Homeostasis Investigation

Core Concepts

The Scientific Method

The scientific method is a rigorous process for scientific inquiry. It consists of the following steps:

1. Ask a question about what you wish to investigate. The question will drive your investigation, and by the end you will answer this question.

2. Perform background research about your question. For instance, if your question is "why are leaves green", you might wish to research about photosynthesis, the evolution of plants, chlorophyll, etc.

3. Create a hypothesis that answers the question. A hypothesis is a prediction that you will attempt to prove (or end up disproving) over the course of your experimentation.

4. Develop an experiment(s) to test your hypothesis. The experiments must be detailed and repeatable so that their results cannot be questioned.

5. Conduct your experiments and collect data. Follow your procedures accurately and record all relevant observations.

6. Analyze your data by synthesizing it together. This usually includes creating a table or graph that lets you easily visualize the data.

7. Draw conclusions from your data. Determine whether your data proves your hypothesis, disproves it, or is inconclusive. Optionally, develop further experiments to conduct that will answer the unanswered questions, and repeat the process.

Independent Variable

An independent variable is what you will be changing in your experiment to get different results. For example, in our investigation the independent variable was which stimulus the subjects were being exposed to — this is what we were changing to test differences.

Dependent Variable

The dependent variable is the "result" of the experimentation that depends on the independent variable. In our investigation, this was the heart rate, as depending on what stimulus was given the heart rate was different.

Control

A control is something that will not change throughout the experiments. In our experimentation, this was the "baseline" heart rate reading. It could also be some material used throughout all the experiments or a certain procedure that was kept the same.

Homeostasis

Homeostasis is the collective name for the processes that an organism carries out in order to maintain balance. Every organism has many different ways it performs homeostasis, and humans are no exception. Our heart rate and breathing rate changes to deliver more or less oxygen when it is needed (balancing oxygen supply with oxygen demand), our blood vessels dilate in order to divert more heat to the skin (and thus radiating away from the body) when the body gets warm in order to cool it once again, our body releases the hormones insulin and glucagon to either lower or raise blood sugar when it gets too high or low (respectively), and so on. There are countless processes that our body uses to keep itself in a stable state even when the environment around it changes. This is critical, since if the body were unable to perform homeostasis it could never stabilize in the constantly-changing world and we would thus be unable to survive for long. For more information about homeostasis, see the lab report above.

Hormones

Hormones are the body's regulatory messengers. Hormones are used by many homeostatic processes to deliver messages between receptors (which sense when an imbalance is present), controllers (which decide what to do with the signal), and actors (which perform the action that the controller decides). A good example of this is the heart rate. When nerve receptors detect that, for instance, the muscles are using more oxygen, they send their electric impulses to the sympathetic nervous system — in the spinal cord — which then decides to release catecholamines, a type of hormone. This hormone, when it reaches the heart, instructs the heart to beat faster. If, conversely, the receptors detect that the muscles are using less oxygen, the parasympathetic nervous system — in the lower brain and spinal cord — releases acetylcholine, a hormone that instructs the heart to beat slower.

Feedback Loops

A feedback loop is exactly as it sounds — a loop where the output of some process "feeds back" into itself as a controller of that process. This is best illustrated with an example: the blood glucose cycle. If the body detects that there is too little glucose in the bloodstream, it releases glucagon, a hormone which tells the liver to release its reserve glucose. This increases the glucose in the bloodstream, bringing it back to normal. Conversely, if the glucose levels go too high, the body releases insulin, a hormone that allows more glucose to be used by the cells (and thus the blood glucose level gets used up faster in order to be lowered). So, in either case, this is a feedback loop; the "input", the glucose level, determines whether glucagon or insulin should be released, but these "outputs" cause changes in the input. It is a loop that "feeds back" into itself.

There are two kinds of feedback loops: positive feedback and negative feedback. Negative feedback is like the blood glucose cycle — it is when the input is dampened or corrected by the output. In the case of the blood glucose levels, the output always pushes it back in the other direction (towards a middle balance). This means the output is subtracting from the way the input is trying to go. Positive feedback is like a speaker and a microphone screeching — it is when the input is amplified by the output. When the microphone hears tiny noises in the room, it plays them on the speaker. Now the microphone hears both the tiny noises and the speaker playing those tiny noises, so the speaker starts playing more. Now the microphone hears even more from the speaker plus the tiny noises in the room, so it keeps increasing and increasing in this manner forever. Thus the output adds to the input.

Reflection

This project was, as usual, quite successful. Our group was able to collaborate very well together, so much so that we were able to conduct even more tests than we had expected during the single class session we were allotted. We worked quickly but carefully together in order to maximize our time, and it allowed us to collect a very large amount of data in a short amount of time. This was perfect for our investigation as it allowed us to identify a clear pattern. Additionally, our critical thinking was a strength in this project, since we were able to put together a suite of tests that would leave no ambiguity in the results. Our results were thus clear and decisive, which proved our tact in developing our experiment set.

Also as usual, there were a few minor things that could be improved. Our conscientious learning could have been somewhat better. While the experimentation was conducted efficiently, our group did not function together as well for the analysis portion of the investigation. This resulted in an uneven balance of work thus more time being spent than would be strictly needed. Finally, our communication had one minor issue. One group member was intended to upload an image of our collected data so that we would all have access to it — however, this did not happen until we met again the next day. While this did not have an adverse affect on the end result, we could have progressed slightly faster had this been available and communicated more effectively.

That being said, the issues were fairly minor and the end result was still essentially unaffected. The project was certainly a success, and we were able to produce a professional investigation in the limited timespan that we were given.