19Class 11 Biology
Chemical Coordination and Integration short notes
Short notes on the endocrine glands and their hormones. It's a chapter of pairs: each gland, its hormone, its effect and its disorder.
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Hypothalamus and pituitary
- The hypothalamus makes releasing and inhibiting hormones that control the pituitary.
- Anterior pituitary: GH, PRL, TSH, ACTH, LH and FSH.
- Posterior pituitary stores oxytocin and vasopressin (ADH).
- Too much GH causes gigantism in children and acromegaly in adults. Too little causes pituitary dwarfism.
Thyroid and parathyroid
- Thyroid makes T3 and T4, using iodine, and thyrocalcitonin (TCT), which lowers blood calcium.
- Iodine deficiency causes goitre, hypothyroidism in pregnancy can cause cretinism, and hyperthyroidism speeds up metabolism.
- Parathyroid hormone (PTH) raises blood calcium.
Other glands
- The thymus makes thymosins and helps T cells mature. It shrinks with age.
- The adrenal medulla makes adrenaline and noradrenaline, the fight-or-flight hormones.
- The adrenal cortex makes glucocorticoids (cortisol) and mineralocorticoids (aldosterone). Low cortex function causes Addison's disease.
- Pancreas: insulin from β-cells lowers blood sugar, and glucagon from α-cells raises it. Lack of insulin causes diabetes mellitus.
- Testis: androgens from Leydig cells. Ovary: estrogen and progesterone.
- Pineal gland: melatonin, which helps regulate the day-night rhythm.
How hormones act
- Protein hormones usually bind receptors on the membrane and use second messengers such as cAMP.
- Steroid and iodothyronine hormones enter the cell and act through nuclear receptors.
Where students slip up
- Mixing up insulin (β-cells) and glucagon (α-cells).
- Thinking the posterior pituitary makes its hormones. It stores them, and the hypothalamus makes them.
- Reversing PTH and TCT effects on calcium.
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