I don't think this is on the DAT but I was just wondering, does anyone know what happens to the ion concentration of blood during dehydration? I know that you excrete concentrated urine (but can that tell you anything about ion concentration in the blood? My thinking is that, because you have less water in your blood you have higher ion concentration in your blood but I don't know if that's the right understanding/logic. Thanks!
Dehyrdation
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You are correct, during dehydration your ion concentration increases, which leads to an increase in osmolarity. This is detected by osmoreceptors, which signal the hypothalamus to release ADH/vasopressin, which causes water reabsorption in nephrons (hence the concentrated urine that you mentioned). The kidneys (juxta glomerular apparatus) also respond to changes in osmolarity and release Renin when osmolarity is high, which forms angiotensin I, which is converted into angiotensin II by ACE, and you ultimately get aldosterone released from adrenal cortex.
However, usually this is not enough to bring osmolarity back to normal levels, that's why you have thirst sensation induced in hypothalamus also.
Make sure you know the Renin-Angiotensin system well.
However, usually this is not enough to bring osmolarity back to normal levels, that's why you have thirst sensation induced in hypothalamus also.
Make sure you know the Renin-Angiotensin system well.