Posted by: Rim | September 1, 2010

The Stress Symphony a Prelude to Neurogensis et Stress

This post was chosen as an Editor's Selection for ResearchBlogging.org

Hi there! Been a long time eh? Not sure what happened there, but I blame Harry. Somehow, somewhere he was involved. So let’s just jump right into it

Stress.

Your reason for not calling your mother, a graduate student’s excuse for overeating, not sleeping, forgetting to hand in an abstract, walking into walls and lying in fetal position whimpering (hey, I am NOT the only one, don’t lie to yourselves people).

Perhaps one of the most used sentiments and recognized ailments. The media has done a fine job with showcasing its multitude of attributes. Over the years (slowly at first) this one word has garnered a “bad boy” reputation and has finally been taken seriously by both the public and health administrators.

Soooo. What is Stress anyway?

We have come to recognize it as the “evil villain” that might very well behind the majority of both physiological and psychological modern disorders.  Looking at it from a layman point of view, the stress response is really quite extraordinary. I mean, think about it for a minute, how does your body respond to stress? And how is a “perceived” individualized stressor being translated into physical and/ or mental ailments? These questions bring us to what is called the stress response. The stress response is your body’s way of coping with the stressor, adjusting the internal environment to cope with the external environment.

The stress response, interestingly, is an adaptive mechanism, its main role is to actually HELP you adapt better to your external environment.  It is made up of a number of different hormonal cascades from both the peripheral and the central nervous system. It is this stress response that leads to alternations in mood, behaviour and physical metabolism. Dependent on the type of stress, these changes are initially short-term but may develop changes that are weaved into the fabric of an individual’s make up as a consequence of chronic stress exposure.

The stress response is widely characterized as mainly two different systems, the Sympathetic Adrenal Medullary Axis (or better known as dear ol’ SAM axis) and the Hypothalamic Pituitary Adrenal Axis (the love of my life, HPA axis).  

The SAM system is primarily triggered during ‘acute’ stressors; this is the famed “fight or flight” response (flight is always the best choice kids).  The “fight/ flight” response is largely due to the increases in circulating epinephrine (aka  adrenaline) that is released by the SAM axis. Epinephrine both aids in the rapid mobilization of the metabolic resources and coordinates the fight/flight response. It basically reroutes your blood flow to increase your heart rate, feed your brain and your muscles. It, in turn, limits the activities of parts of your body that are not useful in say, running around from a lion.

Now, let’s get to know the HPA axis. The HPA axis is involved in the long term effects of both acute and chronic stress. While the SAM axis is activated immediately during the stressor and shuts off after the removal of the stress, the HPA axis is “slower” in activation and continues to be activated long after the stressor has been removed.  Now, I have my nerdfabulous glasses on and I am going to get all science-y on you…The axis is regulated by the paraventricular nucleus (PVN) of the hypothalamus, which secretes corticotropin-releasing hormone (CRH). CRH travels to activate the anterior lobe of the pituitary gland, stimulating the secretion of adrenocorticotropic hormone (ACTH). ACTH then travels down the adrenal glands to stimulate the release of glucocorticoids (cortisol in us humans and corticosterone in rodents). This elegant system is self-regulated by a negative feedback loop. As circulating levels of cortisol increase in the body, it feeds back to the brain to signal the hippocampus, hypothalamus and the pituitary glands to suppress the initial hormone cascade. As you can probably imagine, this negative feedback is essential to protect the individual from excessive amounts of cortisol.  Excessive levels of cortisol have been shown to be harmful, both outside the CNS and within the CNS.
Now, what we are interested in (by we I mean really, me) is the relationship between stress, the hippocampus and neurogensis.

So till next time my dear readers..

Stay nerdfabulous

Rim

NOTE: Ya’ll know feel about being sued (not cool) therefore links are provided below for diagrams. I had tried to make one of my own, but I kept getting distracted..Too many pretty colours. Please do check out the paper that is being referenced here. McEwen is fabulous. Also, if you are interested in reading something that is rated A for AWESOME, check out “Why Zabra’s Don’t Get Ulcers” By Robert Sapolsky. Simply Amazing.  

http://www.nature.com/nri/journal/v5/n3/fig_tab/nri1571_F1.html

http://www.google.ca/imgres?imgurl=http://www.goodpsych.com/storage/Sympathetic_Nervous_System_L.jpg&imgrefurl=http://www.goodpsych.com/stress-psychology/&usg=__Zpfdm1nE4-rsAPm5BJ52fG9dBeA=&h=494&w=393&sz=43&hl=en&start=0&sig2=KccAsPGOJEnA_5sJZhSp5g&zoom=1&tbnid=sX6Mt1YjqYrDYM:&tbnh=136&tbnw=108&ei=0IR-TMTsNoLPnAfElanwAQ&prev=/images%3Fq%3Dsympathetic%2Badrenalmedullary%2Bsystem%26um%3D1%26hl%3Den%26biw%3D1003%26bih%3D596%26tbs%3Disch:1&um=1&itbs=1&iact=rc&dur=312&oei=0IR-TMTsNoLPnAfElanwAQ&esq=1&page=1&ndsp=17&ved=1t:429,r:1,s:0&tx=51&ty=69

ResearchBlogging.orgBruce S. McEwen (2007). Physiology and Neurobiology of Stress and Adaptation: Central Role of the Brain Physiological Reviews, 87, 873-904

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Responses

  1. Amazing, Rim!!

    You impress me everyday! 🙂

  2. […] The Stress Symphony a Prelude to Neurogensis et Stress (via Neurobites) Publicado en General por Alfredo en 4 Septiembre, 2010 Hi there! Been a long time eh? Not sure what happened there, but I blame Harry. Somehow, somewhere he was involved. So let’s just jump right into it Stress. Your reason for not calling your mother, a graduate student’s excuse for overeating, not sleeping, forgetting to hand in an abstract, walking into walls and lying in fetal position whimpering (hey, I am NOT the only one, don’t lie to yourselves people). Perhaps one of the most used sentiments … Read More […]

  3. Thanks for using my third year seminar topic to wow the world….great nerdy work! 🙂


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