The type of muscle found only in the heart is: MCQ with Answer and Explanation

Explanation:
Nitrogen fixation is the process by which atmospheric N₂ is reduced to ammonia, which is then converted into nitrates that plants can absorb. This can be biological (by bacteria like Rhizobium, Azotobacter), physical (lightning), or industrial (Haber-Bosch process). Nitrification is the oxidation of ammonia to nitrates. Ammonification releases ammonia from organic matter. Denitrification converts nitrates back to N₂.

Explanation:
ADH (vasopressin), released from the posterior pituitary, increases water permeability of the collecting duct and distal tubule, promoting water reabsorption and producing concentrated urine. Its secretion is stimulated by increased plasma osmolarity or decreased blood volume. Aldosterone regulates sodium reabsorption. Parathyroid hormone and calcitonin regulate calcium.

Explanation:
Calcitonin is produced by the parafollicular (C) cells of the thyroid gland. It lowers blood calcium levels by inhibiting osteoclast activity and promoting calcium deposition in bones. Parathyroid hormone (from parathyroid glands) raises calcium. Adrenal and pituitary glands have other functions.