Homeostasis help!

[emchun]

Recently we did a experiment where we had to exercise then measure the temperature and heart rate of the subject. Their at rest temperature and heart rate was measured before hand. Then we had another part of the experiment where the subject is put into either hot or cold environments. We took measurements of the temperature of the environment throughout the 30 minutes of the practical for the hot and cold environment. We also measured the subjects heart rate and temperature every two minutes for 30 minutes.
The teacher gave us some questions, and I always have this problem,,
1. Is this a controlled experiment? Explain the importance of this.
And also....
2. Explain how signalling molecules and signal transduction are involved in the temperature regulation of organisms. (How does thyroxine work? How do electrical messages get passed on to effector organ?)

Any help will be much appreciated! Thank you~

Edit: I have another question about variables,,this time it is a general question on homeostasis.
It is about temperature regulation in horses. When horses exercise, their metabolic rate can increase to thirty times their resting metabolic rate. Since approximately 80% of the energy used in exercise is converted to heat, regulating body temperature can be difficult for horses.
We were given a table:
Air temperature    Humidity    Location
20 degrees           40%          London
30 degrees           40%          Barcelona
30 degrees           80%          Atlanta

The question asks: What is the experimental variable that is being tested in your hypothesis?
What results would support your hypothesis?
A previous question asked us to write a hypothesis and I don't even think I wrote it correctly....but it was: The horses in London will be able to regulate their body temperature better than the horses living in Barcelona, the horses living in Barcelona will be able to regulate their body temperature more better than the horses in Atlanta.
Also one question asked: Explain why summer temperatures in Barcelona are more of a problem to horses than those in London.
I answered: Summer temperatures in Barcelona are more of a problem to horses than those in London because the temperature is higher so it adds more heat to the horse that already has 80% of their energy converted to heat. They will have more trouble in regulating their body temperature.

Is that right? Any more information I need to add or change?

[Yacoubb]

1. Yes this is a controlled experiment - note how the experiment is being repeated in different conditions so that you're controlling all these extraneous variables that could potentially affect the dependent variable, which in your case is core body temperature and heart rate. This is important because by controlling all these variables, all effects/changes/restorations of body temperature and heart rate can validly be attributed to the homeostatic (negative feedback mechanisms) of the individual.

2. With core body temperature:
* Thermoreceptors (interoreceptors) detect a decrease in core body temperature. An electrical impulse is transmitted from the thermoreceptors to the hypothalamus, conveying information about the decrease in body temperature.
* In response to this, the hypothalamus will produce TRH, which is Thyrotropin-Releasing Hormone. This travels via a network of capillaries to the anterior pituitary gland.
* The anterior pituitary gland the secretes TSH, which is thyroid-stimulating hormone. This is an endocrine hormone that travels via the bloodstream to the thyroid gland.
* TSH stimulates the production of thyroxin, which increases metabolic rate. As you know, the by-product of many metabolic reactions is heat, thus raising and restoring core body temperature to narrow, clinical range of about 37 degrees C to 38.6 degrees C.

Before I move on, what is the core body temp of horses? This will make everything a lot easier to analyse. I can then help you

[AbominableMowman]

Before I move on, what is the core body temp of horses? This will make everything a lot easier to analyse. I can then help you

It's almost the same as humans, I believe. Something around 38 degrees.

Yep, its 37-38 degrees.

[emchun]

Thank you! I answered the horse questions myself, but its not really detailed  and probably a bit incorrect. Thank you the answers for question 1&2. They were a great help!

I now have a plant question which I'm totally clueless about. A plant (Xanthium)  were separated into groups A and B. A was exposed to a short period of light each day (6hours) and group b was exposed to a long period of light each day (16hours).
This type of response is called photoperiodism right? And is the group of compounds involved in the flowering response of the Xanthium is gibberellins?? I don't really understand what that question was asking.
Also, another set up was where the Xanthium plants were grafted together and exposed to short period of light and long period of light but they were seperated by a lightproof partition. All the plants produced flowers? Why does that happen? And are they most likely to flower in summer or winter? Why?