A&P 2 Kidneys

¶ … blood ion levels, particularly sodium, potassium, and calcium levels, if there is a decrease in overall blood flow to the kidneys. A full credit answer will discuss the mechanisms at the cellular and chemical level. Kidney failure: What occurs when there is a decrease in blood flow to the kidneys? A decrease in blood flow to the kidneys can lead to complete organ failure at worst or at minimum severely disrupt the body's state of homeostasis.

The kidneys play a critical role in the regulation of electrolytes, particularly sodium, potassium, and calcium. As their name suggests electrolytes, or ions, "are the charged particles in body fluids that help transmit electrical impulses for proper nerve, heart, and muscle function" (Astle 2005). In a healthy organism, positive and negative ions are in a state of equal balance. Decrease in blood flow to the kidneys severely disrupts the body's ability to not only regulate electrolytes but the fluid balance those electrolytes help to maintain (Astle 2005).

For example, it is critical that sodium and potassium remain in a state of equilibrium to maintain appropriate blood pressure and a stable heart rate. An imbalance can lead to escalating blood pressure and abnormal muscle function, including the muscle of the heart. Muscle aches and stiffness, a lack of energy, even blindness can result. The kidneys also regulate sodium balance through regulating urine production.

The kidneys release vasopressin or an anti-diuretic hormone (ADH) which "causes the insertion of water channels into the membranes of cells lining the collecting ducts, allowing water reabsorption to occur. Without ADH, little water is reabsorbed in the collecting ducts and dilute urine is excreted" (Fluid and electrolyte balance, n.d). The kidneys are also responsible for osmolality, or the amount of solute per unit volume in every cell. "Extreme variation in osmolarity causes cells to shrink or swell, damaging or destroying cellular structure and disrupting normal cellular function.

To prevent osmolarity from decreasing below normal, the kidneys also have a regulated mechanism for reabsorbing sodium in the distal nephron" using aldosterone, a steroid hormone produced by the adrenals (Fluid and electrolyte balance, n.d). However, in the absence of normal kidney function, excess water or excess sodium can build up.

Two common serious medical conditions that can occur due to an imbalance of sodium and water are hypernatremia, or an excess of sodium and too little water, and hyponatremia, or an excess of water and too little sodium (Astle 2005). Both can produce symptoms of lethargy, irregular heart functions, and require immediate medical attention. Although calcium is primarily thought of in terms of its nutritional function, the kidneys also play a critical role in regulating this electrolyte.

"Calcium is a cation with multiple functions, including transmitting nerve impulses, maintaining cell wall permeability, and activating the body's clotting mechanism. It's also involved in contracting cardiac and smooth muscle, generating cardiac impulses, mediating cardiac pacemaker function, and forming bones and teeth" (Astle 2005). Calcium must be in a balance with phosphate to maintain homeostasis. "Both hypocalcemia and hyperphosphatemia can cause lethargy, fatigue, bone or joint pain, and sudden seizures. Low calcium levels also produce.