Hi, I am Maya and I am going to be your guide to the NERVOUS SYSTEM!!!
The nervous system comprises of 2 major parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS comprises of the brain (the heart of the nervous system) and the spinal cord. The PNS consists of everything else (the bundles of nerves, etc.).
The neuron or nerve cell recieves and sends signals throughout the body. The signal first comes through the dendrites then it passes to the cell body or soma which contains the nucleus of the cell. From there the signal gets passed onto the Axon Hillock from which it passes onto the Axon. On the Axon, there are small insulators called Myelin, and gaps between the Axon called the Myelin Sheath or Nodes of Ranvier. These gaps and insulators help the signals not disintegrating in the middle of the process. From the Axon, the signal passes to the Axon Terminal, from which the neuron sends the signal to the next neuron in a process called 'Synapses'.
Synapse happens when a nerve impulse (the signals that the neurons recieve and send) is in the Axon Terminal of the nerve cell and has to be passed to another cell. The presynaptic neuron (which has to send the nerve impulse) has small sacs known as Vesicles within its Axon Terminal which stores the impulse. There is a very minor and small gap between 2 neurons and that is called the synaptic cleft, from which the signal is passed due to something called action potential. Action potential is how strong an impulse is, if it is a hardly noticed impulse, it will not be able to be passed to the next neuron, so the action potential has to be high. Once the impulse has been passed to the next neuron, it can be delt with in 2 ways. The first way is disintegration, it occurs when enzymes from outer cell bodies take in the impulse and destroy it. The other way is reusing the signal, so that the next time another signal passes through that neuron, the action potential can be increased. There is a process called 'Reuptake' in which the neuron sucks the signal back into the vesicles. The neuron which recieves the signal through its Dendrites is known as the postsynaptic neuron.
The BRAIN has different parts including: The Parietal Lobe, The Occipital Lobe, The Temporal Lobe, The Frontal Lobe, The Cerebellum and The Brain Stem. The Temporal Lobe controls memory, language, recognition, hearing, vision, speech and emotion. The Frontal Lobe controls thinking, planning and problem solving. The Occipital Lobe controls colour and vision. The Parietal Lobe controls perception, classification, spelling and numbers. The Cerebellum controls balance and eye-hand co-ordination. The Brain Stem controls involuntary movements such as: the beating of the heart, breathing, swallowing and body temperature. Together, the BRAIN is the mastermind of the body and takes in every action that the body and muscles to and give out actions that the body and muscles is supposed to do. This is called 'Reflex Action'.
The Nervous System relies on neurons to pass messages throughout its intricate structure. The spinal cord is a means of communication for the body and the BRAIN. For example: You touch a burning hot pan, your immediate reaction would be to pull you hand away. WHY IS THIS HAPPENING??? Your neurons of your hand pass the message throughout the body and to the spinal cord which goes to the BRAIN, which senses the damage that could be done to the body if burned by the pan. And so the BRAIN sends a signal back the same way it came to the neurons in your fingers. Then the neurons send these signals to the muscles in you hand to contract and pull it away from the source of heat.