Changes

==Roles in the Body==

==Roles in the Body==

Sodium is distributed in [[Bones - Anatomy & Physiology|bone]] (43%) interstitial fluid (29%) and [[plasma]] (12%). The concentration of sodium (i.e., sodium chloride) in blood is approximately 0.9%. The main hormone involved in sodium balance is '''[[aldosterone]]''', which is released by the [[Adrenal Glands - Anatomy & Physiology|adrenal glands]] in response to a low plasma sodium concentration. Aldosterone acts by increasing the renal retention of sodium.

Sodium is distributed in [[Bones - Anatomy & Physiology|bone]] (43%) interstitial fluid (29%) and [[plasma]] (12%). The concentration of sodium (i.e., sodium chloride) in blood is approximately 0.9%. The main hormone involved in sodium balance is '''[[aldosterone]]''', which is released by the [[Adrenal Glands - Anatomy & Physiology|adrenal glands]] in response to a low plasma sodium concentration. Aldosterone acts by increasing the renal retention of sodium.

The high level of sodium in extracellular fluids is responsible for establishing a concentration gradient across cell membranes. Sodium attracts water molecules when in solution, and the size of the hydrated sodium ion prevents it crossing cell membranes as easily as other ions such as [[Potassium - Nutrition|potassium]] and [[Chloride - Nutrition|chloride]]. This means that the permeability of the membrane to sodium is generally very low but when there is a momentary change in the membrane’s permeability, sodium is driven into the cell and this dramatically alters the membrane potential from negative to positive. This change – the '''action potential''' – is responsible for nervous activity. The extra sodium in the cell is then removed by active transport via a sodium pump, which is energy dependent, and this restores the system to its resting state.

The high level of sodium in extracellular fluids is responsible for establishing a concentration gradient across cell membranes. Sodium attracts water molecules when in solution, and the size of the hydrated sodium ion prevents it crossing cell membranes as easily as other ions such as [[Potassium - Nutrition|potassium]] and [[Chloride - Nutrition|chloride]]. This means that the permeability of the membrane to sodium is generally very low but when there is a momentary change in the membrane’s permeability, sodium is driven into the cell and this dramatically alters the membrane potential from negative to positive. This change – the [[Neurons - Anatomy & Physiology#Nerve Impulse Propagation|'''action potential''']] – is responsible for nervous activity. The extra sodium in the cell is then removed by active transport via a sodium pump, which is energy dependent, and this restores the system to its resting state.

==Consequences of Sodium Deficiency==

==Consequences of Sodium Deficiency==