compound action potentials What is a compound action potential, how does a cap d
ID: 82714 • Letter: C
Question
compound action potentials What is a compound action potential, how does a cap differ from an action potential, response of nerve at maximum stimulus, what was an artifact in the cap experiment, what occurs as we increase stimulus to the nerve (think in terms of fibers and the nerve itself) ekg Know the electrical conduction in/through the heart, know the relationship of the cardiac cycle to the ekg (pqrst curve) what are baroreceptors and what is their function, sympathetic and parasympathetic control of heartExplanation / Answer
Answer 5):
Compound action potential(cap)- the sum of the activity in a number of nerve fibers. It applies to the degree of activity in a nerve trunk in which a variable proportion of nerve fibers are discharging.
When a large stimulus is delivered to the compound nerve, many axons respond and the recorded potential is the summation of all the axons firing is recorded, This recording is known as the compound action potential, and it will be visible to the right of the stimulus artifact.
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Action potential is strong enough to depolarize the membrane of the neuron to thresold(55mV), once neuron reaches this thresold the action potential will be fired. Each stimulus reaches thresold will produce an action potential that is equal in magnitude to every other action potential for the neuron. So action potential follow all or none rule. Compound action potential not not exibit this, CAP are bundle of neurons and have different magnitudes of action potential. Thus CAPs are graded, that is the greater the stimulus greater the action potential.
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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. This is the stimulus artifact, which results from virtually instantaneous, passive current spread from stimulating electrodes to recording electrodes.
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CAP increase in size and duration with increase in stimulus strength.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. The conduction velocity of single fibres depends on fibre diameter, and that the nerve bundle is composed of fibres of varying diameter. Fast fibres (large diameter, low threshold) will contribute APs that fall towards the start of the CAP, slower fibres (small diameter, high threshold) will contribute APs that fall towards the tail section. As we gradually increase stimulus strength, we recruit more and more fibres giving rise to a wider CAP, with longer duration.
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