After the nerve impulse has traveled, the positive ions are pumped out of the axon, and the charge returns to negative. The action potential moves from one end of the axon to the other. When the charge reaches a critical level, an electrical nerve impulse known as action potential travels down the axon of the neuron. The sudden arrival of the positive ions inside the neuron causes the charge to change from negative to positive. or by messages from other neurons), the positively charged ions outside the neuron rush inside the neuron at rates as high as 100 million ions per second. When a message arrives and the neuron is stimulated (by external stimuli such as light, heat, and sound etc. The neuron can be compared with a battery with the inside of the neuron representing the negative pole and outside of the neuron representing the positive pole (Koester, 1991). It pumps out the positively charged ions (electrically charged particles) to its outside and only keeps the negatively charged ions. This is called the resting potential of the neuron, which does not come automatically the neuron works to maintain its resting potential. When a neuron is in a resting state, there is a negative electrical charge of about -70 mill volts (a mill volt is one-thousandth of a volt) within the neuron. Ions are found in extracellular fluid and in intracellular fluid as well. On the other hand, positive and negative electrical charges attract each other. Positive electrical charges repel each other, so also the negative electrical charges. The electrical charges carried by ions are of two types, negative and positive. Ions are electrically charged particles when dissolved. Ions are particles formed when a substance is dissolved in fluid. Many chemical substances are broken to pieces when they dissolve in water or any fluid. The fluid contains many dissolved substances. The cell membrane is in between the intracellular fluid and extracellular fluid. The fluid on the outside of the neuron is called the extracellular fluid. The neuron contains fluid, which is known as intracellular fluid. The cell membrane of a neuron is semi-permeable. How does the neuron serve its communicative function? Let us see how nerve impulses or nerve energies are formed. The neurons follow an all-or- none law, i.e., they are either on or off. Like a gun, neurons fire or do not fire there is no in between stage. When a neuron is adequately stimulated, an electrochemical reaction occurs inside. The communicative mechanism is conduction of nerve impulse. Neurons also send nerve impulses when we are asleep. This is the communicative action of a neuron. There are about 10 billions or more neurons firing in our brain, i.e., sending and receiving various nerve impulses. All our behaviours involve the flow of nerve impulses. The inter-neurons are the linking neurons. Sensory (afferent) neurons come from receptors and go to the brain and motor (efferent) neurons go to muscles and glands. The important function of the neuron is to communicate “messages of stimulation” in the form of nerve impulses.
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