An electroencephalogram measures the impulses of which cells?

• A. Impulses of heart muscle cells
• B. Impulses of nerve cells within the brain
• C. Measure the pressure within the eye
• D. Measure the amount of air upon exhalation

Answer: (B)

An electroencephalogram records electrical activity from nerve cells in the brain. Neurons communicate with electrical impulses, and when many neurons fire together, their combined electrical signals create measurable activity that can be detected by electrodes on the scalp. This pattern—brain waves—reflects the brain’s state, such as awake, asleep, or seizure activity. It doesn’t measure impulses from heart muscle, intraocular pressure, or air exhaled, which are assessed by ECG, tonometry, or spirometry, respectively.