Introduction
It is the electric signals that travel down the dendrites in order to form a nerve impulse or an action potential that are known as nerve impulses. When ions flow into and out of the cell, this results in the generation of an action potential. It is specifically associated with the ions sodium and potassium. Through the action of sodium and potassium channels, as well as the sodium-potassium pump, they are transported into and out of the cell.
The presence of active and electronic potentials along the conductors is necessary for the transmission of nerve impulses to occur. The transmission of messages between cells throughout the body is accomplished through the use of synapses. Membrane resistance is relatively high in nerve conductors, but axial resistance is comparatively low in nerve conductors. The electrical synapse is found in the escape reflexes of vertebrates, as well as in the heart and the retina. The majority of the time, they are used when there is a demand for rapid response and speed is critical. When the action potential reaches the stage of such a synapse, the ionic currents travel past the two cell membranes and into the surrounding space.
Mechanism
Nerve Impulse Conduction is the transmission of nerve impulses.
Extruded into a cylinder shape, the axon of nerve fibres have an axoplasm filling inside, and an axolemma covering the outside, this is known as the neuronal structure. The nerve fibres are completely submerged in ECF. There are ionic forms of the solution in the axoplasm and extracellular fluid, which are both present in the body.
In the absence of an axon, the negatively charged chloride ions are neutralised by the positively charged sodium ions present in the environment. Protein molecules that are negatively charged are neutralised in the presence of potassium ions in the axoplasm of the cell. The membrane of a neuron is negatively charged on the inside and positively charged on the outside. The difference in charge would be the difference in resting potential. Depending on the difference in charge, the membrane might be polarised anywhere from seventy to ninety millivolts, depending on the voltage difference. The sodium potassium pump is responsible for maintaining the balance of the resting potential.
The pump is positioned on the axon membrane of the neuron. Potassium ions are now being pumped from the ECF to the axoplasm, while sodium ions are being pumped from the axoplasm to the ECF.
When a stimulus is supplied to the membrane of a nerve fibre, the sodium-potassium pump is forced to shut down its operation. Electrical, chemical, or mechanical stimuli could be used to create the response. As a result of the potassium ions rushing outside the membrane and the sodium ions rushing within the membrane, negative charges are present outside and positive charges are present inside of the membrane.
Nerve Fibres
The nerve fibres are either depolarized or in the action potential, depending on how they are described. The nerve impulse is the name given to the action potential that travels along the membrane. It is approximately + 30 mV. Once the action potential has been completed, the sodium-potassium pump begins to function properly. As a result of this repolarization, the axon membrane will achieve a resting potential and become functional.
The process is now carried out in the opposite direction. It is a reversal of the process that has occurred during an action potential period. A flood of potassium ions will be introduced here, while sodium ions will be introduced outside. During the refractory phase, an impulse would not be conveyed across the nerve fibre to the rest of the body.
In the case of white fibres, saltatory propagation is the process that occurs. In other words, the impulse leaps from node to node and grows in proportion to the rise in the speed of the nerve impulse. When compared to non-medullated nerve fibres, it is approximately twenty times as rapid as the latter. The diameter of the nerve fibre would have an impact on the transmission of nerve impulses. Typical nerve impulses in mammals are one and a half metres per second, whereas the nerve impulses in frogs are thirty metres per second.
Generation and Conduction
STEP -1
When neurons are not transmitting any impulses, they are said to be in a resting-state of activity. In this case, the membrane is impermeable to sodium ions and negatively charged proteins found in the axoplasm, but it is more permeable to potassium ions than sodium ions. Proteins and potassium ions are found in high concentration in the plasma of the axon, whereas sodium ions are found in low concentration in the plasma. The potassium ion concentration in the fluid surrounding the axon is low, but the sodium ion concentration is high in the fluid surrounding the axon. It is as a result of this that a concentration gradient is established
STEP 2
The sodium-potassium pump is responsible for the active transport of ions across the membrane, in which two potassium ions enter the cell and three sodium ions are transported out of the cell at the same time. As a result, the inner surface of the membrane is negatively charged, whereas the outside surface of the membrane is positively charged. The cell has now reached a state of polarisation. The electrical potential difference triggered by the resting plasma membrane is rendered as the resting potential difference.
STEP 3
Upon application of a stimulus, the membrane, at a specific location on the polarised membrane, becomes freely permeable to sodium ions. This results in the passage of sodium ions into the cell. The inner side of the membrane becomes positively charged, whereas the outer side gets negatively charged as a result of this transformation. The membrane is now in a depolarized state, which is undesirable. As a result, a difference in electrical potential is established. A nerve impulse, also known as an action potential, is a variation in electrical potential that occurs at a specific place through the plasma membrane. An neighbouring depolarized membrane region responds to the stimulation provided by the depolarized region close to it. As a result of the sodium ions being expelled from the cell, the previous membrane becomes depolarized again. As a result, there is conduction of impulses
Conclusion
There are three processes involved in the generation and conduction of nerve impulses, and these are polarisation, depolarisation, and repolarisation. The polarised condition of a nerve fibre corresponds to its resting state. An external positive charge exists outside of an axonal membrane while an internal negative charge exists inside, and vice versa when an axonal membrane is in a depolarised state, and the opposite is true. It is obtained when a nerve fibre begins to conduct a nerve impulse that the state of depolarization is reached. The nerve impulse travels through the axon, synapse, and neuromuscular junction before reaching the muscle. The refractory period is the period of time that occurs between depolarisation and repolarisation. An electrical or chemical synaptic connection can be formed between two neurons at their axon ends, allowing the transmission of nerve impulses to occur between them.