Human Homeostasis: Regulating Blood Glucose and Body Temperature
Blood Glucose Regulation and Homeostasis
At 6:30 am, Alyssa’s blood glucose levels increased, likely because she ate breakfast, causing glucose from digested carbohydrates to enter her bloodstream. This rise in blood glucose is detected by the pancreas, which helps maintain stable internal conditions, a state known as homeostasis.
In response, the pancreas releases insulin, a hormone that lowers blood glucose levels. Insulin allows body cells to absorb glucose for energy and signals the liver to store excess glucose as glycogen. As glucose levels return to normal, insulin secretion decreases. This process is an example of negative feedback.
If blood glucose levels drop too low, the pancreas releases glucagon, a hormone that has the opposite effect of insulin. Glucagon stimulates the liver to break down stored glycogen into glucose and release it into the bloodstream, raising blood glucose levels back to normal.
Through the coordinated actions of insulin and glucagon, the body maintains homeostasis, ensuring Alyssa’s blood glucose remains within a healthy, stable range.
Thermoregulation: Responding to Cold Exposure
From 9 pm to 12 am, Alyssa’s body temperature began to decrease when she was exposed to the cold air. As her skin temperature dropped, her body responded through thermoregulation to maintain a stable core temperature.
The hypothalamus detected the fall in skin temperature and triggered heat-conserving responses, such as:
- Vasoconstriction: Blood vessels near the skin surface narrowed to reduce blood flow and minimize heat loss.
- Shivering: Muscles generated heat through rapid contractions, helping to produce heat.
These responses help Alyssa maintain her normal body temperature (around 37°C) despite the cold environment, preventing hypothermia and keeping her body systems functioning normally.
Negative Feedback in Temperature Control
To maintain homeostasis, her body responded through a negative feedback loop. The nervous system (NS) detected the drop in temperature through skin receptors, and the hypothalamus sent signals to keep the body warm.
Physiological Response to Exercise (Hiking)
Heart Rate Dynamics During Physical Activity
According to Graph 2, Alyssa’s heart rate increases sharply between 1 pm and 3 pm when she begins hiking. Her heart rate rises from around 70 beats per minute to a peak of approximately 130 beats per minute, before gradually decreasing again after the hike.
This increase occurs because physical activity requires more energy for her muscles. During hiking, Alyssa’s muscle cells need more oxygen and glucose to perform cellular respiration, which produces the energy (ATP) needed for movement. To meet this higher demand, the heart pumps faster to deliver more oxygen and nutrients to the muscles and to remove carbon dioxide and other wastes more quickly.
The change is controlled by the nervous system and hormonal responses. The PNS increases heart rate and breathing rate to support greater oxygen delivery. After Alyssa stops hiking, her activity level decreases, so oxygen demand falls and her heart rate gradually returns to normal, while maintaining homeostasis.
The Link Between Heart Rate and Breathing Rate
Yes, there is a clear relationship between Alyssa’s breathing rate and heart rate during her hike from 1 pm to 3 pm. Data shows a coordinated increase:
- Heart Rate (Graph 2): Increases sharply from around 70 beats per minute to about 130 beats per minute.
- Breathing Rate (Graph 3): Rises from roughly 15 breaths per minute to around 35 breaths per minute during the same period.