NIMH Brain Basics

8/6/2019 NIMH Brain Basics

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IntroductionWelcome. Brain Basics provides information on how the

brain works, how mental illnesses are disorders of the brain,and ongoing research that helps us better understand andtreat disorders.

Mental disorders are common. You may have a friend,colleague, or relative with a mental disorder, or perhapsyou have experienced one yourself at some point. Suchdisorders include depression, anxiety disorders, bipolardisorder, attention decit hyperactivity disorder (ADHD),and many others.

Some people who develop a mental illness may recover

completely; others may have repeated episodes of illnesswith relatively stable periods in between. Still others live withsymptoms of mental illness every day. They can be moderate,or serious and cause severe disability.

Through research, we know that mental disorders are braindisorders. Evidence shows that they can be related to changesin the anatomy, physiology, and chemistry of the nervoussystem. When the brain cannot effectively coordinate the billionsof cells in the body, the results can affect many aspects of life.

Scientists are continually learning more about how the

brain grows and works in healthy people, and how normalbrain development and function can go awry, leading tomental illnesses.

Brain Basics will introduce you to some of this science,

such as:

How the brain develops

How genes and the environment affect the brain

The basic structure of the brain

How different parts of the brain communicate and workwith each other

How changes in the brain can lead to mental disorders,such as depression.
http://www.nimh.nih.gov/health/topics/depression/index.shtmlhttp://www.nimh.nih.gov/health/topics/anxiety-disorders/index.shtmlhttp://www.nimh.nih.gov/health/topics/bipolar-disorder/index.shtmlhttp://www.nimh.nih.gov/health/topics/bipolar-disorder/index.shtmlhttp://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd/index.shtmlhttp://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd/index.shtmlhttp://www.nimh.nih.gov/health/topics/bipolar-disorder/index.shtmlhttp://www.nimh.nih.gov/health/topics/bipolar-disorder/index.shtmlhttp://www.nimh.nih.gov/health/topics/anxiety-disorders/index.shtmlhttp://www.nimh.nih.gov/health/topics/depression/index.shtml


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The Growing BrainInside the Brain: Neurons & Neural Circuits

Neurons are the basic working unit of the brain and nervoussystem. These cells are highly specialized for the function ofconducting messages.

A neuron has three basic parts:

Cell bodywhich includes the nucleus, cytoplasm, and cellorganelles. The nucleus contains DNA and information thatthe cell needs for growth, metabolism, and repair. Cytoplasmisthesubstancethatllsacell,includingallthechemicalsand parts needed for the cell to work properly including

small structures called cell organelles.

Dendrites branch off from the cell body and act as a neuronspoint of contact for receiving chemical and electrical signalscalled impulses from neighboring neurons.

Axon which sends impulses and extends from cell bodies tomeet and deliver impulses to another nerve cell. Axons canrange in length from a fraction of an inch to several feet.

Each neuron is enclosed by a cell membrane, which separates

the inside contents of the cell from its surrounding environmentand controls what enters and leaves the cell, and responds tosignals from the environment; this all helps the cell maintain itsbalance with the environment.

Synapses are tiny gaps between neurons, wheremessages move from one neuron to another as chemicalor electrical signals.

The brain begins as a small group of cells in the outer layerof a developing embryo. As the cells grow and differentiate,neuronstravelfromacentralbirthplacetotheirnal

destination. Chemical signals from other cells guide neuronsin forming various brain structures. Neighboring neurons makeconnections with each other and with distant nerve cells (viaaxons)toformbraincircuits.Thesecircuitscontrolspecicbody functions such as sleep and speech. The brain continuesmaturing well into a persons early 20s. Knowing how thebrain is wired and how the normal brains structure developsand matures helps scientists understand what goes wrong inmental illnesses.

Scientists have already begun to chart how the brain developsover time in healthy people and are working to compare that

with brain development in people mental disorders. Genes andenvironmental cues both help to direct this growth.


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The Growing BrainThe Changing BrainEffects of Genes and

the Environment

There are many different types of cells in the body. We saythat cells differentiate as the embryo develops, becoming morespecializedforspecicfunctions.Skincellsprotect,musclecells contract, and neurons, the most highly specialized cellsof all, conduct messages.

Every cell in our bodies contains a complete set of DNA. DNA,the recipe of life, contains all the information inherited fromourparentsthathelpstodenewhoweare,suchasourlooksand certain abilities, such as a good singing voice. A gene is

a segment of DNA that contains codes to make proteins andother important body chemicals. DNA also includes informationto control which genes are expressed and when, in all the cellsof the body.

As we grow, we create new cells, each with a copy of ouroriginal set of DNA. Sometimes this copying process isimperfect, leading to a gene mutation that causes the geneto code for a slightly different protein. Some mutations areharmless, some can be helpful, and others give rise todisabilities or diseases.

Genes arent the only determinants of how our bodiesfunction. Throughout our lives, our genes can be affected bythe environment. In medicine, the term environmentincludesnot only our physical surroundings but also factors that canaffect our bodies, such as sleep, diet, or stress. These factorsmay act alone or together in complex ways, to change theway a gene is expressed or the way messages are conductedin the body.

Epigenetics is the study of how environmental factors can

affect how a given gene operates. But unlike gene mutations,epigenetic changes do not change the code for a gene. Rather,theyeffectwhenageneturnsonorofftoproduceaspecicprotein. Scientists believe epigenetics play a major role inmental disorders and the effects of medications. Some, butnot all mutations and epigenetic changes can be passed onto future generations.

Further understanding of genes and epigenetics may oneday lead to genetic testing for people at risk for mentaldisorders. This could greatly help in early detection, moretailored treatments, and possibly prevention of such illnesses.


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The Working BrainNeurotransmitters

Everything we do relies on neurons communicating withone another. Electrical impulses and chemical signals carryingmessages across different parts of the brain and between thebrain and the rest of the nervous system. When a neuron isactivated a small difference in electrical charge occurs. Thisunbalanced charge is called an action potential and is caused bythe concentration of ions (atoms or molecules with unbalancedcharges) across the cell membrane. The action potential travelsvery quickly along the axon, like when a line of dominoes falls.

When the action potential reaches the end of an axon, most

neurons release a chemical message (a neurotransmitter) whichcrosses the synapse and binds to receptors on the receivingneurons dendrites and starts the process over again. At the endof the line, a neurotransmitter may stimulate a different kind ofcell (like a gland cell), or may trigger a new chain of messages.

Neurotransmitters send chemical messages between neurons.Mental illnesses, such as depression, can occur when thisprocess does not work correctly. Communication betweenneurons can also be electrical, such as in areas of the brain thatcontrol movement. When electrical signals are abnormal, theycan cause tremors or symptoms found in Parkinsons disease.

Serotoninhelps controlmany functions, suchas mood, appetite,and sleep. Researchshows that peoplewith depression oftenhave lower than normal levels of serotonin. The types ofmedications most commonly prescribed to treat depressionact by blocking the recycling, or reuptake, of serotonin bythe sending neuron. As a result, more serotonin stays in the

synapse for the receiving neuron to bind onto, leadingto more normal mood functioning.

Dopaminemainlyinvolved in controllingmovement and aiding theowofinformationtothefront of the brain, whichis linked to thought andemotion. It is also linked to reward systems in the brain.Problems in producing dopamine can result in Parkinsons

disease, a disorder that affects a persons ability to move asthey want to, resulting in stiffness, tremors or shaking, andother symptoms. Some studies suggest that having too littledopamine or problems using dopamine in the thinking andfeeling regions of the brain may play a role in disorderslike schizophrenia orattention decit hyperactivitydisorder (ADHD).

Glutamatethe mostcommon neurotransmitter,glutamate has manyroles throughout thebrain and nervous

system. Glutamate is anexcitatory transmitter: when it is released it increases thechancethattheneuronwillre.Thisenhancestheelectricalowamongbraincellsrequiredfornormalfunctionandplays an important role during early brain development.It may also assist in learning and memory. Problems inmaking or using glutamate have been linked to manymental disorders, including autism, obsessive compulsivedisorder (OCD), schizophrenia, and depression.
http://www.nimh.nih.gov/health/topics/depression/index.shtmlhttp://www.nimh.nih.gov/health/topics/schizophrenia/index.shtmlhttp://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd/index.shtmlhttp://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd/index.shtmlhttp://www.nimh.nih.gov/health/topics/autism-spectrum-disorders-pervasive-developmental-disorders/index.shtmlhttp://www.nimh.nih.gov/health/topics/obsessive-compulsive-disorder-ocd/index.shtmlhttp://www.nimh.nih.gov/health/topics/obsessive-compulsive-disorder-ocd/index.shtmlhttp://www.nimh.nih.gov/health/topics/schizophrenia/index.shtmlhttp://www.nimh.nih.gov/health/topics/depression/index.shtmlhttp://www.nimh.nih.gov/health/topics/depression/index.shtmlhttp://www.nimh.nih.gov/health/topics/schizophrenia/index.shtmlhttp://www.nimh.nih.gov/health/topics/obsessive-compulsive-disorder-ocd/index.shtmlhttp://www.nimh.nih.gov/health/topics/obsessive-compulsive-disorder-ocd/index.shtmlhttp://www.nimh.nih.gov/health/topics/autism-spectrum-disorders-pervasive-developmental-disorders/index.shtmlhttp://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd/index.shtmlhttp://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd/index.shtmlhttp://www.nimh.nih.gov/health/topics/schizophrenia/index.shtmlhttp://www.nimh.nih.gov/health/topics/depression/index.shtml


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The Working BrainBrain Regions

Just as many neurons working together form a circuit, manycircuits working together form specialized brain systems. Wehavemanyspecializedbrainsystemsthatworkacrossspecicbrain regions to help us talk, help us make sense of what wesee, and help us to solve a problem. Some of the regions mostcommonly studied in mental health research are listed below.

AmygdalaThe brains fear hub, which activates ournaturalght-or-ightresponsetoconfrontorescapefroma dangerous situation. The amygdala also appears to beinvolved in learning to fear an event, such as touching a

hot stove, and learning not to fear, such as overcoming afear of spiders. Studying how the amygdala helps creatememories of fear and safety may help improve treatmentsforanxiety disorders like phobias orpost-traumaticstress disorder (PTSD).

Prefrontal cortex (PFC)Seat of the brains executivefunctions, such as judgment, decision making, and problemsolving. Different parts of the PFC are involved in usingshort-termorworkingmemoryandinretrievinglong-termmemories. This area of the brain also helps to control theamygdala during stressful events. Some research showsthat people who have PTSD or ADHD have reduced activityin their PFCs.

Anterior cingulate cortex (ACC) the ACC has many

different roles, from controlling blood pressure and heartrate to responding when we sense a mistake, helping us feelmotivated and stay focused on a task, and managing properemotional reactions. Reduced ACC activity or damage tothis brain area has been linked to disorders such as ADHD,schizophrenia, and depression.

HippocampusHelpscreateandlenewmemories.Whenthe hippocampus is damaged, a person cant create newmemories, but can still remember past events and learnedskills, and carry on a conversation, all which rely on differentparts of the brain. The hippocampus may be involved inmood disorders through its control of a major mood circuitcalledthehypothalamic-pituitary-adrenal(HPA)axis.
http://www.nimh.nih.gov/health/topics/anxiety-disorders/index.shtmlhttp://www.nimh.nih.gov/health/publications/anxiety-disorders/specific-phobias.shtmlhttp://www.nimh.nih.gov/health/topics/post-traumatic-stress-disorder-ptsd/index.shtmlhttp://www.nimh.nih.gov/health/topics/post-traumatic-stress-disorder-ptsd/index.shtmlhttp://www.nimh.nih.gov/health/topics/post-traumatic-stress-disorder-ptsd/index.shtmlhttp://www.nimh.nih.gov/health/topics/post-traumatic-stress-disorder-ptsd/index.shtmlhttp://www.nimh.nih.gov/health/publications/anxiety-disorders/specific-phobias.shtmlhttp://www.nimh.nih.gov/health/topics/anxiety-disorders/index.shtml


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Brain Basics in Real Life

Brain Basics in Real Life

How Depression affects the Brain

Meet Sarah

Sarahisamiddle-agedwomanwhoseemedtohaveitall.Shewas happily married and successful in business. Then, after aserious setback at work, she lost interest in her job. She hadproblems getting to sleep and generally felt tired, listless, and hadno appetite most of the time. Weeks later, Sarah realized she washaving trouble coping with the stresses in her life. She began tothink of suicide because she felt like things werent going to getbetter and that there was nothing she could do about it.

Worried at the changes he saw, Sarahs husband took her tothe doctor, who ran some tests. After deciding her symptomswere not caused by a stroke, brain tumor, or similar conditions,Sarahs doctor referred her to a psychiatrist, a type of medicaldoctor who is an expert on mental disorders. Other medicalprofessionals who can diagnose mental disorders arepsychologists or clinical social workers.

The psychiatrist asked Sarah and her husband questions

about Sarahs symptoms and family medical history. Epigeneticchangesfromstressorearly-lifeexperiencesmayhavemadeit harder for Sarah to recover normally from her low mood.Its important to remember that everyone gets the bluesfrom time to time. In contrast, major depression is a seriousdisorder that lasts for weeks. Sarah told the doctor that shehad experienced long periods of deep sadness throughout herteenage years, but had never seen a doctor about it. She hasfaced a few bouts since then, but they have never been as badas her current mood.

The psychiatrist diagnosed Sarah with major depression and

gave her a prescription for a type of antidepressant medicationcalled a selective serotonin reuptake inhibitor (SSRI). SSRIs arethe most common type of medication used to treat depression.

SSRIs boost the amount of serotonin in the brain and helpreduce symptoms of depression. Sarah also has severalfollow-upvisitsscheduledwiththepsychiatristtocheckhowshes responding to the treatment. She also begins regular talktherapy sessions with her psychiatrist. In these sessions, shelearns how to change the way she thinks about and reacts tothings that may trigger her depression. Several months later,Sarah feels much better. She continues taking SSRIs and has

joined an online support group. Sharing her experiences withothers also dealing with depression helps Sarah to better copewith her feelings.


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Brain Research

Modern research tools and techniques are giving scientists

a more detailed understanding of the brain than ever before.

Brain Imaging

Using brain imaging technologies such as magnetic resonanceimaging(MRI),whichusesmagneticeldstotakepicturesofthe brains structure, studies show that brain growth in childrenwith autism appears to peak early. And as they grow thereare differences in brain development in children who developbipolar disorder than children who do not.

Studies comparing such children to those with normal brain

development may help scientists to pinpoint when and wheremental disorders begin and perhaps how to slow or stop themfrom progressing. Functional magnetic resonance imaging(fMRI) is another important research tool in understanding howthe brain functions.

Another type of brain scan called magnetoencephalography,orMEG,cancapturesplit-secondchangesinthebrain.UsingMEG,somescientistshavefoundaspecicpatternofbrainactivity that may help predict who is most likely to respond tofast-actingantidepressantmedications.Currentlyavailableantidepressants usually take four to six weeks to reach their full

effect,whichcanbeadifcultwaitforsomepeoplestrugglingwith depression. However, recent research points to a possiblenew class of antidepressants that can relieve symptoms of theillness in just a few hours. Knowing who might respond to suchmedications could reduce the amount of trial and error andfrustration that many people with depression experience whenstarting treatment.

Gene Studies

Advanced technologies are also making it faster, easier, andmore affordable to study genes. Scientists have found manydifferent genes and groups of genes that appear to increaserisk or provide protection from various mental disorders. Othergenes may change the way a person responds to a certainmedication. This information may someday make it possibleto predict who will develop a mental disorder and to tailor thetreatmentforapersonsspecicconditions.

Such brain research help increase the understanding ofhow the brain grows and works and the effects of genes and

environment on mental health. This knowledge is allowingscientists to make important discoveries that could change theway we think about and treat mental illnesses.

The National Institute of Mental Health supports many studieson mental health and the brain. You can read about some ofthese studies online at www.nimh.nih.gov.
http://www.nimh.nih.gov/health/topics/autism-spectrum-disorders-pervasive-developmental-disorders/index.shtmlhttp://www.nimh.nih.gov/http://www.nimh.nih.gov/http://www.nimh.nih.gov/health/topics/autism-spectrum-disorders-pervasive-developmental-disorders/index.shtml


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Glossary

action potentialTransmission of signal

from the cell body to the synaptic terminalat the end of the cells axon. When theaction potential reaches the end of theaxon the neuron releases chemical(neurotransmitters) or electrical signals.

amygdalaThe brains fear hub,whichhelpsactivatetheght-or-ightresponse and is also involved in emotionsand memory.

anterior cingulate cortexIs involvedin attention, emotional responses, andmany other functions.

axonThelong,ber-likepartofaneuronby which the cell sends information toreceiving neurons.

cell bodyContains the nucleus andcytoplasm of a cell.

cell membraneThe boundaryseparating the inside contents of a cellfrom its surrounding environment.

cytoplasmThesubstancellingacell,containing all the chemicals and partsneeded for the cell to work properly.

dendriteThe point of contact forreceiving impulses on a neuron,branching off from the cell body.

dopamineA neurotransmitter mainlyinvolved in controlling movement,managing the release of varioushormones,andaidingtheowofinformation to the front of the brain.

DNAThe recipe of life, containing

inherited genetic information that helps todenephysicalandsomebehavioraltraits.

epigeneticsThe study of howenvironmental factors like diet, stressandpost-natalcarecanchangegeneexpression (when genes turn on oroff)without altering DNA sequence.

geneA segment of DNA that codesto make proteins and other importantbody chemicals.

glutamateThe most common

neurotransmitter in a persons body, whichincreases neuronal activity, is involved inearly brain development, and may alsoassist in learning and memory.

hippocampusA portion of thebraininvolvedincreatingandlingnew memories.

Hypothalmic-pituitary-adrenal (HPA)axisAbrain-bodycircuitwhichplaysa critical role in the bodys responseto stress.

impulseAn electrical communicationsignal sent between neurons by whichneurons communicate with each other.

magnetic resonance imaging (MRI)An imaging technique that usesmagneticeldstotakepicturesofthe brains structure.

mutationA change in the code for

a gene, which may be harmless oreven helpful, but sometimes give riseto disabilities or diseases.

neural circuitA network of neuronsand their interconnections.

neuronA nerve cell that is thebasic, working unit of the brain andnervous system, which processesand transmits information.

neurotransmitterA chemical producedby neurons that carries messages to

other neurons.

nucleusA structure within a cell thatcontains DNA and information the cellneeds for growing, staying alive, andmaking new neurons.

prefrontal cortexA highly developedarea at the front of the brain that, inhumans, plays a role in executive functionssuch as judgment, decision making andproblem solving, as well as emotionalcontrol and memory.

serotoninA neurotransmitter thatregulates many functions, includingmood, appetite, and sleep.

synapseThe tiny gap between neurons,where nerve impulses are sent from oneneuron to another.


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Links

National Institute of Mental Health (NIMH)

Publications,sciencenews,andfundinginformationrelatedtoFederally-supportedresearchonmentaldisordersNIMH Clinical TrialsClinical trials funded by NIMHMedline PlusConsumer health information provided by the National Library of MedicineNIH Ofce of Science EducationScience education resources developed or supported by the National Institutes of Health (NIH)NIH RePORTER

Public database of active grants funded by the National Institutes of Health
http://www.nimh.nih.gov/http://www.nimh.nih.gov/trialshttp://www.nlm.nih.gov/medlineplushttp://science.education.nih.gov/home2.nsf/feature/index.htmhttp://projectreporter.nih.gov/reporter.cfmhttp://projectreporter.nih.gov/reporter.cfmhttp://science.education.nih.gov/home2.nsf/feature/index.htmhttp://www.nlm.nih.gov/medlineplushttp://www.nimh.nih.gov/trialshttp://www.nimh.nih.gov/


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More Information

National Institute of Mental Health (NIMH)

Science, Writing, Press & Dissemination Branch6001 Executive BoulevardRoom 8184, MSC 9663Bethesda,MD20892-9663

Phone: 301-443-4513 or1-866-616-NIMH(6464)toll-freeTTY: 301-443-8431 or1-866-415-8051toll-freeFAX: 301-443-4279

Email: [email protected]

Web site: http://www.nimh.nih.gov
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