Our hearts beat continuously to power our circulatory system, and if we listen closely, we can actually see and hear the electrical impulses that drive each contraction. In this experiment, you will learn how to record an electrocardiogram, or EKG, using the Human SpikerBox to observe the waveforms behind each beat and explore how your heart communicates with your brain in real time.
This experiment helps you explore the basics of electrocardiography and discover how your brain regulates heart rate through its control center in the medulla oblongata. You will learn how pacemaker cells start each beat and how heart-muscle cells’ long action potentials coordinate the contraction and how changes in activity or emotion can alter your heart’s rhythm.
The heart relies on specialized pacemaker cells to produce rhythmic electrical impulses, causing coordinated muscle contractions that pump blood throughout your body. Heart-muscle action potentials last much longer than skeletal-muscle spikes, and their combined activity across the heart appears on the EKG as waves labeled P, Q, R, S, and T. You can visualize them by placing electrodes on your skin and recording with the Human SpikerBox. Your heart rate can be adjusted by nerves from your brain and by hormones such as adrenaline, in response to exercise, emotions, or stress.
You will place adhesive electrodes on the inner side of your wrists and on the back of one hand (Configuration 1 below), then connect them to the SpikerBox. Relax and hold your arms still so muscle activity does not interfere with the recording. Connect the SpikerBox to the SpikeRecorder software. Open the config menu (gear icon in the top left) and select the ECG filter setting. Observe the rhythm that appears on the screen and note how these waveforms correspond to the electrical signals coordinating your heartbeats.
If you find too much noise in your signal, try using a battery-powered laptop or improve electrode placement by moving them closer to your chest. After you have a stable waveform, try increasing your heart rate by a brief exercise like jumping jacks before reconnecting, and watch the heart rate change as your body recovers from exertion. Pay attention to how your heart adapts automatically, guided by the nervous system’s instructions to speed up or slow down as needed.
Consider whether you are recording the spontaneous cardiac action potentials initiated by pacemaker cells or the muscle potentials that follow them. Think about how your waveforms might change when you adjust the electrode positions or your posture. Reflect on how factors like caffeine, adrenaline, or recent exercise might affect what you see on screen. Imagine measuring heart rates under various conditions such as standing outside on a cold day or after sipping a warm drink, and see if you observe measurable differences in how your heart responds.
Draw the loop that speeds your heart up during jumping jacks and slows it down afterward: sensors in your body, the control center in your medulla oblongata, the nerves to your heart, and its pacemaker cells. Label where your wrist electrodes recorded.
MS-LS1-3 Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells.
The nervous system and the heart interact: the brain's medulla speeds or slows the beat.
HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.
Draw the loop from body sensors to the medulla to the heart's pacemaker cells: parts that work together to set the beat.
HS-LS1-3 Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.
After jumping jacks the heart rate rises, then settles back: the nervous system's feedback keeps the body steady.
2 Developing and Using Models
Draw the loop that speeds your heart up during exercise and slows it afterward, and label where you recorded.
3 Planning and Carrying Out Investigations
Record your EKG at rest and again after brief exercise.
4 Analyzing and Interpreting Data
Relate the waveforms to each heartbeat and follow the heart rate as you recover.
Patterns
Each beat repeats the same P-QRS-T waveform.
Structure and Function
Specialized pacemaker cells set the rhythm.
Stability and Change
Heart rate returns toward its resting value after exercise.
LS1.A Structure and Function
Feedback keeps heart rate within limits; specialized cells coordinate each beat.
Backyard Brains mapping using the book's method. Not in the book.
