REACH-DL | Muscle4: The Electrogastrogram (EGG)

Note – to do this lab you must start with an EMPTY stomach. This means not having eaten for AT LEAST 3 hours.

EMG Cable Setup

Plug the red, black, and green electrodes into the REACH.

Snap the lead wires onto the stickie electrodes before putting them on yourself:

The green lead is attached to the electrode adjacent to the belly button.
The red lead is attached to the electrode above the green lead.
The black lead is attached to the electrode below and to the left of the green lead.

EGG on an Empty Stomach

Aim

To determine the relationship between the frequency and power of EGG activity on an empty stomach.

Procedure

Note: You must have an empty stomach. You should not have eaten any food for at least 3 hours prior to this experiment.

You will be lying down for this recording, so have the REACH and computer somewhere where you can do this. Make sure to be lying face up (supine). It is important that you are lying VERY still during the recording.
Click the Record button to begin recording.
Record for a minimum of 15 minutes while you are lying down, face up. Clinical EGG recordings are approximately 2 hours in length; however, a general understanding of the muscle activity can be seen in less time. The longer the recording, the more accurate the data. Do not record for longer than 30 minutes.
Click the Stop button after the desired length of recording.
Click File ---> Save As, name the file "EGG", and save your data to your LabScribe Data folder on your Desktop.

EGG on a Full Stomach

Aim

To determine the relationship between the frequency and power of EGG activity on a full stomach.

Note: You will need to eat a small meal. Have some food ready to eat. This can include a sandwich, fruit, desert and a small non-carbonated drink.

Sit up and eat your small meal within 15 minutes.
Then get back into a lying down position. Make sure to be lying face up (supine). It is important that you are lying completely very during the recording.
Follow the same directions as in Exercise 1, recording EGG activity for the same length of time.
Click the Stop button after the desired length of recording.
Click on the Save button to save the data file.

Data Analysis for both Exercise 1 and Exercise 2

The stomach muscles contract at regular intervals, giving a repeating rhythmic electrical signal that is recorded by the electrodes placed on the abdomen. In a person at rest with an empty stomach, the rhythm of the contraction is approximately three cycles per minute or about 0.05 Hz. The power and frequency of the signal will change after the individual eats a small meal.

Click the "two mountains" icon to double the display time to show the entire set of EGG muscle contractions for an Empty Stomach on the Main window. You may have to click the icon a few times.

Click and move the two vertical cursors so they are at either end of the data shown.
Look at MEAN on both the Power and Frequency channels. These values represent the Mean Power (strength) and Frequency (how often) of the contractions of your gut muscles.
Make a note of these values on a data table.
Select Save from the File menu.
Repeat Steps 1 through 8 for the data in Exercise 2 when you had a full stomach.
Save your data.

Answer the following:

Was there a change in the frequency and power of the EGG waves before and after eating?
What is the physiologic relationship between frequency and power of the EGG contractions, whether before or after ingesting food?
Why is there a change in the frequency of the contractions after eating?
Why is there a change in the power of contractions after eating?

Note – if you do not see a change, or the change is not what you expected, be sure to explain this.

What are the physiologic causes for any changes seen in your EGG after eating?