Are you sleeping restlessly, feeling irritable or moody, forgetting little things, and feeling overwhelmed and isolated? Don't worry. We've all been there. You're probably just stressed out. Stress isn't always a bad thing. It can be handy for a burst of extra energy and focus, like when you're playing a competitive sport, or have to speak in public. But when its continuous, the kind most of us face day in and day out, it actually begins to change your brain. Chronic stress, like being overworked or having arguments at home, can affect brain size, its structure, and how it functions, right down to the level of your genes. Stress begins with something called the hypothalamus pituitary adrenal axis, a series of interactions between endocrine glands in the brain and on the kidney, which controls your body's reaction to stress. When your brain detects a stressful situation, your HPA axis is instantly activated and releases a hormone called cortisol, which primes your body for instant action. But high levels of cortisol over long periods of time wreak havoc on your brain. For example, chronic stress increases the activity level and number of neural connections in the amygdala, your brain's fear center. And as levels of cortisol rise, electric signals in your hippocampus, the part of the brain associated with learning, memories, and stress control, deteriorate. The hippocampus also inhibits the activity of the HPA axis, so when it weakens, so does your ability to control your stress. That's not all, though. Cortisol can literally cause your brain to shrink in size. Too much of it results in the loss of synaptic connections between neurons and the shrinking of your prefrontal cortex, the part of your brain the regulates behaviors like concentration, decision-making, judgement, and social interaction. It also leads to fewer new brain cells being made in the hippocampus. This means chronic stress might make it harder for you to learn and remember things, and also set the stage for more serious mental problems, like depression and eventually Alzheimer's disease. The effects of stress may filter right down to your brain's DNA. An experiment showed that the amount of nurturing a mother rat provides its newborn baby plays a part in determining how that baby responds to stress later in life. The pups of nurturing moms turned out less sensitive to stress because their brains developed more cortisol receptors, which stick to cortisol and dampen the stress response. The pups of negligent moms had the opposite outcome, and so became more sensitive to stress throughout life. These are considered epigenetic changes, meaning that they effect which genes are expressed without directly changing the genetic code. And these changes can be reversed if the moms are swapped. But there's a surprising result. The epigenetic changes caused by one single mother rat were passed down to many generations of rats after her. In other words, the results of these actions were inheritable. It's not all bad news, though. There are many ways to reverse what cortisol does to your stressed brain. The most powerful weapons are exercise and meditation, which involves breathing deeply and being aware and focused on your surroundings. Both of these activities decrease your stress and increase the size of the hippocampus, thereby improving your memory. So don't feel defeated by the pressures of daily life. Get in control of your stress before it takes control of you.
Spavate li nemirno, nervozni ste ili mrzovoljni, zaboravljate sitnice, osjećate se preopterećeno i izolirano? Ne brinite se. Svi smo to prošli. Vjerojatno ste samo pod stresom. Stres nije uvijek loš. Može biti koristan jer naglo podiže energiju i koncentraciju, naprimjer kad se bavite natjecateljskim sportom ili morate govoriti u javnosti. Ali ako ste stalno pod stresom, kao što je to većina nas iz dana u dan, on počinje mijenjati vaš mozak. Kronični stres, naprimjer premorenost ili obiteljske svađe, može utjecati na veličinu mozga, njegovu građu i na njegov način rada, sve do razine gena. Stres započinje takozvanom osovinom hipotalamus - hipofiza - nadbubrežna žlijezda (HPA), nizom interakcija između endokrinih žlijezda u mozgu i žlijezda na bubregu. koje određuju kako će organizam reagirati na stres. Kad mozak uoči neku stresnu situaciju, osovina HPA istog se trena aktivira i počne lučiti hormon kortizol, koji priprema organizam za brzu reakciju. No visoka razina kortizola tijekom dužeg vremenskog razdoblja stvara pravi kaos u mozgu. Naprimjer, kronični stres povećava aktivnost i broj neuronskih veza u amigdali, centru straha u mozgu. I kako razina kortizola raste, tako električni signali u hipokampusu, dijelu mozga koji je povezan s učenjem, sjećanjima i kontrolom stresa, postaju sve slabiji. Hipokampus također koči aktivnost osovine HPA i kad se ona smanji, smanji se i naša sposobnost da kontroliramo stres. No to nije sve. Pod utjecajem kortizola mozak se može doslovno smanjiti. Previše kortizola reducira broj sinapsi među neuronima i smanjuje prefrontalni korteks, dio mozga koji regulira funkcije kao što je koncentracija, donošenje odluka, prosuđivanje i socijalna interakcija. Dovodi i do toga da se u hipokampusu stvara manje novih moždanih stanica. To znači da kronični stres može otežavati učenje i pamćenje te otvoriti put ozbiljnijim psihičkim problemima, kao što su depresija i s vremenom Alzheimerova bolest. Utjecaj stresa može se očitovati čak i na molekulama DNK u mozgu. Jedan je eksperiment pokazao da briga koju ženka štakora posveti novorođenom mladuncu utječe na to kako će taj štakor kasnije u životu reagirati na stres. Mladunci koji su imali brižnu majku bili su manje osjetljivi na stres zato što se u njihovom mozgu razvilo više receptora za kortizol, koji vežu na sebe kortizol i smanjuju utjecaj stresa. Mladunci koji su bili zanemareni doživjeli su suprotan ishod te su postali osjetljiviji na stres, a takvi su ostali cijeli život. Takve promjene nazivaju se epigenetskim promjenama, što znači da utječu na to koji će geni doći do izražaja, ali ne i na sam genetski kod. Te se promjene mogu poništiti ako se majke zamijene. No došlo se do iznenađujuće spoznaje. Epigenetske promjene koje je uzrokovala jedna ženka štakora naslijedili su mnogi naraštaji štakora nakon nje. Drugim riječima, posljedice njenog ponašanja bile su nasljedne. No nije sve tako crno. Mnogo je načina da se ponište posljedice djelovanja kortizola na mozak. Od najveće su koristi tjelovježba i meditacija, odnosno duboko disanje i usredotočenost na ono što nas okružuje. Obje aktivnosti smanjuju stres te povećavaju volumen hipokampusa, i tako poboljšavaju pamćenje. Zato ne dozvolite da vas skrše pritisci svakodnevnog života. Preuzmite kontrolu nad stresom prije nego što on počne kontrolirati vas.