Thermoregulation
Objectives:
Specific heat and heat of vaporization: Thermoregulation. Why are there less temperature changes in areas near the sea? Why do we sweat?
THEORY:
What is the thermoregulation in an organism ?
It's all the ways that the body do to keep a constant temperature. It's all based on a constant balance between heat inputs and losses.
When a body creates or earns heat, we call this"thermogenesis". But when it looses heat, we call this "thermolysis"
Increased thermogenesis
Muscle thrill
It is an excessive increase in muscle tone with desynchronized contractions of neighboring muscle fibers.
When intense, the shivering becomes conscious, even unpleasant. It is predominant in the jaw and on inspiration.
Increased chemical thermogenesis
It is an increase in cellular metabolism in response to cold.This increase occurs primarily in a certain type of fat cell that makes up brown fat (Brown fat replaces muscle chills for baby). But in adulthood, there is no more brown fat. This mechanism is therefore insufficient to allow satisfactory adaptation to the cold. The chemical thermogenesis causes an acceleration of the metabolism, it is induced by the secretion of certain hormones: adrenaline, glucagon and glucocorticoids rather for the short-term response, and thyroid hormones for the long-term adaptation.
Limitation of thermolysis
Skin vasoconstriction
Under the effect of cold, peripheral circulation may be reduced by vasoconstriction of the vessels (reduction in the diameter of the blood vessels) which results in the maintenance of heat in the central and vital parts of the body. Blood flow (20 mL / min) may be reduced (1 mL / min). If exposure to cold is prolonged, periods of vasodilation (dilation of blood vessels) and vasoconstriction alternate. This phenomenon is known as the “Huntington reaction”. To observe this reaction, the tissue temperature should be between 7 and 12 ° C.
Cutaneous vasoconstriction has two objectives:
Reduce skin temperature, therefore heat loss;
Limit exchanges between the core and the bark, and therefore the cooling of the core temperature.
Decreased heat loss
Horripilation, commonly referred to as "goose bumps", is an erection of the hair. The purpose of this mechanism is to trap, between the hairs in contact with the skin, a layer of buffer air which will act as insulation. This principle works well in both furry and feathered animals. But in humans, very little hairy, it is only an archaic system inherited from his animal ancestors, which no longer has any real effectiveness.
Reducing or stopping sweating (sweating) helps reduce heat loss
Role of perspiration in thermoregulation
Perspiration participates in thermoregulation, because it allows to decrease the body temperature by releasing heat in the skin. Perspiration should prevent the body from overheating, for example during exposure to strong heat or during sports. There is also emotional sweating, caused by stress.
When the body temperature rises too much, the center of thermogenesis located in the hypothalamus is inhibited, while the center of thermolysis is activated. Sympathetic nerve fibers stimulate the sweat glands to release more sweat. Evaporation of sweat allows cooling. If the body's cooling mechanisms are ineffective, there is a risk of hyperthermia, or heat stroke, which can be fatal. To reduce body temperature, it is advisable to rest in a cool place and drink water.
Specific heat and heat of vaporization
The specific heat of a certain substance is the heat that we have to supply to a kg of the substance to increase its temperature one-degree centigrade. Each substance has its specific heat.
The heat of vaporization is the amount of energy required for a mole of a substance (which is in its melting temperature and at the pressure of 1 atm) to pass completely into the gaseous state.
Experiment:
During the transition from liquid to gas (at 98.9Cº) is kept at the same temperature since the water has not evaporated completely (because there is still water to evaporate and this makes the temperature stable).
In this video, we explain our experiment related to thermoregulation.
drive.google.com/file/d/1THlgA6cbCq5EmpGiC473eB4ra6f98t33/view?usp=sharing
Consequences to daily life:
Water has a great capacity to absorb heat. Thanks to this, a mass of water can absorb a lot of heat with little temperature change.
Water uses heat to break its hydrogen bonds, and that's why it takes so long to warm up.
This causes fewer temperature changes in places that are close to the sea because the seawater absorbs a part of the heat and regulates the temperature of the area.
This happens, for example, in cities like Barcelona.
The same thing happens when we sweat.
Sweat is a very important secretion for the body as it helps regulate body temperature.
Sweating is a mechanism that cools the body. When body temperature rises, the sweat glands secrete sweat, a liquid made up of water and mineral salts. Sweat water evaporates using body heat and consequently reduces body temperature.
Sweat also cleans the skin and allows us to remove toxic substances.
Kahoot
Personal opinion
What we have learn?
Aina: I have learned a lot about the properties of water and also the reason why we sweat. I have also improved my skills to edit videos and create kahoots.
Paula: I have learned that it is the thermoregulation of our body, the reason why we sweat or have chills. And also many properties of water, such as: that it is specific heat or evaporation heat.
Simon: During this challenge, I learned a lot of notions like vasoconstriction or thermogenisis. Even if I didn't do some parts, it was very pleasant to read and to learn.
What we want to improve in this activity?
Paula: Improving can always be improved, but considering that this work has been done by three people and some with difficulty in the language, I suppose we could improve the language and our lack of communication to carry out a project like this.
Simon : Like as writed Paula, We were only three to do the work and not seven, so I'm sad that students didn't do the work or even not help us. And we have a lack of communication as writed Paula. But I'm sure we'll do a great job for the next project.
Aina: I would like to improve what my classmates have already said before: communication and participation, since it has been pretty difficult to do everything with so few participants. I hope the next challenges go better!
What is the best thing for us?
Paula: The most important thing I've learned is that it makes thermo-regulation in us. That is, how it affects our organism.
Simon: For me, the best thing is communication and mutual aid. It was very good to talk with a foreigner and to improve my english
Aina: The best thing for me has been to communicate with people outside the center and in this way improve my English and my communication in this language.
Aina, Simon & Paula