Pure Biology - Homeostasis

anpanman SG

A person takes a cold bath. Temperature of bath water was 22 deg celsius. Explain why the person's body temperature falls.

May I know whether you explain in terms of body temperature regulation on a hot day or a cold day? My take is the former since the initial temperature of the person was warmer than that in the bath tub. Here is the explanation I have been given/have constructed based on my notes:

Since blood and skin temperature is higher initially, temperature receptors in skin detect change and send nerve impulses to brain which causes the heat loss centre in hypothalamus of brain to be stimulated, sending nerve impulse to relevant body parts.

The arterioles in skin dilate to allow more blood to flow to blood capillaries in skin and more heat would be lost by radiation, convection and conduction. Secretion of sweat is INCREASED since sweat glands are more active and evaporation of sweat removes latent heat of vaporization from the body. There is rapid breathing to remove more heat through exhalation.

Metabolic rate in body slows down generating less heat in respiration of cells.

Sounds weird. You are taking a bath and you are sweating and exhaling heavily to remove heat However, explaining using the regulation of body temperature on a cold day doesn't seem right either.

Could someone offer me an alternative? Please reply ASAP as this is pretty urgent. thanks.

Garrick_3658 SG

Marks allocated for this question?

I'll start from here: The arterioles in skin dilate to allow more blood to flow to blood capillaries in skin and more heat would be lost by radiation, convection and conduction.

The rest you given seems pretty irrelevant and impractical to me.

"The arterioles in skin dilate to allow more blood to flow to blood capillaries in skin and more heat would be lost by radiation, convection and conduction" to the environment. This is the initial state as the body is generating heat during metabolic activities.

As he enters a cold bath, the cold water will cause him to lose more heat than usual as the arterioles are still dilated (maybe there's a "concrete" explanation for this, but I haven't touched bio so I ain't sure). As such, the temperature of his body falls.

iamapebble SG

Explain why the person's body temperature falls.

I was actually wondering, they are asking about why the person's body temperature falls, the above you guys mentioned about are the conditions when a person's body temperature rises, that's why the arterioles will dilate etc etc do release heat, no?

Garrick_3658 SG

"The arterioles in skin dilate to allow more blood to flow to blood capillaries in skin and more heat would be lost by radiation, convection and conduction" to the environment. This is the initial state as the body is generating heat during metabolic activities. Hence body temperature > room temperature.

Darkness_hacker99 SG

Explain why the person's body temperature falls.

Yea. They're saying about the conditions when the temperature rises. It's wrong wrong.

When the person is immense in 22C water (assume from a normal conditions 36.9C). These are the areas that would be affected namely Blood vessels, Sweat Glands and Skeleton muscles.

Response to this: A low blood flow to surface (to conserve heat/ constrict blood vessels near the skin), decrease sweating (to prevent lose of heat) through constricting the glands on the skin, Shivering to produce heat (involves the muscles). All these happens throught a negative feedback mechnism.

Darkness_hacker99 SG

Breathing heavily is a cold shock respond.

anpanman SG

Yea. They're saying about the conditions when the temperature rises. It's wrong wrong.

When the person is immense in 22C water (assume from a normal conditions 36.9C). These are the areas that would be affected namely Blood vessels, Sweat Glands and Skeleton muscles.

But then again, they are asking how the body temperature falls. The regulation of body temperature on a cold day helps increase heat production not decrease. That's why you wouldn't feel too cold on a freezing day.

Occam's Razor SG

Explain why body temperature falls.

Cos the body loses heat by conduction, convection and radiation to the cold water. lol!

The Q nvr ask u to explain how the body responds.

UltimaOnline SG

That's the problem with question ambiguity. Again I advise you, if you encounter this in the exams, write both answers (yes it'll take up more time to do so, but at least your marks are secure). Write a short note to explain to the examiner/marker how the question could be interpreted in both ways, then proceed to address the question in both ways. You'll get your marks in this way (because after showing the examiner that the question's ambiguity is at fault, you've most importantly demonstrated to the examiner you know all your facts/concepts that the question is asking for, whichever interpretation turned out to be the one the question setter or mark scheme had in mind), while candidates who only write one interpretation have a 50% chance of getting zero marks (assuming the question really is 50-50% ambiguous, not that uncommon, even in the actual 'O' and 'A' levels).

anpanman SG

that helps. thanks. :)

UltimaOnline SG

that helps. thanks. :)

You're welcome!

Examples of Qn ambiguity :

Eg. "Dear Examiner Sir, the question did not specify clearly the exact reaction conditions used. If the temperature is below X deg C, then the following mechanism pathway (which I've drawn) on the left applies. If the temperature is above X deg C, then the following mechanism pathway (which I've drawn) on the right applies."

Eg. "Dear Examiner Sir, the question did not specify clearly exactly which two beakers are used.

If beaker A and B, then ....

If beaker A and C, then ....

If beaker B and C, then .... "

Eg. "Dear Examiner Sir, the question did not specify clearly whether the body temperature had decreased due to ambient environmental temperature, or due to physiological homeostatic response. If the former, then the following explanation applies... If the latter, then the following explanation applies..."

Eg. "Dear Examiner Sir, the question did not specify clearly which categories of isomers are to be considered.

If structural isomers only, then the answers are...

If stereoisomers only, then the answers are...

If structural and stereoisomers, then the answers are...

(Note : Structural isomers are futher subdivided into functional group isomers vs positional isomers vs chain isomers. Stereoisomers are futher subdivided into enantiomers (optical isomers (d vs l; r vs s; (+) vs (-))) vs diastereomers (conformational isomerism vs geometric isomers (cis vs trans; E vs Z))).

davidche SG

Examiner Sir i see.

davidche SG

Btw, since it is on the topic of homeostasis, i always wanted to ask this question. Why and how is the amount of urine affected when the temp is warm or cold.

UltimaOnline SG

Btw, since it is on the topic of homeostasis, i always wanted to ask this question. Why and how is the amount of urine affected when the temp is warm or cold.

Sweat lots = lose lots water = less urine

Sweat less = lose less water = more urine

(This is to maintain constant water potential of blood, the other function of kidney, other than excretion)

davidche SG

Sweat lots = lose lots water = less urine

Sweat less = lose less water = more urine

(This is to maintain constant water potential of blood, the other function of kidney, other than excretion)

thanks. i was thinking along the line of since it is cold, there shld be less urine since heat is lost thru urine. lol

thanks for the help

UltimaOnline SG

thanks. i was thinking along the line of since it is cold, there shld be less urine since heat is lost thru urine. lol

thanks for the help

That's a much less important/significant source of heat loss (such heat loss occurs incidentally and inevitably, rather than deliberately or by design); as compared to the much, much, much more important vital function of maintaining/regulating water potential of blood/tissue fluid (which can only be effectively regulated via urine output).

Welcome.