Biology Lab: Homeostasis and Exercise - Weebly

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Biology Lab: Homeostasis and Exercise

Background: Homeostasis (Greek for "staying the same") is a process by which the body maintains a stable internal environment. The hypothalamus is a part of the brain that helps the body maintain homeostasis. It is located in the brain just above the brain stem and is a group of neurons that forms the primary link between the nervous system and the endocrine system. This small part of the brain is responsible for regulating many key body processes including internal body temperature, hunger, thirst, blood pressure, and daily (circadian) rhythms.

Most body systems maintain homeostasis by using positive or negative feedback mechanisms. When the brain receives messages from the body about an internal change in one of its systems, it works to restore the system to its normal state. Negative feedback mechanisms are found in the regulation of blood pressure, heart rate, and internal temperature controls. For example, the normal internal temperature for the human body is approximately 98.6? F. If the body temperature rises because of exercise, the body will start to try and cool itself off. This happens through coordination between the hypothalamus and the various body systems that are affected. Signals are sent that allow blood vessels to return to the normal state, sweat to be produced, pores to be dilated, and heart and breathing rate to normalize. This is very similar to the way a thermostat works. When the temperature of a room becomes too warm, the thermostat will switch on the air conditioning and cool the room. When the room temperature reaches a set desired temperature, the system turns off.

Body systems work to maintain homeostasis in ways we are not even aware of. For example, the body is constantly working to maintain a normal glucose level in your blood. When you eat something that contains a lot of sugar, the glucose concentration in your body rises above normal. When glucose levels are too high, the body releases a hormone called insulin which stimulates the absorption of glucose by the pancreas to help return the blood sugar level to normal.

Positive feedback is a mechanism that is much rarer in a healthy body. Instead of restoring the body to a normal state, the positive feedback mechanism causes an even greater change. An example of positive feedback can be found in the release of oxytocin, a hormone that intensifies the contractions that take place during childbirth. As the baby's head is ready to move out of the mother's body, oxytocin increases and the levels of contractions increase thus pushing the baby out. In this instance, the body responds to an event with more "force" or in a stronger way.

Problem:

How does exercise affect a person's heart rate, breathing rate, and perspiration level?

Hypothesis:

Write a hypothesis about the effect of exercise on the responding variables. Use the "If..., then..., because..." statement. (READ the procedure first, to gain a better understanding before writing your hypothesis) __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________

Materials:

You, plus two other group member (groups of 3) A clock (you may use your phone)

Procedure:

1. Choose one volunteer to complete jumping jacks at a pace that can be maintained for eight minutes. Make sure the volunteer is inactive for a two minutes before the experiment begins.

2. Measure the heart rate by taking his or her pulse; you can do this one of two ways. (1)Radial Pulse: This is probably what we're most familiar with when visiting the doctor's office. Take two fingers, preferably the 2nd and 3rd finger, and place them in the groove in the wrist that lies beneath the thumb. Move your fingers back and forth gently until you can feel a slight pulsation - this is the pulse of the radial artery which delivers blood to the hand. Don't press too hard, or else you'll just feel the blood flowing through your fingers! (2)Carotid Pulse: The carotid arteries supply blood to the head and neck. You can feel the pulse of the common carotid artery by taking the same two fingers and running them alongside the outer edge of your trachea (windpipe). This pulse may be easier to find than the radial artery. Since the carotid arteries supply a lot of the blood to the brain, it's important not to press on both of them at the same time! Count the number of beats in 15 seconds. Your partner will use the clock or stopwatch to tell you when to start and when to stop.

3. Multiply the number of beats in 15 seconds by 4 to calculate the beats per minute. Record the data in the Table 1 under the 0 minutes box.

# of beats X 4 = beats per minute

4. Measure the person's breathing rate by counting the number of breaths taken in 15 seconds. The multiply this number by 4 to calculate breaths per minute. Add this information to the table.

# of breaths X 4 = breaths per minute

5. Rate the person's perspiration level from 1 to 5 (1 = none; 5 = droplets dripping down the face). Record this observation in the table.

6. Have the volunteer do jumping jacks for 2 minutes. After 2 minutes, measure heart rate, breathing rate, and perspiration level (refer to Steps 2 through 5), and record the data. Measure the pulse, breathing and perspiration levels as quickly as you can so that the volunteer can resume exercise. Do not have volunteer wait while you do the calculations and enter the data.

7. Repeat Step 6 three more times and record your data at each point. (4min, 6min, 8min)

8. After the final recording, wait 1 minute and 30 seconds with the volunteer at complete rest. Then measure the pulse, breathing and perspiration levels again. Record this data under the "9.5 Time (min.) box".

TABLE 1. EFFECTS OF EXERCISE

Time (min.)

0 2 4 6 8 9.5

Heart Rate (beats/min.)

Breathing Rate (breaths/min.)

Perspiration Level

Analyze and Conclude:

1. What is the manipulated variable in this experiment? __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________

2a. Graph the relationship between the manipulated and responding variables. Create one graph to display all of your data.

2b. Explain why you think it would be important to graph all 3 responding variables on one graph. __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________

3. What are the effects of exercise over time on the circulatory and respiratory systems? On perspiration level? __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________

4. What other processes could you have measured to determine the external and internal effects of exercise on the body? List at least 3. __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________

5. How is perspiration level related to body temperature? How is perspiration related to homeostasis? __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________

6. How is a negative feedback mechanism being represented in this lab? __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________

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