Explanatory gaps in the formation and propagation of action potentials?

What affects the propagation of an action potential?

The speed of propagation largely depends on the thickness of the axon and whether it’s myelinated or not. The larger the diameter, the higher the speed of propagation. The propagation is also faster if an axon is myelinated. Myelin increases the propagation speed because it increases the thickness of the fiber.

What causes an action potential to propagate down an axon?

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.

What is responsible for the initiation and propagation of the action potential?

In neurons, voltage-gated sodium conductances play an essential role in action potential initiation and propagation (Hodgkin and Huxley, 1952). Voltage-gated sodium channels activate and inactivate within milliseconds.

What causes the propagation of an action potential along a plasma membrane?

Going down the length of the axon, the action potential is propagated because more voltage-gated Na+ channels are opened as the depolarization spreads. This spreading occurs because Na+ enters through the channel and moves along the inside of the cell membrane.

What prevents the action potential from propagating backwards?

The refractory period

The refractory period prevents the action potential from travelling backwards. There are two types of refractory periods, the absolute refractory period and the relative refractory period. The absolute refractory period is when the membrane cannot generate another action potential, no matter how large the stimulus is.

How is an action potential started and propagated quizlet?

How is an action potential propagated along an axon? An influx of sodium ions from the current action potential depolarizes the adjacent area. [the influx of sodium ions depolarizes adjacent areas, causing the membrane to reach threshold and cause an action potential.

What does the synaptic gap do?

The synaptic cleft, also known as the synaptic gap, is the space in between the axon of one neuron and the dendrites of another and is where the electrical signal is translated to a chemical signal that can be perceived by the next neuron.

What is plant propagation?

Plant propagation is the process of creating new plants. There are two types of propagation: sexual and asexual. Sexual reproduction is the union of the pollen and egg, drawing from the genes of two parents to create a new, third individual.

In what direction does an action potential propagate in the axon quizlet?

Action potentials travel in only one direction down an axon because potassium channels in the neuron are refractory and cannot be activated for a short time after they open and close. Action potentials travel in only one direction down an axon because sodium channels in the neuron are refractory.

How does continuous propagation take place?


When an action potential in an axon spreads to a neighboring region of its membrane by a series of small steps. The process is called continuous propagation.

Why do action potentials not propagate passively?

In the absence of myelin, the action potential would propagate actively through the simple mechanisms discussed above. However, now the myelin occludes all the voltage-dependent sodium channels so the action potential can not propagate actively.

How does action potential propagate along a long fiber?

These experiments showed that when a nerve cell has lower external Na+ ion concentration the rise of amplitude of the action potential decreases. Action potential propagates to long distances by the movement of the ions through voltage-gated ionic channels embedded in the plasma membrane of the neurons (Fig. 10).

How an action potential is propagated along the length of an axon?

An action potential moves along a myelinated axon by saltatory propagation , which is faster and uses less energy. In saltatory propagation, the local current produced by the action potential “jumps” from node of Ranvier to the next.

What does an action potential rate of propagation depend on?

If the space constant is large, a potential change at one point would spread a greater distance along the axon and bring distance regions to threshold sooner. Therefore, the greater the space constant, the more rapidly distant regions will be brought to threshold and the more rapid will be the propagation velocity.

What is the relationship between action potentials and impulses?

A nerve impulse is a sudden reversal of the electrical gradient across the plasma membrane of a resting neuron. The reversal of charge is called an action potential .

What is the relationship between action potentials and nerve impulses quizlet?

A momentary change in electrical potential on the surface of a neuron or muscle cell. Nerve impulses are action potentials. They either stimulate a change in polarity in another neuron or cause a muscle cell to contract. You just studied 26 terms!

Which of the following have higher action potential propagation rate?

Explanation: Nerve cell have a higher rate of propagation for action potential( 20-140 m/s).

How impulses are transmitted across a synapse?

An electrical nerve impulse travels along the first axon. When the nerve impulse reaches the dendrites at the end of the axon, chemical messengers called neurotransmitters are released. These chemicals diffuse across the synapse (the gap between the two neurons).

What are the 5 steps that take place in transmitting information across a synapse?

Neurotransmitter release from the presynaptic terminal consists of a series of intricate steps: 1) depolarization of the terminal membrane, 2) activation of voltage-gated Ca2+ channels, 3) Ca2+ entry, 4) a change in the conformation of docking proteins, 5) fusion of the vesicle to the plasma membrane, with subsequent …

How impulses are transmitted across a synapse Igcse?

1) An electrical impulse travels along an axon of the presynaptic neuron. 2) When the impulse reaches the nerve-ending, it releases chemical messengers called neurotransmitters. 3) These chemicals diffuse across the synapse and bind with specific receptor molecules on the membrane of the next neuron.