Models of human thermoregulatory responses can predict how the body will react in nature. Comment by kristina nair: Way too broad – talk about it Humans react to extreme heat through homeostasis Function well 20+
Thermoregulation
The claim ‘Human thermoregulatory responses can predict how the body will react in nature’ is ambiguous and non-specific. The research on human thermoregulation is still fairly new and therefore the amount of research is limited on the topic. Although there have been numerous trails on the topic for example the research on military personnel (Andrew J. Young) “Thermoregulation is a process that allows the body to maintain its core internal temperature.” (Thermoregulation, n.d.) the core internal temperature for humans is 36.5 to 37.5. The temperature cycles regularly up and down throughout the day. Thermoregulation is crucial to human life. Without thermoregulation humans would not be able to adequately function and inevitably expire. The brain controls thermoregulation. Comment by kristina nair: Need to put in a source!!! Otherwise it’s a potential lose in mark.
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Hypothalamus
The hypothalamus senses external temperature growing too hot or too cold and will automatically send signals to the skin, glands muscles and organs. Sweating is the body’s approach to cooling down. When the body is hot the hair on your skin lies flat, sweat is emitted and muscles relax. When the body is cold the skeletal muscles tense up which leads to shivering and bodily hair follicles are raised which traps the heat and create warmth. (Osilla & Sharma., 2019). The hypothalamus is small and located at the base of the brain near the pituitary gland. When the hypothalamus doesn’t work properly it is called hypothalamic dysfunction.
Eating Disorder
Eating disorders such as bulimia can cause hypothalamic dysfunction. the hypothalamus motivates people to eat. When people have eating disorders the brain sends signals to other regions that override the hypothalamus. This study suggests that can ultimately condition the brain to reject signals from the hypothalamus. Comment by kristina nair: Need a source here
Temperature
Extreme cold is any temperature well below zero. Hypothermia is when the body temperature is lower than 35 degrees Celsius. Hypothermia may be characterised into primary and secondary types. Primary is when a human’s body heat balancing mechanism are working properly but are introduced to extreme cold conditions. Secondary is when a human’s body heat balancing mechanism are impaired and cannot respond to mild cold weather. Comment by kristina nair: Need source here
Bulimia
Bulimia is a binge eating disorder. the binge episodes are associated with a sense of loss or control and immediately followed with feelings of guilt and shame. A person who has bulimia can become lost in a dangerous cycle of out of control eating and attempts to compensate by then throwing it back up which can lead to feelings of shame guilt and disgust. Many people experience weight fluctuations so they may lose or gain weight but they normally stay in a normal weight range. (national eating disorder , n.d.) people who have immediate family who have eating disorders are more likely to develop an eating disorder. Being overweight as a child or teen can also be a risk. (Mayo Clinic, 2018) bulimia is chronic and can last for years or even lifelong. There is an increased risk of suicide among those with bulimia with 34% of people self-harming. (Mirror Mirror eating disorder help, 2015 )
Extreme Heat
Extreme cold is classified as temperature below 0 degrees, although in some countries below zero degrees is the normal temperature. Extreme cold becomes dangerous when the body’s temperature reached 35 degrees Celsius or below. The body then exhibits hypothermia. Which can lead to serious injuries or death. When the body begins to get cold the body starts to shiver and the hair follicles raise to trap the heat. The heat is retained to the centre of the body where all the organs are.
Homeostasis
Homeostasis is the ability of a living organism to regulate its internal conditions, despite changing environments. If our body gets too high or too low, key cellular processes would break down this is known as thermoregulation. Homeostasis occurs in two stages
- The body detects a change from the stable state, In either the internal or external environment
- These changes are counteracted by responses in the body
This is known as negative feedback or stimulus response. Messages in the body are either carried out by the nervous system or hormones, which are produced by glands of the endocrine system. For example, in thermoregulation the skin is an effector, which causes a response such as sweating or hairs raising. Effectors are either muscles (which contract in response to neural stimuli) or glands (which produce secretions) once the stimulus has caused a response, there is feedback sent to the receptors about the new conditions. the feedback helps regulate the intensity of the response, and this is called negative feedback. Comment by kristina nair: The effector is the part of the body which brings about the necessary change needed to achieve homeostasis
Analysis
The extremities are more affected by cold exposure more than other parts of the body. When the human body cools, blood flow is reduced to the hands and feet decreasing the amount of warm blood flowing to these areas. The hands and feet have a low metabolic heat production. The balance of control within the human system depends on the response to cold exposure and interaction between the skin and the core body temperatures with the central nervous system. The preoptic-anterior hypothalamus contains neurons that respond to the temperature in the brain and receive input from the thermo-receptors from the skin and spinal cord. The system is even more sensitively programed, certain neurons in the hypothalamus that respond to cold stimuli also respond to chemical changes. For example, when the hypothalamic neurons are exposed to low glucose the cold sensitive neurons fire. In a study observations were recorded during a training operation where, personal complained of being cold when they were dehydrated or hungry. (ROBERT S. POZOS & and DANIEL F. DANZL) The intake of food plays a major part in maintaining and enhancing the metabolic rate of the subject. Figure 1 exhibits how when the human body is exposed to cold temperatures the skin temperature senses the change and the body increases its core temperature. A message is then sent from the spinal cord lateral to the central nervous system and then psychological outcomes are made.
Although the sample size of the studies was not known it was published by a professor in biology at San Diego state university and professor and chair, department of emergency medicine, university of Louisville, school of medicine. This is a reliable group as the group has many reputable locations. University of San Diego state has come out with credible studies before. Although the sample size and method was not known the study has credible source. the field in human thermoregulation Specifically in models predicting an outcome is still emerging and therefore there isn’t adequate testing as it poses ethical issues. The sample size and method of testing are also limited due to an emerging field and ethical issues that are faced. Comment by kristina nair: Limitations Don’t get published if it’s not fact.
Heat is lost from the body surface faster than it is replaced. As a result, whole body cold exposure causes skin temperature over the entire body surface to decline. Insulation begins to increase when skin temperature decreases below 35 degrees Celsius and becomes maximal when skin temperature is about 31 degrees Celsius. Figure 2 shows how over the 90-minute exposure time the skin temperature decreases to about 19 degrees Celsius. In addition to mechanisms that limit heat loss humans employ other means to defend body temperature. Metabolic heat production can increase in order to replace heat lost during cold exposure. Cardiac output increases with cold exposure. Figure 3 depicts the increase in terms of heart rate, stroke volume, and cardiac output. The cardiac output increases primarily because of an increase in stroke volume with little change in resting heart rate during cold exposure.
Shivering depends on adequate supply of substrate for the metabolic processes producing energy for the contractions. Those who are not adequately protected from the cold by clothing and shelter will shiver, and their nutritional energy requirements will be greater than in warmer climates. the national energy requirement will be proportional to the duration and severity of cold exposure. Carbohydrates and fat oxidation provide 18 percent and 59 percent respectively of the total energy expenditure in the neutral condition compared to 51 percent and 39 percent in the cold condition. These finding indicate that both fat and carbohydrate metabolism sustain shivering, but that carbohydrate is the dominant energy source. either blood glucose, muscle glycogen stores or both may provide the source of carbohydrate for shivering thermogenesis.
The sample was fairly small for each of the studies, where it was about 7-8 people for the study. Due to the fact it is an emerging field the sample size was reasonable, although an improvement would be getting different genders and ages. The intuition of medicine that published the study. The intuition of medicine is a reliable group that produces reliable information. The studies used military personnel, which is reliable as they cannot alter the results. The author Andre J. Young is in the thermal physiology and medicine division, environmental physiology and medicine directorate, U.S Army Research Institute of Environmental Physiology and Medicine Directorate, U.S. Army Research Institute of Environmental Medicine. The work was also copyrighted by the national academy of sciences. (Andrew J. Young)
Interpretation
Source 1 indicates that when the hypothalamic region lacks nutrients the hypothalamus cannot work to its full efficiency. Therefore, when someone with bulimia is exposed to cold conditions their hypothalamus isn’t able to detect temperature changes to the best of its ability die to the lack of nutrients. The hypothalamus can’t send messages to the receptors in the spinal cord and central nervous system. If the hypothalamus is lacking in nutrients it can’t respond to the cold stimuli due to the chemical changes.
Source 2 establishes that when heat is lost from the body’s surface faster than it is replaced. If someone with bulimia is in extreme cold environments and due to a chemical imbalance the hypothalamus, models can predict how the body will react. The body also relies on metabolic heat production although someone with bulimia may not have a metabolism sufficient enough to sustain themselves. This can lead to an increase in cardiac output and stroke volume can increase to an unhealthy level. In Figure 3 the resting heart rate increases post accumulation to about 80 bpm.
It shows the effect of immersion in 18 degrees’ Celsius water and the glycogen concentration in the muscle. The glycogen concentration is high for a few of the men although most remained low. This would affect someone with bulimia differently as the glycogen concentration in their muscles would be lower than normal as they would lack nutrition due to improper intake of food. Therefore, the shivering would burn too much energy in a pre-existing weak body.
Evaluation
The quality of evidence was limited ad the field is still an emerging field with many ethical issues emerging with it. The sample size for the studies is often small and limited. In source 2 the study was done with military personal, they were all Caucasian males. The assumption can be made that the military personnel all had the same if not similar training and therefore are build similar to each other. They are fitter then the average male and therefore the study also doesn’t take into account the sedentary lifestyles of many people. The study was also done with purely males and didn’t take into account how the female body would react to the tests. An improvement to the studies would be to include more people from different types of lifestyles, with different mental health positions. Although none of the studies included anyone with bulimia it would improve predictions.
Conclusion
Models of human thermoregulatory responses can predict how the body will react in nature. Models of human thermoregulatory response can predict how the body will react in nature to certain extent. Prediction of human thermoregulatory responses has a small range as it doesn’t factor in the differences in each person. Although the models do have an accurate representation of what would happen to a human body in the cold temperature. The condition bulimia would affect the human thermoregulatory on harsh climates. The limits in the investigate were that the information available to the public on the topic is low as the field is an emerging field and as a student some information may not be open to students. In conclusions bulimia affects the human thermoregulatory system in harsh climates.
References
- Alberto Coccarelli, E. B. (n.d.). Modelling accidental hypothermia effects on a human body under different pathophysiological conditions. Retrieved from US National Library of Medicine: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5680406/
- Andrew J. Young, M. N. (n.d.). Nutritional Needs In Cold And In High-Altitude Environments: Applications for Military Personnel in Field Operations.
- G.P. Kenny, A. F. (2014). The human thermoregulatory system and its response to thermal stress.
- Hypothalamic mechanisms in thermoregulation. (n.d.). Retrieved from PubMed: https://www.ncbi.nlm.nih.gov/pubmed/6273235
- Lenhardt R, K. A. (n.d.). Thermoregulation and hyperthermia. Retrieved from PubMed: https://www.ncbi.nlm.nih.gov/pubmed/8901936
- MARILL, M. C. (2019, 07 03). Wired. Retrieved from How extreme heat overwhelms your body and becomes deadly: https://www.wired.com/story/how-extreme-heat-overwhelms-your-body-and-becomes-deadly/
- Mayo Clinic. (2018, May 10). Retrieved from Bulimia Nervosa: https://www.mayoclinic.org/diseases-conditions/bulimia/symptoms-causes/syc-20353615
- Mirror Mirror eating disorder help. (2015 ). Retrieved from Statistics on Bulimia: https://www.mirror-mirror.org/bulimia/statistics-on-bulimia.htm
- national eating disorder . (n.d.). Retrieved from Bulimia Nervosa: https://www.nedc.com.au/eating-disorders/eating-disorders-explained/types/bulimia-nervosa/
- Osilla, E. V., & Sharma., S. (2019, March 16). Physiology, Temperature Regulation. Retrieved from NCBI- PUBMED: https://www.ncbi.nlm.nih.gov/books/NBK507838/
- ROBERT S. POZOS, & and DANIEL F. DANZL. (n.d.). Chapter 11 HUMAN PHYSIOLOGICAL RESPONSES TO COLD STRESS AND HYPOTHERMIA.
- Thermoregulation. (n.d.). Retrieved from HealthLine: https://www.healthline.com/health/thermoregulation#takeaway
- Thermoregulation. (n.d.). Retrieved from Healthline : https://www.healthline.com/health/thermoregulation
- Wang, F. (2014). Modelling of cold stress and cold strain in protective clothing.
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