Chemical Coordination and Integration Test 12

Aldosterone secreted by the adrenal glands of the body is responsible for maintaining the sodium potassium ratio in the extracellular and intracellular fluids. It thus helps in the maintenance of electrolytes,body fluid volume ,osmotic pressure and blood pressure.

Steroid hormones can pass through the plasma membrane by simple diffusion because they are lipid derived hormones, which means that they are capable of passing through every cell of our body. Unlike other types of hormones, steroid hormones do not have to bind to plasma membrane receptors. Instead, they can interact with intracellular receptors.

Second messengers are the organic molecules and sometimes the metal ions, acting as intracellular signals, whose production or release usually amplifies a signal such as a hormone, received at the cell surface.
Sodium (Na) is not a second messenger to be discovered.
In addition to cyclic AMP, Cyclic Guanosine Monophosphate (CGMP) functions as a second messenger in certain cases.
Calcium ions (Ca⁺⁺) also act as second messenger in phospholipase C-Ca⁺ second messenger system.

Hormones which with membrane bound receptors normally donot enter the target cells, but generate secondary messengers ( e.g : cyclic AMP, cGMP, DAG etc.) which in turn regulate cellular metabolism.

Hormones are a diverse group of biochemicals, which perform a variety of roles in biological systems. Hormones are produced in endocrine glands. Hormones are responsible for maintenance of internal balance and developmental changes in the animal body. 

Chemically, hormones may be peptide (e.g., insulin), amines (e.g., catecholamines), proteins (e.g., growth hormone), steroid hormones (e.g., androgens).