Inspired by 7th Grade Science

By Ronak Dhingra

My son Ronak savored his seventh grade life science class.  He savored it so much that when I asked him to do some summer writing, he chose to write an essay on homeostasis.  Ronak wanted to thank  his teacher, Dr.K, for a great year of science and for inspiring him to write this essay.  (He also wanted to mention that two of the three examples of homeostasis in his essay were from his class while the third was researched on his own.)
I asked Ronak what he thinks about when I say 7th grade Science:
I think about all the labs we did – I like how we had to map out our purpose, materials, procedure, data and analysis in each lab.  If you didn’t understand the lab, that kind of made it more clear.  The labs were really interactive.  They weren’t like – pour water into something and wait a week to see what happens.  We used new equipment like carbon dioxide sensors, heart rate monitors and also new substances like Benedict’s solution and Sudan III.  We learned how to be careful in a lab while handling glassware, and we gathered more interesting data.  Science was my favorite class this past year and I hope Science stays this fun for the rest of School!
Here is Ronak’s reflection on an important concept he learned about in Life Science this year:
Homeostasis:
Our body manages to keep all of its conditions constant. The maintenance of a constant internal environment is called homeostasis. Examples of homeostasis in the human body are the regulation of blood pressure, the regulation of blood glucose, and thermoregulation (maintenance of a constant body temperature). There are many more examples of homeostasis in the body than the ones listed. Homeostasis occurs in different organ systems and in different ways but we need all of them to live the lives that we do.
Baroreceptors are receptors that are found in the walls of the carotid artery and read blood pressure and send it to the brain. They maintain homeostasis by working with the brain to do something called the baroreceptor reflex. The baroreceptor reflex happens when blood pressure is too low or too high. If blood pressure is lower then the American Heart Association standard for a healthy blood pressure, which is 120/80 mmHg (120=systolic, 80=diastolic), the baroreceptors send the reading to the brain and the brain will tell the heart to beat faster. Without baroreceptors to maintain homeostasis in this manner our organs will not receive an adequate serving of glucose and the other nutrients found in blood. If blood pressure is too high then the baroreceptors will send the signal to the brain and the brain will slow down heart rate. Baroreceptors maintain homeostasis by helping to maintain blood pressure levels. Without them our organs would not be getting enough blood or our heart would be working too hard.
The regulation of blood glucose is another example of homeostasis in the human body. The liver and the pancreas work together to maintain blood glucose levels. When blood glucose levels are too low the pancreas releases glucagon, which converts glycogen (the storage form of glucose that is stored in the liver) to active glucose that is into the blood. When there is too much glucose in the blood, the pancreas releases insulin, to convert glucose to glycogen. Without the liver and pancreas working together to maintain homeostasis in this manner our blood sugar would be too high or low. We could also have diabetes, which happens when the pancreas no longer is able to produce enough insulin.
Thermoregulation is the regulation of a constant body temperature that is regulated by the skin. The skin works to maintain a constant body temperature of 37˚C or 98.6˚F. The sensory nerves in the skin sense the temperature reading they send it to the hypothalamus. Once the brain reads the signal it does two things.  First it tells the skin to make sweat to cool down. The second thing it does, if it’s cold, is to tell the capillaries to decrease to blood flow to the skin so heat is not lost. If it is hot, it increases blood flow to let heat pass out of the body. The hypothalamus can also tell little muscles to contract, causing body hair to stand up.  This traps heat.  When it is hot, the body  hair lays flat to increase heat loss.  Below is a diagram of how the skin thermoregulates the body when it is too cold or too hot. If the skin fails to maintain homeostasis, you are at risk for major health problems such as heat stroke (caused by a sudden rise in body temperature), or hypothermia (when body temperature is lower than 35˚C). Lastly, problems with thermoregulation can lead to thyroid problems.

What Happens in Skin When it is too Hot or too Cold by BBC

In the Heat

A – Hair muscles pull hairs on end.
B – Erect hairs trap air.
C – Blood flow in capillaries decreases.

In the Cold

D – Hair muscles relax. Hairs lie flat so heat can escape.
E – Sweat secreted by sweat glands. Cools skin by evaporation.

F – Blood flow in capillaries increases.

Homeostasis occurs in different forms and in different systems. If one system breaks down we are at risk. Our baroreceptors in the carotid artery work with the brain to maintain blood pressure. We need a constant blood pressure so that our organs get an adequate serving of energy and our heart is not working too hard. Our liver and pancreas work to make sure that there is enough glucose in the blood by releasing glucagon and insulin to higher or lower the amount of blood glucose. Lastly, the skin keeps the body temperature at a constant so that there is no heart stroke, hypothermia, or thyroid problems. As shown, homeostasis occurs in different parts of the body and for different reasons.
If anyone of these three systems failed, the other two would not be able to function. If baroreceptors did not function, blood pressure would be too low. As a result, heat would not effectively pass from capillaries resulting in the individual ‘s body temperature being too warm. Also, blood glucose levels become affected because the pancreas and liver need blood to flow at a certain speed to maintain the blood glucose level at the right levels. In conclusion, homeostasis occurs in many different parts of the body but in the end, all homeostatic mechanisms lead to the same goal – to maintain a constant internal environment.