Your Metabolism Doesn't Know It's The New Year

This is a more scientific, detailed continuation of a discussion started on my other blog.  Fat Fun Fit: Why I'm Not Making Resolutions: A Case Against Dieting.  From that post (in blue):

How will your body react if your norm is to eat around 2,500 calories per day, and only a little walking as your physical activity, and you suddenly cut your food intake by HALF and jump up to a "perfect" workout regimen?  My body reacted like this, as would most:  "Holy crud!!  What the hell is going on?!!  We must be starving, and running to try to find food! What apocalypse is going on out there?  Oh man, this is it, this is the end.  Emergency!  Emergency!  Going to code red- crisis management mode!"  My body senses a sudden catastrophic world event on many January 1st's.

Now time for the science nerd in me to come out.  What happens physiologically while on a low-calorie diet that your body is not used to, is that all food coming in as much as possible will be stored as fat for later in case the emergency gets even worse, and muscle gets broken down to be used for quick energy.  Cause if you're in a crisis, keeping your brain well-fed, and planning for the worst is top priority.  Your brain is not able to use energy from fat, and if you are starving your brain by eating a severely low-calorie diet, muscle is the quickest way to get energy to your brain.  Your body doesn't really have a way to tell how much fat it already has stored so that it can "cap" it at a certain amount, which is why you can get very morbidly obese people.  Your body will just keep making more fat when it is in these crises even though you already have a lot, or when there is a plain old excess of energy coming in.  Losing that muscle lowers my energy and makes sustaining this plan much more difficult.

Continuing on....

Your brain needs glucose.  Your body does too.  It's the energy that gets broken down into usable energy for your body, known as ATP.  You can also use other simple sugars like fructose, but those actually just get converted to glucose before being used to make energy.

Glucose can be stored in a number of ways.  The easiest way is as glycogen.  That is a ginormous molecule of glucoses linked together in a network.  Your liver and muscles store glycogen so that your body and brain have enough energy between meals.  They can only store enough to last for a few hours (between meals).  When there is no glucose in your blood from a recent meal and there is a need for energy, the glycogen gets broken down to glucose.

In the muscle glycogen, the glucose is used right there in the muscles so you can still walk around, type at your computer, chase your kids, etc. between meals.  The liver is the bank account for your brain.  The glycogen in the liver is broken down to send glucose into the blood for the brain to use.  Brain always has priority.  If the brain doesn't get enough, the body must supply.

When glycogen is gone, the body will go to the next source.  Muscle.  There are a lot of Amino Acids - building blocks of proteins - in your muscles, cause that's what muscles are made of- loads and loads of proteins.  Those proteins can then be made back into glucose to send to the brain so it has energy.  This process is called gluconeogenesis  (gluco=glucose, neo= new, genesis= make;  make new glucose).

When you are on a very low-calorie diet or starvation, your body will break down some muscle to feed your brain.  In the absence of readily useable glucose in the diet, the same happens.  This is why people on Atkins/ low carb diets lose a lot of weight quickly at the beginning.  They are starving their brains of glucose, so the muscle gets broken down.  Well, muscle weighs A LOT.  It is much more dense and heavy than fat.  It also takes a lot more water to metabolize muscle, so the majority of those pounds you are dropping on those diets are muscle and water.  Great if all you care about is the number on the scale.  Terrible if you care about your body composition, shape/ size, and actual health.

The other way for glucose to be stored is for PARTS of it to be put into fat. Glucose has 6 Carbons in it, but a bunch of 2-carbon subunits (Acetyl-CoA) can be put together into a long chain: a fatty acid.  Then 3 of these chains can be attached to a glycerol and stuck in adipocytes- fat cells.  A lot of energy can be tucked away this way.  You get loads and loads of energy out of fat.  You are probably familiar with this if you pay attention to nutrition labels.  There are 9 Calories per gram of fat, but only 4 Calories per gram of carbohydrate or protein.  That's equalizing the weight.  Fat takes up a lot more space, so all that extra energy stored in your body also makes your body bigger than the same amount of energy stored in muscles or glycogen.

So, how and when does this fat energy get used?  That's the tricky thing.  Your brain lacks the proper gateways and enzymes to metabolize the subunits from fatty acids (acetyl CoA) directly.  It can only take in glucose or ketone bodies.  The glycerol from the triglyceride can be made into glucose, so those get sent off to the liver to do that.  But the fatty acids are better used by the cells of the body cause they have the right enzymes and gates to allow that to happen.

But since fat is long-term storage, just like a trust fund, the body is not going to break into it at the first sign of trouble.  It waits to see if it can get by with the cash on hand, the checking and savings account.  (Glucose in blood from your meal, then glycogen, then muscle as explained already.)  Then if it's dire enough it will go for those fatty acids IF the body is in need of it.  So, from what I have heard from a Physiology professor about some research (but haven't located the research myself yet so I have no link, sorry), is that the mark for the fat getting mobilized is about 45 minutes of exercise.  After that point you would start to break down the fat for your body to use.  So the recommendation of 30 minutes of exercise most days doesn't even touch that.  If I want to reduce body fat, the best thing is to go on hours-long hikes as much as possible.  (The regular aerobic exercise IS crucial to your health in other ways though, and should still be maintained for your cardiovascular, respiratory, muscle and mental health.  Benefits of regular exercise are nearly endless.)

I mentioned the brain can use ketone bodies.  In severe starvation, the fatty acids can be made into ketone bodies, which can get into the brain and used for energy.  But they are very dangerous because they turn the blood acidic and it is detrimental to your body.  This is the last ditch effort during severe starvation, to keep your brain alive, cause without your brain, the show is over.

Blood Brain Barrier

No one would argue blood is very important to our bodies!  It carries very important things to all parts of the body we need such as glucose and oxygen.  It also takes out the trash by removing wastes like lactic acid and carbon dioxide.

Blood is the highway by which our immune system cells gets around our body to take care of anything that invades.  Blood is also how medications, drugs, poison and toxins, hormones, etc. can get around our bodies.

But let's talk about blood and the brain.  Our brain is a very special organ that deserves special protection.  It's the only part of our body that is protected by a 7 mm thick covering of bone, in addition to cerebrospinal fluid cushioning and protective layers of meninges.  That protects from the outside in, but we also have protection from the inside out, called the blood-brain barrier (I will abbreviate it BBB).

Blood supply is very important to the brain so it has a constant supply of energy and waste removal.  Here are some diagrams showing the blood vessels supplying the brain.

Notice the arch at the bottom of this diagram is the aorta which comes right off the heart itself

The Common carotid artery is the one you are feeling when you take your pulse on your neck

This "Circle of Willis" shows the blood supply on the inferior/ ventral side of the brain.  You can see in the image on the right where this is in relation to the brain.

Alright, so we need that blood and it definitely is there.  But how to protect it?  Some may think the "Blood-brain Barrier" is some kind of a gate the blood goes through when it enters the vicinity of the brain, but that isn't the case.  There isn't a particular spot for the BBB, but rather, it exists as protection on the capillaries (smallest blood vessels where material exchanges happen) themselves in EVERY location within the area of the brain.  It's not a matter of filtering all the blood as it travels through your head, but it's a matter of being more selective about what things cross over FROM that blood into the brain tissue.

We have special gate-keepers to protect things from getting into our brains.  Here's a cross-section of what a blood vessel in the brain looks like compared to a regular one elsewhere in the body:

Not only are the capillary cells (red in the diagram) closed more tightly so things can't leak through, but the entire blood vessel is covered with the "feet" of astrocytes.  (My favorite glia!  Here's a post about them.)

Here's a more 3D view:

See how is it a gatekeeper?  Anything in the blood must go through the astrocyte in order to get to the neuron.  Astrocytes are like the bouncer, protective big brother, or best friend: "if you want to get to the neuron, you have to [quite literally] go through me first!"

Astrocytes are really integral to the chemical integrity in the brain and are a bit of the "unsung heroes" of the brain.  Not only are they gatekeepers, but they act as a kind of mop-up crew and storage unit for any leftovers the neurons leave around (like ions, some neurotransmitters), and they serve to make sure the neuron stays well-fueled, like a mother who keeps snacks in her purse for her toddler.  No wonder astrocytes far outnumber neurons in the brain.

How do these tight blood vessels and "feet" of the astrocytes actually protect it? They are cells, which means they are surrounded by membrane- a phospholipid bilayer, which looks like this up close:

Because of this configuration, stuff that is polar (charged) or water-soluble can't get through the membrane- it can't get past all those hydrophobic fatty tails. 

YOU SHALL NOT PASS!!!
Water-soluble stuff such as nutrients (Amino Acids, Glucose, vitamins)
Polar stuff
Chemicals & toxins
Viruses
Bacteria

Stopping viruses and bacteria for the win.  Stopping nutrients? FAIL.

So to fix that, we have special transporters to let the good stuff in.  They can be super specific, so a glucose transporter will ONLY let glucose in.

Okay, you can go in...
Non-polar/ uncharged/ fat soluble stuff: this includes oxygen going in and carbon dioxide going out
Drugs that are fat-soluble
Other important stuff with special transporters embedded into the membrane to let them in, like water, glucose, amino acids, vitamins, etc. (Glucose has a wicked-awesome backstage pass, AND it knows the lead singer of the band.)


Whew!  That's a big job and an important one for the BBB.

Stay curious!

Blood Clotting

Blood clotting or coagulation (also called hemostasis), is complex, but we want to try to understand this in "big picture" form first off.

When an injury occurs in a blood vessel, here are the steps we go through.

Classes.midlandstech.com

Platelets and Fibrin are the important things that we actually get as products of coagulation that seal up a wound.  But the activation of them is a complicated process.  Which is a good thing for your body!  If it were an easy reaction, we could get our blood spontaneously clotting on us and that would be BAD.

Here's another way to visualize this:

studyblue.com

In first forming the platelet plug, it's important to note that it's the exposed collagen fibers that are attracting platelets.  The normal, healthy state of things is to NOT have platelets sticking to blood vessels.  The ability to not stick is ensured by the blood vessel lining cells (endothelial) releasing prostacyclin to prevent platelet sticking.  But with damage, that isn't released and instead collagen causes platelets to stick.  This can be visualized here:

dc416.4shared.com

Now for the actual clotting part after the platelet plug, for now I have some videos.  If you want to cut right to the chase and a great explanation, watch the last video.



Videos
Here's a not fabulous animation but an animation nontheless...


This short clip I just found helpful to visualizing how the different factors work together to activate factor X then prothrombin, to activate thrombin which they refer to as the "thrombin burst" because it creates a large amount then creates a positive feedback loop to further increase the effect.


This is the best video I found!  I like how concise and understandable he makes it, looking at the big picture and working backward from there.  Hope it's helpful for you too.

All clotting factors are made by the liver, except 8 and PAF3. (Platelet activating factor is made by white blood cells.)

Neuron Ion Channels - Detailed

Inward rectifying potassium channels.  This is what started all this.  Just a little paranthetical aside in my Neuroscience teacher's notes that left me curious.  One thing led to another, and here we are.  Ion channels.  Hope you learn something like I did.  Enjoy!

A plethora of potassium channels
Here is a short video showing the molecular structure of a Potassium channel and how it can be perfectly selective to allow Potassium and not Sodium through.

And look at this beautiful top view of a potassium channel with a little purple potassium ion in the center.

Inward-Rectifying Potassium Channels
What does inward-rectifying mean?  Simply put, it just means that voltage travels inward more easily than outward.  So this name tells us that Potassium will move into a cell when open.
(Example - cardiac muscle cells- responsible for the long refractory period between beats, to avoid tetany; kidneys, regulating potassium ions

Action Potentials: Delayed Rectifier Potassium Channels & A Type Channels (outwardly rectifying)



Tandem Pore Domain Potassium Channels (Leak Channels)

Voltage Gated Potassium Channels




********This post under construction!  I just found a textbook with an entire chapter on ion channels, so after I study for my test I will dive into this and finish the post...  thank you for not hating me too much for leaving you hanging.  You'll just have to subscribe to learn more! :)

Neuroglia

Neuroglia are support cells for the neurons in the nervous system.  They have a very wide variety of functions, and I'm sure it hasn't all been discovered.

Now, here's the interesting thing.  Studies done on (supposedly) Einstein's brain, show that he didn't really have any greater number of neurons, but actually had more neuroglia, particularly astrocytes, which were concentrated in the area of the brain involved in imagery and complex thinking (NPR news article on the subject, June 2010).

Picture source

My thought is that we don't know which came first - the astrocytes or his genius.  Perhaps using your brain well leads to making more astrocytes in order to support how much you're using certain areas of the brain, rather than the astrocytes coming first and giving natural intellectual ability.

So, on that note, we'll take a look at these cells. :)  Here is a good way to categorize them, from interactive-biology.com.  I'll expound on these more.

Source (interactive-biology.com)

 And for the visual folks out there, here are a couple of diagrams.

Source

Source

Neuroglia in the Central Nervous System 

Source

Oligodendrocytes (a type of macroglia)

• Support neurons in the CNS by myelinating.  Have multiple "arms" with which they myelinate several axons.
• Myelination insulates axons of neurons which allows their conduction to go much more quickly.  (For some info on how this works, go to this post on action potentials and scroll to the bottom for "saltatory conduction".)
• Similar function in PNS is performed by Schwann cells

Astrocytes (a type of macroglia)

• Named for their star appearance (astro = star, cyte=cell)
• Maintain neuronal environment
• Part of the blood-brain barrier
• Control what substances are transported from blood to neural tissue (Source article)
• Have their own signalling system and can regulate messages of neurons
• Topic of much research - some are calling these "the other brain" (Source article)

  

  Source

  
  

My note on Astrocytes: wow, these look like such an exciting topic right now!  These are the cells that Einstein's brain had more of, and it looks like we are just discovering how integral they really are to the function of neurons!

Microglia

• Immune cells of the CNS - these bad boys take care of infection by foreign pathogens, and keep any abnormal neurons in check, gobbling up anything that shouldn't be there.  In short, they are the macrophages of the brain and spinal cord.
• Named for being small (micro), which allows them to get around to whatever small spaces necessary for fighting infection.

Source

Ependymal glia

Source on brainyinfo.com

• Ciliated epithelial tissue
• Line the ventricles and choroid plexus of the brain
• Make Cerebrospinal fluid (CSF)
• (Very good source article on brainyinfo)

Neuroglia of the Peripheral Nervous System
Schwann Cells/ Neurolemmocytes

Source

• Schwann cells have the same function in the PNS that Oligodendrocytes have in the CNS, namely myelination.
• The cell wraps itself around the axon of a neuron, insulating it, as seen below.  Pretty cool, eh?

Source on brainyinfo.com

Satellite Cells

• Cushion neurons
• Help control the environment of neurons and maintain synaptic integrity by insulating areas where there shouldn't be additional synapses on the neuron.

Kidney Physiology

Great overview

Urine Production Video - Osmotic Gradients

This is kind of fast, but it shows the counter-current diffusion of water and ions from the Nephron loop and vasa recta.

.


Here's a fun video - why coffee and alcohol make you pee more.

Respiration, Oxygen, and Hemoglobin

By decreasing pressure inside the thoracic cavity, we are able to inspire air.  By contracting the diaphragm, intercostal muscles, and others, we increase the size of the thoracic cavity, which in turn lowers the pressure to the point that it is lower than the outside air, causing a pressure gradient so the air rushes into the lungs.  To exhale, it is the opposite- relax the muscles, decrease the space in the cavity, which increases the pressure inside until higher than outside, so the air rushes out to where the pressure is lower.

This video is a good summary.  The embedding doesn't work, so you'll have to click the link instead.  Just left the embed on there for the picture. :)

http://youtu.be/V1FAnE31AYs

Partial Pressure
Total Pressure of air can be broken into the partial pressures of all the gases contained in that air.  For instance, if the atmospheric pressure is at 760 mm Hg, and 20% of that is Oxygen gas, 80% Nitrogen gas, then the partial pressure of O₂ would be 20% of 760 = 152 mm Hg.  Partial Pressure of N₂would be 80% of 760 = 608 mm Hg.

This illustrates how increasing the pressure, as in the B picture, causes more gas to diffuse into the liquid.  A simple way to think about it is just that the higher the partial pressure of that gas, the less space it has to bounce around in the air, so more of it will end up in the liquid.

Here's a long video on partial pressure and gases getting into solution, I didn't watch the entire thing yet but it looks like a good detailed explanation for those who feel they could use more information.

Brain Food - Nutrition for Learning & Memory

What are the best foods for learning?  Can your diet help improve your memory?

These are foods you should add to your regular diet which will boost your brain's ability to function and help you do well in school.  For info on what to eat for alertness before/ during studying, I will make another post and put the link here when it's done.

"Top Ten" Brain Foods
(according to this article)

1. Fish - Omega3 Fatty Acids are crucial to neural health, and can even prevent dementia.  They also promote heart health by reducing risk of blood clots, which will reduce risk of heart attack. Bonus!  It's recommended to have at least 2 servings of fish per week.

2. Nuts - high in essential fatty acids which help your brain perform its best, as well as iron which will help in getting oxygen to the brain (because the major component of hemoglobin in your RBCs is iron).  It's also got unsaturated (good) fats which will give sustained energy.




I would also add Avocados to this category, because they have a great amount of unsaturated fats which will give the same benefits as the nuts.  As a bonus, they have no cholesterol or salt!  Here's a site with info on avacados, how to pick a good one, how to slice, etc.: http://sprouts.com/food-tips/avocados-thinking-outside-the-guacs



3. Whole grains (quoted directly) - Eating lots of refined carbs like white bread and pasta is not only bad for your physical health, but it also leads to sleepiness, lethargy, and mental dullness. Luckily, whole grains tend to have the opposite effect and can lead to enhanced memory function and even better grades. Chow down on whole grain breads, crackers, and pasta while you study for a quick energy boost.

This source website has some info on a few whole grains you might not know about

4. Apples - skins of apples contain an antioxidant called quercetin that enhances memory. :)  Plus it's a good source of fiber to help you feel full, and is a very quick, portable source of energy.



5. Cruciferous Vegetables (direct quote) - In case you’re a bit rusty on your vocabulary, “cruciferous” vegetables make up a family of vegetables including broccoli, cauliflower, cabbage, brussels sprouts, and bok choy. A long-term study conducted by Harvard Medical School revealed that these type vegetables had the most positive effect on memory retention, meaning they are the most likely to help you achieve better grades. Eating these vegetables raw is the best way to get the optimal nutritional benefit, since cooking them often cooks out the nutrients your body and your brain need most.


6. Dark Chocolate (direct quote) - Not just any variety will do, but a certain type of chocolate – dark chocolate – can feed the brain, not only by improving memory, but also by increasing blood flow to the brain, increasing alertness and clarity. The darker the chocolate, the more benefits your brain will receive.

Click the following link for another article with more great things about dark chocolate, such as the facts that it has antioxidants, it prevents blood sugar spikes, even helps keep your teeth healthy! (Who knew?) Article on fitday.com

7. Spinach - great source of folic acid which can reverse memory loss, lots of antioxidants, vitamins, fiber, and even some Omega-3 Fatty acids.

8. Berries (direct quote) - Here’s a quick solution for the problem of how to study better—pop a handful of colorful berries in your mouth as you prepare for your next test or exam. Colorful berries such as blueberries, cherries, black currants, raspberries, cranberries, blackberries, gooseberries, and even grapes have significant health effects directly related to brain function. Not only do these flavorful snacks reduce the level of toxins in your bloodstream, but they also contain phytonutrients and antioxidants that improve blood flow to the brain and enhance neural activity as well.

9. Legumes - very high in protein to fuel your brain without blood a sugar spike and plummet, and also have folic acid to help with memory recall.

10.Onions - The compounds in onions, namely anthocyanin and quercetin, have even been shown to prevent Alzheimer’s disease.  Help improve memory and focus.




Another case for some good proteins

Amino Acids Can Excite or Calm Your Brain
The amino acids tryptophan and tyrosine must both cross the blood-brain barrier in the same pathway. If tryptophan crosses the barrier, it will have a calming effect. If tyrosine wins out, then you will be energized and alert. A high-carbohydrate meal can increase the brain's tryptophan levels, and hence the serotonin that promotes contentment and normal sleep. Therefore, a carbohydrate-rich meal may be more appropriate for the evening meal.		On the other hand, one can be energized for hours after a morning meal high in protein, because it raises tyrosine levels in the blood and brain – causing neurons to manufacture norepinephrine and dopamine, two neurotransmitters that promote alertness and activity. Tyrosine is crucial to brain power and alertness in another way. It's also needed for your body to make active thyroid hormones. Low blood levels of tyrosine are associated with an underactive thyroid gland. (Extreme thyroid deficiency causes severe mental retardation known as cretinism.)

Source above text is from

Tyrosine is actually made from phenylalanine in the body.  It's used to make neurotransmitters including epinephrine, norepinephrine, and dopamine.  Here are some dietary sources:

Tyrosine is found in soy products, chicken, turkey, fish, peanuts, almonds, avocados, bananas, milk, cheese, yogurt, cottage cheese, lima beans, pumpkin seeds, and sesame seeds.

(Source)

Another source has some info on Amino Acids boosting brain function, on livestrong.com.

Brain Food No-No's
Some things NOT to eat (avoid as much as possible): alcohol, caffeine, and sugar (as in simple carb sweets).  There are many ways these items are bad for your health, a couple of which are their propensity for being addictive, help you gain weight, and to produce a giant sugar crash that will put your brain out of commission.  Here is another nice physiological reason, related to the neurotransmitter Dopamine.

Dopamine
Dopamine is the neurotransmitter needed for healthy assertiveness and sexual arousal, proper immune and autonomic nervous system function. Dopamine is important for motivation and a sense of readiness to meet life's challenges. One of the most vulnerable key neurotransmitters, dopamine levels are depleted by stress or poor sleep. Alcohol, caffeine, and sugar all seem to diminish dopamine activity in the brain. It's also easily oxidized, therefore eat plenty of fruits and vegetables whose antioxidants help protect dopamine-using neurons from free radical damage. More and more healthcare professionals recommend supplementing with vitamins C and E and other antioxidants.		Age-related cognitive decline is associated with dopamine changes in the brain. People whose hands tremble from Parkinson's disease have a diminished ability to synthesize dopamine, which is crucial to fine muscle coordination. Attention deficits are also connected to dopamine.

Source above text is from
.

Stanford

.
Visualization for Alertness & Success
Another tip while you are studying and taking tests, you want to make sure your Reticular Activating System is active (as I'm sure you already know, this part of the brain is what controls your awake and alert state- it determines what you focus on).  A great way is to actually visualize yourself succeeding.  You hear a lot about thinking positively.  Well it's true.  Successful people visualize themselves being successful, and that actually makes them more successful.  Here's an article if you want to learn more: http://www.ginabellinc.com/successgps/

By the way, since the RAS includes the Thalamus which takes in sensory info - so if you use a multi-sensory approach to visualizing and studying, you can trigger your brain during the test.  For instance, if you always chew the same flavor of gum while studying Physiology and visualizing your success, then chew that same gum during the quiz/ test, it could help your RAS pay attention to being successful!  Just a thought. :)

Hey, if you remember from the post about the brain anatomy and functions, I pointed out that the Reticular Activating System is just as active while you're dreaming as when you're awake - perhaps that's the logic behind listening to lectures, music, etc. while you're sleeping or meditating too!  Interesting...