What is the stimulus artifact?

The stimulus artifact is present whether or not the nerve is in the tube, though its form may be altered by the electrical properties of the nerve. It is called an artifact because it is a product of human intervention and is not produced by the nerve.

Why does the peak of the compound action potential change with different stimulus strengths?

Q: Why does the CAP increase in size and duration with increasing stimulus strength? A: The CAP is the algebraic sum of all individual fibre action potentials of the nerve. As stimulus strength increases, we recruit more fibres, therefore more APs add up to produce a larger bell-shaped curve.

How does compound action potential work?

A compound action potential (CAP) is a signal recorded from a nerve trunk made up of numerous axons. The different conduction velocities of the axon population results in a shift in time of the amplitude peaks as the recording site moves further from the stimulation site.

What is meant by compound action potential?

a recording of the action potentials from several axons of a nerve when different axons are stimulated together. The different amplitudes and conduction velocities of the fibers account for the compound nature of the response.

What causes stimulus artifact?

When an electrical stimulus is used to evoke action potentials in peripheral nerves or the spinal cord, the stimulus causes an artefact which may interfere with measurement of the evoked potentials. This artefact, unlike all other sources of noise in the measurement, cannot be reduced by ensemble averaging.

How does duration of stimulus affect action potential?

In reality, the ability of a neuron to fire an action potential does not only depend on stimulus strength, it also depends on stimulus duration. This is because the neuron’s membrane potential has the ability to integrate its inputs over time, until it reaches the threshold potential to fire an action potential.

How does a stimulus cause an action potential?

Action potentials are caused when different ions cross the neuron membrane. A stimulus first causes sodium channels to open. Because there are many more sodium ions on the outside, and the inside of the neuron is negative relative to the outside, sodium ions rush into the neuron.

How did the action potential at R1 or R2 change as you increased the stimulus voltage above the threshold voltage How well did the results compare with your prediction?

How did the action potential at R1 (or R2) change as you increased the stimulus voltage above the threshold voltage? The action potential didn’t change as the stimulus voltage increased. This is because once threshold is met, the event it all or none, not graded. An action potential is an “all or nothing” event.

Does conduction velocity increase with stimulus?

As stimulus voltage was increased from minimal to supramaximal, amplitudes of nerve action potentials increased, latencies decreased, but conduction velocities remained unchanged. Furthermore, the fastest conducting sensory fibres in the human median nerve do have a lower threshold than slower conducting fibres.

At what stimulus voltage S did an action potential occur?

At what stimulus voltage(s) did an action potential occur? An action potential occurred at 6v and 8v. 4. What was the membrane potential at the axon hillock when the action potential was generated?

Does a stronger stimulus cause a stronger action potential?

Because of the predictable changes that occur once threshold is reached, the action potential is referred to as “all or none”. A stronger stimulus, which might depolarize the membrane well past threshold, will not make a “bigger” action potential.

What happens after a neuron receives a stimulus?

When a stimulus reaches a resting neuron, the gated ion channels on the resting neuron’s membrane open suddenly and allow the Na+ that was on the outside of the membrane to go rushing into the cell. As this happens, the neuron goes from being polarized to being depolarized.

How does compound action potential work in mammals?

Mammalian Nerves and the Compound Action Potential Mammalian nerves consist of many axons running in parallel with each other. Larger diameter axons conduct action potentials faster than smaller fibres, and when electrical stimuli are applied, the voltage necessary to initiate an action potential in large axons is smaller than for smaller ones.

Is there a cap on the compound action potential?

By setting the A to D range, you change the A to D (hardware) gain, in order to more accurately view the CAP signal. With a low initial stimulus amplitude, no CAP will be visible, but you will see a brief, biphasic deflection near the beginning of the display.

How is the threshold stimulus voltage determined in compound action potential?

The threshold stimulus voltage is determined by raising and lowering the stimulus voltage a little to find the voltage at which the CAP is just discernible. The maximal stimulus voltage is the point at which a further increase in stimulus voltage produces no further increase in the CAP amplitude.

How is the compound action potential of the nerve determined?

The delay dial on the stimulator is adjusted so that the stimulus artifact begins exactly 1 ms from the start of the sweep. As we slowly increase the stimulus voltage, using the control knob on the stimulator, at a certain point a second deflection will appear in the displayed waveform. This is the Compound Action Potential of the nerve.