Introduction
Thirst is essential in maintaining body fluid homeostasis and may cause deficits in intracellular or extracellular fluid volume. It is a subjective perception that urges individuals to drink fluids. It is crucial for the survival of an individual. When the body loses water, it may be depleted from both extracellular and intracellular compartments. The amount of water lost from both compartments may not always be equal. Hence it is vital to maintain fluid levels for the proper functioning of the cells.
How Is Water Balance Regulated?
When an individual consumes food, the salivary gland secretes saliva, which helps to break down the food and passes it to the stomach, where gastric juices act upon it. Then the food enters the small intestine, where the pancreatic juice is secreted. All the mentioned fluids contain large quantities of water. Generally, about ten liters of water get exchanged. This process of water exchange within the body is called osmoregulation. The main aim of osmoregulation is to balance the water output with the water input.
The total water output per day averages approximately 0.6 gallons, and the tissues produce about 0.07 gallons of water through metabolic processes. The adequate intake of water for adult males is 0.97 gallons and 0.71 gallons for females. There is still a debate about the amount of water to be consumed per day. The amount of water to be consumed varies according to the climate change body requirements.
What Is the Process of Water Movement and Storage in the Body?
While consuming water, it is extracted through the food being digested and travels through the body via the process called osmosis. It usually takes place when the water is absorbed via semi-permeable membranes of the cells and tissues. It means the water can pass to a certain extent based on the size of the substance. If the water concentration is higher in one location, it gets transferred to another area with a lower concentration.
Generally, water gets stored in the body in spaces referred to as compartments. The compartments are separated and closed off to provide barriers based on their structure. The three compartments where the water in the body gets stored are:
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Intracellular fluid.
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Extracellular fluid.
Intracellular fluid usually holds water in the cells, which is held by the plasma membrane. Around 60 percent of the fluids inside the human body are held in these compartments. Excess storage of water within the cells can cause the cells to burst eventually, and too less water can have a negative impact on the body's functions and may cause the cells to shrink.
The plasma makes a smaller portion for fluid storage in the body, which accounts for 15 to 20 percent of extracellular fluids. Plasma usually travels around the body to deliver proteins and nutrients. It also aids in the removal of waste products from the body.
The extracellular compartment is made of plasma and other fluids in the body. It is also known as interstitial fluid, which surrounds the cells and fills the space between tissues and blood vessels. It holds an enormous responsibility in blood clotting and wound healing. Another portion of extracellular fluid is the cerebrospinal fluid. This fluid surrounds the joints and lymph. In addition it also fills the sac that houses major organs like the lungs and heart.
What Is the Thirst Mechanism?
It is an osmoregulatory response to increase the water input in the body. It is activated to change the water volume in the blood. But it is generally driven by sodium actions in the body. The urge to drink is a result of complex interactions of hormones and is caused by neuronal responses that increase water input and contribute towards fluid balance and composition. The thirst center is situated in the hypothalamus, which is the portion of the brain just above the brainstem. In older individuals, the thirst mechanism is not very responsive. With aging, there is a higher risk of dehydration. The following physiological events increase the urge to consume fluids:
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The receptor protein in the kidney and heart identify the decreased fluid volume or increased sodium concentration in the blood.
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These messages are relayed to the brain’s thirst center in the hypothalamus.
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The hypothalamus sends neural signals to higher areas of the brain and stimulates the conscious thought to drink.
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After the fluids are consumed, the receptors in the mouth and stomach detect the mechanical movement of fluid for ingestion.
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The neural signals are sent to the brain, and then the thirst mechanism is shut off. The control of thirst is usually a backup mechanism to increase water input. Fluid intake is controlled by conscious eating and drinking habits.
How Is Daily Water Output Regulated?
There are two types of output: one is insensible water loss, and the other is sensible water loss. In insensible water loss, the body loses about 0.10 gallons of water through exhalation and another 0.13 gallons through the skin. The second type, which is sensible water loss, is the loss of water through urine and feces, which accounts for about 0.39 gallons a day. The primary function of the kidneys is to regulate urine output.
What Causes Hormonal Control of Thirst and Hydration?
There is a communication pathway between the release and retention of water. This communication depends on the body’s current blood pressure, blood volume, and plasma concentration. Certain hormones like aldosterone and antidiuretic hormones contribute majorly to this process.
Every day, there is a loss of body fluids by the body via urination, perspiration, and excretion. The body tries to maintain a homeostatic state to ensure the optimal functioning of cells. They maintain the water balance when an individual feels thirsty and is urged to consume fluids. In case of consuming excess water, the kidneys pass them out from the body in the form of urine.
Conclusion
Water is essential to stay hydrated and ensure the proper functioning of each and every cell in the body. The urge to consume water is induced by thirst, which is the body’s natural way of communicating with the brain to indicate fluid loss. This is regulated by various hormones like aldosterone and antidiuretic hormone that aid with water retention.
