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[HAP-07] Endocrine System Physiology: Hypothalamic–Pituitary Axis, Pancreatic Islets, Thyroid, Adrenal & Calcium Regulation
HAP-07 • 1. Anatomy & PhysiologyLearning Objectives
Trace negative feedback loops across the HPT (TRH → TSH → T4/T3), HPA (CRH → ACTH → Cortisol), and HPG (GnRH → FSH/LH → Estrogen/Progesterone/Testosterone) axes.; Contrast pancreatic islet cell types (α-cells: Glucagon, β-cells: Insulin + C-peptide + Amylin, δ-cells: Somatostatin) and biphasic insulin secretion.; Explain PTH, Calcitriol ([10.12] Cholecalciferol → 25-OH-D3 in liver → 1,25-(OH)2-D3 in kidney via 1α-hydroxylase), and Calcitonin in calcium/bone homeostasis.
Chapter Overview & Core Explanation
The endocrine system uses chemical messengers called hormones secreted into the bloodstream to coordinate metabolism, growth, stress response, blood sugar, bone strength, and reproduction across distant organs.
Key Exam & Clinical Takeaways
- [7.4] Regular Soluble Insulin is the primary insulin formulation safe for intravenous infusion in Diabetic Ketoacidosis (DKA) and severe hyperkalaemia.
- [7.5] Insulin Glargine is formulated at pH 4.0 and forms neutral subcutaneous microprecipitates for a peakless 24-hour release—it must NEVER be diluted or mixed in the same syringe with other insulins.