High School

Jane and Theo are learning about the mechanisms of homeostasis in their biology class. They decide to investigate how their bodies respond to various stimuli. They complete the following tests:

- Sit on a bench in the sunshine on a day that is over [tex]$80^{\circ} F$[/tex].
- Run quickly around the gymnasium.
- Stand in a room that is cooled to [tex]$40^{\circ} F$[/tex].

They use a thermometer to measure the temperatures of their foreheads to determine how their bodies respond to changes. They continue each test for 10 minutes. The results of their tests are as follows:

[tex]
\[
\begin{tabular}{|c|c|c|c|c|c|c|}
\hline
& \multicolumn{2}{|c|}{Starting set-point temperature ($^{\circ} F$)} & \multicolumn{2}{|c|}{Temperature after 5 minutes ($^{\circ} F$)} & \multicolumn{2}{|c|}{Temperature after 10 minutes ($^{\circ} F$)} \\
\hline
& Jane & Theo & Jane & Theo & Jane & Theo \\
\hline
Heat & 98.0 & 98.4 & 99.1 & 99.8 & 98.3 & 99.0 \\
\hline
Exercise & 97.9 & 98.6 & 100.0 & 100.4 & 99.0 & 99.5 \\
\hline
Cold & 98.2 & 98.1 & 96.1 & 96.4 & 97.7 & 97.5 \\
\hline
\end{tabular}
\]
[/tex]

In a follow-up experiment, Jane decides to test her heart rate and how her body responds as it tries to maintain homeostasis. She begins by taking her resting heart rate (normally between 60-100 beats per minute) and exercises until her heart rate reaches the exercising heart rate (normally between 120-200 beats per minute). She stops exercising and continues to take her heart rate every 2 minutes for 10 minutes.

What response is she likely to see as her body works to maintain homeostasis? Drag and drop the correct response into each box to complete the table.

[tex]
\[
\begin{tabular}{|l|l|}
\hline
\multicolumn{1}{|c|}{Time} & Jane's Heart Rate (bpm) \\
\hline
Resting heart rate & 65 \\
\hline
Exercising heart rate (0 minutes after exercise) & 140 \\
\hline
2 minutes after exercise & $\square$ \\
\hline
4 minutes after exercise & $\square$ \\
\hline
6 minutes after exercise & $\square$ \\
\hline
8 minutes after exercise & $\square$ \\
\hline
10 minutes after exercise & $\square$ \\
\hline
\end{tabular}
\]
[/tex]

Options: 50, 70, 75, 90, 105, 125.

Answer :

Certainly! Let's go through the solution step-by-step for Jane's heart rate as her body works to maintain homeostasis after exercising.

1. Resting Heart Rate:
- Jane's resting heart rate is 65 beats per minute (bpm). This is the heart rate when she starts, before any exercise.

2. Exercising Heart Rate:
- Right after exercising, her heart rate is at 140 bpm. This is typical as exercise increases heart rate significantly.

3. Heart Rate Recovery:
- After stopping exercise, her heart rate begins to decrease as her body works to return to its normal resting state. Let's outline Jane's expected heart rate at each interval post-exercise as her body maintains homeostasis:

- 2 Minutes After Exercise:
- The heart rate decreases to approximately 125 bpm. This is a gradual reduction as the body starts to recover.

- 4 Minutes After Exercise:
- Her heart rate continues to decrease to about 105 bpm. The reduction is ongoing as her body cools down and recovers.

- 6 Minutes After Exercise:
- By this point, the heart rate is likely around 90 bpm. This indicates further recovery towards the resting state.

- 8 Minutes After Exercise:
- The heart rate slows down further to around 75 bpm. Jane's body is getting closer to its resting heart rate.

- 10 Minutes After Exercise:
- Finally, Jane's heart rate reaches about 70 bpm. This is near her initial resting heart rate of 65 bpm, showing that her body has almost stabilized back to normal.

These heart rates demonstrate how Jane's cardiovascular system responds by gradually reducing her heart rate to maintain homeostasis after the physical activity. This natural process ensures that her body returns to normal functioning efficiently.