Transmission of Nerve Impulse — Definition

Definition

Imagine your body as a vast, intricate communication network, much like the internet, but instead of cables and Wi-Fi, it uses specialized cells called neurons. The 'messages' that travel through this network are called nerve impulses, or action potentials.

Think of a nerve impulse as a tiny electrical signal that zips along a neuron. \n\nHow does this signal start and move? Well, a neuron, when it's just resting and not sending a message, has a slightly negative electrical charge inside compared to the outside.

This is called the 'resting membrane potential,' maintained by pumps and channels that carefully control the flow of charged particles (ions like sodium and potassium) across its membrane. It's like a battery that's charged and ready to go.

\n\nWhen a neuron receives a strong enough 'trigger' or stimulus, it's like pressing a button. This trigger causes special gates (ion channels) on the neuron's membrane to open up. Suddenly, positively charged sodium ions rush into the neuron, making the inside temporarily positive.

This rapid change from negative to positive is called 'depolarization,' and it's the start of the nerve impulse.\n\nBut the signal doesn't just stay in one spot. This sudden positive charge in one area triggers the opening of nearby gates, causing the impulse to 'jump' or 'flow' down the length of the neuron, much like a domino effect.

As the impulse passes, other gates open to let potassium ions out, quickly restoring the negative charge inside the neuron. This process is called 'repolarization,' and it ensures the neuron is ready to fire another impulse soon after.

\n\nOnce the electrical signal reaches the end of the first neuron (the presynaptic neuron), it can't just jump directly to the next neuron. There's a tiny gap called a 'synapse.' To cross this gap, the electrical signal is converted into a chemical signal.

The presynaptic neuron releases special chemical messengers called 'neurotransmitters' into the synapse. These neurotransmitters float across the gap and bind to specific 'receivers' (receptors) on the next neuron (the postsynaptic neuron).

If enough neurotransmitters bind, they can trigger a new electrical impulse in the postsynaptic neuron, continuing the message. This entire process, from the electrical signal within a neuron to the chemical signal across the synapse and back to an electrical signal in the next neuron, is what we call the transmission of a nerve impulse.