Starvation sequence

In this post I'd like to describe the sequence of total stopping of any food intake, providing the water is still available, even if in minimal amounts. To understand the progression, it would be the best to name all the types of nutrients at the beginning, so the further explanation then makes perfect sense.  Three types of nutrients/energy are:

1. carbohydrates (or carbs)

2. fats (or lipids)

3. proteins

Because I couldn't find any flow diagram (anywhere), which would show this sequence of starvation, I was forced to improvise a little. So don't be discouraged by overt simplicity of this flow diagram. Still, (just in case) I want to clarify that symbols between the lines ( | and V ) are supposed to represent the down-pointing arrows. So let's get to it ! 

-----------------------------------------------------------------------------------------------

Fed state, or so-called postabsorptive state, meaning that
all three energy sources are available for usage
 |
V
after 4 hours - carbs are spent from liver and digestive tract, while
fats and proteins levels are still intact
 |
V
12 - 24 hours - carbs spent from whole body, with
slight increase in usage of fats and proteins
 |
V
2 - 4 days - using fats after converting them into ketone bodies (<100 times of normal level), plus
using proteins in the rate of 90g a day
 |
V
4 - 40 days - further using ketone bodies from fat (100-300 times more then in fed state), plus
decreasing usage of protein each day
 |
V
40 days - 2 months - maximum usage of ketone bodies ( >300 times comparing to normal level), with
usage of proteins in the rate of 20g a day
 |
V
2 - 3 months - Body still have some fat, and ketone bodies for energy, but once the body protein level drops to about half of normal level, the physical death will occur through the infection, because the immune system will fail to work efficiently.

---------------------------------------------------------------------------------------------------

Now, let's get through the whole process in slowly in the text format. After your meal, the body will be absorbing all nutrients, which is called the absorptive state. Once all the nutrients are absorbed, the next state is called post-absorptive state, signifying that the absorption is finished, and there is nothing else to digest.

Normally, those two state rotate, as with every other meal you get back into the absorptive state, and so on. But in the case, you stop eating and prolong the post-absorptive state, the first stage is called fasting. This is relatively still healthy state as you force your body to use all available (plus all excess) nutrients that are possibly accumulated in your digestive system.

Fasting changes into starvation roughly around 1-2 days after not eating any food. As I mentioned at the beginning, the water intake needs to be still available, otherwise without water, only 2-3 days will lead to dehydration, decrease of sodium levels, muscular spasm, and physical death. But that's the different story, so let's get back to our starvation sequence.

Roughly 4 hours after the end of the absorptive state and basically the beginning of post-absorptive state, all glucose in the form of glycogen in the liver is gone. That would represent about 25% of glycogen reserve in the body. The resting 75% in the skeletal muscles is then gone within 12-24 hours. This range differs with the amount of activity or rest. But basically after about 2 days of not eating, all the glycogen, and therefore the glucose in the body is gone/used.

To maintain the stable level of glucose in the blood, which is crucial for normal working of nervous system, the body converts fats into the middle-man called ketone bodies. This middle-man looks half the glucose and half amino acid, from which all the proteins are created. Glucose then feed the brain and nervous system, and amino acids are spent for protein synthesis, to save the built-in protein as much as possible.

In this state, the rate of protein usage is about 90g a day, plus with every other day after 2 days, this rate keep decreasing, finally stabilizing at the level of 20g a day in about 40 days. Meanwhile, the level of ketone bodies in the body increase about 100-300 fold. The state called the ketosis is a heavy burden for the organism, especially for the liver and kidneys, which have to take care of it.

Because ketone bodies are slightly toxic substances, they need to be eliminated from the system straight away after they are being used, and therefore, they can't be reused. Because the proteins in the blood, mainly in form of white blood cells incapacitate the toxins in ketone bodies, their level needs to be constantly updated, which is another load for protein usage.

Once the whole body protein level drops to about half, there will not be enough white blood cells for eliminating ketone bodies quickly enough. And at some point, (somewhere between 2 to 3 months), those ketones will overwhelm the immune system, and the result will the that the body will fall prey to the first virus, bacteria, or toxin which will attack the body, and will collapse.

Ironically, even in the time of death, the level of fats will be still at sufficient level to provide more ketone bodies, therefore the energy. But because of the lack of proteins, the immune system will be very frail and inefficient. So technically, the body will never run out of fat, or the energy until the end. It's the infection that will fire that fatal blow, which will result in physical death.

So I hope that this was simple and clear enough to understand the whole sequence. Of course, if at any point the new food intake is provided, the whole process will be postponed, and the cycle will start from beginning. Mainly if all three types of energy are present in fair amount of that particular meal.

Glycogen window - the essay on glycogen

Glycogen is the molecule built up from small rings of glucose (see the picture). It's structure is highly branched, which left a lot of space inbetween, and this space needs to be filled up with water. Glycogen reserves are located in the liver, holding 25% of it and the resting 75% is in the muscles.

 

Total amount of glycogen, which the body can produce and store is around 500g in average (meaning untrained) person. With the increase of muscle mass in bodybuilders or athletes, this reserve can add up to 1100g. To imagine this, take for example 1 kg loaf of white bread. That would be something over 500g of complex carbohydrates, which would be the exact amount of glycogen created from eating that whole loaf.

 

Supposing you eat that loaf on 3-4 times during the whole day. Your body needed to cover the energy for that day, and the night that follows. So when you wake up in the mornig, out of those 500g, you can have something less then half left. Plus, if you add up some exercise during the day, the demand of your body for carbohydrates will be even bigger. So here's where the phrase glycogen window start to pick up a proper meaning.

 

Glycogen window metaphorically means eating a lots of carbs and still not having enough of them for the body to process. It's like you would throw them out of window, literally. They disappear somewhere in your stomach, and get soaked into your muscles. That, of course, under the condition that you trained to stimulate growth, and provided sufficient rest for recuperation and restoring all used up nutrients.

 

Muscle growth is not facilitated only by storing extra glycogen. As mentioned earlier, additional mass contain a lots of water, as it's estimated to count 2-3g of water as an addition to every gram of glycogen itself. Plus, after training, muscles stock up on extra fats, and extra creatine phosphate to cover the energy. All together looks as pure muscle on the outside, because all those substances are inside of muscle, or around muscle fibres.

 

Otherwise, after reaching the adulthood, the number of muscle fibres stays the same for the rest of the life for everybody. Muscles are getting bigger only by storing the extra energy. And the volume can be added right into the muscle cells or fibres, or around them in so-called sarcoplasm, as an extra storage.

 

 This flow diagram shows the pathways from glucose to glycogen and back. The whole process take place in the liver cells. Glucose from blood enter liver cells and gets phosphorylated twice before start stacking them into branches of glycogen. The process of creating glycogen out of glucose is called glycogenesis, and the opposite process of breaking it down back to glucose is called glycogenolysis.

Basics of human metabolism

I found quite good flow diagram in the book Principles of anatomy and physiology, 7-th edition. It covers the  basics of metabolism, mainly the view of certain key molecules involved in it. There could be dozens of similar ones, which would involve different molecules on different pathways, because in the essence, the flow diagram is about the depicting one or more pathways of certain molecules in the body.

The metabolic pathway is defined as a series of chemical reactions that take place somewhere in the body. It can be cyclical or straightforward, and it can be executable in one direction or in both directions. The total sum of all metabolic pathways in the body is called metabolic network. 

So with the pathways, they have their starts and ends, and maybe even some milestones and/or dimension changes along the way. Good flow diagram brings all this information in simple, graphical way of covering the knowledge about human body, and systems involved within it.

This diagram focuses on chemical pathways of food that breaks down to proteins, carbohydrates and fats. Their further broke-down equivalents are amino acids, glucose and triglycerides respectively. But mainly it focuses on three key molecules, which serves as intermediates in human metabolism, and those are Acetyl co-enzyme A, Pyruvic acid, and Glucose 6-phosphate.

The last one is the ring of glucose with addition of phosphate group on sixth carbon in the chain. This altered glucose molecule, also called phosphorylated glucose, can be then used for energy into Krebs cycle, energy for DNA production, or to convert it to Pyruvic acid, the second intermediate molecule.

This one, in turn, can be used for production of alanine amino acid, or by aerobic and anaerobic reactions, to energy (ATP) with lactic acid, or to convert it to another intermediate molecule - Acetyl co-enzyme A. And this molecule can enter Krebs cycle, or to be converted to ketone bodies, cholesterol, or fatty acids. I hope it's all clear from the picture.

Each component or even word in this diagram could be enough to write about for the separate post. In whole, this is the representation of human metabolism, or at least one possible side from which it can be viewed. Plus the metabolism itself could be topic for whole books, and it is. It can be divided by particular substances into fat metabolism, protein metabolism, or carbohydrate metabolism. Or simply the metabolism of any other substance with its own characteristic pathway and chemical changes along the way.

PROCESSES

Some parts of diagram, or words, describe a process, like for example glycolysis, aerobic reactions, or Krebs cycle. So in this case, glycolysis would mean breaking down of glucose rings down to the Pyruvic acid. Aerobic reactions would be those that require oxygen for successful execution, and anaerobic reaction are on the other hand those that don't, and can work without the oxygen.

Krebs cycle represent many different reactions involving many different substances. But just to give you a hint, there is 9 steps or chemical reactions in cyclic manner, which starts and ends with the same substance - Acetyl co-enzyme A. Those then involve 9 different enzymes, 9 substrates and end products for each step. Again, each of these processes could be picked up and fill the text for the whole chapter.

So the topic is complex, and thank God there are such a things as simplifiers of it in the form of flow diagrams. The way I see it, the understanding of processes within our bodies is priceless and irreplaceable. Moreover, it cost nothing these days as there are tons of websites and library books dedicated to bringing the light on the topic. So you can watch, read, think, learn, understand and I'll see you next time around.

Muscle contraction

Muscle contraction is a complex process with one simple objective of enabling the movement to an organism. This complex process can be studied from many different levels, and the knowledge about the musculo-skeletal system reaps benefits in a number of different areas or professions. Generally, the human health during the lifespan is very closely related to normal and effective function of this particular system.

 

D I V I S I O N S

 

Two basic types of muscle contractions are isotonic and isometric. With isotonic, the muscle gets shorter during the contraction, and with isometric, it stays the same lenght. The special type of excercise called isometry is using isometric contractions for developing the strenght of muscles and joints. It's used during the rehabilitations, like for example after having a cast for certain period due the broken bone. The muscle is feeble and significantly smaller so normal exercise is out of question.

 

It's also benefitial for those confined to bed temporarily or long-term. Isometry is basically flexing the muscles without moving or twisting of arms or legs during the contraction. It can be executed by pressing against unmovable object ( for example wall or bed), or simply by pressing two hand against each other. The best thing is that it doesn't require any equipment or skill, and it can be done anywhere and by anyone.  

 

Another special type of involuntary muscle contractions would be cramp or twitching. Stretching and massage are usually very effective in calming down the muscle, as those things usually happen after prolonged exercise or fasting, where the fine balance of electrolytes in the body is disturbed.

 

Muscle contraction works on all-or-none basis as there is no such thing as partial contraction. Plus, it's followed by so-called refractory period, during which the muscle is getting back ready for another contraction.

 

There are three basic types of muscle tissue in the body:

  a) cardiac - muscle of the heart

  b) smooth - muscle in the gut / involuntary

  c) striated - skeletal / voluntary muscles

 

Striated muscles then divides further into two types:

  a) tonic - slow fibres holding mostly the posture

  b) phasic - twitch fibres of two types:

        1 - slow (red fibres)

        2 - fast (white fibres)

 

Another division could be seen depending on the conditions around the muscle contraction. More specifically, it can be done with the presence or the absence of oxygen.

  a) aerobic - with oxygen / using oxygen

  b) anaerobic - without oxygen / creating oxygen dept

 

This oxygen dept is then compensated in the body by flooding the muscle with toxic compound called lactic acid. Accumulation of this substance in the muscle gives that characteristic feeling of burning in the muscle, during and at the end of very vigorous exercise. Lactic acid needs to be quickly eliminated that's why the burning stops soon after you stop moving. Because it's toxic, it's presence is dangerous to the organism, which is dealing with it three possible ways:

 

a) oxidize to pyruvic acid

b) convert to carbs

c) neutralized and excreted

 

Lactic acid and it's effect will make you stop moving, as any further movement at that precise point is litterally painful. It can flood the blood and liver and destroy the living tissue. Regular aerobic exercise and intake of quality food increase the resistance of body towards lactic acid, and more lean muscle tissue the person possess, longer the person can excercise without being stopped by accumulated lactic acid.

 

This diagram shows nicely how muscle contraction actuallly work on the tissue level. Actin and myosin myofilaments work together to create the complex called actomyosin. This complex is then capable of sliding the actin and myosin against each other, and sort of fold them up, shortening the overall lenght of the muscle fibre. Sarcomeres is a fancy term for the muscle cells, and all this model is called sliding filament hypothesis.

 

For muscle contraction to occur, there is a number of conditions that needs to be met, and there is actually a stream of insights coming from knowing those conditions. For the sake of simplicity, I created a simple list:

 

- the presence of the protein called actin

- the presence of the protein called myosin

- the presence of Ca

- the presence of Mg

- the presence of ATP

- the presence of creatine phosphate

- calcium pumps has enough of Ca pumped in

 

Simply put, calcium pumps located on the plasma membrane, pumps in calcium, which triggers all the other processes. Creatine phosphate is another, alternative source of energy in the muscles. They chip in when there is a shortage of ATP, or the exercise is so vigorous, that all energy sources are in the action.
 

3 FORMS OF ENERGY

On molecular level, the muscle has three big sources of energy to reach for. All three are continously available at all times, what differ is the ratios between them, which correlate with the state or activity of body. Plus they differ in how long they can be available, and the time for their recovery. Three form of energy are:

1. fats - triglycerides
2. glucose - monosaccharides
3. creatine phosphate

Fats are the biggest contributor supplying heart and all energy needed for keeping the posture, along with very slow movement. Fat are continuously used by muscles even if you don't move at all. Technically, fats can never run out completelly from the whole body, but their usage by muscles is limited, because it depends on the oxygen input. And that, in turn, depends on the state of your lungs, heart, and basically the whole body. So to burn more fat than you usually do, you need to improve the state of almost whole body.

Glucose is the type of monosaccharide and serves as main energy source for the brain with whole nervous system, which runs only on glucose. Then, muscles use glucose along with its secret source of it - the glycogen. This is sort of animal version of complex carbohydrates and it can be stored in muscles and liver. From there it can be used at any point, and when you then eat carbs again, you refill it.

Interesting thing is the ratio of fats and glucose in which muscles use them. Supposing you are lying down on the bed without moving. Fat / glucose ration would be about 70/30. But the moment you start moving fat goes down and glucose up. The quicker you will move, further the fats will go down, and glucose up in the ratio. Get the picture?

Creatine phosphate is very interesting substance stored in the muscles only. It start working only when we move very fast, or for longer time. It's the additional source of energy that is available for the muscles in the times of shortage of both fats and glucose. There is quite limited amount of creatine phosphate in muscles, so suppose you start running as fast as you can, it can last for about ten seconds. When you stop, and not move for another 30 seconds, it will be replaced with freshly-new made one.

The storage of this substance can be increased by involving the body or muscles in heavy exercise in short bursts. This is the case of sprinters or bodybuilders for example. They train muscles to develop bigger creatine phosphate stores in order to achive greater performance, or appearance. Those three types of energy can be then combined to bring about the movement or sport we need.

 

 This very nice flow diagram describes the muscle contraction cycle in four steps. The diagram is pretty much self-explanatory, so it's all the question of reading and trying to understand. First I recommend to map out the symbols from the key in the grey box, and then reading the steps should make easily a lot of sense on closer observation and study. Good luck and enjoy.
 

ATP - cell's rechargeable battery

ATP, or adenosine triphosphate, could be put in an analogy of a mini rechargeable battery that cells are using to feed the energy for many different processes within the body. It contains three basic parts.  The adenine molecule, sugar molecule (ribose), and three phosphate groups - which are really one phosphorus atom surrounded by four oxygen atoms.

The energy we talk about here is in the form of high-energy bond between those phosphate groups. When they separate, the energy is released, and then used. To put back on that last phosphate group, and therefore recharging it, it requires the energy which the body needs to get from the food we eat. This principle is explained on this picture.

 

When you take away that last phosphate group, you create the molecule called ADP - adenosine diphosphate (only 2 phosphate groups). That would be the representation of empty battery in this analogy. Rotating those two chemical reactions, then provides the means of an empty and full battery, which are moving from the place of using up to the place of recharging it. And back again and again cyclically.

 

For example, one molecule of glucose can bring up the production of as much as 38 ATPs, provided there is an oxygen present in the process. This is called an aerobic respiration. In the absence of oxygen, however, only two ATPs can be made - the process called anaerobic respiration. For more detailed view of how and where ATPs are made in the body, this flow diagram does a great job.

 

Here you can see that some ATPs are made in mitochondrion, some in the cytosol, and some in the gut - where happens the basic breaking down of food from the meals we eat. In the gut, the proteins, complex carbohydrates, and lipids are digested into the final products, which are in form of amino acids, glucose, fatty acids, and glycerol respectively.

 

First round of freshly made ATPs is happening in the cytosol, where the glucose and the glycerol are used for creating it. Cytosol is semi-fluid matrix inside of the cells, in which all the organelles are suspended. Mitochondrion is a special organelle for making ATPs and many other functions. There in the middle, there is a cyclical sequence of chemical reactions called TCA, or Krebs cycle (or citric acid cycle). This represents the biggest system for ATP production in the body.

 

Stress response

The stress response, commonly known as the fight-or-flight reaction, is the first part of so-called General Adaptation Syndrome (GAS). It's a short lasting physical reaction of the body (or organism) towards the real (or even any imagined) threat. This response can be seen from multiple of levels - molecular, cellular, anatomic or atomic. It can be defined by physical or/and chemical processes which are triggered by it, or by any physical symptoms on the perception level. Or by some other means.

Three phases of GAS are:

1. stress response (fight-or-flight reaction)
2. resistance
3. exhaustion

So in the hypothetical situation where your life is in danger and you are forced to run away, the first part is very explosive and effective accumulation of energy at your disposal. If the threat persists, the next phase called resistance, is much longer sustainable state of increased level of disposable energy, but decreasing with time. After a while, depending on physical condition of that particular person, the third phase called exhaustion will follow. This is the state where the most of the energy is already spent, and the body is no longer in a position to fight or flight anymore. 

But from those three phases the first one is by far most interesting, so let's go deeper into particular physiological and chemical changes that are triggered by the stress response. It's all happening in real time, so the stress response is occurring on the observable level (to a certain degree of course). The consequences of the stress response could be put into two broad categories:

a) short-term consequences

b) long-term consequences

and those two differ substantially, so let's elaborate both of them.

SHORT-TERM

In the short-term, the stress response can be useful and helpful by presenting some information (a lesson learned), the impulse for the body to improve, or get stronger. In the short-term, it can be even perceived as a pleasurable event, providing it's happening within well-known boundaries (like for example in adrenalin sports). But it can be harmful in the case when the impulse is too strong to handle, and it slips the person into any negative experience of stress. And in the big proportions we talk about trauma (on mental level) or the injury (on physical level).

The principle behind the stress response in the short-term is to provide the organism the opportunity to improve, or strengthen itself in some way. Providing there is the sufficient and quality recovery time, and handling the stress is still manageable (to the comfortable level), the result should be the improvement of the body in dealing with that particular type of stress or condition.

The analogy could be used of learning how to drive the car. The frustration and stress associated with handling new circumstances evoke the stress response on the number of occasions. But if handled, it leads into the ability of driving the car, which in turn becomes a very useful skill in life.

LONG-TERM

By the long-term consequences of stress response I don't mean cyclical and continual short-term stress response with recovery time on day-to-day basis. But mainly it means some degree of continual residue of stress, which hasn't been handled within the manageable (or comfortable) level. Or, in the case when there isn't sufficient recovery time provided to the organism, even if the impulse itself is handled well. This stress is not really used for an improvement of the organism, but instead it builds up as some form of toxic substances within the body, or it can manifest as the lack of useful (energy) substances in the body.

Now here, we really talk about quite negative consequences of the stress response. Those can be recognizable on physical level, as well as on the perception level. It's roughly summarized in the flow diagram bellow:

Noise, heat, infection, isolation, aggression, and many more other factors persisting in the experience of the individual, can lead into some sort of negative long-term consequences of the stress response. Concrete physical symptoms then follow, for example the memory loss, the rapid (unhealthy) weight loss, ulcers, heart diseases, loss of sexual function, and many many others.

DISSECTION OF STRESS RESPONSE:

Once we have cleared the function of it, and the differences between long-term and short-term, we can now go deeper into many particular changes within the body. For easier grasping of so many processes, I created a simple list of direct physical and/or chemical processes that follow immediate stress response. In brackets, I present the particular hormone, which is responsible for that particular physical response - even if only in those cases (of course) where it can be determined. So simply put, the stress response causes:

- increased heart rate (adrenalin)
- increased blood pressure (noradrenalin)
- decreased pain sensitivity (endorphines)
- stopped/slowed down the activity of digestive system (cortisol)
- stopped/slowed down the activity of reproductive system (cortisol)
- alerted mind (adrenalin)
- enriched blood with:
    a) glucose  (glucagon)
    b) fatty acids (cortisol)
- started up/kicked in of the immune system (ACTH)
- started up the proliferation (building up) of T-cells
- inhibited production of GH (growth hormone)
- stimulated release of CRH from hypothalamus into blood
- stimulated anterior pituitary to release ACTH
- stimulated cortisol synthesizing from cholesterol in adrenal cortex
- increased carbohydrate metabolism (glucagon, cortisol)
- stopped/slowed down the tissue repair (less GH)
- increased rate of blood circulation (adrenalin+noradrenalin)
- enhanced memory formation (adrenalin)
- increased signalling of sympathetic part of nervous system
- suppressed signalling of parasympathetic part of nervous system
- prepared body to deal with challenges (adrenalin)
- inhibited inflammatory response (cortisol)
- suppressed stomach activity
- reduced secretion of digestive acids
- decreased blood flow to the walls of the stomach
- slowed down epithelial cell replacement in the gut
- reduced thickness of mucous membrane in the gut
- reduced production of reproductive hormones
- loss of sexual desire (less testosterone)
- disruption of sexual performance (less testosterone)
- enhanced brain activity - agility - learning
- more relaxed lung muscles - prepared for more oxygen getting in
- increased volume of lungs / their effectiveness