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 ! 

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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.

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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.

Ode to the water - the life giving fluid

This post is a collection of arguments about why is the water so important for life, health, beauty, and many other things. So let's start with the starters. The water is a medium in which nearly all chemical reactions of the body occur. It's essential to health and life, mainly because of the ability to form solutions and suspensions. Because it participate as both the reactant and the product, it is really the ideal medium for metabolic reactions inside the body.

When it comes to heat, the water can absorb or release a large amount of it with only a modest change of its own temperature. A characteristic that's called the high heat capacity. Plus the water is a major part of mucus and other lubricating fluids in the body. Let me name just a few of them: saliva, blood, milk, lymph, urine, bile, semen, sweat, tears, vaginal fluids, digestive juices, cerebrospinal fluid in your spine, and synovial fluid in your joints.

Now some more technical details of the body:

For the newborn, the water content of the body is about 75%. This will get down to about 55-60% by the second year of life, and stays roughly the same for the rest of the life. Otherwise, the adipose (fat) tissue is the only tissue in body without the water in it, so fatter people has logically less proportion of water in the body than lean people.

The kidneys are the organs that take care of filtrating the blood. Each day, they filtrate about 150 litres of it in women, and about 180 litres in men. That is about 65 times the whole volume of the blood in the body, even if  99% of it goes back to the bloodstream. Which redirects the rest of  1-2% into the urine, making about 1-2 litres of urine every day.

Mass of the kidneys is changing with the age as well, so for 20 years old person it weight about 260g, but in 80 years old person, it weights only about 200g. And the filtration rate decline by 50% between ages 40-70 too. Speaking of filtration rate, it is the quickness by which kidneys can filtrate, and it is 125 ml per minute for men, and 105 ml per minute for women.

Think of it as something over one liter in about 10 minutes. That brings me to my first flow diagram, which describe the situation, where you would about to drink one liter of water, and wait less than 10 minutes, and keep on drinking. The state that your body is going to get in is called the water intoxication.

To understand this flow diagram, it's good to mention one important rule: "The water follows the salt (NaCl), and the salt follows the water". Or in other words: "Where the salt goes, the water follows". So in the first stage sweating, vomiting, and diarrhea support the loss of the salt from the body. Moreover, any further drinking the plain water, is another factor contributing to that loss. This results in the decrease of Na concentration in the plasma (liquid portion of blood), and interstitial fluid, which is the fluid in the space outside of cells (or between cells if you like).


Decreased osmolarity means that because there is less salt, then there has to be less water as well (in the same space). So then cells compensate this event by taking up the water inside of them through the process called osmosis, and they become swelled. The state of swelled cells is basically defined as the water intoxication. If the intake of water was too large at the beginning, or it is continuing, then the convulsions, coma, and possible death can occur.


Water and the sea

Now, let's go back in the evolution and make clear about how really important the water is. By the definition, most of the life forms share the marine origin, meaning that all life basically comes from the sea. Moreover, the conditions inside of cells of most organisms living on the planet, are remarkably uniform.

Or, to put it another way, the fluids inside the most of our cells have the concentration of salt highly comparable with the salt water in the sea. Because the ocean presents itself as the very stable environment for development of organisms, those organisms living outside of the sea are quite sensitive to even slight changes in the salt concentration within their cells.

Basically, the biggest problem of any organism living outside the ocean, is to maintain this salt concentration inside of cells, which is achieved only by regular intake of water and salt. Ideally, the sea salt of course. Technically, kidneys can function on as little as 0.5 litre of water for a day or so, which they keep circulating over and over. By the end of the day, however, the urine can be as much as 1000 times more acidic than the blood.

Also, the fluid balance depends highly on electrolyte balance. Electrolytes are minerals, or inorganic compounds, which dissociate into ions - atoms, molecules, or compounds with the positive or negative charge. So the regular intake of those electrolytes with the water is essential, because normally, the water loss equals the water gain during the day. This way the body fluid volume remains constant and stable. The flow diagram bellow shows clearly how the body deals with the differences in input and output of the water during the day.

Generally, the recommended intake of water is about 1 liter for every 1000 calories of solid food. So it would mean that for recommended 2500 calories a day, you need to drink about two and half of liters of water. I know I'm getting my fair share of water everyday, and especially during the exercise, where you lose additional water through sweating and increased metabolic rate of the body. That increase can be even up to 20 times higher than the metabolic rate of the body during the rest. Along with up to 20 times higher of the oxygen consumption, but that's another topic for another post.

ADH negative feedback

And just as I promised to you in my last post, I'm bringing here nice flow diagram that very nicely explains how the body regulates the amount of water in the blood and therefore the body itself. It comes from GCSE book on Human biology (Letts, 1994).  The diagram is pretty much self explanatory, so I don't have to say very much about it.

Maybe only that on the most left and most right sides of the picture the text says: "Norm with just the right amount of water". It's the same text on both sides. Just wanted to make sure that you know, because it came out a bit blurry on sides. Otherwise, the picture describe so-called negative feedback loop. It's called negative because it negates any too big alteration from the constant norm level of certain molecule or hormone in the blood. If it goes too up, something happen to make it go down, and vice versa.

In this case, ADH goes up when body's reserves of water are going short, and no new water is getting into system. ADH means anti-diuretic hormone, which could be translated that it goes against of(anti) the loss of water in the urine (diuretic). That happens the way that kidney increases the process of reabsorbtion to the level that is needed, in order to save the water that is already in the system (or in this case in the blood). When ADH goes down, kidney decrease reabsorbtion of water, so more of the water in the blood end up in the urine.

The content of water in the body is controlled by Hypothalamus. This very small part of the brain regulates the content of the water by measuring the osmolarity of the blood. Osmolarity could be simply described as the amount of dissolved particles in the water. It can be solid particles or gases. To give you a clearer picture, imagine two pint glasses of water. One would be filled by pure water and in the other, there will be a lots of salt, sugar, or some other stuff in it. So the difference between those two pints would be the amount of empty space between water molecules, despite of the same volume, or even the mass of the content in the pint glass.

Now, once the Hypothalamus detect the change in the osmolarity in the blood (up or down), it signals the pituitary gland to secret more or less of ADH hormone. This hormone then travels by blood into kidneys, and those interpret it as the signal to reabsorb more or less water, respectively. The mechanism by which this is done, is the inserting the special proteins called aquaporins into the cell membranes. Those proteins work as a channel for the water to be able to cross the membrane, as the name itself suggest - the pore for the water. The more aquaporins, the more water is reabsorbed. So the less ADH hormone means less aquaporins, which means less water reabsorbed and let go into the urine. Simple as that. 

Introduction

Hello everyone who is into any information about the human body. Be it a biochemistry, human biology, or physiology, flow diagrams are here to interpret some very complex information flow within our bodies in the simplest possible terms. As the saying goes, seeing once is better than hearing a hundred times, I found flow diagrams very useful tools for remembering things I want to remember, and understand the thing I want to understand.

 

Because human body is so complex and delicate at the same time, informations about it could be seen as layered into many dimensions. So many flow diagrams are here trying to reflect as many of those dimensions working together, and plus present the picture that shows links between them. For example, some flow diagrams are purely about endocrine system (or hormones), some purely about nervous system (or nerves). But some are about interconnected cooperation of those systems, and that's where it starts to be interesting.

 

Seeing a bigger picture is very important, as it gives a many ideas about connections between different parts of body. So here in this blog, I'll try to collect and comment many of those flow diagrams I found across various literature and internet. This blog is the result of my dedication to pursuing the understanding of many complex processes that are happening inside us. I only hope that you will find useful my explanations along with those diagrams. I'll try go as simple as possible, as the basics are usually most important, so every new or seemingly complicated term will be explained in simple laymen terms.

So how would you translate for your self the human body flow diagram mania? It doesn't have to be necessarily a set of flow diagrams about human body, like you found plenty in biochemistry books. But rather see it as a collection of diagrams concerning human body, which represents flow of molecules, substances, time, energy, information (you name it) in the human body. As I said, the bigger picture must be seen, and that's my motto, so here is the flow diagram to illustrate my point.

 



 This flow diagram basically represents the biggest picture possible. The ultimate structure of reality or the existence, mainly on the planet earth, but possibly not only here. Technically, all is composed with very small parts called atoms, even if those has its component too - protons, neutrons, and electrons. Either two or more atoms put together create so-called inorganic molecules, or commonly called inorganic compounds.

 

By the definition, those are very small, with very simple structure, and not containing the carbon atom. The only two exceptions are carbon dioxide, and bicarbonate ion, which contain carbon, but are still classified as inorganic - mainly due to simple structure. Other examples are water, salts, bases, acids, and separate ions called electrolytes. In the body, there's about 55-60% water, and 1-2% of all other inorganic molecules.

 

Once a lots of those are put together, the organic molecule is created. Those are big, complex, and contain carbon, or a lots of carbon atoms. The resting 40% of the body is built with those organic molecules. Types of those are carbohydrates, lipids, proteins, nucleic acids (building blocks of DNA), and ATP - the energy molecule of the body.

 

So once those already big and complex organic compounds (or molecules) start to react with each other, even bigger molecules are created. If big enough to start fulfilling some particular function, they become an organelles - like mitochondria, nucleus, ribosome, lysosome, plasma membranes, centrosomes, etc, etc. Those are the functional parts of the cells, the building units of every living organism.

 

On cellular level there is about 200 different types of cells in the body. Those close to each other, and with similar (or the same) function group together and make a functional unit called the tissue. Different tissues which are working on the same basic function create an organ, and different organs working on the same basic function create a system.

 

Altogether 12 systems in the body make the whole organism, in our case, the human body. Two basic types of body (male and female) can create a so-called breeding pair, and bring about another organism into the existence. This way populations are created leading to represent certain species, differenciating themselves from many other species on the planet. So that would be the flow diagram above put into the words.

 

Levels of structural organization

 

Still there is a number of dimensions within an organism, or human body, which I'd like to list nicely from the smallest to the biggest:

 

1. chemical level - atoms and molecules (e.g. water, oxygen, protein, ...)

2. cellular level - different types of cells (nerve, sperm, muscle, goblet, ...)

3. tissue level - different types of tissues (adipose, bone, connective, ...)

4. organ level - different types of organs (heart, brain, kidney, spleen, ...)

5. system level - 12 different systems (skeletal, digestive, urinary, ...)

6. organismal level - whole human body, or some other organism