Coordination and Control

A hormone is an organic chemical secreted by a cell that carries a message through the blood to organs and tissues, and over 50 of them are known, governing metabolism, blood sugar, growth and temperature. What the paper tests is the chemistry underneath that list, because it asks you to sort hormones into classes, and the class tells you where the hormone came from. Chemically most hormones are amines, peptides, proteins, glycoproteins or steroids. The lipid-soluble steroids are cortisol, corticosterone, aldosterone and the sex hormones; the amines are adrenaline and thyroxine; the peptides are insulin, oxytocin, antidiuretic hormone, FSH, ACTH, TSH, prolactin and growth hormone. One item asked what aldosterone, the sex hormones and cortisol share and keyed steroids, and two others each asked which single hormone is a steroid, both keying cortisone.

Positions earn their keep, because a stem usually hands you the position. The thyroid sits below the larynx in two lobes, with the parathyroids embedded in the posterior part of its lateral lobes; a pair of adrenals sits one on top of each kidney, the gland the paper calls the gland of emergency; the islets of Langerhans carry insulin from the $\beta$ cells and glucagon from the $\alpha$ cells. The anterior pituitary secretes prolactin, growth hormone, TSH, ACTH, FSH and LH, and the posterior lobe holds ADH and oxytocin, both made in the hypothalamus. The pituitary lies in the sella turcica, linked by the infundibulum, which is why it is keyed as the structure that is not part of the brain, a point worth flagging, since the Federal and Sindh books set it beside the hypothalamus. Inside the adrenal the two layers earn different marks: the medulla makes adrenaline and noradrenaline, adrenaline dilating vessels in parts of the body such as the skeletal muscles and raising the heart's output while noradrenaline constricts vessels in selected areas such as the gut, and the cortex makes corticosteroids, of which cortisol is the glucocorticoid and aldosterone the principal mineralocorticoid, conserving $Na^{+}$ by preventing its loss from the kidney tubules.