What is Isotonic Solution?
An isotonic solution is any external solution that has the same solute concentration and water concentration compared to body fluids. In an isotonic solution, no net movement of water will take place.
Isotonic solution is the name given to a solution that compares with another with the same osmotic pressure, or solute concentration, between two sides of a semi-permeable membrane.
This state allows the free movement of water molecules across the membrane without changing the concentration of solutes on either side of the membrane, even though the water is moving in both directions.
In biology, some living cells must be maintained in a constant environment of isotonic solution to facilitate cell functions. At this time, the new cell wall is stable, maintaining its structural shape, protecting the internal organelles and acting as a semi-permeable membrane, helping the cell exchange water with the external environment.
Based on this principle, the plasma surrounding the blood cells is an ideal isotonic solution, allowing the cells to move water and nutrient molecules in and out of the cells. This is a necessary condition for blood cells to carry out their function of delivering oxygen and nutrients to other parts of the body.
If the cells are in the environment of a hypertonic solution, water from the inside of the cell will be lost to the outside, and the cells will shrink and become exhausted. Conversely, if cells are in a hypotonic solution, water from outside the cell will rush inside, the cell will swell and burst.
In medicine, when a large amount of fluid is lost from the body, for whatever reason, the fluid of first choice for resuscitation is an isotonic solution relative to blood.
Fluids can be rapidly administered via intravenous infusion, both restoring effective circulating volume and re-establishing a relatively equilibrium plasma environment without damaging the cell walls.
Importance of Isotonic Solution
It is a solution where two solutions that are thrown apart by a semipermeable membrane have an equal concentration of the solute and the water as well.
Let say we are in a party and there is an equal number of guests in the living room and the same in the kitchen.
You have such space that you can move there easily. You have equal reach for the food. This party is similar to an isotonic solution. Here everything is equal from room to room.
Medical use of Isotonic solutions
- Oral Rehydration Therapy uses the isotonic solution for electrolyte supplementation and maintenance of hydration in cases like enteritis, diarrhea, etc.
- Saline treatment for treating extreme dehydration and hypernatremia (a condition wherein the serum concentration of sodium is increased).
- Saline solution is used as a vehicle for parenteral, especially intravenous, administration of drugs as saline solution and blood plasma are isotonic.
- Lactated Ringer’s solution and Hartmann’s solution are isotonic with blood plasma and used for the treatment of hypovolemia (blood volume is reduced may be due to injury or any other reason) and acidosis (blood acidity increases).
- Saline solution is used for treating rhinosinusitis.
- Saline solution is used as a vehicle for drugs that are to be administered via nebulization.
- For ophthalmic disorders
Non-Medical use of isotonic solutions
- Sports drinks for providing hydration and electrolyte supplementation
- Phosphate buffer saline is also used as a vehicle for maintaining cell cultures during experimentation
Example of Isotonic Solution
1. Alcohol Proof
We know that a shot of beer produces fewer effects on us. Whereas, a shot of whiskey causes less effect on us. This happens because the amount of whiskey in alcohol is more than that in the beer.
Scientifically, whiskey has more ethanol. It is the molecule that is responsible for the effect of alcohol in comparison to beer.
2. Relieving Dehydration
A saline solution contains water mixed with sodium chloride i.e. NaCl. Saline solutions are useful in the hospital. Useful for patients experiencing severe dehydration.
However, it is also useful for patients suffering from the problem of fluid intake through traditional consumption.
Moreover, unlike hypertonic and hypotonic saline solutions, these solutions have the same concentration of NaCl as a cellular fluid in the body of a human being.
3. Exercises
Whenever a physical activity is isotonic, it consists of a lifting phase and a lowering phase as well. On the other hand, isotonic muscles have a similar tone of muscle.
The bicep curl is an isotonic activity. It involves raising and lowering the arm. It is done for the building of the muscles.
However, they may not contribute to these muscles. This is because the person that is performing this exercise may focus more on the left or the right bicep.
Isotonic Muscle Contraction
Isotonic contraction definition: In physiology, when the muscles change in length of the muscles resulting in a movement without a change in the muscle tension then this movement of the muscle is known as isotonic muscle contraction (Isotonic meaning-‘iso’ means same; ‘tone’ means tension).
On the other hand, muscles can cause a change in the muscle tension without a change in the muscle dimension or movement via isometric muscle contractions (Isometric meaning-‘iso’ means same; ‘metric’ means length).
These contractions are commonly seen in the muscles responsible for grip in the hand and forearm.
Isotonic muscle contraction can be further subdivided into:
Concentric contractions
During this contraction, the muscles shorten to generate force to overcome resistance. For eg: Weight lifting towards the shoulders involves concentric muscle contractions.
Eccentric contractions
During this contraction, the muscles increase in length to generate force to overcome resistance. These contractions can be voluntary as well as non-voluntary.
Isotonic exercise definition
Exercises that involve a lifting phase and a lowering phase is considered to be isotonic exercises, like bicep curls and push-ups. Bicep curls involve raising the arm and lowering it while push-up exercise involves raising the body and lowering it in a plank position.
Here, it is important to understand that isotonic muscles will exhibit the same muscle tone. Hence, isotonic exercise may not result from isotonic muscles.
For example, in bicep curls, a person may exert more unequal focus on the right or left biceps thus resulting in non-isotonic muscles. On the contrary, in the push-ups both the sides of the body work equally, and hence they result from isotonic muscles.