Pre-AP Homeostasis Lab



Homeostasis Lab: The Effects of Exercise on Homeostasis

Objectives

• identify conditions that need to stay constant to keep the body in equilibrium.

• describe how organisms maintain stable internal conditions while living in changing external environments.

Pre-lab Questions: (Write the Q & A in your lab notebook)

Your heart’s job is to pump blood throughout your body. The blood carries oxygen from your lungs to all of the cells in your body.

1. Does your heart always beat at the same rate?

2. List some activities or stimuli that you think may increase a person's heart rate. An activity is something a person does, and a stimulus is an input from the environment around a person.

3. Why would it be useful for the heart to beat faster during these activities or in response to these stimuli?

4. Are there any activities or stimuli that you think may decrease a person's heart rate?

5. What is homeostasis?

6. Differentiate between positive and negative feedback mechanisms.

7. Which feedback mechanism (+/-) is used to maintain homeostasis? Explain why?

Hypotheses:

Write a hypothesis for your lab (in your lab notebook).

Materials

Thermometer Alcohol Stopwatch Cotton balls

Background

Exercise causes many factors of homeostasis to kick in to maintain internal equilibrium.

How exercise affects some of these factors can be determined by measuring and observing certain conditions of the human body. Some of these conditions are:

change in skin color on arms and face perspiration level

external body temperature breathing rate

heart rate blood pressure (optional)

Pre-lab Notes

1) .Working in your group, select a student that will be able to do JUMPING JACKS well and will be able to maintain jumping for 8 minutes. The group member jumping will stop just long enough for the needed measurements and observations to be collected. No more than 20 seconds between cycles.

2).The following observations will be made:

• skin color of hands and face if noticable(pale, pink, red)

• perspiration level (none, mild, medium, high)

• external body temperature (place the thermometer under the subjects arm pit for 10 sec.; the thermometer should be directly against the skin between the armpit)

• breathing rate (count the number of breaths in 1 minute= 10 sec. x 6)

• heart rate (find the pulse at the wrist and count the number of beats in 1 minute= 10 sec. x 6)

• blood pressure (use the blood pressure monitor to get a reading) (OMIT)

Have data table prepared before lab!

Procedure

1. Determine who is the SUBJECT (the person exercising) and the EXPERIMENTERS (the persons taking and recording data). The EXPERIMENTERS will take the subject’s standing heart rate, temperature & breathing rate as well as make observations on the SUBJECT’S color & perspiration. (Heart rates are obtained by taking the radial pulse or carotid pulse for 10 seconds.) **Convert all your heart rates to beats per minute by multiplying by 6 and record them on the group data table. **Convert all your breathing rates to breaths per minute by multiplying by 6 and record them on the group data table.

2). Make observations and measurements of the SUBJECT doing JUMPING JACKS while they are sitting down and resting. Record your observations on the data table.

3).The student jumping should begin jumping when the person with the stopwatch gives the signal and continue jumping for 2 minutes. After 2 minutes quickly make observations (10 seconds) and measurements then record ALL DATA on the data table.

4).The student will continue jumping jacks. After each 2 minute interval, observations and measurements should be made.

5).When the 8 minutes are up, the student doing jumping jacks will rest for 1 minute. After 1 minute, observations and measurements will be taken.

6). Make the final recording after another minute of rest. Don’t forget to record the data on the data table.

7). Clean the thermometer with alcohol and return it and all other lab materials to the designated area.

Data and Results:

Make a separate graph for each of the following:

A. External Body Temperature at Various Intervals of Exercise vs. time

B. Breathing Rate at Various Intervals of Exercise vs. time

C. Heart Rate at Various Intervals of Exercise vs. time

D. Graph your heart rate (HR), class average HR, boys average HR and girls average HR (4 lines on one graph).

9). Answer the questions in the conclusion section to describe & explain the results of the lab.

Data Table 1: Observations and Measurements During Various Intervals of Exercise

| | | | | | | |

|Time Intervals |Body Color |Perspiration |Body Temperature |Breathing Rate |Heart Rate |Blood Pressure |

| | |Level | | | | |

| | | | | | |X |

|Rest | | | | | | |

| | | | | | |X |

|2 Minutes | | | | | | |

| | | | | | |X |

|4 Minutes | | | | | | |

| | | | | | |X |

|6 Minutes | | | | | | |

| | | | | | |X |

|8 Minutes | | | | | | |

|Rest After Exercise | | | | | |X |

|1 Minute | | | | | | |

|Rest After Exercise | | | | | |X |

|2 Minutes | | | | | | |

Data Table 2: Heart Rate at Various Intervals of Exercise vs. time

| | | | | |

|Time Intervals |Your HR |Class Average HR |Boy Average HR |Girls Average HR |

| | | | | |

|Rest | | | | |

| | | | | |

|2 Minutes | | | | |

| | | | | |

|4 Minutes | | | | |

| | | | | |

|6 Minutes | | | | |

| | | | | |

|8 Minutes | | | | |

|Rest After Exercise | | | | |

|1 Minute | | | | |

|Rest After Exercise | | | | |

|2 Minutes | | | | |

Conclusion: (Write the Q & A in your lab notebook)

1. What are the changes you observed in the body color and perspiration level in response to?

2. How do the changes help the body adjust to maintain equilibrium (homeostasis)?

3. Why do you think a change in body temperature occurs?

4. Your body uses which mechanism (+ or -) feedback to maintain a constant body temperature?

5. Why does an increased breathing rate accompany exercise?

6. Why does an increased heart rate accompany exercise?

7. Looking at the graph, explain why HR rises sharply and then levels off.

8. List at least two other changes that occurred during exercise that we did not observe on our data table. Explain how these help maintain homeostasis.

9. In conjunction with the observed bodily changes occurring during exercise, list at least two changes that probably occurred inside the body that you could not observe.

10. Write a paragraph about the conclusions you can draw about your body’s ability to maintain equilibrium (homeostasis). Be sure to include the answers to the questions above.

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