine system on both circulation and digestion before continuing on to your Case and SLP assignments.
Stress and the Cardiovascular and Digestive Systems
In this Case Assignment, you will address the following in a 2- to 3-page essay:
First complete this exercise to identify the factors that have an effect on heart rate.
In your introductory paragraph, explain:
Which factors contributed to an increase in HR, and
Which factors contributed to a decrease in HR?
Now view the video Stress effects on the heart and read the following resources on hypertension and stress:
Stress and Blood Pressure, by the American Heart Association
Effect of psychological stress on blood pressure increase: a meta-analysis of cohort studies. Gasperin, D et al. 2009. Cad. Saúde Pública, Rio de Janeiro, 25(4):715-726.
Based on what you read and observed, address the following questions in the body of your essay:
What is the risk of stress on the heart?
What are the contributions of the nervous system to the increased workload that the heart experiences when an individual is stressed?
Do some additional research to define “myocardial infarction risk.” What do Gasperin et al. (2009) say about the relationship between stress and myocardial infarction risk?
Using the resources above, define “hypertension.” Summarize the results reported by Gasperin et al. (2009) about stress and hypertension. What was successful in lowering hypertension?
In a conclusion paragraph write about what surprised you as you completed the readings/video for this Case study?
You are provided with many scholarly references to complete this assignment. Include a References section that lists these sources (refer to the Background page). For any additional research you are required to do to complete your assignment, please use scholarly references such as a peer-reviewed journal article or a government-sponsored or university-sponsored website.
As you read through your sources, take notes from your sources and then write your paper in your own words, describing what you have learned from your research. Direct quotes should be limited and must be designated by quotation marks. Paraphrased ideas must give credit to the original author, for example (Murray, 2014). Direct copying from “homework help” websites will not receive credit.