What is the significance of the axon hillock

The axon hillock is located at the end of the soma and controls the firing of the neuron. If the total strength of the signal exceeds the threshold limit of the axon hillock , the structure will fire a signal known as an action potential down the axon. An action potential occurs when a neuron sends information down an axon, away from the cell body. Neuroscientists use other words, such as a "spike" or an "impulse" for the action potential.

Action potentials are caused when different ions cross the neuron membrane. A stimulus first causes sodium channels to open. Asked by: Jeanetta Pothof asked in category: General Last Updated: 30th June, What is the significance of the axon hillock in the conduction of an action potential? The axon hillock is the last site in the soma where membrane potentials propagated from synaptic inputs are summated before being transmitted to the axon.

For many years, it was believed that the axon hillock was the usual site of initiation of action potentials —the trigger zone. What is the function of Axon? An axon, is a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body.

Myelinated axons are known as nerve fibers. The function of the axon is to transmit information to different neurons, muscles and glands. Can an action potential travel in both directions? Action potentials can travel in both directions on the axon. Threshold is the minimum current required for the cell membrane to generate an action potential.

How does depolarization occur? Depolarization and hyperpolarization occur when ion channels in the membrane open or close, altering the ability of particular types of ions to enter or exit the cell. The opening of channels that let positive ions flow into the cell can cause depolarization. These action potentials are outward-bound, i. Sequential abrupt changes in the electric potential or the voltage across the plasma membrane are the action potential.

This action potential of the neuronal cells is equivalent to the non-neuronal cells. This depolarization is followed by repolarization , i. The action potential moves along the axon toward the terminal part of the axon wherein at the chemical synapses it incites the release of neurotransmitters for further propagation of the signals. The cell body is the core of the neurons that contain the genetic information, upholds the neuronal structure, and provides the energy for the neuronal activities.

The nucleus and the other cellular organelles like endoplasmic reticulum , Golgi apparatus , mitochondria , ribosomes , secretory vesicles, etc. Figure 1. The bridge between the cell body and the axon is known as the axon hillock. The generation of the action potential occurs at the axon hillock. Most of the neurons possess one key axon and multiple dendrites. The terminal point of the axon is the presynaptic terminal also referred to as terminal bouton. These terminal buttons connect with other neuronal cells to form a synapse.

Thus, signals from one neuronal cell are transmitted to the other neuronal cell via these synapses. The neuronal action potential is usually created at the axon hillock.

It is a cone-shaped area in the neuronal cell body from where the axon originates. Figure 1-A. The initial segment is the site for the initiation of the action potential. Characteristically, the axon hillock does not contain ribosomes and most of the other cell organelles. However, it does contain cytoskeletal elements or microtubular structures and organelles that move along the axon. Figure 2-B The neurofilaments in the axon hillock form a cluster, which is referred to as fascicles.

The terminal portion of the axon and its collaterals i. Another distinguishing feature of the axon hillock region in the neuron is the presence of a high density of voltage-gated sodium ion channels.

What is the function of the axon hillock? Why does an action potential occur at the axon hillock? The axon hillock acts as an administrator, sums up the total signals received, both inhibitory and excitatory signals. If this sum exceeds the limiting threshold, the action potential is triggered.

This results in the transmission of the generated electrical signal through the axon away from the neuronal cell body.

These signals are mediated through certain ion channels. This action potential is triggered by the alteration in the gated voltage sodium ion channels and the potassium ion channels that are sensitive to the changes in polarization.

On receiving the signals, sodium ions enter the cell, thereby, reducing the axonal polarization. In case this depolarization of the axon, due to the entry of sodium ion, crosses a specific threshold, an action potential is generated.

This action potential will, then, be transmitted as an electrical signal through the axon to the synapses. The generation of the action potential is an example of all-or-none phenomena, wherein either the neurons are fired or not, and the transmission of complete signal occurs transmission of the partial signal never occurs.

The whole process of action potential generation can be broadly divided into the following different stages Figure 6 :. It is interesting to note that action potential always moves or transmits in one direction only, i. Action potentials never go in reverse This is attributed to the presence of the voltage-gated sodium ion channels that once closed, remain closed for a period of milliseconds, i.

As a result, the refractory period forces the action potential to move only in one direction. This process is called hyperpolarization. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Neurons are the basic building blocks of the nervous system.

These specialized cells are the information-processing units of the brain responsible for receiving and transmitting information. Each part of the neuron plays a role in communicating information throughout the body. Neurons carry messages throughout the body, including sensory information from external stimuli and signals from the brain to different muscle groups in the body. In order to understand exactly how a neuron works, it is important to look at each individual part of the neuron.

The unique structures of the neuron allow it to receive and transmit signals to other neurons as well as other types of cells. Dendrites are tree-like extensions at the beginning of a neuron that help increase the surface area of the cell body. These tiny protrusions receive information from other neurons and transmit electrical stimulation to the soma. Dendrites are also covered with synapses. Most neurons possess these branch-like extensions that extend outward away from the cell body.

These dendrites then receive chemical signals from other neurons, which are then converted into electrical impulses that are transmitted toward the cell body. Some neurons have very small, short dendrites, while other cells possess very long ones. The neurons of the central nervous systems have very long and complex dendrites that then receive signals from as many as a thousand other neurons.

If the electrical impulses transmitted inward toward the cell body are large enough, they will generate an action potential.

This results in the signal being transmitted down the axon. The soma, or cell body, is where the signals from the dendrites are joined and passed on. The soma and the nucleus do not play an active role in the transmission of the neural signal. Instead, these two structures serve to maintain the cell and keep the neuron functional. Think of the cell body as a small factory that fuels the neuron. The soma produces the proteins that the other parts of the neuron, including the dendrites, axons, and synapses, need to function properly.