By what means does the body regulate temperature?

[wasteofo2]

By what means does the body regulate temperature aside from sweating? And why is it that in the presence of an illness, the body can raise it's temperature, but in the presence of extreme cold the body cannot raise it's own temperature?

 

[Monique]

Good question, well, let me think of a few things:

to cool down:
perspiration, widening of the peripheral bloodvessels, bringing those bloodvessels to the surface, increase peripheral bloodflow, slow metabolism (radiation, conduction, convection too btw)

to warm up:
decrease perspiration, constrict bloodvessels, pull them down, muscular movement by shivering, increase metabolism (by secretion of norepinephrine, epinephrine, and thyroxine), reduce peripheral bloodflow, raise body hairs (more insulation by the airpocket created).

The hypothalamus controls thermoregulation, the parasympathetic nervous system controls sweating and the sympathetic nervous system controls skin blood flow.

Why can't the body increase its temperature when its cold, but it can when its ill? Well, it can, but it looses it faster than it is made.

 

[wasteofo2]

Originally posted by Monique
Good question, well, let me think of a few things:

to cool down:
perspiration, widening of the peripheral bloodvessels, bringing those bloodvessels to the surface, increase peripheral bloodflow, slow metabolism (radiation, conduction, convection too btw)

Could you tell me if how I understand this is correct or not?

Perspiration: Body heat is transferred to the sweat and used in the process of evaporating it, thus heat energy is used up in evaporation of water.

Widening of the peripheral bloodvessels: More bloodflow with less friction of blood against the vessel walls causing less heat. Also greater surface area for heat to disperse.

bringing those bloodvessels to the surface: Allows heat from bloodvessels to more rapidly leave the body since there is less matter between the blood vessels and the skin. Also greater surface area for heat to disperse.

increase peripheral bloodflow: The only thing i can think of that this might do is cause the peripheral blood vessels to be able to expand.

slow metabolism: Less calories from food unlocked, thus less available energy.

(radiation, conduction, convection too btw) You lost me.

Originally posted by Monique

to warm up:
decrease perspiration, constrict bloodvessels, pull them down, muscular movement by shivering, increase metabolism (by secretion of norepinephrine, epinephrine, and thyroxine), reduce peripheral bloodflow, raise body hairs (more insulation by the airpocket created).

decrease perspiration, constrict bloodvessels, pull them down... increase metabolism (by secretion of norepinephrine, epinephrine, and thyroxine), reduce peripheral bloodflow,: Opposites of what I said above

muscular movement by shivering: Friction causing heat.

Originally posted by Monique

The hypothalamus controls thermoregulation, the parasympathetic nervous system controls sweating and the sympathetic nervous system controls skin blood flow.

Waht exactly do you mean by thermoregulation? Do you mean every process you mentioned besides sweating and skin blood flow, or do you mean something else?

Originally posted by Monique

Why can't the body increase its temperature when its cold, but it can when its ill? Well, it can, but it looses it faster than it is made.

Alrighty.

 

[enigma]

Originally posted by wasteofo2
but in the presence of extreme cold the body cannot raise it's own temperature?

Are you referring to why frostbite occurs?

If you're freezing to death, your body is in the process of losing lots of heat to the environment. Generating more heat to raise your internal temperature isn't going to do much to slow the rate of loss down. It'll just kill you quicker: you only have so much stored energy in reserve at anyone time.

What the body does instead is pull as much heat away from the extremities (which you don't need to live) into the central organs (which you do).

 

[Another God]

I feel like all of the explanations you ahve given monique are secondar explanations... I mean, all of those techniques (well,most) are means of using the bodies heat in an effective way. Either preading the warmth out, or releasing it etc. But where does that heat come from?

Well, at least that is what I thought the initial question was.

I know of only one real source of heat in the body (Although I am sure there are more...possibly friction as mentioned by wasteofo2), and that is the final step of the electron transport chain. When the reduction of O₂ to water and CO₂ is completed, many H+ ions have been pumped out of the mitochondria, creating an electrical potential across the membrane. The flow of those protons back across the membranes (as well as powering the ATP pump), act just like any other current flowing across a resistor: It generates heat.

For some of us, we have even more effective heat generating mitochondrion because somewhere in our evolutionary past (claimed to be when humans migrated from Asia into USA via the Bering straight in the middle of an ICE age), someone evolved a semi-decoupled mitochondria. (Thats not the technical name for it, but I can't thnk of it).

Decoupling is when the H+ ions are allowed back across the membrane without powering the ATP pump. By doing this, it creates a flow of protons that do nothing but generate heat. Thus people with this semi-decoupling use more of the energy from their food in heat production than those who do not have the mutation.

Can you think of any other processes that release heat?

 

[wasteofo2]

Originally posted by Another God


Can you think of any other processes that release heat?

Friction is definitely one. Think of it this way: when you do a lot of physical activity, you sweat because you're body is too hot. The only source for the heat that you need to get rid of(which I can think of) is from all the movement your muscles do. Rub your hands together at a moderate speed for a bit, they should feel warm within a few seconds. Now move your forearm up and down at that same speed, think of the small heat rise which must be going on at the location of the joint and the bicep due ot the friction.

Don't most all chemical reactions give off some level of heat as a byproduct?

 

[Monique]

Originally posted by wasteofo2
Could you tell me if how I understand this is correct or not?

Perspiration: Body heat is transferred to the sweat and used in the process of evaporating it, thus heat energy is used up in evaporation of water.

When something evaporates, it extracts heat from its environment. Ethanol for instance, when you put it on your skin it feels cold right? Especially when you blow on it. So no, the heat is not transferred to the sweat, it is used during the evaporation (ask a physicist why).

Widening of the peripheral bloodvessels: More bloodflow with less friction of blood against the vessel walls causing less heat. Also greater surface area for heat to disperse.

No, not friction, but it increases the surface area where heat dissipation can take place, also, it slows down bloodflow in that area, also increasing the timeframe.

bringing those bloodvessels to the surface: Allows heat from bloodvessels to more rapidly leave the body since there is less matter between the blood vessels and the skin. Also greater surface area for heat to disperse.

First comment is correct, second one is above.

increase peripheral bloodflow: The only thing i can think of that this might do is cause the peripheral blood vessels to be able to expand.

No, on the skin is where heat dissipation can take place, so that is where the blood is directed to.

slow metabolism: Less calories from food unlocked, thus less available energy.

Well, as Another God said, heat is a direct byproduct from our metabolism (we are very inefficient in that regard).

(radiation, conduction, convection too btw) You lost me.

These are all processes that can't be controlled by the body itself. These are all processes based on the physics of heat transfer. Heat radiates from your body, it can be conducted to other objects or leave through convection to air. These things can be adjusted by wearing more/less clothing, standing in/out the wind, or curling up into a ball.

muscular movement by shivering: Friction causing heat.

Again here it is not friction, heat is actually a waste byproduct of metabolism. Moving your muscles means you are burning energy = producing heat.

 

[Monique]

Originally posted by Another God
Can you think of any other processes that release heat?

Isn't heat produced by every metabolic reaction? Does that mean that heat is taken away during an anabolic reaction?

 

[wasteofo2]

Are you guys sure that friction has nothing to do with heat when you're doing physical activity?

 

[Monique]

Rubbing your hands would..

 

[russ_watters]

Originally posted by Monique
No, on the skin is where heat dissipation can take place, so that is where the blood is directed to.

This works exactly like any other heat exchanger - think of your car's radiator. When the engine/coolant is too cool, there is a valve that reduces the flow of water to the radiator, allowing the heat from the engine to warm the water. When the engine/coolant is too warm, the valve opens, allowing more water to flow through the radiator, cooling it.

Are you guys sure that friction has nothing to do with heat when you're doing physical activity?

What friction? Inside your joints? Insignificant, otherwise you'd wear away your bones.

One thing you guys forgot related to low ambient regulation of your body temperature (cold weather): shivering. Shivering is your body's way of increasing the amount of energy you are burning in order to cope with the rate of energy loss. As said before though, there is a limit to how fast you can burn energy. I run outside in shorts and a t-shirt down to about 35F and still sweat. That's about my limit though because body temp gets very uneven when I do that (I'll be sweating, but my hands will be cold).

 

[Monique]

Didn't forget it

Originally posted by Monique
muscular movement by shivering

 

[russ_watters]

Originally posted by Monique
Didn't forget it

Obviously I don't pick everything up when I'm only skimming... Ooops.[b(]

 

[Monique]

CTRL+F always does the job

 

[nautica]

Actually, the original question asked how the body regulated temperture, not how it produced heat.

The simple answer is hypothalamus. It is what "regulates temperature".

Nautica

 

[mark1]

i think that you guys are forgetting fever. like when a phagiocytes ingest bacteria and are therefore stimulated to secrete interlukin 1, which raise body temprature through the hypothalamus in an effort to kill the bacteria

 

[Monique]

Originally posted by nautica
Actually, the original question asked how the body regulated temperture, not how it produced heat.

The simple answer is hypothalamus. It is what "regulates temperature".

Nautica

Actually, the question was by what means

 

[nautica]

Originally posted by Monique
Actually, the question was by what means

Yes, and you were correct in your original answer. I was only pointing out that the others were dealing with heat production, which is different than temperature regulation.

Nautica