11. The Human Body Nervous System (Part III) HOW THE NERVOUS SYSTEM WORKS Life and the hum of electric flow The function of the nervous system depends on the neurons (nerve cells) present in the CNS, PNS and ANS. Each nerve has a long arm (axon) that carries on electric signal to the next neuron where it is converted into a chemical signal. The next neuron on receiving the chemical transmitters then conveys the electric signal to the next cell till it reached the target cells. It also has short branching arms (dendrites) nerve signal enter through these short arms. Nerve Impulse Chemicals - ions and electric charge This impulse is brought about by the movement of chemical ions either into or out of a neuron. - These ions have an electric charge this causes the flow of an electric current. - When it reaches a junction between two neurons (synapse). It causes the release of a neurotransmitters to stimulate the ion movement in the next neuron. - This impulse flows at a speed of 320 kilometers per hour. - This is much slower than the speed of electricity. Thus there is a delay in reaction or reaction time for every action. Nerve Facts Speed of Signals Each neuron has only one axon, but this can be anything from 1mm long to over 1m long. Myelinated nerves can transmit nerve signals 200 times faster than unmyelinated ones. The faster nerve signals travel at over 120 meters a second over 250 mph. After passing a signal, a nerve recovers ready to pass another signal in less than one hundredth of a second. There are 100 billion neurons in your brain. Each neuron is linked to hundreds of other. Nerve Synapse. Nerve function Excitement and inhibition If every nerve signal was passed on by the synapse, we would be overwhelmed by nerve signals. So at some synapses the receiving cell reacts to the neurotransmitter by passing on the signal, but others react by blocking it. This is called excitation and inhibition. Some tranquillizing drugs work by increasing inhibition. some stimulants increase excitation. Neurotransmitters Chemistry of Signals There are over 40 neurotransmitting chemicals. Acetylcholine is involved in making muscles contract. Noradrenaline helps control heartbeat and blood flow. Dopamine works in parts of the brain that control movement. Poo response to dopamine may cause Parkinson's disease. Endorphins are 'neuropeptide' transmitters produced and used by the brain to control pain. CNS Nerves Symptom to remember - Loss of sensation – numbness - Tingling } } sensation in hands and feet - Burning } - Weakness of muscle Any question should be address to: firstname.lastname@example.org you will receive further information regarding your question.