A Primer on the Brain and its Functions Dr. Stan Kutcher Katie Radchuck Jillian Soh Sun Life Financial Chair in Adolescent Mental Health Dalhousie University IWK Health Centre
The Human Brain: A Brief Tour The brain is a remarkableorgan, controlling everything from heartrate to digestion to sexualfunctioning, and everything in-between!It produces our thoughts andspeech, and allows us to create worksof art – complex activities which helpdefine our humanity.
The Human Brain: A Brief Tour The human brain weighs approximately1100-1200 grams, or around 2.5 pounds. Your body and organs are made up of cells, and the brain is no different. Neurons are a type of nerve cell which form networks in your brain to relay information. Glial cells tend to provide support to the brain (nourishment, mechanical support, immune response, etc.). DID YOU KNOW? The brain contains an estimated 100 BILLION nerve cells, more cells than there are stars in the Milky Way galaxy. That‟s not all, glial cells are thought to outnumber the nerve cells by as many as 10 to 50 times! Source: Encyclopedia Britannica. Astronomy. 2000
The Human Brain: A Brief Tour Neurons are cells specialized to send and receive information.Generally, a neuron is made up of three basic parts: Dendrites: consisting of many branches, this isthe area where the cell receives information Soma (Cell Body): contains the cellnucleus, which acts like a blueprint for theproduction of proteins and other materials thatkeeps the cell running smoothly Axon: carries information received by thedendrites, sometimes over long distances, to othercells. The axon is sometimes covered in myelinsheaths, another type of cell that speeds up thesignal.
What’s This “Information” Anyway? In the same way humans use sounds to talk to one another and share information, neurons use both electricity and chemicals to talk to each other. These chemical messengers are called neurotransmitters.Just a few examples of neurotransmitters: (Glutamate) (Dopamine) (Serotonin) (Epinephrine/ (Acetylcholine) Adrenaline) Photo credit (CC 2.0): Anselm Hook
What’s This “Information” Anyway? These neurotransmitters play a major role in the brain andheavily influence consciousness, emotions, and behavior. In agroup of people, if someone is whispering their ideas may not beheard. In the same way, too little of a neurotransmitter may causecommunication failures between brain areas, affecting how wethink, feel, and act. Photo credit (CC 2.0): Anselm Hook
What’s This “Information” Anyway? You can see then, how importantcommunication is in the brain. If it isdisrupted, either through chemicalimbalances or problems with theneurons themselves, this maycontribute to brain dysfunction andmental illness. Photo credit (CC 2.0): Anselm Hook
The Human Brain: A Brief Tour Two basic layers of the brain can beseen with the naked eye. There is theouter layer, known as grey matter, aswell as the inner layer, known as whitematter. The gray matter is made up of densely packed neuronalbodies, whose long axons make up the white matter. Rememberhow axons are sometimes covered in myelin sheaths? This myelinis quite fatty, giving the tissue a white-ish color.
Grey matter, containing the cell bodies, is where all the thinking happens. This is your brain‟s processing centre.White matter, containing thoselong axons, are like a superhighway. They transportinformation to different partsof your brain. Photo credit (CC 2.0): facemepls, MSVG
The Central and Peripheral Nervous System The brain, along with your spinalcord, makes up your body‟s CentralNervous System (CNS). From thespinal cord extend nerve cells thatreceive sensory information (suchas the roughness and heat of thebeach) and transmit that to the brain.These outside nerves make up thePeripheral Nervous System (PNS).It‟s a two-way street, The brain canalso send signals through the spinalcord and PNS to control themovement of your limbs and trunk.
The CNS and PNS It takes around11.5 milliseconds to transmit a signal from the tip of your toe to your brain. This may seem pretty fast but in some cases – like when accidentally putting your hand on a hot stovetop – this delay is too long and would cause your hand to burn. Instead of sending a signal all the way to the brain and waiting for a return signal to move your hand away, a network of cells within the spinal cord receive the sensory information, then pass it on to motor neurons, which are cells that control your muscles. Bypassing the brain like this is called a reflex. Your muscle will contract causing you to pull away from the hot stovetop – it is only after a short delay that your brain catches up and realizes your hand hurts!Photo credit (CC 2.0): Ndecam
The CNS and PNS Speaking of signal transmission speeds, some nerve fiberstransmit signals faster than others. Usually it depends onwhether they are myelinated or not (remember that myelinspeeds up transmission!). Think about when you stub your toe. You definitely feel itright away since the touch signals reach your brain almostinstantaneously. However it‟ll take a few seconds before thepain signal will reach your brain, and when it does –YEOWCH!Photo credit (CC 2.0): Ndecam
So now we know what the brain is made of. We know that different parts of the brain communicate with one another using neurotransmitters, and this communication can extend down the spinal cord to the rest of your body. But what does the brain actually DO and HOW does it do it?Photo credit (CC 2.0): perpetualplum
There are 6 functions of the Brain 1. Thinking & Cognition 2. Emotion & Feeling 3. Signaling (being responsive and reacting to the environment) 4. Perception & Sensing 5. Physical Functions 6. Behavior
Thinking and Cognition Thinking & Cognition includes all of our internal mental processes and functions Higher Cognitive FunctionsCommunicating Processing Arithmetic Reading Insight Focusing Planning Attending Judgement MemoryComprehension Contemplation
Thinking & Cognition Overview FACT SHEET Location: Frontal Lobes Neural Pathways: 2-way connection between Your frontal lobes are responsible cortical and limbic areasfor the majority of your conscious Main Neurotransmitters:thought. This area works closely with Dopamine, serotonin, andthe limbic system, a section deep adrenalinewithin the brain responsible formood, emotion, and storage ofmemories.
Thinking & Cognition The Limbic System The limbic system includes severalbrain structures: theamygdala, hippocampus, anteriorthalamic nuclei, and limbic cortex. The hippocampus, responsiblemainly for the storage of long-termmemory, is one of the first placesaffected by Alzheimer’s Disease.
Thinking & Cognition Attention Your frontal lobes also include anarea called the prefrontal cortex,which controls many of your cognitiveabilities, such as attention. However, this area of the brain changes drastically duringadolescence, and is one of the last brain areas to maturecompletely!
Thinking & Cognition Attention Is your attention drifting right now? Don’t worry! Scientistshave measured attention in adolescents, and have discoveredthat performance increases with age. So that means… Yes, attentional capacity might improve as you and your brain matures! Anderson et al. (2001)
Thinking & Cognition Phineas Gage We know that some parts ofthe brain are specialized forcertain tasks. An injury tospecific, limited parts of thebrain can help scientists knowfor sure what that part of thebrain is responsible for. Takefor example the case of poorPhineas Gage.Photo credit: From the collection of Jack and Beverly Wilgus.
Thinking & Cognition In 1848, Phineas was a young man working on clearing out some rock for the construction of a railroad. An explosive was set off accidentally, thrusting a large iron rod under Phineas‟ left cheek bone and out the top of his head. The force of the explosion was so severe that the rod completely left Phineas to land 90 feet away, taking with it most of the left frontal lobe.Photo credit (CC 2.0): Kevin Dooley
Thinking & Cognition His recovery was long and at some points bleak, but he eventually regained his memory and physical strength. He suffered no motor or speech impairments, however a startling change had occurred with his personality and behavior.Photo credit (CC 2.0): Kevin Dooley
Thinking & Cognition He became rash, where before he was mellow. He used to be a good worker, but now his colleagues could not handle his temper. He had trouble forming and executing plans, didn‟t think before he acted, and often made choicesPhoto credit (CC 2.0): Kevin Dooley against his best interests.
Thinking & Cognition Phineas Gage Although the front left portionof his brain was destroyed,Phineas was still able tofunction well. He could walkand talk, since the brain areasresponsible for that wasn‟taffected. However, the frontal lobesare responsible for judgment,planning, and defining yourpersonality. All of thesechanged after his brain injury.Photo credit: From the collection of Jack and Beverly Wilgus.
Thinking & Cognition Speech and Comprehension Your brain also has specificareas dedicated to speech andlanguage comprehension.Broca’s AreaMainly responsible for languageproduction. People who havedamage to this area are still able to understand language, and knowwhat they want to say, they just can‟t „get it out‟.Wernicke’s Area Mainly responsible for language comprehension. People whohave damage to this area can still produce speech but it tends tohave no meaning. This is known as „word salad‟: Example: “Colorless green ideas sleep furiously.”
Emotion is the ability to experience feelings and to express those feelings to others. Happy Sad Anxious Excited Depressed Worried Calm Guilty Fearful Peaceful Ashamed Nervous Content Angry Panicky Serene Irritated Inferior Joyful Annoyed Inadequate Pleased Resentful Lonely Carefree Frustrated Discouraged We can also call our emotions and feelings “MOODS”
Emotion & Feelings Overview FACT SHEET Location: Prefrontal Regulating your emotions is yet cortex, amygdalaanother complex thing your brain has Main Neurotransmitters:to do. Your prefrontal cortex Serotonin and dopamineproduces cognitive emotions(“thinking with you head”) while theamygdala produces instinctiveemotions (“thinking with your heart”). Serotonin and dopamine and twovery important neurotransmittersneeded to regulate your emotionalstate.
Emotion & Feelings Neural Correlates Different parts of your brain areactive depending on what type ofemotion you are feeling. For example, the top brain scanshows which areas of our brain areactive when we feel sadness. Thebottom brain scan shows which areasof our brain are active when we feelhappiness. The brain really does create all ofour emotions.
Emotions & Feelings Serotonin and Mood Since the brain produces much ofwhat we feel, when something goeswrong with the brain ouremotions can get messed up.Clinical depression ischaracterized by a persistent,intense negative mood,which affects a person‟snormal life. Photo credit (CC 2.0): Alejandro Cordon
Emotions & Feelings Serotonin and Mood Research has found thatserotonin is important forcommunication between theprefrontal cortex andamygdala areas ofthe brain. Remember howthose two areas areimportant for regulatingemotions?Photo credit (CC 2.0): Alejandro Cordon
Emotions & Feelings Serotonin and Mood Some people with major depression don‟thave a good connection between theprefrontal cortex and amygdala.By increasing the amount ofserotonin in the brain with drugs,this connection can bestrengthened and help peopleregain a better mood. Photo credit (CC 2.0): Alejandro Cordon
Signaling is the brain’s way of responding to a perceived threat, danger, or stress from the environment.Photo credit (CC 2.0): GE Healthcare
Signaling Overview FACT SHEET Location: Your brain is constantly alert, taking Cortex, thalamus, amygdanote of your surroundings. When it la, hippocampusperceives a danger, such as an Main Neurotransmitters:oncoming car, the brain begins a Adrenalin, serotoninphysiologic cascade with the help ofneurotransmitters like adrenalin andserotonin. Your heart rate andalertness go up, more blood ispumped to your muscles, and yoursenses become sharper. Your brainthen makes a decision whether to runfrom the danger, or stay and fight it.
Signaling Fight or Flight Sensory Perception (Ears, eyes, smell, taste, touch) + Internal SignalsWhen faced with DANGER, your 5 senses perceive it and sends a signal to the BRAIN Your brain initiates a Physiologic Cascade Heart Rate Alertness Perception Now you are ready to Tension FIGHT or FLEE for your safety and protection Photo credit (CC 2.0): Mangpages, Phillipe Put
Signaling Anxiety Sensory Perception (Ears, eyes, smell, taste, touch) + Internal Signals Anxiety happens when the brain believes there is danger, but there isn‟t any Your brain initiates a Physiologic This Cascade produces Heart Rate feelings of Alertness ANXIETY Perception Tension Photo credit (CC 2.0): Mangpages, flequi
Signaling AnxietyNormal anxiety happens to all of us. A situation Which causes can trigger it: feelings of anxiety: First date Preparing for an exam Apprehension Performing at a concert Nervousness Giving a speech Tension Moving from home Edginess Climbing a tall ladder Nausea Etc. Sweating Trembling
Signaling AnxietyNormal anxiety: Is transient, which means that it will go away after a while Does not significantly interfere with a person‟s well-being Does not prevent a person from achieving their goals
Signaling AnxietySome people suffer from pathologic anxiety. A situation, or nothing Which causes can trigger it: intense anxiety: Feels like a heart attack First date Feels like you‟re dying Preparing for an exam Feels like you‟re going Performing at a concert crazy or having a Giving a speech nervous breakdown Moving from home Climbing a tall ladder This happens when there is a dysfunction in the NOTHING! signaling mechanisms.
Signaling AnxietyPathological anxiety: Is persistent, meaning symptoms stay around for a lot longer than they should Is excessive, intense, and inappropriate to the situation – feeling like you are having a heart attack before giving a speech is not how the brain should react Leads to impairment in a person‟s everyday life, where they may avoid people and act withdrawn in an attempt to avoid trigger situations
Perception is the way yourfive senses work with yourbrain to take in yoursurroundings.Photo credit (CC 2.0): Mohamed Malik
Perception & Sensing OverviewWe have five senses that work together to give awareness of our environment:See Hear Smell Taste Touch
Perception & Sensing Vision For us to see, light must enter into ourpupils and hit the retina lining the backof the eye. Cones are cells in the retina that giveus our color vision, while rods are cellsthat give us black and white (night)vision. The optic nerve carries the signalthrough the lateral geniculate nucleus tothe back of the brain, the primaryvisual cortex.
Perception & Sensing VisionThe primary visual cortex transmits thesignal to two different areas of the brain:Temporal lobes Responsible for object recognition, “what” the object is Conscious processingParietal Lobes Responsible for object location, “where” the object is Unconscious processing of the relationship between the object and your body
Perception & Sensing Vision: Blindsight People who sustain damage totheir temporal lobes may developa condition known as blindsight. Since the temporal lobes are responsible for the consciousprocessing of vision, they would not be able to „see‟ normally,and would be considered legally blind. However, theirunconscious, spatial processing has not been damaged, soeven though they may not be able to identify objects in a roomthey can walk around tables and chairs without bumping intothem. They can follow objects with their fingers and may even beable to catch a ball thrown at them. Photo credit (CC 2.0): Jim Simonson
Perception & Sensing Hearing Many tiny hairs in your innerear vibrate to sounds in theenvironment. Those vibrationsare felt by cells in the ear and thesignal is transferred along thebrain to eventually reach theprimary auditory cortex. DID YOU KNOW? As people age, their ability to hear very low and high frequency noises diminishes. An anti-loitering alarm was developed that plays a high-pitched, annoying noise that only teenagers can hear. Talk about discrimination!
Perception & Sensing Smell Smell exists as tinymolecular odorants that travelup your nose to be detectedby cells in the olfactoryepithelium. This signal travelsthrough the olfactory nerve toyour brain, where the signalis processed by the olfactory cortex. Some of the signal makes it tothe limbic system, where long-term, emotional memories are stored.This is why smells can sometimes help you remember strongmemories, maybe of your home or childhood! Photo credit (CC 2.0): DrJimiGlide
Perception & Sensing Taste Taste buds which cover the surfaceof the tongue allows us to distinguishdifferent flavors in our food. There arefive basic tastes: Sweet Sour Salty Bitter Umami (savoury) Photo credit (CC 2.0): Zoe Shuttleworth
Perception & Sensing Taste Information from the taste buds travel up cranial nerves to reachthe brain stem, where the signal is passed onwards to the primarygustatory cortex. DID YOU KNOW? Not everyone perceives food the same way! Some people have a lot more taste buds than average, and are known as „super tasters‟. Your genes determine whether you are a „super taster‟, „taster‟, or even a „non-taster‟. Super tasters tend to be very sensitive to different foods, especially bitter things like broccoli and coffee, and may be picky eaters. Tepper et al. 2009; Photo credit: Zoe Shuttleworth
Perception & Sensing Touch Your body is full of touchreceptor cells near the surface ofthe skin. When activated, theysend a signal up to your brain tolet it know. Some areas of yourbody have many more touchreceptors than others, and thushave a larger representation inthe brain, in a place called thesomatosensory cortex. Photo credit (CC 3.0): btarski
Perception & Sensing Touch A homunculus is arepresentation of what a humanwould look like if made in the sameproportions as the brain areaassigned to it. The hands and facialareas, especially the lips andtongue, are highly sensitive! Dr. Penfield, the famous Canadianneuroscientist (yes, the „burnt toast‟guy!) came up with the homunculusby mapping limb locations to differentareas of the brain.
Signaling is the brain’s way of responding to a perceived threat, danger, or stress from the environment. Your brain takes care of many different physical functions, such as digestion, breathing, c ontrolling your muscles, etc.Photo credit (CC 2.0): GE Healthcare
Physical Functions Voluntary Movement In the same way thatdifferent brain regionsare assigned forsensing different areasof your body, differentbrain regions controldifferent areas of yourbody. Places wherefine motor control isneeded, such as your hands and mouth (for producing speech andeating), take up a larger area in the brain! This place is called themotor cortex.
Physical Functions Voluntary Movement Your prefrontal cortex – which if youremember is where all your thinkinghappens – sends a signal to the motorcortex area assigned to a body part.This signal travels down the spinalcord to alpha motor neurons, whichtell muscles to contract. This wholeprocess allows us to produce thought-directed, voluntary movements. This entire complex arrangement is known as the somatic nervous system.
Physical Functions Involuntary Movement What about involuntary movement?Stuff you can‟t control consciously?Your heart needs to keep beatingand your stomach needs to keepchurning for you to stay alive. If youhad to consciously think about everybreath you took you probably wouldbe too distracted to think about muchelse. This is where the autonomic(from „automatic‟) nervous systemcomes in. Photo credit (CC 2.0): David DeHetre
Physical Functions Involuntary Movement Your autonomic system is basically incharge of all your internal organs, andcontrols what they do unconsciously(although some things, like yourbreathing, can be taken over by theconscious mind). It is divided into twoparts: the Sympathetic NervousSystem, and the ParasympatheticNervous System.
Physical Functions Involuntary MovementSympathetic Nervous System Remember how signaling and anxiety works?Your sympathetic nervous system controls that„fight or flight‟ mechanism (makes the heart pump faster, inhibits digestion, raises blood pressure,etc.). It also maintains equilibrium, or homeostasis.Stuff like making sure your body temperatureis just right, and balancing yourblood sugar levels. Photo credit (CC 2.0): Mark Robinson
Physical Functions Involuntary MovementParasympathetic Nervous System While the sympathetic nervoussystem is most active when you‟restressed, the parasympatheticnervous system works when you areresting, so it‟s known as the „restand digest‟ system. Think of itworking in the opposite direction,instead of speeding up your heartrate it slows it down. It lowers yourblood pressure. Since, at rest, yourbody can expend energy to relax andeat, much more saliva is produced.
Behavior is simply the way we act, usually in response to our environment. It includes everything from running to joking, from reading toPhoto credit (CC 2.0): Jamie Davis working.
Behavior Overview Teens don‟t „get‟ their parents.What‟s with all the rules andrestrictions? And parents don‟t like thethings teens do – they always seem tobe experimenting and takingunnecessary risks. This seeming rift between teens andadults has a lot to do with behavior,and behavior has a lot to do with thebrain. Photo credit (CC 2.0): Ollie Crafoord
One example of a behavioral difference is Behavior motivation. Motivation is your drive to do Motivation stuff – like studying hard to do well on a test, or finishing a marathon, or beating one more level of a video game.Photo credit (CC 2.0): shirokazin
Behavior Motivation Motivation is influenced heavily bythe reward pathway in the brain. Areward doesn‟t have to besomething physical, it can be gettinga good mark or a positive feeling.Drug addiction causes your brain toconstantly seek out that positive„feeling‟, and your brain becomesdependant on it as a reward. Thedanger comes when that feeling canonly be achieved by drugs! Photo credit (CC 2.0): Ollie Crafoord
Behavior Motivation In teens, the reward pathway of thebrain is stronger than in adults. Also,the cognitive parts of the brain thatthink about things logically and weighsthe pros and cons are not asdeveloped in teens. This means teensmay be motivated to try riskierbehaviors and be more impulsive thanadults would be, and are more proneto push beyond their limits andboundaries without weighingconsequences (Smith et al., 2011).
Behavior This isn‟t always a bad thing. Motivation Since the brain matures in this way, young people can be extremely passionate about the things they care about, they work hard to achieve things that are important to them. They open their eyes to the world and have new experiences, and become better people for it. It‟s all about the choices you make.Photo credit (CC 2.0): James Tosh
So now we know thesix basic functions of thebrain, but how does sucha complex organ develop? NewScientist (2009)suggests that there are 5different „ages‟ of the brain: 1. Gestation 2. Childhood 3. Adolescence 4. Adulthood 5. Old AgePhoto credit (CC 2.0): Neil Conway
Gestation Overview Gestation is the stage of developmentwhere you are still in your mom‟s womb.It is this time where your brain undergoesinitial development, and your cellsdifferentiate to create your first neurons(this process is called neurogenesis). Neurogenesis is a hot topic right now,because while people are really good at making new neurons whenthey are fetuses, it gets much harder when they are adults. If we learnhow to create new neurons where we want them, we may be able tohelp people with brain diseases and spinal cord injuries.
Childhood Overview Childhood is the stage where ourbrains probably undergo the biggestchanges. It is this time where welearn language, how to storememories, and how to think.Timeline: 6 years: 2-3 months: 18 months: apply logic and trust, understandscortex develops develop a sense of self personal thought process 6-12 months: 3-4 years: frontal lobe sense that other people develops have minds too
Adolescence Overview Adolescence is the teenageyears. It is around this time that yourbrain areas start to fully mature anddevelop. Your sensory and motorareas are the first to mature, which is why teens can be „sensationseekers‟. Your prefrontal cortex matures last, which helps in decisionmaking, emotional control, and temper. Most teens pass through these years without severe or prolongeddifficulties, but 15% of teens will experience significant mental healthproblems during their adolescent years.
Adolescence Overview Adolescence is the time whereyour brain gets rid of neuralpathways that it doesn‟t need.When you‟re young, you havea high volume of gray matter inyour brain. During adolescence,this gray matter is pruned away.This is thought to make the brain more efficient. What gets removeddepends a lot on usage. It‟s really „use it or lose it!‟ It is important tokeep your brain active and healthy during these years.
Adulthood Overview You‟ve finally made it to your adultyears! People‟s brains peak aroundthe age of 22. This is when they canprocess things the fastest and learnnew things easier. When you hit 27years, your brain will progressivelystart to decline. However, adults are excellent at crystallizedintelligence, or wisdom, which is the ability to use and applyeverything you‟ve learned up till now. You can keep your brain sharp and slow down that decline by beingmentally and physically active.
Old Age Overview In your golden years, you brain is in themost danger of deteriorating. Death of braincells in the hippocampus area can lead tomemory loss. Again, by keeping fit andeating healthy, you can stimulate braincell growth and slow this decline. The elderly are more prone to diseasessuch as Alzheimer’s – plaques and tangles are seen in the brainwrapped around cells responsible for memory and retrieval.Parkinson’s is another disease which mainly affects the elderly, andis caused by the death of cells responsible for movement.
Old Age The chance of experiencing a stroke also increasesOverview when you‟re older. A stroke occurs when the blood supply to the brain has been disturbed. A portion of your brain may lose its functioning (causing paralysis on one side of the body, loss of speech, etc.). Neuroplasticity is the brain‟s ability to rearrange neural pathways and repair itself. It used to be thought that this could only occur in very young people, but recent research has shown that neuroplasticity can still occur in older adults, even in the elderly. There‟s a lot of science being done now to see if we can enhance neuroplasticity to help treat stroke patients and speed up their recovery. Photo credit (CC 2.0): TheArches
Think upon this… We‟re using the Brain to study the Brain And there’s still a lot to learn! Whatyou’ve read here is just the tip of ourcurrent knowledge, and our currentknowledge is just the tip of what is goingon in that spongy mass of tissue. Asscience advances, the brain will come tobetter understand itself. So keep learning!Photo credit (CC 2.0): dierk schaefer
Sun Life Financial ChairIn Adolescent Mental Health For more information visitWWW.TEENMENTALHEALTH.ORG
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