Respiratory System Lab, 2018

“Holding Your Breath”

     All parts of your body need energy to do their work.  For example, muscles need energy to contract, and all parts of your body need energy to synthesize needed molecules. Your body gets the energy it needs by combining food molecules with oxygen in a process called cellular respiration.  For example, in your body, the sugar glucose is combined with oxygen to release energy your body can use.  This is shown in the following chemical reaction.

C₆H₁₂O₆ + 6 O₂ --> 6 CO₂ + 6 H₂O + Energy Your Body Can Use

     You know that a fire needs fuel and oxygen from the air to keep burning.  Similarly, your muscles and other parts of your body need to have a continuous supply of glucose (or other high-energy molecules) and oxygen to provide the energy for muscle contraction and other body functions. When your body breaks down glucose, carbon dioxide is produced.  Too much carbon dioxide can result in damage to muscles or other body parts, so there must be some way to get rid of this carbon dioxide. Normally, you breathe automatically, without even thinking about it.  However, you can control your breathing voluntarily when you want to.  For example, you can stop breathing and hold your breath for a while. However, you cannot hold your breath forever.  Obviously, it would be very unhealthy to hold your breath for too long!  Why? All parts of your body, including the muscles and the brain, depend on the breathing muscles and the circulation working together to deliver the oxygen needed by all body cells and to remove the carbon dioxide produced by all body cells. The part of your body that is the most sensitive to lack of oxygen is your brain.  If the brain is deprived of oxygen for a few minutes, parts of the brain can be permanently damaged.  If oxygen deprivation continues, the person can become "brain dead". Because it is so important to maintain a continuous supply of oxygen, in a healthy person the part of your brain which controls breathing will not let you hold your breath forever.  When you try to hold your breath for a long time, after a while this part of your brain will automatically start the breathing rhythm again, even if you try very hard to hold your breath. Dr. Ingrid Waldron and Jennifer Doherty, Department of Biology, University of Pennsylvania

Method

Apparatus:

13gallon plastic bag per student

Timer

Procedure: Answer the following prior and after each procedure

A:

1. How long do you think you can hold your breath? (Specify if your estimate is in seconds or minutes)

Now, take a deep breath and hold your breath as long as you can, while someone in your group times you.  Be sure to hold your nose while you hold your breath.

2. How long did you hold your breath? (Specify if your estimate is in seconds or minutes)

B:

You will now carry out a simple experiment to test whether changes in the levels of oxygen and carbon dioxide in your blood provide the signal to stop holding your breath.  Before you actually carry out this experiment, predict what you think will happen by answering the following questions. (Note: Predict correctly because these are for points)

1. What will happen to the levels of carbon dioxide in the bag?

2. What will happen to the levels of carbon dioxide in your lungs?

3. What will happen to the levels of carbon dioxide in your blood?

4. What will happen to the levels of carbon dioxide in your brain?

5. What will happen to the levels of oxygen in the bag? 

6. What will happen to the levels of oxygen in your lungs, blood, and/or brain? 

7. What change would you predict in how long you can hold your breath after breathing  

     into the bag? 

Now, breathe normally for a few minutes.  Then, open a 13-gallon plastic bag and swish it through the air to fill it with air.  Hold the bag over your mouth and nose and breathe into the bag as normally as you can for 5 minutes or as close to 5 minutes as you can.  At the end of your time breathing into the bag, take a deep breath of the air from the bag, hold your breath by removing the bag from your mouth and holding your nose as long as you can while someone in your group times you. 

8. How long did you hold your breath?

9. Was there a difference in the amount of time you could hold your breath after breathing into the bag, compared to after normal breathing (from question #2) ?

10. After breathing in the bag, what was your immediate reaction to do?  Why do you think this happen (hint: what was building up in your system)

C:

You will now test whether you breathe differently after holding your breath for as long as you can.  First, observe how you breathe during normal breathing for 1 minute.  Next, hold your breath as long as you can.  Then, observe how you breathe after holding your breath. 

11. Describe the differences in breathing after holding your breath, compared to your normal breathing: