I need help on this... can't seem to find an answer and I'm finding it difficult.

What are the probable homeostatic resonses to chnges in the internal environment during exercise?

You need to know what is the meaning of homeostasis, the process, what does it involves.

Let me google that for you

From there, you'll have to 'see' what is its role during exercise. In exercise, you are using energy, your body is warming up, you sweat, you feel tired, you feel hungry and thirsty afterwards. These are hints. Let's see what you come up with.

I just want to know what does it mean when it says 'internal environment'

Your internal environment is everything inside your body.

Not only concerning the organs, but the substances involved too, like water, oxygen, carbon dioxide, etc amongst others.

What Unknown said.

Chances are good your question is primarily about temperature. I'll leave that to you.

But you could also consider fluid balance. Since you sweat during exercise, you lose water. If you lose enough water, your blood becomes a bit more concentrated and has less volume. So the hormones reduce the volume of your arteries to maintain your blood pressure. So that's one homeostatic response. Another would be to get thirsty and drink water. Thirst is mediated in the brain.

Here's more, which may or may not be useful to you. The internal environment consists of two parts--inside the cells (the intracellular environment) and outside the cells but still inside the body (the extracellular environment).

Also, inside your gut (mouth, stomach, intestines, etc) is sometimes considered external because it's continuous with the outside world. It's full of bacteria, undigested food, and is not sterile, like inside other parts of your body.

During exercise, your body tends to shunt blood away from the digestive tract and into the legs or whatever muscles are working hardest.

This is everything I have come up with... can you please check and see if this explains what I asked for... thanks.

Exercise disrupts homeostasis by changes in pH, O2, CO2 and temperature. The control systems are capable of maintaining a steady state during sub-maximal exercise in a cool environment. Intense exercise or prolonged exercise in a hot/humid environment may exceed the ability to maintain steady state, and severe disturbances of homeostasis may occur.
Our bodies' burn fuel so when we exercise it is like we are pushing down on our own accelerator pedal that pumps more sugar and oxygen into our muscles to produce more power. Our heart rate and breathing increases to allow us to burn more of our fuel which, instead of gas, is adenosine triphosphate (ATP).
When we exercise our muscles need more energy and oxygen to move and so we need to breathe more air. Then the air goes down the trachea, through the bronchi and bronchioles and finally into air sacs called alveoli where the oxygen is diffused through the thin walls of blood vessels called capillaries. At the same time carbon dioxide is diffused through the wall from the blood vessel to the air sac and back out the same way the oxygen came in. Then the oxygen is transported around the body through the blood vessels and into the muscles. Then the deoxygenated blood goes to the heart and lungs to become oxygenated. This supplies oxygen to all the body tissues. As more energy is needed in the muscles more oxygen is needed in the blood so respiration increases. Also when you exercise, your muscles need more oxygen and fuel to continue working. Your heart rate then increases to get more fuel and oxygen to them more quickly. Depending on how hard you are exercising, your heart will speed up accordingly to give your muscles the power to keep going.
In addition, your skeletal muscles metabolize faster so they require more oxygen and nutrients than when they are in the resting phase. As a result of this, the heart pumps blood faster and harder to compensate for this demand. Since the heart works double time to supply blood, the lungs also take in more oxygen and your breathing rate gets high so you tend to hyperventilate also. Aside from that, the energy and fluid stores also gets depleted especially during intense workout so you tend to feel hungry and thirsty after.

Hmm, those are facts yes... but what you've done here is missing the point. In an exam (if I had gave this answer in one of my exam papers), I would have been told that I gave too much importance to 'energy' and 'respiration' instead of the process itself.

1. Exercise produce heat, so the homeostatic responses of the body are:
a. erector muscles in hair relax. (less air is trapped between hair, hence less insulation so that heat is lost)
b. sweat gland become more active. (sweat helps in cooling down and remove the increased metabolic wastes.
c. breathing is faster, warmer air is then removed faster.

2. Exercise uses food (mainly glucose) and convert them into energy. Glycogen stored in the liver and fats from under the skin are used to meet the energy requirements (the heart pumps blood faster too) and the glucose is also used to restore the glucose level in the blood.

3. While exercising you sweat a lot, hence you lose a lot of water. As a result, your kidneys will reabsorb more water before delivering the urine in the bladder. (You also become thirsty, but that's not what the body in itself makes to restore the loss in water)

4. As you said, oxygen is used and carbon dioxide produced in greater quantities. Hence, to increase the amount of oxygen and reduce that of carbon dioxide, the rate of breathing increases.

I think that summaries it enough. I just hope I did not forget anything! It's been a year I've not looked at those things.