AddictionHow Drugs Work In The Brain Part 1IntroductionThis is the first page of a thirteen page article that will attempt to explain how the brain works, and how and where drugs such as heroin and cocaine work in the brain. Although it is thirteen pages long, it is easy to follow and contains illustrations to help clarify textual descriptions. The Central Nervous SystemThe central nervous system is a network of specialized tissue that controls actions and reactions of the body, enabling it to adjust to its environment. The system functions by receiving signals from all parts of the body, relaying them to the brain and spinal cord, and then sending appropriate return signals to muscles and body organs.
 A Picture Of The Brain And Spinal Cord Virtually all multicellular animals have at least a rudimentary nervous system; in vertebrates the system is most complex. The basic unit of the nervous system is the nerve cell (neuron). Of the billions of neurons in humans, half are in the brain. The neuron consists of a cell body, containing the cell nucleus; dendrites, branch like extensions that receive incoming signals; and the axon, the long cell extension that carries signals long distances. A neuron works by receiving chemical signals-some excitatory, some inhibitory-through its dendrites and sending electrical impulses along its axon. Chemicals (NEUROTRANSMITTERS) released at the terminal fibers of the axon diffuse across a junction called the synapse and bind to dendrites of recipient neurons. Dendrites and axons are called nerve fibers; a nerve is a bundle of nerve fibers. The nervous system has two divisions: the central nervous system and peripheral nervous system. The central nervous system, consisting of the brain and spinal cord, receives impulses from receptors in the skin and organs via sensory (afferent) nerve fibers; it returns impulses via motor (efferent) fibers to terminals in muscles and glands. Peripheral nerves mediate these pathways. The peripheral nervous system comprises cranial nerves, controlling face and neck; spinal nerves, radiating to other parts of the body; and autonomic nerves, which form a subsidiary system regulating the iris of the eye and muscles of heart, glands, lungs, stomach, and other visceral organs. The autonomic nervous system, in turn, comprises the sympathetic nervous system, which functions in response to short-term stress (e.g., increasing heart rate), and the parasympathetic nervous system, which acts in opposition to the sympathetic (e.g., lowering heart rate). © Columbia University Press. Central Nervous System DrugsCentral nervous system drugs (that is, drugs that affect the spinal cord and the brain) are used to treat several neurological (nervous system) and psychiatric problems. For instance, anti epileptic drugs reduce the activity of over excited brain areas and reduce or eliminate seizures. Antipsychotic drugs are used to regulate certain brain chemicals called neurotransmitters, which do not function properly in people with psychoses, major mental disorders often characterized by extreme behaviors and hallucinations, such as in schizophrenia. Antipsychotic drugs can often significantly alleviate hallucinations and other abnormal behaviors. Antidepressant drugs reduce mental depression. Antimanic drugs reduce excessive mood swings in people with manic-depressive illness, which is characterized by behavioral fluctuations between highs of extreme excitement and activity and lows of lethargy and depression. Both types of drugs act by normalize chemical activity in the emotional centers of the brain. Antianxiety drugs, also referred to as tranquilizers, treat anxiety by decreasing the activity in the anxiety centers of the brain. Sedative-hypnotic drugs are used both as sedatives to reduce anxiety and as hypnotics to induce sleep. Sedative-hypnotic drugs act by reducing brain-cell activity. Stimulatory drugs, on the other hand, increase neuronal (nerve cell) activity and reduce fatigue and appetite. Analgesic drugs reduce pain and are generally categorized as narcotics and non-narcotics. Narcotic analgesics, also known as opioids, include opium and the natural opium derivatives codeine and morphine; synthetic derivatives of morphine such as heroin; and synthetic drugs such as meperidine and propoxyphene hydrochloride. Narcotics relieve pain by acting on specific structures, called receptors, located on the nerve cells of the spinal cord or brain. Non-narcotic analgesics such as aspirin, acetaminophen, and ibuprofen reduce pain by inhibiting the formation of nerve impulses at the site of pain. Some of these drugs can also reduce fever and inflammation. General anesthetics, used for surgery or painful procedures, depress brain activity, causing a loss of sensation throughout the body and unconsciousness. Local anesthetics are directly applied to or injected in a specific area of the body, causing a loss of sensation without unconsciousness; they prevent nerves from transmitting impulses signaling pain. © Microsoft Encarta Books Buzzed: |