Tutor profile: Emma W.
Subject: Public Health
Describe the epidemiological triangle and how it can be used to prevent the spread of a disease.
The Epidemiology Triangle is comprised of 3 elements - the host, agent and environment. Time is also a very important component that ties all three elements together. Take the flu, for example. The agent would be the influenza virus, and the host would be a human. The environment is flu season (the colder months of the year) and especially heavily populated areas in which close contact in common. With regards to time, people who have contracted the flu are typically contagious 1 day before showing symptoms until about 5 to 7 days after the onset of symptoms. In order to prevent the spread of a disease, we need to alter/change/remove an element of the triangle, therefore stopping the mode of transmission and routes of infection.
Does temperature affect the function of cholesterol in the body?
Yes - about a quarter of the body's cholesterol is in cell membranes to enforce structure and permeability. In higher temperatures, cholesterol decreases membrane fluidity to prevent any lysing that may occur. In colder temperatures, cholesterol actually increases membrane fluidity in order to prevent cells from becoming too stiff or rigid.
Describe the Renin-Angiotensin-Aldosterone System (RAAS) with low blood pressure (hypotension).
If a person has low blood pressure, the body will work to re-establish homeostasis. The kidneys act through the RAAS system. The first sign of disequilibrium is decreased arterial pressure within the nephrons of the kidney. This leads to a decreased glomerular hydrostatic pressure and thus decreased glomerular filtration rate (GFR). The lower GFR also indicates that less sodium (Na) is being filtered. This triggers Juxtaglomerular (JG) cells to release Renin, which cleaves inactive Angiotensinogen into its active form, Angiotensin I. As Angiotensin I accumulates, it is converted into Angiotensin II by Angiotensin Converting Enzyme (ACE), an enzyme typically found in the lungs. Angiotensin II works in two main ways: 1- constricts vessels to increase blood pressure and to trigger the release of ADH (or vasopressin), which increases the aquaporins and water reabsorbed (more volume reabsorbed means larger blood volume and increased blood pressure); 2- trigger the secretion of aldosterone, which increases the amount of sodium reabsorbed in the kidneys (this helps because water will follow sodium/solutes through osmosis). All of this works together to restore a homeostatic blood pressure.
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