Ch 19 covers the endocrine system — endocrine glands, their hormones, mechanisms of hormone action, and disorders related to hormonal imbalance.
Hypothalamus: neuroendocrine, releases releasing/inhibiting hormones to control pituitary. Pituitary (master gland): anterior — GH, TSH, ACTH, FSH, LH, prolactin; posterior — oxytocin, ADH/vasopressin. Thyroid: T₃/T₄ (metabolism, iodine-dependent; deficiency → goitre). Parathyroid: PTH (increases blood Ca²⁺). Adrenal cortex: cortisol (stress), aldosterone (Na⁺ balance). Adrenal medulla: adrenaline/noradrenaline (fight-or-flight).
Pancreas (dual function): exocrine (digestive enzymes) + endocrine (islets of Langerhans). α-cells: glucagon (raises blood glucose — glycogenolysis). β-cells: insulin (lowers blood glucose — glycogenesis). Diabetes mellitus: insufficient insulin or insulin resistance. Feedback mechanisms: negative feedback — high hormone levels inhibit further release (e.g., high T₄ inhibits TSH). This maintains homeostasis.
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The pituitary gland controls the secretion of many other endocrine glands: TSH controls the thyroid, ACTH controls the adrenal cortex, FSH and LH control the gonads. However, the pituitary itself is controlled by the hypothalamus through releasing and inhibiting hormones, so some call the hypothalamus the "master of the master gland."
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