let's take a look at Thermo regulation which is um heat regulation by the body our concept map includes interrelated Concepts the first one being infection some of the symptoms of infection are fever and chills so that's tied to Thermo regulation the hypothalamus is involved in regulating body temperature um inter cranial regulation is associated with that uh there can sometimes be a traumatic brain injury or something that involves brain swelling and that could affect the temperature control center profusion is uh related to Thermo regulation because uh one way to minimize or maximize heat loss is vasod dilation and basoc constriction the skin plays a role because it U acts to uh reduce heat loss uh tissue Integrity also requires intact skin to help maintain optimal temperature um and finally fluid and electrolytes with ex uh with loss of fluids um we may be it's it's very closely tied to loss of heat and malnutrition increases the risk for hypothermia because of an inability to generate adequate heat so let's start by looking at some terms uh first of all Thermo regulation pretty straightforward the process of Main containing core body temperature at a pretty constant um amount constant value so we will define core body temperature on one of the next slides uh so you can see the other ones are just you know the the the normal the hyper and the hypo so hypo is is low hyper is high and normal is just what it says normal uh range if we look at this uh Continuum of U from one end to the other from um severe hypothermia um with mild hyp hypothermia to normal normothermia then hyperthermia and finally hyperpyrexia which is fever uh so these are uh there's a lot of numbers here I'm not going to ask you to know all the numbers uh on the upcoming slide we'll ask you to know the number for set point so uh core temperature is the temperature of the internal environment of the body looking at major organs and it's maintained in a within a range of 97 to 995 uh sometimes they'll say that the average is 986 but um we know that everybody's not exactly on that particular number and so there's kind of an average uh but the core body temperature is definitely more accurate than skin temperature there are dial variations uh in in internal core temperature with the highest point in the late afternoon and the lowest point in the early morning so uh temperature is going to reflect the difference between heat production and heat loss so sweating can increase uh heat loss and keep the body temperature from rising too high and shivering will increase and actually raise temperature so the hypothermic hypo hypothalamus a little slip of the tongue there is the the thermal control center for the body um I once did a little breakdown of the brain different brain structures and what all they did and I think the hypothalamus is like one of the the organs that works over time so uh it receives information from peripheral and Central Thermo receptors and Compares that with its temperature set point and um communicates that to the brain okay um so again um this little diagram I I like um a little bit of review from the last time with a decrease in body temperature there's a process which is more complicated but we can keep it simple that leads to the release of epinephrine into the blood which increases heat production by increasing metabolic rate phasal constriction and the sympathetic nervous system is stimulated to increase muscle tone and initiate shivering then the reverse happens with an increase in increase in body temperature and it discontinues the EP pfron which then leads to vasod dilation decreased muscle tone and sweat production and dissipation of Peete through perspiration and evaporation so we'll look at heat production and then heat loss so first of all metabolism is the body's main source of heat production and lots of factors impact that and of course that involves the uh cell metabolism skeletal muscle contraction hormonal activity uh the sympathetic transmitters of course epinephrine norepinephrine are released when an increase in temperature is needed and then we talked about uh shivering uh and it's you know it's reg its ability to um raise temperature looking at mechanisms of heat loss most of the bodies heat losses occur at the skin surface as heat from the body moves to the skin and then to the environment so interestingly um I always learn something when I'm teaching this there are numerous arterovenous anastomoses Under the Skin there are little short vessel segments that directly connect arteries and veins acting as shunts to bypass the capillary bed uh so they're kind of like radiators when the shunts are open the body heat is freely dissipated to the skin and environment and when they're closed the heat is retained in the body and controlled almost exclusively by the sympathetic nervous system in responses to core changes in core temperature and environmental temperature we also have just the smallest little detail but it's the contraction of the pyomo muscles of the skin which raise skin hairs and produce Goose pumps to Goosebumps to help um Aid in heat conservation these are several mechanisms of heat loss and that includes radiation so transfer of heat through the air or a vacuum as we know happens with the sun conduction is direct transfer of heat from one molecule to another and sometimes from one person to another or one surface to another I think our textbook talks about um somebody that has a high temperature and we put them on a cooling mattress and so the heat from that person's body is transferred to the cooling blanket convection is heat transfer through air currents so normally a layer of warm air tends to remain near the body surface and convection causes removal of that warm layer and replaces it with with air from the environment and finally evaporation which uses body heat to convert water on the skin to water vapor looking now at populations at risk for alterations in body temperature there's always the Aging Factor so infants and young children have um lack the ability to conserve heat produced um so Rel large surface area relative to their Mass makes them susceptible to temperature loss and they have limited subcutaneous fat uh older adults have diminished ability to regulate their temperature uh because their sweat glands uh decrease in number and efficiency uh people who are living in very hot or cold climates and individuals of low socioeconomic status with limited ability to maintain their temperature so we're going to talk about fever on this slide and on an upcoming slide we're going to talk about hyperthermia so those are two things that you want to pay attention to and we will compare and contrast them fever involves a response by the hypothalamus hypothermia does not so both of them involve an increase in temperature but only fever is associated with the hypothalamus so uh the other word for fever is pyrexia elevation of the body temperature caused by an upward movement or displ placement uh of the hypothalamic uh set point so from 98.6 it's going to rise a little bit and this involves an immune response to pyogens which are fever producing agents and there's external pyrogens and internal pyrogens so the external ones are usually bacteria or viruses and the internal ones are just various chemical substances so what happens is let's say you have an infection these ex exogenous or external pyrogens induce the host cells in your body to produce mediators or chemicals these endogenous pyrogens these cyto kindes uh so that the when bacteria um are broken down the products of that bacteria are present in the blood or tissues and then fosic cells of the immune system engulf them and digest them um and so you know kind of a long story short it's it's going to uh end up with the release of prostag gland in E2 now we talk a lot about prostaglandins this semester prostaglandins are um they're hormonik substances they're they're um somewhat like a lipid and so this one is a very specific prostag glandon that's involved with fever which is prostag gland and E2 so prostagland and E2 will then bu to receptors and the hypothalamus to um specifically raise that thermostatic set point and once that happens um the hypothalamus is going to initiate shivering and vasil constriction again shivering involves some muscle contractions and that's going to raise the the body's core temperature to a net a new set point and fever is established so continuing with fever um fever very often will signal the presence of an infection or some other condition that's going to Warrant treatment in the class lecture we will look at drug fever so there are certain medications that can induce fever and also fever of Unknown Origin which can be caused by a whole host of conditions uh fever is is not you know so much a disease process it's really more of a Associated manifestation uh with the various conditions so it does tend to resolve when whatever is going on resolves um so um fever that is regulated by the hypothalamus uh the normal kind of mechanism usually won't go above 15.8 Fahrenheit um sometimes when it is these other situations like a seizure or maybe somebody has a a tumor of the hypothalamus uh or they do have one of these Fe of Unknown Origin then that temperature could go above 105.8 um some evidence supports that small temperature elevations will enhance or facilitate uh te- cell production um and we sometimes ask the question you know what is the purpose of fever is there a purpose and and the one answer we do have is that certain uh organisms that cause fever grow best near normal body temperature 98.6 and so by raising that set point um to a higher temperature then it could uh inhibit the growth of those organisms um but on the other hand even mild temperature elevations can have a negative effect uh people that have um cardiac or pulmonary diseases uh fever is going to increase the workload of the body so it increases oxygen demand and if you are already what compromised in that way then then that could be more problematic fever can also cause confusion so hyperthermia we've got a kind of a general hypothermia and then malignant hypothermia uh so hyperthermia is defined as increase in the body temperature above 37.6 Centigrade with an unchanged hypothalamic set point so it can occur um when it heat related conditions that uh uh impair the body's ability to dissipate heat uh when there's increased muscle exertion um think about people like athletes or outdoor workers uh so their ability there's an increase in body temperature that exceeds heat loss uh and then malignant hypothermia is a little bit different it's generated by uncontrolled skeletal muscle contraction um there's several reasons for for this this but I think probably the most common is general anesthesia agents and certain uh I think genetic factors uh trigger this sometimes people go to an go to surgery and this happens under anesthesia our last topic is hypothermia which occurs due to excessive heat loss insufficient production of heat or it could be there's dysfunction of hypothal regulatory mechanisms Although our por text says that there's not typically a primary disorder of the temperature regulating Center so I my understanding of this is that it's not a you know a a malfunctioning hypothalamus but more a situation of the hypothalamus being overwhelmed and we'll talk more about specifics with hypothalamus and clinical manifestations during our class lecture thanks very much sh