Human Anatomy and Physiology

What is the all or nothing response of an action potential?

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Answered 2008-04-10 10:51:39

All or nothing response of an action potential (AP), refers simply to the fact that an AP will either occur, or not. There is no gradient, no half APs or double APs. The only option is AP, or no AP. Like in computer binary, the response is either 1 (an AP) or 0 (no AP).

All the factors trying to induce (or inhibit) an action potential (i.e other action potentials, EPSPs and IPSPs) add up (summate) at the axon hillock, (aka the trigger zone). Here, if the stimulation is big enough an action potential will occur. If the stimulation is not big enough, no action potential occurs.

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What is the all or nothing respones?

a threshold must be reached for the action potential to occur. So if the threshold is reached it will produce a response. If the threshold isnt reached, there will not be a response.

An action potential either fires completely or not at all. this is know as?

All-or-none response

Do nerves fire slowly and continuously or is it more of an all or nothing reaction?

The action potential of a nerve, which causes the nerve to "fire", is all or nothing.

An action potential is all or nothing event. explain what is ment by this phrase?

The action potential is an all-or-none phenomenon, it either happens completely or doesn't happen at all. this means, the properties of the action potential are independent of the relative strength of the depolarizing stimulus as long as that stimulus exceeds threshold.

How does end plate potential differ from action potential?

End plate potential is the change in potential from neurotransmitters. It can be excitatory or inhibitory. If the action potential wants to continue, it will be excitatory and vice versa. It can be additive, if more action potentials are fired it will increase the end plate potential. An action potential is an all or none response. It will either proceed or it will not proceed depending on the terms of the threshold. It cannot be additive, because there is an absolute refractory period where no additional action potentials can be fired.

Do action potentials always have the same amplitude and the same duration?

Yes, this is due to the all or nothing law that neurons follow: "an excitable membrane either responds to a stimulus with a maximal action potential that spreads nondecrementally throughout the membrane, or it does not respond with an action potential at all." "

Is an action potential is a phenomenon that either happens completely or doesn't happen at all?

The action potential is an all-or-none phenomenon.

Why does the frog sciatic nerve give a graded response?

The frog schiatic nerve gives a graded response because the nerve is a bundle of axons and not a single axon (thus it does not show the all or none response of an axon-either generating an action potential or not). If one axon is generating an action potential then a small nerve impulse is witnessed, if all axons are simultaneously generating action potentials then a large nerve impulse is witnessed. Thus the nerve impulse is graded (it can be none, small, medium, large, larger, maximal).

What is the all-or-nothing response of neurons?

the all or nothing effects refer to the activation of the cell

How a nerve impulse is propagated along the length of a neuron through an action potential?

Neurons, or nerve cells, are stimulated when the polarity across their plasma membrane changes. The polarity change, called an action potential, travels along the neuron until it reaches the end of the neuron. An action potential is capable of traveling long distances. If a depolarizing graded potential is sufficiently large, Na+ channels in the trigger zone open. In response, Na+ on the outside of the membrane becomes depolarized . If the stimulus is strong enough additional Na+ gates open, increasing the flow of Na+ even more, causing an action potential, or complete depolarization (from -70 to about +30 millivolts). This, in turn, stimulates neighboring Na+ gates, farther down the axon, to open. In this manner, the action potential travels down the length of the axon as opened Na+ gates stimulate neighboring Na+ gates to open. The action potential is an all-or-nothing event. When the stimulus fails to produce depolarization that exceeds the threshold value, no action potential results, but when threshold potential is exceeded, complete depolarization occurs.

Is an action potential fired in response to any nerve stimulus?

No, there must be a sufficient voltage summed up from all the inputs to be at or above the trigger voltage. Usually a single input is not sufficient.

What happens when a graded potential reaches the axon hillock?

It is either inhibitory and nothing happens or excitatory and causes depolorization again. If the axon hillock on the postsynaptic neuron reaches threshold potential then an impulse is transmitted and action potential is reached all over again.

What is the difference between a compound action potential and a single action potential?

Single action potentials follow the "all or none" rule. That is, if a stimulus is strong enough to depolarize the membrane of the neuron to threshold (~55mV), then an action potential will be fired. Each stimulus that reaches threshold will produce an action potential that is equal in magnitude to every other action potential for the neuron. Compound action potentials do not exhibit this property since they are a bundle of neurons and have different magnitudes of AP's. Thus compound action potentials are graded. That is, the greater the stimulus, the greater the action potential.

Explain what the ap is an all or none?

it depends on the stimulation. if the stimulation is not strong enough, there might be no action potential. However, if the stimulation is strong enough, there will be an action potential

What does action potential mean in Biology?

Action potential in biology is a short event, when the electrical membrane potential of a cell quickly rises and falls, following a consistent trajectory. This can occur in all types of cells.

How does a nerve impulse follow the all or nothing principle?

The action action potential produced needs to reach the threshold for the AP to be propagated. If it doesn't reach the threshold, there is not enough Na+ to stimulate the positive feedback system which allows the action potential to be self-propagated. Instead, K+ channels will be opened, and it will enter repolarisation phase, and the AP wll not be conducted.

What is the 'all or none' response?

The generation of an action potential (AP) is generally considered a 'all or none' response as opposed to a graded response. This has to do mainly with single motor units. Once an AP is triggered in the neuron body (soma) the AP travels along the axon to the neuro-muscular junction where it releases acetylcholine (Ach). The muscle then either fires (if enough axons discharge) or not, but there is no halfway response.

Is action potential all or none?

In terms of the nervous system, yes.

What is the chemical portion of the nerve impulse called?

The chemical involved in the transmission of a neuralsignal is called a neurotransmitter.A neural impulse is technically just the firing of the neuron, the action potential, an all-or-nothing spike, not the transmission of the signal across the synapse, nor down the dendrite & soma via electrotonic conduction in a graded response.

What is a positive response when your boyfriend asks what do you want out of me?

You say "Nothing. All I want is you."

What is stimulus threshold?

ST - In regards to excitable cell (i.e. neurons) the minimum mV need to trigger a AP (action potential) and is around -40mV (although this may vary depending on the cell). In additional to this; excitable cells (i.e. neurons) shows an all-or-nothing property, such that if the stimulus threshold is not met the action potential will not be created.

Difference between action potential and excitory postsynaptic potential or ihibitory postsynaptic potential.?

Postsynaptic potentials (PSPs) are depolarizations/hyperpolarizations that increase the likelihood that a cell will have an action potential (AP). PSPs are fast, graded responses and their signal travels passively through the neuron's membrane and are therefore decremental (getting weaker as it gets farther from the site of generation). In other words, these are the inputs to neuron that could make the neuron fire. APs is what happens if enough PSPs sum up. This is the neuron firing. There is a massive but short reversal of the membrane potential. The signal travels actively down the axon (read about voltage-activated sodium and potassium channels), so the AP is not decremental and is an all-or-nothing response.

Action potentials originate at the?

Action potentials are how nerve impulses are transmitted from neuron to neuron. An action potential is formed when a stimulus to the nerve cell causes the membrane to depolarize and open all of its sodium ion channels toward the threshold potential.

The different charge between the outside and the inside of a neuron at rest is called?

Potential, ok well we all know it's a potential, but which one? Is it Action Potential, Synaptic Potential or Membrane Potential. Just saying Potential isn't saying much?

Summarize the events involved in the synaptic transmission of a nerve impulse?

As a nerve impulse propagates along its axon it reaches the synapse and stimulates calcium ion gates to flow into its end bulb, this stimulates vesicles inside the bulb holding a particular neurotransmitter (commonly acetylcholine in humans) to exocytose out into the synaptic cleft (a small junction between the synapse end bulb and the receiving neuron/muscle cell, etc). After the neurotransmitter is released it migrates across to synaptic cleft and attaches to proteins attached to the membrane wall to stimulate a particular response. It can be an excitatory or inhibitory response to either stimulate another action potential or inhibit it. Normally to propagate the action potential, a series of excitatory channels would open allowing an influx of sodium ions into the cell creating a positive membrane potential changing the resting potential (~-70mv) to become more positive. If the number of excitatory signals elevates the potential to -35mv then an all out response in the cell will occur resulting in an action potential that can propagate along the new cell