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Concentrations of many ions are also regulated by hormones.
Homeostatic mechanisms work to maintain the concentration of salt in water (about 70% of body weight) and blood pressure. This is done in a variety of ways including active, coupled, and passive transport of water and solutes across cell membranes, and control of smooth muscle fibers in the walls of blood vessels. The osmoregulatory organs (e.g. kidney and G.I. tract) function independently under constant conditions. Blood pressure can vary as a function of activity and osmoregulatory state. Constant environmental conditions rarely prevail for long and osmoregulatory/blood pressure adjustments are inevitable from time to time. Water is lost through the skin and respiratory tract (especially in hot and arid climates). In addition sweat glands lose both water and salt. Water and salt are voided in urine. Some must be voided to assist excretion of wastes (e.g. urea). Excess water and salt are also voided this way. At intervals, considerable losses may be incurred during parturition or hemorrhage. These deficits are made up by feeding and drinking. Salt and water are replenished through the G.I. tract and can be retained by the kidney. Blood pressure is directly regulated by the heart and by smooth muscles fibers in some blood vessels. Hormone Systems for Osmoregulation, Pressor Effects.
Vasopressin Prolactin (in specialized cases such as lactation) Renin – angiotensin – aldosterone system. Glucocorticosteroids from the adrenal cortex Atrial and brain natriuretic factors. Some hormones of the gastro-intestinal tract (uptake of ions and water). Autonomic nervous system and epinephrine (alpha and beta adrenergic receptors). Hormone Systems for Osmoregulation, Pressor Effects.
Vasopressin Prolactin (in specialized cases such as lactation) Renin – angiotensin – aldosterone system. Glucocorticosteroids from the adrenal cortex Atrial and brain natriuretic factors....
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- Spring '09