Brain Energy And Oxygen Metabolism: Emerging Role In Normal Function And Disease
- 1Queensland Brain Institute, The University of Queensland, St. Lucia, QLD, Australia
- 2Development and Stem Cells Program, Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
- 3Centre for Mental Health Research, The Australian National University, Canberra, ACT, Australia
Appraising The Brain’s Energy Budget
In the average adult human, the brain represents about 2% of the body weight. Remarkably, despite its relatively small size, the brain accounts for about 20% of the oxygen and, hence, calories consumed by the body . This high rate of metabolism is remarkably constant despite widely varying mental and motoric activity .
The metabolic activity of the brain is remarkably constant over time.
Despite these well-known facts about the brain’s large energy budget, a clear understanding of how it is apportioned among the many ongoing functional processes in neurons and glial cells has not been clearly spelled out. Understanding these relationships has assumed new importance because of the rapidly increasing use of modern imaging techniques such as positron emission tomography and functional magnetic resonance imaging to study the functions of the living human brain in both health and disease. Both of these techniques and their derivatives use measurements related to the brain’s metabolism and circulation to draw inferences about brain function in terms of its cellular activity .
Ketones For The Brain
Ketones are water-soluble elements that are created when fatty acids are broken down. Your body turns to fatty acids as an energy source for its activities, including for brain energy, when you body does not have enough glucose, either from diet or in storage. When your body is low on glucose, but glycogen stores are not fully depleted, ketones are broken down primarily to fuel your brain function, as your other organs and muscles can be fueled through stored glucose.
Do We Sleep So That We Can Save Energy
Evolutionists offer an explanation to what may be the main purpose of sleep. Taken that humans are warm-blooded, they, just like other warm-blooded animals, need a significant amount of energy to retain body temperature and keep the important body functions running. For example, although small, our brains use 20% of our total energy. Sleeping helps us recharge and retain the valuable energy.
During sleep, our energy expenditure levels decrease by 5-10% metabolism slows down, body temperature decreases, heart rate and breathing also slow down.
On the other hand, cold-blooded animals require significantly less sleep time, making this theory plausible.
However, although it does offer some energy conservation, if we consider other benefits of sleep , we would have to agree that the primary function of sleep is not energy saving.
Neurobiology: How Much Oxygen Does The Brain Need
- Ludwig-Maximilians-Universität München
- The brain has a high energy demand and reacts very sensitively to oxygen deficiency. Neurobiologists have now succeeded for the first time in directly correlating oxygen consumption with the activity of certain nerve cells.
The brain has a high energy demand and reacts very sensitively to oxygen deficiency. Ludwig-Maximilians-Universitaet in Munich neurobiologists have now succeeded for the first time in directly correlating oxygen consumption with the activity of certain nerve cells.
The brain requires a disproportionate amount of energy compared to its body mass. This energy is mainly generated by aerobic metabolic processes that consume considerable amounts of oxygen. Therefore, the oxygen concentrations in the brain are an important parameter that influences the function of nerve cells and glial cells. However, how much oxygen is consumed in the brain and how this is related to neuronal activity was so far largely unknown. LMU neurobiologists Hans Straka, Suzan Özugur and Lars Kunz have now succeeded for the first time in directly measuring this in the intact brain and correlating it with nerve cell activity. The scientists report on their results in the journal BMC Biology.
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Why Does The Brain Need So Much Power
New study shows why the brain drains so much of the body’s energy
It is well established that the brain uses more energy than any other human organ, accounting for up to 20 percent of the body’s total haul. Until now, most scientists believed that it used the bulk of that energy to fuel electrical impulses that neurons employ to communicate with one another. Turns out, though, that is only part of the story.A new study in Proceedings of the National Academy of Sciences USA indicates that two thirds of the brain’s energy budget is used to help neurons or nerve cells “fire” or send signals. The remaining third, however, is used for what study co-author Wei Chen, a radiologist at the University of Minnesota Medical School, refers to as “housekeeping,” or cell-health maintenance.Researchers reached their conclusions after imaging the brain with magnetic resonance spectroscopy to measure its energy production during activity shifts. Chen says the technology, which has been around for three decades and is used to track the products of metabolism in different tissues, could prove instrumental one day in detecting brain defects or to diagnose tumors or precursors of neurodegenerative diseases early.
The Brains Resting Process
New ideas and theories are proposed quite often in the world of sleep research. One of the most groundbreaking discoveries happened when scientists realized through experimentation that not every part of the brain rests at the same time and that different parts of the brain experience different sleep intensities. It isnt a trait thats specific to us as humans, mind you other species have shown similar behavior during experiments. If you hook up a dolphin to an EEG, the readings will show that their cerebral hemispheres dont exhibit high-amplitude delta waves at the same time during NREM sleep. The blood distribution to our brain is different between REM and NREM stages, solidifying the idea that different parts of the brain rest at a different time and intensity.
An example thats been talked about is that of sleepwalkers. Sleepwalkers are often considered to be both asleep and awake at the same time. They retain the ability to move around objects and navigate their immediate surroundings similar to a waking person, but theyre as unresponsive to various external stimuli as a fully asleep person. If every part of the brain rested and was inactive at the same time, this would not be possible.
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Glucose Requirements To Support Energy And Anabolic Demands During Brain Development
Glycolytic byproducts are a crucial source of carbons to produce glutathione, NADPH, and riboses along the pentose phosphate pathway , which are themselves essential for the synthesis of fatty acids and nucleotide sensitive, respectively, and to maintain oxidative stress homeostasis . Biosynthesis of macromolecules from glucose metabolites is critical to support key physiological processes behind proper brain growth and maturation it has been shown, for example, that axon growth, synapse formation, and myelination rely critically on aerobic glycolysis . Interestingly, aerobic glycolysis is predominant in the white matter compared to the gray matter, and it has been shown that glycolytic byproducts, such as lactate, are especially important for myelin production by oligodendrocytes . While it has been assumed that most of the glucose is used for ion pumping to maintain synaptic activity, these findings highlight that glucose is critically involved in anabolic requirements beyond energetic demands during neurodevelopment .
Word Of Caution World Of Hope
Dr. Frohlich says more studies are needed, and he cautioned against using electrical brain stimulation to boost creativity or brain functioning in healthy brains.
We dont know if there are long-term safety concerns, he says. We did a well-controlled, one-time study and found an acute effect. Also, I have strong ethical concerns about cognitive enhancement for healthy adults, just as sports fans might have concerns about athletic enhancement through the use of performance-enhancing drugs.
Instead, Dr. Frohlich is focused on treating people with mental and neurological conditions, such as depression, schizophrenia and even Alzheimers disease, for which cognitive deficits during everyday life are a major problem. Dr. Frohlich thinks tACS has the potential to help millions of people with mental or neurological illness navigate life.
For example, people with schizophrenia or major depressive disorder may have periods of severe symptoms or breakdowns separated by periods of relative calm. During these times, their brains are still impaired by illness. Electrical brain stimulation might provide additional relief in these periods.
Dr. Frohlich and his colleagues have also showed that tACS restores alpha waves and potentially reduces auditory hallucinations in patients with schizophrenia.
Sign up for the Carolina Center for Neurostimulation mailing list to be contacted with updates about studies.
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What Happens During Or After Brain Lesions
There are no reported cases of complete insomnia after the patient experiences a stroke or other kind of brain lesion . If they survive as a whole, a sleeping rhythm is re-established among the surviving groups of neurons despite the overall damage caused to the brain. It leads scientists and sleep researchers to believe that sleep is a property of individual neuron groups, not necessarily of the brain as a whole. Additionally, if the blood supply is limited to any part of the brain, neurons will immediately shut off to maintain a base level of brain operation.
Alcohol And The Brain
Long-term alcoholism can lead to a number of health problems, including brain damage.
It is not, however, as simple as saying that drinking alcohol kills brain cells this is a myth. The reasons for this are complicated.
If a woman drinks too much alcohol while pregnant, it can affect the brain development of the fetus, and even cause fetal alcohol syndrome.
The brains of babies with this condition may be smaller and often contain fewer brain cells. This may lead to difficulties with learning and behavior.
Does Alcohol Really Kill Your Brain Cells
Theres no question that alcohol affects the brain in negative ways. It can impair brain function even in the short term. In the longer term, it can lead to serious brain damage. It doesnt actually kill brain cells, though.
Long-term heavy drinking can cause shrinking of the brain and result in deficiencies in white matter. This can lead to:
- slurred speech
- family history of substance abuse
Alcoholics are prone to developing a brain disorder called Wernicke-Korsakoff syndrome. Symptoms include:
- mental confusion
- paralysis of nerves that control eye movement
- muscle coordination problems and difficulty walking
- chronic learning and memory problems
Drinking during pregnancy can affect your babys developing brain, a condition known as fetal alcohol syndrome. Children with fetal alcohol syndrome tend to have smaller brain volume . They can also have fewer brain cells or normally functioning neurons. This can cause long-term behavioral and learning problems.
Alcohol may interfere with the brains ability to grow new brain cells, which is another reason this myth may persist.
Why is it so easy to believe these myths about the brain? Theres a grain of truth running through some of them. Others seep into our own brains through repetition, and we fail to question their validity.
If you previously bought into some of these brain myths, take heart. You werent alone.
Power Of A Human Brain
|Drubach, Daniel. The Brain Explained. New Jersey: Prentice-Hall, 2000.||“Although the brain accounts for less than 2% of a person’s weight, it consumes 20% of the body’s energy.”||20 W|
|“Body, Physics of.”Macmillan Encyclopedia of Physics. New York: Macmillan, 1996.||“The average power consumption of a typical adult is about 100 W.”||20 W|
|Brown, Guy. The Energy of Life. New York: Free Press, 1999.||“The human brain is only 2% of the weight of the body, but it consumes about 20% of the total energy in the body at rest.”||20 W|
|Hart, Leslie. How the Brain Works. New York: Basic Books, Publishers, 1975.||“Even so, the brain when awake demands a greedy share of the body’s energy supply: thought weighing about 1/50 of the body total, it may use as much as 1/5 of all the energy that is consumed.”||20 W|
|Yang, Eric. Think Dinner. Mac Evolution. 13 February 1998.||“It’s well known that the human brain accounts for about 20% of the total oxygen consumption when a person is at rest, so let us assume that the brain accounts for 20% of the total body energy consumption.”||20 W|
The brain makes up 2% of a person’s weight. Despite this, even at rest, the brain consumes 20% of the body’s energy. The brain consumes energy at 10 times the rate of the rest of the body per gram of tissue. The average power consumption of a typical adult is 100 Watts and the brain consumes 20% of this making the power of the brain 20 W.
Based on a 2400 calorie diet
Jacqueline Ling — 2001
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Is It True That You Get New Brain Wrinkles When You Learn Something
Not all brains are wrinkled. In fact, most animals have fairly smooth brains. Some exceptions are primates, dolphins, elephants, and pigs, which also happen to be some of the more intelligent animals.
The human brain is exceptionally wrinkled. Thats probably why people conclude that we gain more wrinkles as we learn new things. But thats not how we acquire brain wrinkles.
Your brain starts developing wrinkles before youre even born. The wrinkling continues as your brain grows, until youre about 18 months old.
Think of the wrinkles as folds. The crevices are called sulci and the raised areas are called gyri. The folds allow room for more gray matter inside your skull. It also decreases wiring length and improves overall cognitive functioning.
Human brains vary quite a bit, but theres still a typical pattern to brain folds. Research shows that not having the major folds in the right places could cause some dysfunction.
- motivate you to do things you probably wanted to do anyway
Learning entirely new things is far more complicated.
Say youve been studying a foreign language. Theres only a small chance that listening to vocabulary words in your sleep can help you remember them a bit better. A 2015 study found that this is true only under the best of circumstances. The researchers noted that you cant learn new things during your sleep.
How Much Energy Does Your Brain Use
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According to Pierre Magistretti, the brain accounts for around 2% of your total body mass, but accounts for around 25% of your body’s total energy use. Interestingly, scientists and medical professionals have only begun to scratch the surface when it comes to understanding the mechanisms behind signaling, metabolic processes and more.
I spoke with Magistretti recently about this and more on KAUST Live. He’s a distinguished professor of bioscience and dean of the Biological and Environmental Science Division at KAUST. A conference was recently held in his honor at the Brain Mind Institute at École polytechnique fédérale de Lausanne to recognize his more than 30 years of research on brain-energy metabolism and brain imaging as well as the behavioral, cellular and molecular determinants of neuronal and glial plasticity.
Read about Magistretti and his work on the KAUST website. I’d love to hear your thoughts on this series. Please get in touch through and follow me on Twitter .
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How Many Calories Does Your Brain Burn
Though thinking burns calories, its not enough to cause weight loss. The increase in calorie burn is small.
You need to burn 3,500 calories to lose 1 pound. In 1 week, this equals out to 500 calories a day.
If you were to solely depend on mental tasks, youd need to exert yourself for many hours.
For example, as mentioned earlier, a 155-pound person burns about 42 calories in 30 minutes of reading. This person would have to read for almost 6 hours to burn 500 calories in a day.
Granted, occasionally moving around will increase calorie burn per hour. But it still wouldnt be enough to cause weight loss.
Its still beneficial to work out your brain. Examples of brain exercises and their benefits include:
- Brain teasers. A
Power Saving In The Brain
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The brain expends a lot of energy. While the organ accounts for only about 2% of a persons bodyweight, it is responsible for about 20% of our energy use at rest. Neurons use some of this energy to communicate with each other and to process information, but much of the energy is likely used to support learning. A study in fruit flies showed that insects that learned to associate two stimuli and then had their food supply cut off, died 20% earlier than untrained flies. This is thought to be because learning used up the insects energy reserves.
If learning a single association requires so much energy, how does the brain manage to store vast amounts of data? Li and van Rossum offer an explanation based on a computer model of neural networks. The advantage of using such a model is that it is possible to control and measure conditions more precisely than in the living brain.
Studies in living brains have shown that transient memories of this type do in fact exist. The current results hence offer a hypothesis as to how the brain can learn in a more energy efficient way. Energy consumption is thought to have placed constraints on brain evolution. It is also often a bottleneck in computers. By revealing how the brain encodes memories energy efficiently, the current findings could thus also inspire new engineering solutions.
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