Exploring the human brain and how it responds to stress (1/3)

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Wor­ry is like a rock­ing chair. It gives you some­thing to do, but it gets you nowhere.
— Erma Bombeck

The brain is the con­trol cen­ter for all of our thoughts, actions, atti­tudes, and emo­tions. It’s the pilot­house on the river­boat of our lives. It’s Mis­sion Con­trol for all of our flights into space or time. It’s the air traf­fic con­troller that helps us nav­i­gate and reroute our paths based on incom­ing and out­go­ing infor­ma­tion and how we’re feel­ing about it at the time. It’s the John Williams of our per­son­al sym­pho­ny. It’s the Moth­er Ship to our Starfleet; it’s … (Uh, sor­ry, I got car­ried away there, but I think you get my point!)

As I was work­ing on the drafts of my lat­est book book, my own brain was very active, to say the least.

Seri­ous­ly! How was I ever going to write an intro­duc­tion to the brain, the most com­plex organ in the human body, that you, my read­er, would want to read, and that you would understand?

Hun­dreds of thou­sands of text­books and schol­ar­ly arti­cles con­tained deep and dense dis­cus­sions by bril­liant sci­en­tists all over the globe who were try­ing to explain the mys­ter­ies of this incred­i­ble organ, and I had to do it in 70,000 words!

Yet, the best way to com­bat stress is to gain some con­trol over what­ev­er it is that threat­ens you.

My own stress lev­el began to go down dra­mat­i­cal­ly as I real­ized I didn’t have to tell the entire sto­ry. I just need­ed to focus on the parts and sys­tems of the brain that are most involved in the per­cep­tion and pro­cess­ing of stress. As a neu­ropsy­chol­o­gist, I find this part of the sto­ry incred­i­bly inter­est­ing, and hope you will as well. Try­ing to tell the sto­ry of stress with­out putting it in the con­text of the brain is like writ­ing a nov­el with­out giv­ing the char­ac­ters a set­ting in which to act out their dra­mas. With­out con­text, the read­er can’t see where the action is tak­ing place.

Putting the char­ac­ters of this sto­ry —the symp­toms of stress— in the con­text of the brain and cen­tral ner­vous sys­tem makes it pos­si­ble to under­stand their nature and their pur­pose in a way that makes sci­en­tif­ic sense. So … stay with me as I set the stage for an amaz­ing tale about how the brain deals with stress.

A BRIEF TOUR OF THE HUMAN BRAIN

To most peo­ple, the brain is ter­ra incog­ni­ta, a price­less piece of neu­ro­log­i­cal real estate that we’re glad we own but tend to take for grant­ed unless or until some­thing bad hap­pens to it. So let’s take a brief tour, just so you can appre­ci­ate the ines­timable val­ue of this mirac­u­lous organ called the brain.

The aver­age adult human brain weighs about three pounds (a kilo­gram and a half), which is a lit­tle big­ger than a small can­taloupe or a large grape­fruit, depend­ing on the grow­ing sea­son. It starts out sub­stan­tial­ly small­er, of course, but as cer­tain kinds of cells devel­op and change as a child moves into adult­hood, the brain grows in size. As a result of myeli­na­tion (the devel­op­ment of the out­er coat­ing of the long stem of brain cells, or neu­rons), and the pro­lif­er­a­tion of glial cells (the term glial comes from the Greek word for glue), which hold the brain togeth­er and feed it, an adult brain is about three times heav­ier than it was at birth. This is why you occa­sion­al­ly have to buy new hats.

The largest and most rec­og­niz­able part of the brain is the large dome — shaped cere­brum, which is the out­er­most lay­er of brain tis­sue. If you lift off the skull and look down on the brain from above, it looks rather like what you see when you lift half the shell off a wal­nut. How­ev­er, the cere­brum is not stiff like a nut; it has a thick, jel­ly-like con­sis­ten­cy that allows it to lit­er­al­ly bounce around inside the skull, which is why it ’ s so impor­tant to pro­tect the head from encoun­ters with immov­able objects.

A sheet of neur­al tis­sue called the cere­bral cor­tex forms the out­er­most sur­face of the cere­brum. It includes up to six lay­ers, each one dif­fer­ent in terms of the arrange­ment of neu­rons and how well they con­nect and com­mu­ni­cate with oth­er parts of the brain. The cor­tex is dis­tin­guish­able by its many lit­tle ridges (called gyri) and val­leys (sul­ci). In terms of space, the cor­tex is an eco­nom­i­cal­ly arranged region that folds in on itself many times. This results in a very large but main­ly hid­den sur­face area that con­tains more neu­rons than any oth­er part of the brain.

Gray Mat­ters

The term gray mat­ter usu­al­ly evokes an image of the cor­tex, because that’s the part most vis­i­ble in pic­tures of the brain.  In fact, gray mat­ter makes up not only the cere­bral cor­tex but also the cen­tral por­tion of the spinal cord and areas called the cere­bel­lar cor­tex and the hip­pocam­pal cor­tex.  This dense tis­sue is packed full of neu­ronal cells, their den­drites (branch­ing, root — like end­ings), axon ter­mi­nals (the oth­er end), and those sticky glial cells I men­tioned ear­li­er. The cor­tex is the area of the brain where the actu­al pro­cess­ing of infor­ma­tion takes place.  Because of its rel­a­tive size and com­plex­i­ty, it ’ s easy to under­stand why it plays a key role in mem­o­ry, atten­tion, per­cep­tu­al aware­ness, thought, lan­guage, and consciousness.

A Divi­sion of Labor

A cen­tral groove, or fis­sure, runs from the front to back of the cor­tex, divid­ing it into right and left hemi­spheres. In gen­er­al, the left hemi­sphere con­trols func­tions on the right side of the human body and the right hemi­sphere con­trols the left side, but there are sig­nif­i­cant excep­tions and much sophis­ti­cat­ed inter­ac­tion between the two hemi­spheres. This com­mu­ni­ca­tion between the left and right hemi­spheres is facil­i­tat­ed by the cor­pus cal­lo­sum, a wide, flat bun­dle of axons locat­ed in the cen­ter of the brain, beneath the cor­tex. Think of it as the Lin­coln Tun­nel, con­nect­ing Man­hat­tan and Jer­sey City. (I’ll leave it to you to decide which one rep­re­sents which hemisphere.)

The cor­pus cal­lo­sum makes up the largest area of so—called white mat­ter in the brain. White mat­ter is made of bun­dles of axons each encased in a sheath of myelin. These nerve bun­dles lead into and out of the cor­tex and the cere­bel­lum, and branch to the “ old brain, ” the hip­pocam­pus. About 40 per­cent of the human brain is made up of gray mat­ter, and the oth­er 60 per­cent is white mat­ter. It’s the white mat­ter that facil­i­tates com­mu­ni­ca­tion between dif­fer­ent gray mat­ter areas and between the gray mat­ter and the rest of the body. White mat­ter is the Inter­net of our brains. (Al Gore did not invent it.)

Evo­lu­tion, tem­pered by expe­ri­ence, has employed gray mat­ter to build what might be con­sid­ered very well—developed “cog­ni­tive con­dos” that sit above the hip­pocam­pus. This arrange­ment is very impor­tant to a dis­cus­sion of stress. Our old or prim­i­tive brain was primed for sur­vival in our ances­tors’ envi­ron­ment. It’s inter­est­ing to note that the brains of low­er ver­te­brates like fish and amphib­ians have their white mat­ter on the out­side of their brain. We are blessed (and cursed) with lots of gray mat­ter that gives us the abil­i­ty to think things through (espe­cial­ly if we are anx­ious). Frogs and sala­man­ders and their pond—side friends don’t think about dan­ger so much — they just get out of its way! (And while I can’t be sure, I don’t think that they have night­mares about giant human chil­dren armed with nets.)

How do you feel about that? In case you ever get this ques­tion on Jeop­ardy or in a game of Triv­ial Pur­suit, the lim­bic sys­tem is made up of the amyg­dala, the hip­pocam­pus, the cin­gu­late gyrus, for­ni­cate gyrus, hypo­thal­a­mus, mam­mil­lary body, epi­thal­a­mus, nucle­us accum­bens, orbitofrontal cor­tex, parahip­pocam­pal gyrus, and thal­a­mus. These struc­tures work togeth­er to process emo­tions, moti­va­tion, the reg­u­la­tion of mem­o­ries, the inter­face between emo­tion­al states and mem­o­ry of events, the reg­u­la­tion of breath­ing and heart rate, the pro­duc­tion of hor­mones, the “ fight or flight ” response, sex­u­al arousal, cir­ca­di­an rhythms, and some decision—making sys­tems. Pret­ty impres­sive job descrip­tion, eh?

The word lim­bic comes from the Latin word lim­bus, which trans­lates to “belt” or “bor­der,” because this sys­tem forms the inner bor­der of the cor­tex. The lim­bic sys­tem is part of the old brain and devel­oped first, fol­lowed by the new brain: the cor­tex, which is some­times referred to as the neo­cor­tex. Put sim­ply, the lim­bic sys­tem feels and remem­bers; the cor­tex acts and reacts. And they com­mu­ni­cate with each oth­er. Why is this impor­tant? The lim­bic sys­tem fig­ures promi­nent­ly in what’s called the stress response.

These days, both our old and new brains are acti­vat­ed when we’re under stress. The prim­i­tive part, the lim­bic sys­tem (notably the hip­pocam­pus), sniffs out dan­ger well before the new brain (the neo­cor­tex) actu­al­ly process­es it. The old brain responds first, act­ing as a sort of fire alarm sys­tem. It is the neo­cor­tex, and in par­tic­u­lar, the frontal lobe (the pre-frontal cor­tex), that helps us make sense of the alarms.

 

–> Con­tin­ued here: On World Health Day 2020, let’s dis­cuss the stress response and the Gen­er­al Adap­ta­tion Syn­drome (2/3)

 

Dr. Jerome (Jer­ry) Schultz is a Clin­i­cal Neu­ropsy­chol­o­gist, author and speak­er who has pro­vid­ed clin­i­cal ser­vices, con­sul­ta­tion and staff devel­op­ment to hun­dreds of pri­vate and pub­lic schools in the US and abroad dur­ing his 35-year career. This is an adapt­ed excerpt from his lat­est book Nowhere to Hide: Why Kids with ADHD & LD Hate School and What We Can Do About It, which exam­ines the role of stress in learning.

 

Resources to regulate stress:

Four tips to prac­tice good men­tal hygiene dur­ing the coro­n­avirus outbreak

Study finds a key ingre­di­ent in mind­ful­ness train­ing: Accep­tance (not acquiescence)

Pos­i­tive soli­tude, Feel­ing active and Future-mind­ednes: Three Keys to Well-being

New study rein­forces the impor­tance of walk­ing through forests for men­tal and gen­er­al health

Six tips to build resilience and pre­vent brain-dam­ag­ing stress

About SharpBrains

SHARPBRAINS is an independent think-tank and consulting firm providing services at the frontier of applied neuroscience, health, leadership and innovation.
SHARPBRAINS es un think-tank y consultoría independiente proporcionando servicios para la neurociencia aplicada, salud, liderazgo e innovación.

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