Nerve Impulse: Conduction and Transmission Mechanism

Nerve impulse constitute the chemical, electrical, and mechanical signals which are the basis for the functioning of the sense organs in the human body.

• The concept of nerve impulse is associated with the voluntary and involuntary actions of the human body.
• Nerve impulses are triggered by stimuli, but only strong ones lead to quick and urgent responses.
• These responses involve complex chemical and mechanical processes within the nerves.
• The nervous system in humans and animals is extremely complicated.
• This mechanism helps us in reacting to stimuli and responding properly.
• Through the nerves and nerve cells, there is a constant exchange of information between various parts of the body.

Key Terms: Nerve, Nervous system, Neurons, Stimulus, Human body, Axolemma, Membrane, Nerve fibre, Mechanism of nerve impulses

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What is Nerve Impulse?

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A nerve impulse is the basic unit and mechanism that facilitates the functioning of the human body.

• All the sense organs and the neural coordination work due to the fluent mechanism of the nerve impulse.
• A nerve impulse is considered as the kind of signals which are generated in the neuron.
• The factor responsible for the generation of nerve impulses is called stimulus.
• This stimulus can be either physical or chemical but it has to be strong enough in order to be recognized by the bodily mechanisms to function efficiently.
• Mainly, nerve impulse comprises electric and chemical signals that stimulate due to the existence of stimulus on the human body.
• Nerve impulses are responsible for the potential actions that are taken over by the human body voluntary or involuntary.

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Conduction of Nerve Impulse

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Nerve impulses generated in neurons are the chemical signals that are a result of the presence of a strong stimulus and are carried forward through the dendrites.

• Chemical signals consist of sodium and potassium ions.
• Such ions form strong signals which in turn facilitate the potential actions based on the requirement and intensity of the stimulus.
• Such chemical signals move in and out of the cells in the human body.
• This movement is facilitated with the help of a sodium-potassium pump.
• The transmission of signals across the dendrites takes place via a synapse, which is a gap filled with a fluid for facilitating the movement.
• This ultimately leads to better and timely generation of potential and required actions.

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Mechanism of Transmission of Nerve Impulse

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The movement and generation of nerve impulses in the neurons involve a mechanical procedure that is responsible for each and every action of the human body. The presence of stimulus sends signals that facilitate actions. Let us understand the actual process behind this.

Physical Structure of Nerve Impulse

The structure of the nerve impulse or the axon is cylindrical.

• This cylindrical shape has a covert layer upon it which is called an axolemma.
• Whereas, axoplasm consists of ionized fluid and is present inside the axon.
• Extracellular fluid is also a form of substance present around the nerve fibre.

Chemical Structure of Nerve Impulse

The membrane of a neuron in which the nerve impulse is present is negative in nature from the interior portion while it is positive from the outside.

• This happens because of the neutralizing effect of negatively charged chloride ions by positively charged sodium ions which are also present outside the axon.
• Similarly, the negatively charged protein molecules are also neutralized in the presence of potassium ions within the axoplasm.

Mechanism of Transmission

After understanding the structure, let us see its mechanism. The structure of nerve impulses and associated chemicals comprises the main place in the transmission mechanism of nerve impulses.

• Now, the process begins with the actions of chemical ions.
• Firstly, potassium ions are pumped from the extracellular fluid with the help of a sodium pump.
• The pump is placed on the membrane of the axon which effectively pumps the ions.
• These potassium ions then move into the axoplasm and similar action takes place for sodium ions which are pumped from the axoplasm to the extracellular fluid.
• After the period when the stimulus is finally applied to a membrane of nerve fiber, the pump of sodium-potassium halts its functions.
• Simultaneously, this leads to the presence of negative charges in the exterior portion and positive charges in the interior.
• This is further followed by the movement of potassium ions and sodium ions outside and inside the membrane of the nerve fiber respectively.
• The potential travelling that now takes place along the membrane is called a nerve impulse which has the potential of approx. +30 mega volts.
• After the action potential is completed, the pump begins its functions and the axon membrane gets back to the resting potential.
• Now the reverse procedure takes place.
• This time potassium ions will move inside and sodium ions will outside.
• Although, now, the refractory period would not witness the transmission of the nerve impulse through the nerve fiber, this completes the entire procedure involving nerve impulse.

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Things to Remember

• Nerve impulses are chemical, electrical, and mechanical signals that serve as the foundation for the operation of the human body's sensory organs.
• In saltatory propagation, nerve impulse jumps from one node to another causing an increase in the speed of the nerve impulse.
• During the saltatory propagation, the speed of nerve impulses remains around twenty times faster than in the normal case.
• The main facilitators of nerve impulses are chemical ions that are of potassium and sodium, which move to make the action potential.
• A nerve impulse is nothing more than the action potential which takes place through dendrites.
• Stimulus are the regulators of nerve impulses and such stimuli must be strong to have a quick and urgent response.