Explain how messages travel to and from the brain through the nervous system
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Your body is made up by trillions of cells that do various things, and the cells associated with the Nervous System are called neurons. The human Nervous System can be divided into two components: The Central Nervous System, made up of the Brain (which is inside your head) and the Spinal Cord (inside your spinal column which is your backbone); and the Peripheral Nervous System, composed of various nerves, like Cranial nerves (around your head), and peripheral nerves (that go all around your body). Nerves are bundles of neuronal fibres that transmit signals, which are electric impulses. These signals are transmitted from the periphery, for example, the toe, to the Spinal Cord and the Brain by sensory neurons. Signals can also go the other way around, from the Central Nervous System to the various parts of your body, through motor neurons. Show Now, all over your body you have sensors that detect different types of information. Your eyes, for instance, detect light. All over your skin you have sensors that detect pressure. Your ears detect sound. Also, all over your body you have sensors that detect pain. All these different sensors are neurons that specialise in the detection of different types of information. When these specialised sensors detect something, they generate an electric impulse that is transmitted through a neuronal fibre, bundled in a nerve, all the way to Central Nervous System. This happens extremely fast. Then, in the Central Nervous System, you have specialised groups of different neurons to process the information and generate the appropriate responses. Those responses are then transmitted (as electric impulses) down motor neurons to the muscles. An example of this is what happens when you hurt yourself: for instance when you accidentally prick yourself in the hand, your immediate response is to lift your hand away from the thing that pricked you. This happens because your skin creates a pain signal that travels through sensory nerves to the Central Nervous System, first to the Spinal Cord and then the Brain. Once there, the neurons create a response that travels down motor neurons that communicate with muscles, driving your hand to move away. The nervous system is made up of all the nerve cells in your body. It is through the nervous system that we communicate with the outside world and, at the same time, many mechanisms inside our body are controlled. The nervous system takes in information through our senses, processes the information and triggers reactions, such as making your muscles move or causing you to feel pain. For example, if you touch a hot plate, you reflexively pull back your hand and your nerves simultaneously send pain signals to your brain. Metabolic processes are also controlled by the nervous system. There are many billions of nerve cells, also called neurons, in the nervous system. The brain alone has about 100 billion neurons in it. Each neuron has a cell body and various extensions. The shorter extensions (called dendrites) act like antennae: they receive signals from, for example, other neurons and pass them on to the cell body. The signals are then passed on via a long extension (the axon), which can be up to a meter long. The nervous system has two parts, called the central nervous system and the peripheral nervous system due to their location in the body. The central nervous system (CNS) includes the nerves in the brain and spinal cord. It is safely contained within the skull and vertebral canal of the spine. All of the other nerves in the body are part of the peripheral nervous system (PNS). Regardless of where they are in the body, a distinction can also be made between voluntary and involuntary nervous system. The voluntary nervous system (somatic nervous system) controls all the things that we are aware of and can consciously influence, such as moving our arms, legs and other parts of the body. The involuntary nervous system (vegetative or autonomic nervous system) regulates the processes in the body that we cannot consciously influence. It is constantly active, regulating things such as breathing, heart beat and metabolic processes. It does this by receiving signals from the brain and passing them on to the body. It can also send signals in the other direction – from the body to the brain – providing your brain with information about how full your bladder is or how quickly your heart is beating, for example. The involuntary nervous system can react quickly to changes, altering processes in the body to adapt. For instance, if your body gets too hot, your involuntary nervous system increases the blood circulation to your skin and makes you sweat more to cool your body down again. Both the central and peripheral nervous systems have voluntary and involuntary parts. However, whereas these two parts are closely linked in the central nervous system, they are usually separate in other areas of the body. The involuntary nervous system is made up of three parts:
The sympathetic and parasympathetic nervous systems usually do opposite things in the body. The sympathetic nervous system prepares your body for physical and mental activity. It makes your heart beat faster and stronger, opens your airways so you can breathe more easily, and inhibits digestion. The parasympathetic nervous system is responsible for bodily functions when we are at rest: it stimulates digestion, activates various metabolic processes and helps us to relax. But the sympathetic and parasympathetic nervous systems do not always work in opposite directions; they sometimes complement each other too. The enteric nervous system is a separate nervous system for the bowel, which, to a great extent, autonomously regulates bowel motility in digestion. Sources
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