Neurons and Neurotransmitters

June 12, 2014

Neurons and Neurotransmitters-The Brains of the Nervous System

Neurotransmitters neuron is a specialized nerve cell that receives, processes, and transmits information to other cells in the body.

The body of a human being is presumed dead when the brain stops functioning. This is because all the functions of the body are controlled by the various segments of the brain. Majorly the nervous system is responsible for the body’s control and communication network. While discharging this function in humans, they do so in three ways and that is to say that they:

Senses changes both in and outside the body-the sensory function.
Interprets and explains the changes-the integrative function.
Responds to the interpretation by making muscles interact and glands secrete hormones or other chemicals into the bloodstream-the motor function.

The nervous system itself has two main parts:

The central nervous system includes the brain and spinal cord which acts as a control center.

The peripheral nervous system includes all other nerve elements. All these elements connect the brain and spinal cord to muscles and glands.

Neurons power their functions

It is important to note that the body of a human being is made up of billions of cells which are ordinarily the basic unit of all living things. This also applies to the single-celled organisms like the bacteria which can perform the basic functions needed to sustain life. These basic functions may include gathering energy from food, reproducing and producing waste materials. Looking at the cells, nearly all of them have three parts which are:

An outer wall also known as membrane
A nucleus that contains essential chemicals
A body of clear fluid called the cytoplasm

Plants, animals and human beings are multicellular meaning creatures with many-cells. Of these cells billions of them are specialize in certain specific functions. For example, some cells would become:

Part of muscle tissue and help us to move.
Other cells make up organs, glands, blood, veins, arteries, and bones.

Neurotransmitters cross the gaps between neurons

For it to effectively serve its three functions, the nervous systems which includes the vast circuits of delicate cells which are very much elaborately interconnected and in fact the brain, spinal cord and nerves all over the body are all made up of one kind of cell. These are the nerves cells and they are also known as neurons and as had been indicated that the brain of human beings has billions of neurons. Now the question you need to ask yourselves is does your spinal cord and all the nerves that fan out from the spinal cord to your glands, organs, and muscles.

The specific functions of the neurons are to allow your brain to learn reason and be able to remember things. Through these activities the body responds and adjusts to changes in the environment. These changes are also called stimuli, they will set off impulses in our sense organs like: the eye, the ear and other organs of taste and smell and sensory receptors located in the skin joins, muscles and other parts of the body. Now having listened to all these it is important to note that every time you feel something including the effects of a drug, know that millions of neurons are firing messages to form one another.

Each neuron may have thousands of branches that connect it to other neurons and these branches are called dendrites or axons. Dendrites carry messages towards the cell body while axons carry messages away from the cell body to another neuron. Axons can extend as long as four feet in humans and in some animals even longer.

In the beginning it was believed that axons and dendrites simply run through the body continuously like a wire but letter on a space was discovered between each axon and dendrite. This space in known as a synaptic gap or synapse and it is the space between the axon of one neuron and the dendrite of the next neuron in a nerve pathway. This gap is negligibly small and it is about one millionth of an inch, it is that small.

Research finding originally believed that electrical impulses jumped these gaps like electricity does across the gap in spark plug but this theory has been ruled out as it is now known that this was never true. It is the chemicals which travel across the gap and not electrical impulses and these chemicals are also neurotransmitters.

A number of chemical building blocks for neurotransmitters such as amino acids come from the kinds of food we eat meaning that our bodies have the ability to manufacture or produce neurotransmitters. Neurons offer a storage package for neurotransmitters known as vesicles which are located very close to the endings of each axon. They (neurons) synthesize some neurotransmitters right in the vesicle while other neurotransmitters are synthesized in the body of the cell and transported to the vesicle. Most of the addictive substances have the ability to change the effects of neurotransmitters on neurons. We will be able to better comprehend how these substances work when we get to know about neurotransmitters and how they act as chemical messengers

Neurotransmitters meet three criteria

Neurotransmitters are molecules-groups of atoms joined by a chemical bond which act as a unit. For them to be called neurotransmitters a molecule must meet the following three criteria:

The molecule must be present and evenly distributed in the brain meaning that the molecules must not just concentrate in one segment but must spread out among different types of neurons and across all segments of the brain that have different functions.
Chemical criteria that is to say the enzymes which help in creating the neurotransmitter must be available in the brain. An enzyme is a catalyst protein which speeds up chemical reactions within the body. It is also important that these enzymes be available in areas where the neurotransmitters are found.
The criterion of mimicry assuming that we inject directly a neurotransmitter into a section of the brain known to contain certain neurons, this injection should be able to imitate the effects of electrically stimulating the same neurons.

Neurons and Neurotransmitters-The Brains of the Nervous System

The brain exposed to stimulants abuse causes addiction

April 10, 2014

The brain exposed to stimulants abuse causes addiction-How it happens

It doesn’t have to go this far addiction can be eradicated if you avoid substance abuse, be it stimulant or otherwise.

Over the last several decades, research on substances of abuse has vastly improved our understanding of human behavior and physiology and the nature of substance abuse and dependence. Basic neurobiological research has enhanced our understanding of the biological and genetic causes of addiction. These discoveries have helped establish addiction as a biological brain disease that is chronic and relapsing in nature. By mapping the neural pathways of pleasure and pain through the human brain, investigators are beginning to understand how abused psychoactive substances, including stimulants, interact with various cells and chemicals in the brain.

For the purpose of this article I will tell you the effects of cocaine and methamphetamine (MA) use, have on the user’s brain and behavior, which in turn leads to the stimulant user’s unique needs. Understanding these effects provides the foundation for stimulant-specific treatment approaches and gives treatment providers greater insight into stimulant users and why certain treatment approaches are more effective.

The brain exposed to stimulants abuse causes addiction-Stimulant Abuse and the Brain

The fundamental problem in dealing with any substance of abuse is to understand “the target” (the user). Therefore, to understand why people take drugs such as cocaine and MA and why some people become addicted, we must first understand what these drugs are doing to their target; that is to say, how stimulants affect the user.

Proper engagement of substance abuse and dependence often involve some discussion of the root causes–the societal and risk factors that lead to these conditions. To date, investigators have identified as many as 72 risk factors for substance use and dependence. Among them are poverty, racism, social dysfunction, weak families, poor education, poor upbringing, and substance-abusing peer groups. These risk factors–as well as other environmental and genetic factors–only influence an individual’s initial decision to use substances of abuse. But after initial use, an individual continues to use a substance because she likes its effects: Use modifies mood, perception, and emotional state. All of these effects are modulated through the brain; basic understanding of neuroscience will help us understand this phenomenon.

For substances of abuse to exert their effects, they must first get to the brain. The four most common routes of administering psychoactive (mood-changing) substances are:

Oral consumption (i.e., swallowing)

A swallowed substance goes to the stomach and on to the intestinal tract. Some substances easily pass through the digestive tract into the bloodstream. Other substances are broken down into their chemical components (i.e., metabolized) in the digestive system, thereby destroying the substance.

Intranasal consumption (i.e., snorting)

Inhalation into the lungs (generally by smoking)

Substances that are inhaled into the lungs adhere to the lining of the nasal passages (the nasal mucosa) through which they enter directly into the bloodstream. Inhaled substances are usually first changed into a gaseous form by igniting (e.g., marijuana) or volatilizing by intense heat (e.g., crack cocaine, the ice form of MA). The lungs offer a large surface area through which the gaseous form may quickly pass directly into the bloodstream.

The brain exposed to stimulants abuse causes addiction-Intravenously via hypodermic syringe

Injected substances obviously enter the bloodstream directly, although at a somewhat regulated rate. In these last three routes of administration, substances enter the bloodstream in none metabolized form.

Once a substance enters the bloodstream, it is transported throughout the body to various organs and organ systems, including the brain. Substances that enter the liver may be metabolized there. Substances that enter the kidney may be excreted. If a female substance user is pregnant, and the substance is able to cross the placenta, then the substance will enter the fetus’ bloodstream. Nursing babies may ingest some substances from breast milk.

To enter the brain, a substance’s molecules must first get through its chemical protection system, which consists mainly of the blood-brain barrier. Tight cell-wall junctions and a layer of cells around the blood vessels keep large or electrically charged molecules from entering the brain. However, small neutral molecules like those of cocaine and MA easily pass through the blood-brain barrier and enter the brain. Once inside the brain, substances of abuse begin to exert their psychoactive effects.

The brain exposed to stimulants abuse causes addiction-The Nervous System

The human nervous system is an elaborately wired communication system, and the brain is the control center. The brain processes sensory information from throughout the body, guides muscle movement and locomotion, regulates a multitude of bodily functions, forms thoughts and feelings, modulates perception and moods, and essentially controls all behavior.

The brain is organized into lobes, which are responsible for specialized functions like cognitive and sensory processes and motor coordination. These lobes are made up of far more complex units called circuits, which involve direct connections among the billions of specialized cells that the various substances of abuse may affect.

The fundamental functional unit of the brain’s circuits is a specialized cell called a neuron, which conveys information both electrically and chemically. The function of the neuron is to transmit information: It receives signals from other neurons, integrates and interprets these signals, and in turn, transmits signals on to other, adjacent neurons.

The brain exposed to stimulants abuse causes addiction-The Limbic Reward System

The brain circuit that is considered essential to the neurological reinforcement system is called the limbic reward system (also called the dopamine reward system or the brain reward system). This neural circuit spans between the ventral tegmental area (VTA) and the nucleus accumbens. Every substance of abuse–alcohol, cocaine, MA, heroin, marijuana and nicotine–has some effect on the limbic reward system. Substances of abuse also affect the nucleus accumbens by increasing the release of the neurotransmitter dopamine, which helps to regulate the feelings of pleasure (euphoria and satisfaction).

Dopamine also plays an important role in the control of movement, cognition, motivation, and reward. High levels of free dopamine in the brain generally enhance mood and increase body movement but too much dopamine may produce nervousness, irritability, aggressiveness, and paranoia that approximates schizophrenia, as well as the hallucinations and bizarre thoughts of schizophrenia. While too little dopamine in certain areas of the brain results in the tremors and paralysis of Parkinson’s disease.

Natural activities such as eating, drinking, and sex activate the nucleus accumbens, inducing considerable communication among this structure’s neurons. This internal communication leads to the release of dopamine. The released dopamine produces immediate, but ephemeral, feelings of pleasure and elation. As dopamine levels subside, so do the feelings of pleasure. But if the activity is repeated, then dopamine is again released, and more feelings of pleasure and euphoria are produced. The release of dopamine and the resulting pleasurable feelings positively reinforce such activities in both humans and animals and motivate the repetition of these activities.

Dopamine is believed to play an important role in the reinforcement of and motivation for repetitive actions and there is an increasing amount of scientific evidence suggesting that the limbic reward system and levels of free dopamine provide the common link in the abuse and addiction of all substances. Dopamine has even been labeled “the master molecule of addiction.”

The brain exposed to stimulants abuse causes addiction-How it happens

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