Every human being uses a brain but ironically many people can not successfully name every part of this crucial organ. Nor do they understand how the brain communicates with the rest of their body. The goal of this knol is to give a very rough summary of the various parts of the brain and nervous system.
The Ancient Egyptians believed that the human heart was what held one’s soul, thoughts, and memories. To them, the brain was nothing but a giant glob of mucus that passed snot down to the nose.  For hundreds or even thousands of years, the Egyptians and various other cultures around the globe did not recognize the brain’s true role. Slowly over time, however, people began to realize just how important the three pound organ is. Fast forward to the 20th and 21st century, and there has been a lot of information unearthed about the brain through various sciences. We are getting closer and closer to understanding each and every part of the central nervous system, including the brain. We are now able to control external devices using nothing but technology that deciphers their brain waves.  Scientists are also trying to build an artificial brain that fills in the link between technology and biology.  The human brain is arguably the most complicated thing in the entire universe. With it we are able to use five senses to experience the world around us, remember our past, and create for the future. We can do this thanks to our nervous system. Though there is still a lot we don’t know, the level at which we now comprehend our brain and nervous system is impressive to say the least.
The brain is the main organ belonging to the human nervous system. Information is sent to the brain through the nervous system. Likewise, the brain is able to send information out into the nervous system. This allows us to run, write, see, talk, etc. The nervous system is an intricate system comprised mostly of nerve cells (or neurons). Nerve cells are able to process, relay, and store information and there are over 50 variations of neurons and each is specifically suited to the requirements of that area of the body or brain. The nervous system can be divided into two parts, the central nervous system and the peripheral nervous system.
Central Nervous System
There are three main components that make up the central nervous system (CNS); the brain, spinal cord, and nervous tract.  The central nervous system is encased in the backbone and a system of membranes called the meninges which both act as protection. The meninges is composed of three layers: the dura mater, arachnoid, and pia mater.
The blood brain barrier also acts as protection for the CNS. All of these protective factors are vital for our survival because if they are damaged then it can lead to serious injury or death.
Peripheral Nervous System
The peripheral nervous system (PNS) is comprised of the branches of nerves that extend from the central nervous system to the rest of our body.  These nerve fibers are not protected like the central nervous system which means they are more vulnerable to damage. There are a number of different kinds of nerve cells that are part of the PNS
- Afferent Neurons – Nerves in the peripheral nervous system that carry information toward the central nervous system are called afferent neurons (or nerves).  Afferent neurons communicate with interneurons that connect afferent and efferent neurons together. Feelings, such as pain in the legs or arms, are sent along afferent neurons to the brain where the pain can be registered.
- Efferent Neurons – Also known as motor neurons, efferent neurons (or nerves) carry information from the brain and spine our into the other areas of the body.  Efferent neurons, for example, keep our hearts beating, our lungs breathing, and also allow us to move our bodies.
Interneurons - These are mostly found in the spine and brain. Interneurons connect nerves to other nerves and therefore do not connect to any muscles or other sensory cells. They can connect afferent neurons to efferent neurons. There are about 100 billion interneurons in the human body. 
Glial Cells – Keeping all of the nerves protected and in place are the glial cells. There are around ten times as many glial cells as there are other neurons in the brain.  They surround neurons and ‘glue’ our neural networks together. They also provide neurons with oxygen and nutrients as well as destroy pathogens and help control neurotransmission.
The nervous system is extremely complex and has around 100 billion neurons that communicate with one another. Neurons work through a process called action potential, which involves chemical reactions that determine whether or not electrical impulses are sent through the nerve cells. Action potentials occur when cells are excited beyond their threshold level. Positively charged sodium ions move through the membrane and into the cell, which creates a disturbance in the cell and leads to the discharge of electric impulse.
Neurons react to neurotransmitters in various ways, depending on the neurotransmitter. Neurons have receptor sites for neurotransmitters. Some famous neurotransmitters are serotonin, dopamine, GABA, norepinephrine, and acetylcholine. All of these can be found in varius parts of the body, including the brain or spinal cord. Neurons also have dendrites, axons, and synapses.
Dendrites – These are branch projections stemming out of a neuron that bring information into the cell. Dendrites are very important in carrying out action potentials and integrating synapses.  They reach out to surrounding neurons and detect electrical signals as they are sent through the nerves. Once a dendrite has detected an electrical signal it will send it down into the cell body it is branched out from. There can be many dendrite branches on one neuron.
Axons – Also known as nerve fibers, these are projections which take information away from the cell.  Much like dendrites, they branch away from the cell body and have electrical impulses coursing through them, only this time they are heading away from the cell body. There can be only one axon on each neuron.
- Myelin Sheaths – Axons are insulated with a myelin sheath that ultimately give the brain its white color. Myelin sheaths reduce the chance of short circuits and help speed up signals along the axon. Every millimeter or so the sheath is broken up with protein packed gaps called Nodes of Ranvier. At these gaps, the electrical signal is able to recharge through saltatory conduction and then continue on into myelin. This keeps the signal strong and capable of travelling long distances in the body.
Synapses – The synapse is the point on a neuron where information, in the form of ions, is able to pass. Synapses are very tiny gaps that allow signals to diffuse from one nerve to another. This is a crucial part of the nervous system and brain because it allows for communication among the nerve cells. The synapse contains three different parts: a presynaptic ending, postsynaptic ending, and synaptic cleft. 
- Presynaptic - This contains mitochondria, neurotransmitters, and other cell
- Postsynaptic - Receptor site for neurotransmitters.
- Synaptic Cleft - A space between the presynaptic and postsynaptic where neurotransmitters are diffused and transferred over to the neighboring dendrites.
There are three different kinds of synapses: Axodendritic, Axosomatic, Axoaxonic. Synaptic terminals have vesicles to amplify or modulate electrical signals being passed along the neurons. The chemical signals that the terminals recieve will determine whether or not the cell will decrease the strength of the signal. The electrical impulses recieved in the cell are called action potentials. Action potentials continually repeat as the brain and its neurons do their job.
At the top of the spinal cord, before the brain, there is a junction that connects the two and is called the brain stem (reptilian brain). The brain stem goes from the base of the skull and up toward the center of the brain. This is about ten percent of the entire nervous system.  There are three parts that make up the brain stem.
- Medulla Oblongata – This is the lower part of the brain stem and is mostly in control of involuntary, autonomic functions like breathing, heart rate, blood pressure, and digestion. It also relays nerve signals between the brain and spinal cord.
- Pons – Above the medulla oblongata is the pons. The pons helps the medulla oblongata with some of its functions, but mostly it relays sensory information that helps us with our movement, arousal, and respiration. The pons helps the cerebellum and cortex communicate with each other.
- Midbrain – The midbrain is a curving structure at the top of the brain stem and helps to control and coordinate the body’s sensory and motor functions. The midbrain might also influence aggressive behavior.
The cerebellum sits behind the brain stem at the base of the entire brain. Though the cerebellum is about one tenth of the entire brain’s volume it houses almost half the amount of neurons in the brain! The surface of the cerebellum has many more lines running across it and is therefore more compact than the rest of the brain. The cerebellum has two hemispheres and was one of the first parts of the brain to ever evolve.  It is one of the most important parts of the brain for its ability to integrate sensory perception, motor control, and coordination. It provides us balance and movement, as well as deciphering information from the ears and eyes. Some scientists also believe that the cerebellum helps us process language and music and gives us our ability to pay attention, among other things.  The cerebellum sends information into the brain stem which is then delivered to the rest of the brain.
Between the cerebral hemispheres and above the midbrain there is a region of the brain called the diacenphalon. It contains two very important substructures.
- Thalamus – A dual-lobed structure made of grey matter, the thalamus recieves and deciphers sensory information.  Once it has processed sensory information the thalamus chooses whether or not that information should be relayed to the cortex. The thalamus recieves information from parts of the brain and body that have to do with movement and sensory information. Signals from the cerebellum and cerebral cortex are sent to the thalamus and the thalamus sends signals out into the cortex.
- Hypothalamus - The hypothalamus is in charge of making sure that we stay motivated. It sits beneath the thalamus and is connected to most everything in the brain. The hypothalamus causes us to seek pleasurable activites like having sex, eating and drinking, listening to music, or doing drugs. It regulates hormones that influence how much we eat or drink and how we behave.  The hypothalamus also manages the circadian rhythm, our body temperature, and instinctual reactions such as the fight or flight response. It maintains homeostasis.
The limbic system is comprised of a group of brain structures that are important in the processing of information and the formation of memories and emotions. There are three key areas in the limbic system.
The Basal Ganglia
The basal ganglia is connected to the thalamus and cortex. It is comprised of a group of structures that sit inside of the brain and look like two curving tubes. The basal ganglia recieves most of its information from the cortex and is critical to our ability to move.  When the basal ganglia is damaged it severely impairs someone’s ability to control their body, as can be seen in those with Hutchinson’s Disease or Parkinson’s Disease.
A small but powerful area of the brain, the amygdala is below the hypothalamus and helps us process the world at large. The amygdala is responsible for regulating emotions, affecting our relationships and well-being. It also plays a part in causing arousal. Automatic reactions like fear are in large part caused by the amygdala. 
Next to the amygdala and part of the forebrain is the hippocampus, which is shaped somewhat like a seahorse. The hippocampus is key in creating new memories by forging new neural pathways in our minds.  The hippocampus also helps us with spatial orientation and sleep patterns.
The Cerebral Cortex
The cerebral cortex is the largest, most apparent part of the brain. It is the outer layer of the brain that is the main source of human intelligence. The cerebral cortex is folded so that all the space can fit inside of a single skull. These folds are what give the brain its wrinkled appearance. The surface of the cortex is grey matter and has six different layers with many neural networks. Beneath these layers is white matter and when all of these are put together we are given a huge number of connections that facilitate our ability to think, feel, and reason.
The cerebral cortex has two hemispheres and each hemisphere helps to manage different things and perform various tasks. Both the hemispheres can communicate with one another, and can be divided into four different lobes.
- Frontal Lobe – The frontal lobe is behind and beneath the forehead. It gives humans their higher level thinking skills, such as the ability to plan, pay attention, use language, and move.  It is able to control much of the other areas of the brain. The frontal lobe can also help us to form memories. It gives us the ability to decide how we want to act based on the information we recieve from the rest of our mind and body.
- Parietal Lobe – The parietal lobe is behind the frontal lobes and at the top of the brain. Its job is to integrate sensory input and give us perception. It also gives us ability to do math, use language, draw and more. Since it is linked to visual systems, the parietal lobes help us to do things like button our shirts or throw footballs. 
- Occipital Lobe – The occipital lobes make up the main visual processing center in our brain. It sits at the very back of our brain, slightly below the parietal lobe.  It controls color recognition and vision. It gives us ability to spatially orientate ourselves with the external world. Without the occipital lobe we would not be able to do anything which requires sight.
- Temporal Lobe – The temporal lobe spans across the brain and is below and in between the other three lobes. It gives us our ability to hear by processing auditory information.  This auditory processing center helps us learn and use language. The temporal lobe contains the hippocampus which makes it important in the formation and retrieval of memories.
The corpus callosum connects the brain’s two hemispheres together. It is a huge bundle of nerve fibers that allows information to pass between the two parts of the brain.  The corpus callosum allows for optimal performance from the brain. Some epillepsy patients will have their corpus callosum cut, leaving the two hemispheres of their brain separated from each other. These people are still able to function but are not able to process things the same way a person with an intact corpus callosum can. There are experiments and studies done on “split-brain” patients, as they are called, to try and figure out how the corpus callosum affects consciousness and cognitive abilites.
The nervous system and brain are very complicated and cannot be completely summed up in just one knol. However, this article has outlined all of the major points regarding these systems. Keep in mind that there are always studies going on to try and unravel the secrets of the brain and nervous system. We know a lot but there is still a huge amount of information still undiscovered. The better we understand these parts of our bodies, the better we can understand humans and their societies as a whole.