The How the Brain works.

HOW THE BRAIN WORKS
PART I

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How does the brain work?



Everybody has a brain and this major organ plays a part in everything you do from the time you are born throughout your entire life. Every action, every word, even the smallest decisions are all a result of the brain performing its intended function. What may be even more amazing about the brain is that not only does every one person have one, but every living animal has one as well. The human brain is much more complex than the brain of any other species and the way it works is truly fascinating.

Although the brain is only the approximate size of a small head of cauliflower, it plays a major role in every function of the human body. It controls the body’s temperature, blood pressure, heart rate, and breathing. It also controls the five different senses of sight, smell, touch, hearing, and tasting. In this way, it allows you to experience the world. Not only does it control the physical aspect of the body such as walking and talking, it also controls the emotional aspects, such as thinking, feeling, and dreaming.

Neuroscience is the complex study of the brain, spinal cord, and peripheral nerves. This complex system is the neurological system and controls information both internally, meaning things that are happening inside the body such as temperature, and externally, meaning things that are taking place outside the body, such as hearing music or touching someone’s hand. The totality of the brain’s role is extremely complex but the most basic functions it performs are motor control, processing visual stimuli, auditory stimuli, different sensations, and memory and emotional functions.

The first thing to understand when discussing the brain is the function of neurons and what they are made of as well as the different types of neurons. The entire brain is made up of neurons, which are nerve cells. One brain has approximately 100 billion of these neurons. It is these neurons that collect and distribute information through electrochemical signals. These cells are built like other cells in the body but the fact that they have electrochemical elements means that they can send messages over long distances.

Neurons are made up of three different parts. The cell body, the axon, and the dendrites, or nerve endings. The cell body holds the nucleus, which contains DNA, the endoplasmic reticulum, which develops proteins, and mitochondria, which creates energy. The axon is a long branch extending from the cell body. These long branches are what carry the electrochemical signal to the cell. Some axons are covered with myelin, which is a layer of fat to help the axon carry the signal more quickly. Dendrites are at one or both ends of the cell and are a way of allowing the different cells to communicate with each other. It is dendrites that are also responsible for analyzing and understanding the environment.

These parts that make up a neuron have four different types. Sensory neurons are responsible for carrying external signals from the outer parts of the body (the periphery) to the central nervous system. Motor neurons do the opposite. They take signals from the central nervous system and take them to the outer parts of the body such as the glands, the muscles, and the skin. Receptors analyze the environment, such as light and sound, and the sensory neurons carry and communicate the information they receive from the receptors. Interneurons connect these different neurons of the brain and the spinal cord and make them one cohesive unit.

These neurons travel along paths and the simplest type of path is the monosynaptic reflex pathway. This is one single connection and the knee-jerk reaction works on this type of pathway. When the doctor bangs on the reflex in the knee with a rubber hammer, the receptors analyze this action and send it to the sensory neurons. The sensory neuron then carries the message to the motor neuron that handles the leg muscles. The nerve impulses in this motor neuron are what cause the leg to respond to the stimuli. This action is really quite simple and is called a hard-wire reflex. There are multiple hard-wired reflexes within the human body, none of which require the brain to work. As the pathways become more complex, the brain must get involved to ensure that functioning will happen properly.

Along with understanding neurons, it’s important to understand the different parts of the brain to understand how it really works. There are four major components that make up the brain. The brain stem is comprised of the medulla, which is the uppermost part of the spinal cord, pons and midbrain. It is the brain stem that leads the reflexes and major functions, such as heart rate, blood pressure, and temperature. It also controls how the limbs move and the visceral functions, such as when food is digested and eliminated.

The cerebellum takes the information from the vestibular system and using this information, interprets movement. With this information, the limbs move accordingly. The hypothalamus and pituitary gland work in commanding the visceral functions and in turn, creating a behavioral reaction. The cerebrum is also called the cortex or the cerebral cortex and is comprised mainly of large fiber tracts, and other complex structures. It is the cerebrum that gathers information from all of the sensory organs and starts the motor functions. It is also responsible for emotions, and keeps memory and thought processes.

The lower brain is a basic system that is comprised of the brain stem, the spinal cord and the diencephalon. Each of these parts of the lower brain contain nuclei that are responsible for particular functions. The medulla contains nuclei that control blood pressure and breathing transmits the information from the cranial nerves to the sensory nerves. The pons holds nuclei that carry movement and position signals from the cerebellum to the cortex. The midbrain has nuclei that connects the different sections of the brain that are responsible for motor functions, eye movements, and controls the auditory senses. The substantia nigra area of the midbrain controls voluntary movements. When it ceases to function, Parkinson’s Disease sets in.

The thalamus delivers the sensory pathways to different parts of the cortex. The thalamus also determines which information will actually be delivered to the consciousness and also plays a part in the trading of motor information with the cerebellum, basal ganglia, and the cortex. The nuclei in the hypothalamus issue hormonal secretions from the pituitary gland. The hypothalamus participates in almost every behavioural reaction, including sexual reproduction, eating, growth, and lactation.

The cerebellum is divided into many different lobes and is placed just above and behind the pons. The spinal cord takes information from the sensory input of the spinal cord, the motor input from the cortex and basal ganglia, and the position information from the vestibular system. The cerebellum receives all of this information and coordinates it to the motor pathways moving away from the brain to control movements. This is why pointing your finger is done in one motion. If the cerebellum were to be compromised in any way, the pointing finger would be accomplished through a very jerky motion.

PART II

the Brain.

 The How the Brain works of the Brain.

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