How can oscilloscope traces be used to analyze resting potentials and action potentials in neurons?

Sourav PanNovember 9, 2024

Answered

Oscilloscope traces are valuable tools for analyzing resting potentials and action potentials in neurons. By graphically representing changes in membrane potential over time, these traces provide insights into the electrical activities of neurons during synaptic transmission.

Understanding Oscilloscope Traces

1. Measurement of Membrane Potentials:
   • An oscilloscope measures the voltage difference across a neuron’s membrane by placing electrodes inside and outside the neuron. This setup allows for the visualization of membrane potentials, including resting and action potentials, on a graph where time is plotted on the x-axis (in milliseconds) and membrane potential is on the y-axis (in millivolts).
2. Resting Potential:
   • The resting potential is typically around -70 mV, represented as a straight, horizontal line on the oscilloscope trace. This stable state reflects the neuron’s readiness to respond to stimuli.

Analyzing Action Potentials

1. Initiation of Action Potential:
   • When a neuron is stimulated and reaches a threshold potential (approximately -55 mV), voltage-gated sodium channels open, causing rapid depolarization. This initial phase is characterized by a sharp upward spike in the oscilloscope trace, reaching around +30 to +40 mV.
2. Phases of Action Potential:
   • Depolarization: The rising phase of the trace indicates depolarization due to sodium influx.
   • Repolarization: Following depolarization, potassium channels open, allowing K++ ions to exit the neuron, resulting in a downward slope on the trace as the membrane repolarizes .
   • Hyperpolarization: Often, after repolarization, there is a brief period where the membrane potential dips below resting levels (hyperpolarization), which can be seen as a slight dip below -70 mV on the trace .
3. Refractory Period:
   • After an action potential occurs, there is a refractory period during which the neuron cannot fire another action potential immediately. This period can be observed as the trace returns to resting potential levels due to the action of the sodium-potassium pump restoring ion concentrations .

Importance of Threshold Potential

• The threshold potential is critical for determining whether an action potential will occur. If the initial depolarization does not reach this threshold, no action potential will be generated. Oscilloscope traces can show failed initiations where depolarizations do not reach threshold, indicating that synaptic inputs were insufficient to trigger an action potential