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2021-05-14

What happens when the action potential reaches the end of the axon at the axon terminal?

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What happens when the action potential reaches the end of the axon at the axon terminal?

When the action potential reaches the end of the axon (the axon terminal), it causes neurotransmitter-containing vesicles to fuse with the membrane, releasing neurotransmitter molecules into the synaptic cleft (space between neurons).

What happens when an action potential reaches the axon terminal quizlet?

When an action potential reaches the axon terminal: neurotransmitter molecules are released from the axon terminal and bind to receptors on the postsynaptic neuron, causing either an inhibitory hyperpolarization or an excitatory depolarization.

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What happens when the action potential reaches the terminal button?

When the electrical impulse from the action potential reaches the end of the axon, it signals the terminal buttons to release neurotransmitters into the synapse. When the nerve impulse reaches the terminal button, it triggers the release of neurotransmitters into the synapse.

When an action potential reaches the end of an axon the release neurotransmitters?

When an action potential reaches the axon terminal, the depolarization causes voltage-dependent calcium gates to open. As calcium flows into the terminal, the neuron releases neurotransmitters into the synaptic cleft for 1-2 milliseconds. This process of neurotransmitter release is called exocytosis.

What happens just after an axon is depolarized to threshold?

What happens just after an axon is depolarized to threshold? Some sodium channels open. all stimuli great enough to bring the membrane to threshold will produce identical action potentials. Neurotransmitter binds to receptors on the postsynaptic cell membrane.

What is the typical duration of a nerve action potential?

about 1 ms.

What are the 6 steps of action potential?

An action potential has several phases; hypopolarization, depolarization, overshoot, repolarization and hyperpolarization. Hypopolarization is the initial increase of the membrane potential to the value of the threshold potential.

What are the 5 steps of an action potential?

The action potential can be divided into five phases: the resting potential, threshold, the rising phase, the falling phase, and the recovery phase.

Why is it harder to generate a second action potential?

Why is it harder to generate a second action potential during the relative refractory period? A greater stimulus is required because voltage gated potassium channels that oppose depolarization are open during this time.

How did the threshold for the second action potential?

How did the threshold for the second action potential change as you further decreased the interval between the stimuli? The threshold for the second action potential will be higher, which indeed requires increased strength in the stimulus.

Why is there no response at R3?

Why is there no response at R3 when you apply a very weak stimulus to the sensory receptor? You correctly answered: c. The very weak stimulus does not depolarize the axon of the sensory neuron to threshold. The stimulus induces a graded receptor potential at R1.

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Why is the resting membrane potential the same value?

1. Why is the resting membrane potential the same value in both the sensory neuron and the interneuron? The resting membrane potential is the same value because this is the typical resting membrane potential regardless of the type of neuron.

Which ion is responsible for resting membrane potential?

potassium ions

What must be met in order for a neuron to initiate an action potential?

A stimulus from a sensory cell or another neuron depolarizes the target neuron to its threshold potential (-55 mV), and Na+ channels in the axon hillock open, starting an action potential. Once the sodium channels open, the neuron completely depolarizes to a membrane potential of about +40 mV.

What effect did increasing the extracellular potassium have on the resting membrane potential?

What effect did increasing the extracellular potassium have on the resting membrane potential? The resting membrane potential became less negative.

How would an increase in extracellular K+ affect repolarization?

How would an increase in extracellular K+ affect repolarization? It will decrease the concentration gradient, causing less K+ to flow out of the cell during repolarization. That means that during repolarization, less K+ will diffuse out of the cell.

What happens if you decrease extracellular sodium?

As the concentration of sodium in the extracellular solution is reduced, the action potentials become smaller.

What effect did decreasing extracellular concentration of Na+ have on the resting membrane potential Why?

What effect did decreasing the extracellular sodium have on the resting membrane potential? The resting membrane potential disappeared. The resting membrane potential became less negative. Only a small change occurred, because the resting neuron is not very permeable to sodium.

Which of the following will change the equilibrium potential for Na+?

The concentration of Na+ ion is higher outside the cell while it is lower inside the cell while the concentration of K+ ion is higher on the inner side of the cell as compared to the outer side of the cell. The ion gate is responsible for maintain this equilibrium.

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What is responsible for restoring the resting membrane potential back to at the end of the action potential?

Depolarization is caused by Na+ ions coming into the cell through gated sodium channels. To restore the resting potential (repolarize), K+ flows out via gated potassium channels.

What happens after action potential is completed?

After the action potential peak is reached, the neuron begins repolarization (3), where the sodium channels close and potassium channels open, allowing potassium ions to cross the membrane into the extracellular fluid, returning the membrane potential to a negative value.

What happens when a neuron’s membrane Depolarizes?

During depolarization, the membrane potential rapidly shifts from negative to positive. As the sodium ions rush back into the cell, they add positive charge to the cell interior, and change the membrane potential from negative to positive.

What is more likely to promote an action potential?

A small, local depolarization called an EPSP moves the membrane potential closer to threshold. If threshold is reached, an action potential is triggered. Thus, an EPSP is more likely to promote an action potential while an IPSP is less likely to promote an action potential.

What is responsible for the repolarization phase of an action potential in a nerve?

Repolarization is a stage of an action potential in which the cell experiences a decrease of voltage due to the efflux of potassium (K+) ions along its electrochemical gradient. This phase occurs after the cell reaches its highest voltage from depolarization.

Which type of postsynaptic potential makes an action potential more likely?

excitatory postsynaptic potential

What happens to the membrane potential if you increase sodium permeability?

If you experimentally increase the permeability of an axonal membrane to sodium ions, the equilibrium potential for sodium in the cell will a. increase, because the influx of sodium depolarizes the neuron. decrease, because the influx of sodium depolarizes the neuron.

Why is the membrane more permeable to K+ than Na+?

The cell membrane contains protein channels, called leak channels that allow Na+ or K+ to leak down their concentration gradients. Cell membranes are considerably more permeable to K+ than to Na+ because they have many more K+ leak channels than Na+ leak channels.