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Water and Electrolytes
Water and Electrolytes in Health / Homeostasis

You may wonder why we have a section devoted to water. After all, water is well.. merely water.. We tend to take this liquid for granted, not realising the importance it has to our survival. Water covers nearly three-quarters of the earth's surface, and it is no surprise that we were made with it and to be dependant on it. We are full of water ! Each cell in our body is filled with roughly 75% water. Most of the chemical reactions in our body are dependant on water. These essential chemical reactions either need water as a reactant, or as a solvent. Let's begin our discussion of water by elaborating on its chemical and physical attributes in relation to our health.

Osmosis

All types of substances flow through the membranes of cells. This, of course, is needed in order for nutrients to pass into cells, and waste products to be excreted from the cell. Water is the substance in greatest abundance to pass through cells. Water, like other substances, has to pass through a cell membrane in order to get inside a cell. The cell membrane acts as a selectively permeable barrier for passage into and out of the cell. If this selective membrane didn't exist, or work properly, substances would move uninhibited, through the cell, damaging the cell, or causing cell death. Although the cell membrane selects what can enter and leave a cell, there is another force that plays a role in movement in and out of cells. This is called osmosis.

Osmosis is the movement of fluid through a semipermeable membrane. This is an important regulator of water movement for the cell. To make osmosis more understandable, let's look at the figure below.


Osmosis is action. this U-shaped tube has a semipermeable membrane in its middle. By semipermeable, we mean that water can pass through in either direction, but the solute cannot. The solute, which in this case is salt, is added on the left side of the membrane. As we can see, the water level rises on the side of the salt, demonstrating osmosis.

From the illustration above we can see the process of osmosis in action. Water can pass either way through the membrane, but salt cannot. Therefore, no matter what side we would have added the salt, the water level would have risen. This is because water will accumulate where there is salt. Salt in a respect, is an attractant for water. In more exact terms, the water molecules bounce off of the salt ions and molecules, keeping them on the "salted" side for a longer period of time. As a water level rises on the side of the added solute.

Osmosis occurs in cells as well. With their selectively permeable membranes, they can keep solutes such as salt inside the cell in varying concentrations. If a cell allows a certain amount of NaCl (salt) to pass through its membrane, then the water pressure inside the cell will rise. This is osmosis in action. If we look at the illustration below, we can see that osmosis in the cell occurs the same way as in the demonstration in the tube. An overall net movement of water occurs towards the side of the membrane with the solute, as shown below.

Osmosis in the cell. Water moves from the extracellular environment to the intracellular (inside the cell) space. The net water movement is due to the salt concentration. This is used to regulate pressure inside of the cell.

The salt concentration inside the cell is regulated by dedicated pumps in the membrane. These pumps contribute to the selectiveness of the cell membrane. These pumps, called sodium-potassium pumps are a protective mechanism for the cell. Otherwise, salts and water would travel in and out of the cell unimpeded causing irreversible damage to the cell.

Applications of water to health and disease


Hypertension
From this discussion, we can apply this logic in understanding the body's attempt on strict control of salt intake. Since increased amounts of salt can cause water accumulation, blood pressure can be significantly affected. Since blood is water, with cells, proteins and ions in suspension, increased amounts of salt can cause increased blood volumes (increase in the water portion of the blood). An increase in the amount of blood in a closed space (the vessels that hold it) puts a greater pressure on the blood vessel walls. The pressure of blood against the blood vessel wall is called blood pressure. When this measurement increases over the norm, we refer to this as hypertension. Hypertension for brief periods does not cause any significant problems, provided there are not any existing cardiovascular anomalies. Long term hypertension causes defects in the the blood vessel walls through the damage from the increased pressure on them. Since damaged blood vessel walls have defects in them, they become "sticky" to other substances such as cholesterol, fats, sugars and perhaps other substances. This is the start of vessel-occluding process of arteriosclerosis. Increased pressure of blood against vessel walls can also stretch the wall, and perhaps rupture it. An aneurism is the balloon-like dilated blood vessel which results from increased pressure on it. Think of it, like a bleb in a garden hose, which may stretch or balloon. If the vessel ruptures, resulting in blood leakage then it is a ruptured aneurism. If this occurs in the brain, it is referred to as a stroke, of CVA (cerebral vascular accident). Hypertension also makes the heart's work more difficult. Increases in blood pressure, mean that the heart must pump harder to actually pump the blood effectively. This is because increases in blood pressure, mean that the blood rubs against the vessel walls with more friction. This "pressed" blood is obviously more difficult to pump. Over the years, the heart of the hypertensive individual increases in size (muscular size). This increase in size because of hypertension is different than the increase in size and strength due to athletics, and is harmful. The hypertensive heart has an increased chances of developing myocardial infarctions (heart attacks) and other complications.



Learn more water and ELECTROLYTES

Water and Electrolyte - Intakes and Requirements

Sodium

Chloride

Potassium



Is there anything else I can do on my own to help low CSF volumes?
Review this with your doctor - but adequate fluid intake sometimes helps, along with proper nutrition - since Cerebrospinal Fluid is a filtrate of the blood, higher water intakes accordingly increasse blood volume - the theory here is that this will cause CSF production to increase.

also, see water and electrolytes

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