Orexin Neurons and the Fight or Flight Response

The “fight or flight” response is an involuntary chemical and physical reaction controlled by the autonomic nervous system. More specifically, the Hypothalamus has been proven to play a key role in the triggering of the response, but the exact “mechanisms” have been elusive (Tomoyukast, 2011). New research from the Kagoshima University in Japan has located the origins of the so called “defense response” and how,” the hypothalamus seems to act as a master switch for the fight or flight response” (Tomoyukast, 2011). The answer is orexin (hypocretin) neurons.

The orexin neuron or hypocretin neuron is also referred to as a hypothalamic neuro- peptide. These neurons are found in the dorsomedial hypothalamus, which has been known to be the area that controls the reward process, pain process, and regulates the autonomic response of the cardiovascular, respiratory, and nuroendocrine system (Natsuk, Akihiro, Kanako, Yo, & Kilduff, 2005). These Orexin neurons are however, found all throughout the cerebral cortex, brainstem, and other areas of the body. This has shown scientists that these neurons have widespread connections throughout specific parts of the body but most importantly the cardio-respiratory areas that are controlled by the fight or flight response (Tomoyukast, 2011). A study preformed on mice was devised to show the relationship to the fight or flight response and the orexin neurons. Mice were exposed to extreme cold to induce hyperthermia. The cold acts as a stressor which turns on the fight or flight response mechanisms. The orexin neurons then send signals to one another that in turn regulate the cardio vascular and reparatory stress responses, and at the same time also work to control body temperature to prepare the body for “fight or flight behavior” (Tomoyukast, 2011).

Orexin neurons are intricately connected within a very precise network of autonomic reflex pathways and conscious and unconscious receptors and regulators. These neurons connect the biological clock as well as the sleep/ wakefulness autonomic responses to the dorsal hypothalamus; which can then in turn send appropriate signals down the orexin neurons to trigger the fight of flight mechanisms (Natsuk, Akihiro, Kanako, Yo, & Kilduff, 2005). This network sends all the appropriate information simultaneously through the body by way of the orexin neurons. This seemingly instantaneous system is the mechanism in which the fight or flight response is accomplished. Orexin neurons are a very specific type of neuron with a very specific function; unfortunately the neurotransmitters used by these neurons are still unknown but some have been proposed such as; 5HT-1A and 5HT-3 (Tomoyukast, 2011). These two neurotransmitters are proposed to be used during the defense response within the cardiovascular reflex pathways (Natsuk, Akihiro, Kanako, Yo, & Kilduff, 2005).

From the dorsal hyper thalamus to the cerebral cortex and brainstem to the cardiovascular, respiratory, and endocrine systems (the list continues) one can find an orexin neuron. Without the specificity of this neuron the basic stress response of the fight of flight mechanism may not have been possible, and this would have had an unexplainable effect on a species survivability in the wild.

REFERENCES

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Tomoyukast, K. (2011). A key role of orexin (hypocretin) neurons in the fight-or-flight response. Physiology News Magazine, 1(83), Retrieved from http://www.physoc.org/uploadedfiles/documentlibrary/824.pdf

Natsuk, T., Akihiro, Y., Kanako, I., Yo, M., & Kilduff, T.S. (2005). Cholecystokinin activates orexin/hypocretin neurons through the cholecystokinin a receptor. The Journal of Neuroscience, 25(32), 7459-7469.

Drink water and lose weight!

Recent research is saying that an effective, inexpensive way to lose weight is to drink water upon the first signs of hunger and wait 15 minutes to see if you are then satisfied. This is effective because many people confuse thirst signals as hunger signals, prompting them to overeat. This confusion is due to an inability to read the body’s signals as well as the fact that, according to Nutritional Therapist Pat Reeves, “the sensations of thirst and hunger are often generated simultaneously. …we assume both indicators mean that food is needed by the body: So we eat food when the body should, ideally, only be receiving water” (p . 1). Hunger and thirst are both controlled by the hypothalamus, which can trigger them at the same time, resulting in confusion.

Thirst, which is a perception that provides the urge for fluid consumption, is regulated by neural signals under both hormonal and osmotic influence. Vomiting, diarrhea, excess salt and sugar consumption, perspiration, and simply being alive cause fluid loss. Breathing, sweating and urinating are all daily activities that cause a depletion of body fluid.

When there is a decrease in fluid volume, the urge to drink is formed in order to maintain homeostasis by increasing fluid consumption. According to Johnson and McKinley (2004), “specific sensors in the brain, termed osmoreceptors, respond to cellular dehydration to initiate neural mechanisms that result in the generation of thirst” (p. 1) Other responses such as sympathetic activation and reduced water excretion attempt to minimize any further changes in fluid volume by reabsorbing and retaining water and sodium. However, body fluids will not be restored until the fluid losses are replenished. Thirst is the perception that will cause this to occur.

Several hormones, such as peptides and steroids, also play a part in thirst regulation. For example, relaxin, which is a peptide, stimulates fluid consumption by stimulating vasopressin secretion. Vasopressin is a hormone that is secreted when there is a reduced volume of extracellular fluid. It is an anti-diuretic hormone that causes re-absorption of water and reduced fluid excretion.

When feeling thirsty, the optimal solution is to drink water, not other liquids. Reeves stated that, “The reason why people often become addicted to coffee and diet fizzy drinks is because the water does not stay in the body long enough to satisfy thirst and also has a direct action on the brain, giving a sensation of pleasure” (p. 2). Other liquids such as juice or soda do not fully satisfy thirst, causing people to then go to food for satisfaction when water is what is needed.

Also, hunger signals are sent when blood sugar is low, but water can be a source of energy similar to food. Energy is released when water molecules are split into hydrogen and oxygen during hydrolysis, which releases energy and ATP, the most essential compound in cellular metabolism.

In conclusion, knowing how to interpret your body’s signals and drinking water consistently throughout the day can aid weight loss by maintaining hydration and preventing over-eating. It is widely known that water is essential in every aspect of the body and that dehydration is very dangerous. However, over-eating is dangerous as well, since it can lead to excess weight gain and all the problems associated with being overweight. Ensuring proper fluid volume through constant water intake is the only way to prevent these issues.

References:

Reeves, P. Overweight- the water connection. Retrieved from http://www.foodalive.org/articles/overweight.htm.

Johnson, A. K. & McKinley, M. J. (2004). The physiological regulation of thirst and fluid intake. News in Physioloical Sciences, 19. Retrieved from http://physiologyonline.physiology.org/content/19/1/1.full.pdf+html.

Image:

http://madamenoire.com/wp-content/uploads/2010/06/water.jpg

Coffee and the Fight Against Type 2 Diabetes

Great news for all you coffee lovers out there! According to a recent study conducted at the University of California in Los Angeles, habitual caffeinated coffee consumption of at least 4 cups a day may decrease your risk for developing type 2 diabetes. This news could not have come at a better time as diabetes, especially type 2 diabetes, is sharply on the rise. The American Diabetes Association estimates that, “nearly 24 million children and adults in the U.S. -- nearly 8 percent of the population -- have diabetes. Type 2 diabetes is the most common form of the disease and accounts for about 90 to 95 percent of these cases”. Many of the risk factors for developing type 2 diabetes are modifiable, especially diet. Can it really be as simple as adding some “java” to your morning routine? Researchers at UCLA say it’s a possibility.

It has long been thought that there is an inverse association between drinking coffee and type 2 diabetes risk but the actual reason as to why this is true has baffled scientists for years. Researchers at UCLA believe they may have finally discovered the mechanism behind this relationship. It is a protein called sex hormone-binding globulin (SHBG). Its job is to regulate the body’s sex hormones which have been associtaed with the development of type 2 diabetes. It appears that the higher the plasma level of SHBG the lower the risk for an individual to develop type 2 diabetes. Coffee it turns out raises the plasma level of SHBG in the blood. The more coffee consumed the higher the plasma level of SHBG. SHBG is also metabolized in the liver and caffeinated coffee alters the activity of liver enzymes. This suggests that SHBG metabolism may be affected by components found in coffee which leads to the increase in plasma SHBG.

The researchers at UCLA drew their test subjects from a Women’s Health Study that was “originally designed to evaluate the benefits and risks of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer”. The study spanned 10 years and followed roughly 40,000 women. Out of those subjects 359 postmenopausal women with newly diagnosed type 2 diabetes were matched to 359 control subjects. With the results of this study researchers were able to make a positive association between caffeinated coffee intake and plasma SHBG levels. In fact their results showed that habitual coffee drinkers “were 56 percent less likely to develop diabetes than were non drinkers”.

A previous genetic study conducted by Dr. Simin Liu further supports the proposed association. They found two mutations in the gene coding of SHBG that demonstrate an effect on the risk of developing type 2 diabetes. Carriers of the rs6259 minor allele had a ten percent higher concentration of plasma SHBG which decreased their risk. However, carriers of an rs6257 minor allele had a ten percent lower concentration that put them at greater risk for developing the disease. Liu’s work shows that there is a genetic component as to the propensity for an individual to develop diabetes based on the amount of SHBG in their blood.

Coffee has long been recognized for having a protective effect against type 2 diabetes but the reasoning behind it has been unclear. A high concentration of plasma SHBG has also been shown to have this effect. Upon further investigation it is now proposed that coffee increases plasma levels of SHBG and that this may be the mechanism behind its decreased risk for developing type 2 diabetes. So next time you're debating whether or not to have that extra cup (or four), go for it!



Sources

1. Ding EL, Song Y, Manson JE, et al. Sex hormone-binding globulin and risk of type 2 diabetes in women and men. N Engl J Med 2009;361:1152-1163

2. Jayagopal V, Kilpatrick ES,Jennings PE, Holding S, Hepburn DA, Atikin SL. The biological variation of sex hormone-binding globulin in type 2 diabetes:implications for sex hormone-binding globulin as a surrogate marker of insulin resistance. Diabetes Care. 2004;27:278

3. Wheeler, Mark. University of California - Los Angeles. "Why coffee protects against diabetes." ScienceDaily, 15 Jan. 2011. Web. 17 Jun. 2011 from http://www.sciencedaily.com­ /releases/2011/01/110113102200.htm

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http://rlv.zcache.com/cure_diabetes_ribbon_mug-p1686027042946209762om5b_400.jpg

Meal Frequency and You!

How many of us have been told to eat frequently to keep our metabolism burning? That you need to eat more times a day with smaller meals to keep your body at peak performance while losing more fat.

Yes, I’ve heard it plenty and I finally went outside the box and found there is more to controlling your diet than just size and frequency. I came across a style of eating called intermittent fasting which is built around a 16 hour fasting period followed by an eight hour eating period in which you eat the normal maintenance calories you would in a typical day. While commonplace in gyms and magazines, the evidence against meal frequency was limited but a study, Bellisle F et. al. Meal frequency and energy balance. Br J Nutr. (1997), went through all pertinent studies related to meal frequency and weight loss and determined there was little correlation in the studies showing more or less fat loss in any groups, with most studies coming up neutral.

A more recent study done in 2009 at the University of Ottawa placed 16 obese individuals, split by eight men and eight women, all on a diet restriction the same between each. One group would eat 3 meals and 3 snacks in a day while the other would only eat 3 meals a day. The study last 8 weeks and in all groups the findings of lean body mass, body fat and BMI were all within similar ranges showing no metabolic differences with meal frequency.

The author reviewing the 1997 study points out some common misconceptions leading to the higher meal frequency belief. A primary one being the misunderstanding of the thermal effect of food, which people took as the more you eat, the more calories you burn. In theory, this is a practical explanation. What generally is not accounted for is that eating in this style requires you to eat more food. Though technically you will be burning more calories, it would still be at a same rate of 10% of intake of calories. So, if you take in an additional amount of calories, of course you will burn more, but you will have consumed a higher total number of calories to only have a small percentage burned off.

For people looking to follow a high frequency meal plan, it can be a tedious process to prepare so many meals just for one day and to keep up with it day after day. The studies show there is little value to when you eat and the amount your body can burn off metabolically. There are many alternate styles of eating out there and our bodies react differently. I have tried various diets to see how my body changes with them and thus far for my own case, a version of intermittent fasting has been working extremely well. Had I not opened my mind and tried something everything I had learned up to that point said not to do, I wouldn’t have found an effective plan that works very well for me and my lifestyle. Don’t let myths stop you from trying new things which could keep something you’re looking for out of reach.

Sources:
http://www.bodyrecomposition.com/research-review/meal-frequency-and-energy-balance-research-review.html#more-1389
http://www.ncbi.nlm.nih.gov/pubmed/19943985
http://www.nytimes.com/2010/03/23/health/23really.html?src=sch&pagewanted=all
http://www.news.harvard.edu/gazette/wp-content/uploads/2008/05/27-foodclock.jpg

Cell Phones and Insomnia

As most of us know, college is a time where you tend to lose more sleep than you gain. Late night study sessions, “all nighters” to write papers, and early morning classes all contribute to this lack of sleep. However, recent studies have shown that an object that many of us use, quite frequently, every day can also lead to the insomnia we may experience.

According to a report in the British newspaper, The Independent, sweeping new research has linked the radiation emitted by mobile phones to such symptoms as confusion, sleeping problems and chronic headaches. Scientists studying 35 men and 35 women found that using the phones before bed delays and shortens the deep stages of sleep—the part of sleep that allows the brain and body to repair and rejuvenate from the day's wear and tear, The Independent reported.

In children and teens, who tend to use their phones late at night, the study found that the sleep disturbances caused by the radiation can trigger depression, mood swings, ADHD-like symptoms and personality changes, and impair concentration and academic performance.

“The study indicates that during laboratory exposure to 884 MHz wireless signals components of sleep believed to be important for recovery from daily wear and tear are adversely affected," scientists concluded in the study.

In yet another study conducted by Wayne State University School of Medicine in Detroit, similar results were reported. According to Wayne's Bengt Arnetz, M.D, “The study strongly suggests that mobile phone use is associated with specific changes in the areas of the brain responsible for activating and coordinating the stress system.”

According to study conducted by Sage Associates in Santa Barbara, CA , Mann et al (1996) reported that RFR similar to digital mobile telephones reduced REM sleep in humans and altered the EEG (brain wave) signal in humans during REM sleep. REM sleep is essential for information processing in the brain, particularly with respect to learning and memory functions. It is thought to be needed for selecting, sorting and consolidating new experiences and information received during the waking state, and linking them together with old experiences.

The stage in REM sleep in which reparative hormones are released lies in stage three and four when we enter deep sleep. Cell phone radiation is thought to interrupt brain waves in the first stage of REM sleep, therefore making deep sleep harder to attain.

These studies have shown that sleeping or being near a cell phone while going to sleep exposes you to the radiation that can interrupt your brain wave activity as you are trying to sleep. The benefits that are being lost due to insomnia possibly caused by cell phone radiation are immense. The parts of sleep that are being interrupted are vital to our every day functionality. Although it may not be possible to avoid long night study session, by cutting back on cell phone use before going to bed, you may gain a better night's sleep and improve your academic performance.

Sources:
http://www.scienceagogo.com/news/20080022163453data_trunc_sys.shtml

http://www.thementalfitnesscenter.com/blog/fascinating-information-about-cell-phones-and-sleeplessness/

http://www.foxnews.com/story/0,2933,324140,00.html

http://www.ninds.nih.gov/disorders/brain_basics/understanding_sleep.htm

http://www.salzburg.gv.at/Proceedings_(15)_Sage_2.pdf.

Image:
http://www.google.com/imgres?imgurl=http://www.w-cellphones.com/wp-content/uploads/2010/08/cell-phone-electromagnetic-radiation.jpg&imgrefurl=http://metromanila.inetgiant.com.ph/Manila/AdDetails/CELLPHONE-RADIATION-http-radiationdanger-blogspot-com/2487074&usg=__JvOtcsEmqkFOXLlbQvcmnZKkavE=&h=333&w=444&sz=25&hl=en&start=0&zoom=1&tbnid=9r4PPhQzkzh_iM:&tbnh=108&tbnw=144&ei=Ny3yTdH-Oqbk0QHhm4W4DQ&prev=/search%3Fq%3Dcell%2Bphone%2Bradiation%2Band%2Binsomnia%26um%3D1%26hl%3Den%26safe%3Doff%26client%3Dfirefox-a%26sa%3DN%26rls%3Dorg.mozilla:en-US:official%26biw%3D1280%26bih%3D506%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=425&vpy=72&dur=125&hovh=194&hovw=259&tx=136&ty=98&page=1&ndsp=22&ved=1t:429,r:2,s:0&biw=1280&bih=506