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→Mechanisms of fluid balance
==== Mechanisms of fluid balance ====
==== Mechanisms of fluid balance ====
*Osmosis is the primary means of water movement between intracellular fluid and interstitial fluid, the concentration of solutes in these fluids determines the direction of water movement. Because most solutes in body fluids are electrolytes, inorganic compounds that dissociate into ions, fluid balance is closely related to electrolyte balance. Because intake of water and electrolytes rarely occurs in exactly the same proportions as their presence in body fluids, the ability of the kidneys to excrete excess water by producing dilute urine, or to excrete excess electrolytes by producing concentrated urine, is of utmost importance in the maintenance of homeostasis. ''Sama anayati iti samanam'' is the definition of ''samana vayu''. ''Samana'' has a seat in ''sweda, dosha'' and ''ambhuvaha srotas''. As discussed above maintaining the pH (''sami karoti'') is brought about by specific ionic movement and this particular force is provided by ''samana vayu''. It maintains the pH by maintaining a specific ratio of solutes and solvents and if this specific ratio is disturbed it leads to various diseases for e.g. a decrease in blood volume causes blood pressure to fall. This change stimulates the kidneys to release renin, which promotes the formation of angiotensin II. Increased nerve impulses from osmo-receptors in the hypothalamus, triggered by increased blood osmolarity, and increased angiotensin II in the blood both stimulate the thirst center in the hypothalamus. Other signals that stimulate thirst come from (1) neurons in the mouth that detect dryness due to a decreased flow of saliva and (2) baroreceptors that detect lowered blood pressure in the heart and blood vessels. As a result, the sensation of thirst increases, which usually leads to increased fluid intake (if fluids are available) and restoration of normal fluid volume. Overall, fluid gain balances fluid loss. Sometimes, however, the sensation of thirst does not occur quickly enough or access to fluids is restricted, and significant dehydration ensues. This happens most often in elderly people, in infants, and in those who are in a confused mental state. Even though the loss of water and solutes through sweating and exhalation increases during exercise, elimination of excess body water or solutes occurs mainly by control of their loss in urine.
*The extent of urinary salt (NaCl) loss is the main factor that determines body fluid volume. The reason for this is that “water follows solutes” in osmosis, and the two main solutes in extracellular fluid (and in urine) are sodium ions (Na) and chloride ions (Cl). In a similar way, the main factor that determines body fluid osmolarity is the extent of urinary water loss. Because our daily diet contains a highly variable amount of NaCl, urinary excretion of Na and Cl must also vary to maintain homeostasis. Hormonal changes regulate the urinary loss of these ions, which in turn affects blood volume. The increased intake of NaCl produces an increase in plasma levels of Na and Cl (the major contributors to osmolarity of extracellular fluid). As a result, the osmolarity of interstitial fluid increases, which causes movement of water from intracellular fluid into interstitial fluid and then into plasma. Such water movement increases blood volume.
*Water balance and electrolyte balance are closely linked. The body works to keep the total amount of water and the levels of electrolytes in the blood constant. For example, when the sodium level becomes too high, thirst develops, leading to an increased intake of fluids. In addition, vasopressin (also called antidiuretic hormone), a hormone secreted by the brain in response to dehydration, causes the kidneys to excrete less water. The combined effect is an increased amount of water in the blood. As a result, sodium is diluted and the balance of sodium and water is restored. When the sodium level becomes too low, the kidneys excrete more water, which decreases the amount of water in the blood, again restoring the balance. Water flows passively (by osmosis) from one area or compartment of the body to another. This passive flow allows the larger volumes of fluid in the cells and the area around the cells to act as reservoirs to protect the more critical but smaller volume of fluid in the blood vessels from dehydration.
*Function of ''samana vayu'' needs to be understood. ''Sweda dosha ambuvaha srotas'' is the seat for ''samana vayu''. Maintaining the balance is the function of ''samana vayu'' and it is brought about by ''grahanati'' (to retain food until digested), ''pachati'' (to digest) , ''vivechayati'' (differentiating between waste and useful product) and ''munchati'' (to release waste to ''apana'') action. ''Samana vayu'' is vital for organisms to be able to maintain their fluid levels in very narrow ranges. One set of receptors responsible for thirst detects the concentration of interstitial fluid. The other set of receptors detects blood volume. Arterial baroreceptors sense a decreased arterial pressure, and signal to the central nervous system in the area postrema and nucleus tractus solitarii. Cardiopulmonary receptors sense a decreased blood volume, and signal to area postrema and nucleus tractus solitarii as well. This explains the function of ''srotas sthita maruta'' (''vyana vayu'') and ''mana'' due to its ''satva guna'' helps in getting knowledge about the surrounding.
*Osmometric thirst occurs when the solute concentration of the interstitial fluid increases. This increase draws water out of the cells, and they shrink in volume. The solute concentration of the interstitial fluid increases by high intake of sodium in diet or by the drop in volume of extracellular fluids (such as blood plasma and cerebrospinal fluid) due to loss of water through perspiration, respiration, urination and defecation. The increase in interstitial fluid solute concentration causes water to migrate from the cells of the body, through their membranes, to the extracellular compartment, by osmosis, thus causing cellular dehydration.
The above mechanisms are disturbed in trishna.
The above mechanisms are disturbed in ''trishna''.
Etiopathogenesis of trishna:
In morbid thirst, vata and pitta dosha are predominately involved. Etiological factors aggravate either vata, pitta or both and manifest trishna. Both dosha have absorbent (soshaka) property, vata dosha by its drying property and pitta by its heating property. Therefore excess exposure to various factors in diet and lifestyles leading to dryness and heat inside the body are considered as causative factors for trishna. Some of the commonly observed factors are enlisted below:
==== Etiopathogenesis of ''trishna'' ====
In morbid thirst, ''vata'' and ''pitta dosha'' are predominately involved. Etiological factors aggravate either ''vata, pitta'' or both and manifest ''trishna''. Both ''dosha'' have absorbent (''soshaka'') property, ''vata dosha'' by its drying property and ''pitta'' by its heating property. Therefore excess exposure to various factors in diet and lifestyles leading to dryness and heat inside the body are considered as causative factors for ''trishna''. Some of the commonly observed factors are enlisted below:
*'''Dietary causes''': Regular use of alkaline & sour substances, use of excessive salt, pungent, salty, dry and dehydrated food, extreme starvation, alcoholism
*'''Lifestyle causes''': Excess exercise (Cha.Su.7/33), excess distress, excessive exposure to sunlight, fatigue.
*'''Psychological causes''': Fear, grief, anger
*'''Iatrogenic causes''': Excessive use of purification procedures, improper ''snehapana'' (administration of therapeutic medicated ghee or similar unctuous substance) (Cha.Su.13/71)
*Due to chronic diseases leading to emaciation and excessive loss of basic body forming elements
*Associated symptom of diseases like ''shotha'' (Cha.Su.18/18), ''pitta'' dominant ''gulma'' (Cha.Chi.5/36), ''vrana'' (Cha.Chi.25/30), ''udavarta'' (Cha.Chi.26/9), prameha (Cha.Ni.4/48), kushtha (Cha.Ni.5/11), antarvega jwara (Cha.Chi.3/39), Bahirvegi jwara (Cha.Chi.3/41), rakta dhatugata jwara(Cha.Chi.3/77) , vata pitta jwara (Cha.Chi.3/85), shleshma-paittika jwara (Cha.Chi.3/88), pitta kapholvana hina vata sannipata jwara(Cha.Chi.3/93) , vatolvana kapha pitta hina sannipata jwara (Cha.Chi.3/94), pittolvana madhya kapha hina vata jwara (Cha.Chi.3/98), sama sannipata jwara(Cha.Chi.3/102), pittolvana vata madhya kapha hina jwara(Cha.Chi.3/106), pachyamana jwara (Cha.Chi.3/136), romantika (Cha.Chi.12/92), pittodara (Cha.Chi.13 /28), badhagudodara (Cha.Chi.13 /41 ),chhidrodara (Cha.Chi.13 /44), sahaja arsha (Cha.Chi.14 8/), paittika ajirna (Cha.Chi.15/46), grahani (Cha.Chi.15 /53),vataja grahani (Cha.Chi.15/ 61),paittika pandu (Cha.Chi.16 /20), halimaka (Cha.Chi.16/ 133),vyapeta hikka (Cha.Chi.17 /32), paittika kasa (Cha.Chi.18 /15), kshataja kasa (Cha.Chi.18/ 23), paittika atisara (Cha.Chi. 19/6),raktatisara (Cha.Chi.19 /70), sannitpatika chhardi (Cha.Chi. 20/15), abhyantara visarpa (Cha.Chi.21 /16), paittika visarpa (Cha.Chi. 21/32),vata-paittika visarpa (Cha.Chi.21 /36),paittika madatyaya (Cha.Chi. 24/94), madatyaya general symptom (Cha.Chi.24/101), tikshna madatyaya (Cha.Chi. 24/113),vikshaya (Cha.Chi.24/ 102),paittika vrana (Cha.Chi. 25/13), paittika mukharoga (Cha.Chi.26/ 120),pittavrita vayu (Cha.Chi.28 /61), paittika vatarakta (Cha.Chi.29/ 28), dhvaja bhanga (Cha.Chi. 30/171), paittika shiroroga (Cha. Su.17/23), paittika hridroga (Cha.su.17 /33), vata-kapha kshaya pitta vriddhi (Cha.su.17 /60), alaji (Cha.su.17/88),vata-pittajanya vidradhi (Cha.su.17/ 96 ), pitta nanatmaja vikara (Cha.su.20 /14 ), ambuvaha sroto dushti (Cha. Vi.5 /11),paittika jwara (Cha.Ni.1/24).
• Complication (upasarga) of diseases like jwara, meha, kshaya, shosha, shwasa (Cha.22/17)
• Complication (upasarga) of diseases like jwara, meha, kshaya, shosha, shwasa (Cha.22/17)
General pathogenesis:
General pathogenesis: