True about nerve impulse is:
**Core Concept**
The generation and propagation of nerve impulses in the nervous system involve complex electrochemical processes that ultimately result in the transmission of signals from one neuron to another. The resting potential, threshold potential, and action potential are key concepts in understanding how nerve impulses work.
**Why the Correct Answer is Right**
The correct answer is related to the concept of the action potential, which is a rapid change in the membrane potential of a neuron that allows it to transmit signals. During an action potential, the membrane potential becomes more positive due to the rapid influx of sodium ions, followed by a rapid efflux of potassium ions, resulting in a brief period of depolarization. This process is mediated by voltage-gated sodium channels and potassium channels in the neuronal membrane.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the process of nerve impulse generation. While the resting potential is an important concept, it is not directly related to the transmission of nerve impulses.
**Option B:** This option is incorrect because it is not specific to the generation of nerve impulses. The concept of synaptic transmission is related to the communication between neurons, but it is not the primary mechanism by which nerve impulses are generated.
**Option C:** This option is incorrect because it is not a well-defined concept in the context of nerve impulse generation. The term "electrotonus" is sometimes used to describe the spread of changes in membrane potential along a neuron, but it is not directly related to the action potential.
**Clinical Pearl / High-Yield Fact**
One important clinical correlation to remember is that the myelination of nerve fibers can affect the speed and efficiency of nerve impulse transmission. In conditions such as multiple sclerosis, demyelination can lead to slowed or blocked nerve impulses, resulting in symptoms such as numbness, weakness, and tremors.
**Correct Answer: C. Action potential is a rapid change in the membrane potential of a neuron that allows it to transmit signals.**