THERMOREGULATION PROCESSES OF HUMAN AND ANIMAL BODY TEMPERATURE

In organism body (individual level) always any regulation mechanism  for achieve situation which homeostatic. Homeostatic is effort to defending or making condition which steady state which assure of optimization all process of physiology in body. For achieve this situation, body doing many regulation activity, as mechanism to achieve the homeostatic which be provided. Regulation and homeostatic which happen in big organism level, that are in population level  and community in a ecosystem. Regulation system have function to manage a work in all of organ system which any in the human body. Regulation system is work to accept the stimulation, processing the stimulation and receive the stimulation. (Rikky Firmansyah, 2009: 129)

All of system in organism body play along with the other for defending the homeostatic in our body. Homeostasis as need by cell and tissues of our body to can work very well to confronted the external environment change. Some homeostatic mechanism which important, that are: thermoregulation, osmoregulation, water and electrolit regulation and glucoregulation. In human body, the regulation be done by nerve and hormon. (Tati suryati syamsudin Subahar, 2009: 67)

When any change in our body, any 2 respond mechanism which happen possible, that are:

1.      Negative feedback

A process which happen when our body system need stoping  according to complete  a process which was happening.

The example when the blood pressure increase, receptor in artery carotid will be detecting and sending signal to the brain. The brain will send message to heart to decelerate the throb so the blood current which pumped more little and cause decrease of blood pressure.

2.      Positive Feedback

A respond to make a process physiologist or action from a system. Usually this respond is a siklik process which can be continue to consolidate a action or a process until respond of negative feedback take change position. (Rikky Firmansyah, 2009: 131)

The example of regulation process is thermoregulation. Thermoregulation is a physiological process that is the integration and coordination of activities that are actively used to maintain core body temperature against cold or warm temperature changes. Human is homeothermik creature which can manage a body temperature for achieve a equilibrium so body temperature disposed constant which not influence by environment temperature. Human enzim work effective in 37⁰ C temperature. Center of temperature manage in brain part of hypothalamus. There are some effector which engage between variation mammals. Temperature managed with some mechanism. Fluctuation temperature detected by receptor which called thermoreceptor, the example is skin.

If we very hot or cold because influence from out environment or in our body, so thermoreceptor will be send nerve impuls to hypothalamus. After that hypothalamus will be send message response to effector like skin to increase or decrease the lose of heat from surface with:

a.       Increase body temperature responded with stand hair feather (pyloerection) because contraction skin muscles whereas decrease body temperature responded with restraint body heat with flat the feather hair because skin muscle relaction.

b.      Glands under skin will be secretion sweat to skin surface for increasing the lose of heat with evaporation if temperature body increasing. Secretion of sweat will stop if body temperature have been comeback normal.

c.       Blood vessel which currrent skin will broad for bring a more some heat out from body (vasodilatation) if body temperature increase, and blood vessel will shrink (vasoconstriction) to minimalition loosing of heat through skin if body temperature have been normal again.

If happen decrease long temperature, so hypothalamus will be increasing the secretion of hormon TRH to stimulate output TSH by hypophysis which will be stimulate increase secretion hormon tyrocsin by thyroid gland. This hormon will impedance metabolism which have other product heat energy. Other that, non specific mechanism to bridge decrease body temperature is with contraction of muscles extremity for producting of heat.

In the regulation of body temperature, the animal must regulate heat received or are lost to the environment. Mechanism changes the animal's body heat can occur with 4 processes, namely conduction, convection, radiation and evaporation. Conduction is the change in the animal's body heat due to contact with an object. Convection is heat transfer due to the movement of air or fluids through the body surface. Radiation is the emission of electromagnetic energy. Radiation can transfer heat between objects that are not in direct contact. For example, solar radiation. Evaporation heat loss from the surface of the liquid is transformed in the form of gas.

The hypothalamus is a very sensitive part, which is the main integration center to maintain energy balance and body temperature. The hypothalamus serves as the body's thermostat, to receive information from various parts of the body in the skin. Coordinated with the adjustment mechanism is very complicated in addition and subtraction as appropriate temperatures for core temperature any deviation from the normal reference values​​. The hypothalamus is able to respond to changes in blood temperature as small as 0.01 º C.

The hypothalamus constantly informed of skin temperature and core temperature through specific receptors that are sensitive to temperature called thermoreseptor (receptor warm, cold and pain in the periphery). Temperature receptors are very active during temperature changes. Primary temperature sensation adapted very quickly. Core temperature is monitored by a central termoreseptor located in the hypothalamus and in the central nervous system and abdominal organs.

In the center of the hypothalamus known to have 2 temperature settings, ie in the posterior region and anteror. Posterior region is activated by cold temperatures and then trigger the reflex that mediates heat production and heat conservation. Moderate, anterior region that is activated by a sense of warmth, triggering a reflex that mediates heat reduction.

Thermoregulation in Humans

Human thermoregulation centered on the anterior hypothalamus, there are three components making up the system controller or heat settings, namely thermoreseptor, hypothalamus, and efferent nerves and thermoregulation can maintain body temperature, the temperature-specific constant temperature is usually higher than the surrounding environment.

Body temperature regulation mechanism is a combination of the functions of organs interconnected. regulation of body temperature in mammals, there are two types of temperature control sensors, heat sensors and sensor is cool different places on the network around (outside receivers) and core network (receiver inside) of body. From both types of sensors, the signals received directly transmitted to the central nervous system and then sent to the motor neurons that regulate heat expenditure and heat production to proceed to the heart, the lungs and the whole body.

Once that happens the feedback, which signals, received back by the sensor heat and cold sensors through the bloodstream.

Most heat is lost through the process of radiation, the sweat cooling off. Through evaporation serves to keep the body temperature to remain constant. and modification of the circulatory system in the skin. Contrition blood vessels in the skin and countercurrent heat exchange is one way to reduce the loss of body heat. Human wearing is one of the unique behavior in thermoregulation.

Human body temperature tends to fluctuate at any time. Many factors could cause fluctuations in body temperature. To maintain the temperature of the human body in a state of constant, necessary regulation of body temperature. Human body temperature regulated by a feedback mechanism (feed back), played by temperature regulation center in the hypothalamus. If the temperature of the center of the hypothalamus detects body temperature is too hot, the body will conduct a feedback mechanism. This feedback mechanism occurs when the core body temperature has been over the limit of tolerance for maintaining body temperature, which is called a fixed point (set point). Fixed point so that the body is maintained at a constant core body temperature of 37 ° C. when the body temperature rises over a fixed point, the hypothalamus will be stimulated to undertake a series of mechanisms to maintain temperature by reducing heat production and increase the heat so that the temperature back spending on fixed point.

Our bodies are equipped with various advanced system settings, including the regulation of body temperature. Humans have the central regulation of body temperature (thermostat), located in the part of the brain called the hypothalamus. The body temperature regulation center peg our body temperature at one point called the set point.

The hypothalamus duty to always maintain a constant body temperature, ranging at 37 ° C. That's why, wherever humans are, at the poles or in the desert, the body temperature stable should always be pursued, so that the man referred to as being able to adapt. Hypothalamic thermostat works on intake of nerve endings and the temperature of the blood circulating in the body. Hypothalamus in the cold will make the program so that the body is not cold, by raising the set point alias raise body temperature. How to contract the blood vessels, body shiver and look pale.

While in the hot air, of course, must hypothalamus lowers body temperature to prevent heatstroke. You do this by removing heat through evaporation. Blood vessels dilate, breathing becomes more rapid. Therefore, at the time of the heat, in addition to sweating, we also looked reddish skin (flushing).

Organ Regulatory Body Temperature:

-    Heat regulating center in the body is the hypothalamus, the hypothalamus known as the thermostat is located under the brain.

-    Anterior hypothalamus regulates heat dissipation

-    Posterior hypothalamus regulates heat retention efforts

-    Mechanism of temperature regulation

-    Skin -> Receptor ferifer -> hypothalamus (posterior and anterior) -> Preoptica hypotalamus -> Nerve efferent -> loss / heat generation

Factors Affecting Body Temperature

1. Basal metabolic rate

Basal metabolic rate of each individual is different. It impacts the amount of heat produced by the body to be different. As mentioned in the previous description, it is related to the rate of metabolism.

2. Sympathetic nerve stimulation

Sympathetic nerve stimulation can cause the metabolic rate to 100% faster. In addition, sympathetic nerve stimulation can prevent brown fat that accumulate in tissues to be metabolized. Almost all brown fat metabolism is the production of heat. Generally, the sympathetic nerve stimulation affected individuals stress causes increased production of epinephrine and norepineprin that increase metabolism.

3. Growth hormone

Growth hormone (growth hormone) may cause an increase in metabolic rate by 15-20%. As a result, the body's heat production also increased.

4. Thyroid hormone

Function of thyroxine is increased activity of almost all chemical reactions in the body so that the increased levels of thyroxine can affect the rate of metabolism to be 50-100% higher than normal.

5. Sex hormone

Male sex hormones can increase the basal metabolic rate of approximately 10-15% normal speed, causing an increase in heat production. In women, temperature fluctuations are more varied than in men because the hormone progesterone spending to ovulation increases body temperature approximately from 0.3 to 0.6 ° C above the basal temperature.

6. Fever (inflammation)

The process of inflammation and fever may lead to increased metabolism by 120% for each increase in temperature of 10 ° C

7. Nutritional status

Malnutrition is long enough to lower the metabolic rate of 20-30%. This happens because the cells no nutrients needed to conduct metabolism. Thus, people who are prone to mal nutrition drop in body temperature (hypothermia). In addition, individuals with a thick layer of fat are less likely to develop hypothermia because fat is a pretty good insulator, in the sense of delivering hot fat with the speed of the other one-third the speed of the network.

8. Activity

Activity in addition to stimulating an increase in metabolic rate, resulting in friction between the components of the muscle / organ that produces thermal energy. Exercise (activity) can increase body temperature up to 38.3 to 40.0 ° C.

9. Organ disorders

Organ damage such as trauma or malignancy in the hypothalamus, can cause the body's temperature regulation mechanisms impaired. Pyrogen substances released on infection can stimulate an increase in body temperature. Skin disorders such as number of sweat glands which can also lead to impaired body temperature regulation mechanism.

10.Environment

The body temperature can rapidly exchange with the environment, meaning that the body heat can be lost or impaired due to a cooler environment. Vice versa, the environment can affect the temperature of the human body. Temperature displacement between humans and the environment occur mostly through the skin.

Thermoregulation in Animals

Animals have the ability to adapt to changes in environmental temperature. For example, in cold temperatures, mammals and birds will increase the rate of metabolism by changes in hormones that are involved in it, thereby increasing heat production. At ektoterm (eg, the honey bee), adaptation to cold temperatures by groups in the nest. The metabolism of bees as a group capable of generating heat in the nest.

Some animal adaptations to reduce heat loss, such as the fur and hair in birds and mammals, muscles, and modification of the circulatory system in the skin. Contriksi blood vessels in the skin and countercurrent heat exchange is one way to reduce the loss of body heat. Behavior is important in relation to thermoregulation. Migration, relocation, and was found hiding in some animals to lower or raise the body temperature. Elephants in the tropics to lower body temperature by bathing or wag earlobe to the body. Humans use apparel is one of the unique behavior in thermoregulation.

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Heat Transfer

Heat is defined as the heat energy possessed by a substance. In general, to detect the presence of heat possessed by an object by measuring the temperature of the object. If the temperature is high, the heat contained by the object is very large, and vice versa if the temperature is low, the heat contained slightly.

From the experimental results are often conducted heat required size of an object (substance) depends on three factors:

1.    Mass of matter

2.    Type of substance (specific heat)

3.    Temperature changes

When two or more thermal contact occurs there will be a flow of heat from higher temperature object to a lower temperature object, to achieve thermal equilibrium. This heat transfer process takes place within three mechanisms, namely: conduction, convection and radiation.

a.    Conduction

II. 

III. 

IV. 

V. 

VI. 

If a metal is heated in one end tertenu time interval, the other end will feel the heat. This shows that the metal rod that flow or heat transfer occurs from the high-temperature metal to metal parts of a low temperature. Heat transfer in metal that do not follow the mass transfer is called heat transfer by conduction. So is the conduction heat transfer through an intermediary and agent for the heat transfer occurs, it is not accompanied by the displacement of particles of intermediary substances.

Heat transfer in solids can be explained by atomic theory. Atoms in solids are heated to vibrate strongly. A vibrating atoms will move some of its energy to the nearest neighbor atoms pounded. Then the neighboring atoms are crushed and get this heat will come and strike neighboring atoms vibrate more, so on so that heat transfer occurs in solids.

Terms of heat conduction of a body is the temperature difference between the two places on the object. Heat will move from place to place at high temperature low temperature. If the temperature of both places being the same, then the propagation of heat also be stalled.

Based on the ability of a substance dissipates heat conduction, the substances can be classified into two categories, namely conductors and insulators. Conductors are substances that can conduct heat well, while the insulator is the opposite, ie substances that are difficult to conduct heat. From the experimental results obtained that the heat transfer by conduction depends on the type of metal, cross-sectional area conductor of heat, the temperature difference between the ends of the metal, as well as the length of the conductor through which the heat is.

b.   Convection

At the time of heating water on the stove using a saucepan, heat propagation will occur from the water in the bottom of the pan to the surface by convection. Based on observation, as this heat transfer occurs in a substance that flows, as in liquids and gases. Convection heat transfer in different heat transfer in conduction, convection, where the incident occurred a mass movement or the movement of particles of intermediate particles, whereas the conduction events, this does not happen. The move took place because they kind of mass differences. Due to the heat, the density of the substance at the bottom (which is closer to the heat source) will be reduced, so that will be lighter than the substance in it. This light causes the substance to move upward, while the heavier substances will move downward. So forth, so that the water in the pan will continue to go up and down spins.

From this convection problem will be obtained that the propagation of heat by convection depends on the thermal convection coefficient of heat transfer substance, the heat transfer surface area, as well as the temperature difference between the heat flow with heat dumps.

Convection can happen to:

1.      Liquids

   Terms of the solid liquid convection is the heating. This is due to the particles involved move liquids.

2.      Gases

     Convection occurs also in the gas, for example air. As with the water, propagation (flow) heat the gas (air) occurs by convection. Some of the events that occurred as a result of air convection is as follows.

ü The existence of the sea breeze. Sea breezes occur during the day. During the day, land gets hot faster than the sea so that the air in the land rises and is replaced by air from the ocean.

ü The existence of onshore wind, onshore wind occurs at night. At night, the land to cool faster than the oceans. Thus, the air over the ocean rises and is replaced by air from the mainland.

ü The air circulation in the room at home and the presence of the factory chimneys.

b.   Radiation

Radiation is heat transfer in the form of electromagnetic waves. In radiation, heat or energy propagates without the need for an intermediary substance, unlike the case with conduction or convection is always in need of a medium.

Virtually every object emits and absorbs radiation energy. There are glowing hot objects, and some are not glowing. The second object is dispersive / radiate heat energy in the form of electromagnetic waves with different wavelengths.

Joseph Stefan finds that the rate of propagation of heat by radiation per unit area of surface will depend on the nature and temperature of the object surface. Shiny objects disperse heat more difficult than things that dull. This situation also applies to objects that absorb heat. Glossy surface objects more difficult to absorb heat than a black body and dull the surface. So it can be said that black and dull object is a radio transmitter and a good heat absorbed.

Effect of heat on an object other  than to increase the temperature of an object can result in changes in states of matter. Material change is the change properties of a substance or material into another substance either into a new substance or not. A material usually experience changes in temperature when heat transfer occurs between the materials with their environment. In a given situation, this heat flow does not change its temperature. This occurs when the phase change material. Eg solid to liquid (melting), liquid to vapor (boiling) and changes in crystal structure (solid). The energy required is called heat or latent heat of transformation.

All around us there are a variety of objects such as water, metal, wood. Alcohol, the air we breathe, or helium gas used to fill helium gas.

These objects be grouped into three states of matter, namely:

1. Solids, for example iron and wood

2. Liquid, for example water and alcohol

3. Gas, for example heliun and oxygen

Joseph Stefan finds that the rate of propagation of heat by radiation per unit area of surface will depend on the nature and temperature of the object surface. Shiny objects disperse heat more difficult than things that black and dull. This situation also applies to objects that absorb heat. Glossy surface objects more difficult to absorb heat than a black body and dull the surface. So it can be said that black and dull object is a radio transmitter and a good heat absorber.

Such items are subject to change shape. based on changes nature of the substance changes form the substance can be classified:

1. Merged: Changes in the form of solids to liquid

2. Freeze: Change a liquid form into solids

3. Yawning: Changes in liquid form into a gas

4. Condense: Changes in the form of gas into a liquid substance

5. Sublimes: Change in solid form into a gas

6. Deposed: Changes in gas form into solids

Material change are divided into two kind:

a. Changes in physic

Changes in physics is a process of change in physical appearance of an object with a basic identity unchanged. These changes are temporary and do not produce new substances. For example rice into rice flour.

b. Chemical changes

A chemical change is a material change in circumstances include not only physical, but also the identity of the base. These changes can also occur simultaneously in an event, such as candles are lit, some wax melted and then froze again, some candles burning to gas. Chemical changes are permanent and produce new substances. Material changes chemically accompanied by:

1. Discoloration

2. The occurrence of sediment

3. The emergence of gas

4. The occurrence of heat.

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