⚡ Quick Revision: Endocrine Basics
🔹 Hormones & Glands
- ✔ Endocrine Glands: Ductless glands that pour secretions (hormones) directly into the blood.
- ✔ Hormones: Chemical messengers that act on specific Target Organs.
- ✔ Feedback Mechanism: A regulatory loop that adjusts hormone levels based on body needs (e.g., Insulin).
Heterocrine Gland: A gland that performs both exocrine and endocrine functions (e.g., Pancreas).
Enzymes with Hormones. Remember: Enzymes act at the site of production; Hormones are produced in one place and act on a distant target organ.
⚡ Quick Revision: The Pituitary Gland
🔹 The Master Gland
- ✔ Location: A pea-sized gland hanging from the base of the hypothalamus.
- ✔ Tropic Hormones: It stimulates other glands to produce hormones (e.g., TSH stimulates the Thyroid).
🔹 Major Pituitary Hormones
| Lobe | Hormone | Function |
|---|---|---|
| Anterior | Growth Hormone (GH) | Growth of bones and tissues. |
| TSH / ACTH | Stimulates thyroid/adrenal cortex. | |
| Posterior | ADH (Vasopressin) | Water reabsorption in kidneys. |
| Oxytocin | Uterine contraction / Milk ejection. |
Gigantism vs Acromegaly: Over-secretion of GH in childhood leads to Gigantism; in adults, it leads to Acromegaly (thickening of facial bones).
Dwarfism with Cretinism. Remember: Dwarfism is caused by GH deficiency (normal intelligence); Cretinism is caused by Thyroid deficiency (mental retardation).
⚡ Quick Revision: Thyroid & Adrenal Glands
🔹 Thyroid Gland (The Metabolism Regulator)
- ✔ Hormone: Secretes Thyroxine; requires Iodine for its synthesis.
- ✔ Hypothyroidism: Leads to Simple Goitre, Myxoedema (adults), and Cretinism (children).
- ✔ Hyperthyroidism: Leads to Exophthalmic Goitre (bulging eyes and high BMR).
🔹 Adrenal Glands (Emergency Glands)
- ✔ Adrenal Medulla: Secretes Adrenaline (Epinephrine)—the "Fight or Flight" hormone.
- ✔ Adrenal Cortex: Secretes Cortisones; hyposecretion causes Addison's disease.
- ✔ Location: Like caps on top of each kidney.
Basal Metabolic Rate (BMR): The rate at which the body uses energy while at rest to keep vital functions going.
Simple Goitre with Exophthalmic Goitre. Remember: Simple Goitre is due to iodine deficiency (hypo); Exophthalmic is due to overactivity (hyper).
⚡ Quick Revision: The Pancreas (Dual Gland)
🔹 Islets of Langerhans
The endocrine part of the pancreas consists of clusters of cells called Islets of Langerhans.
- ✔ Alpha Cells: Secrete Glucagon (increases blood glucose levels).
- ✔ Beta Cells: Secrete Insulin (decreases blood glucose levels).
- ✔ Delta Cells: Secrete Somatostatin (inhibits secretion of insulin and glucagon).
🔹 Pancreatic Disorders
| Condition | Cause | Symptom |
|---|---|---|
| Diabetes Mellitus | Hyposecretion of Insulin | Hyperglycemia, Glycosuria (sugar in urine). |
| Insulin Shock | Hypersecretion of Insulin | Hypoglycemia, dizziness, loss of consciousness. |
Glycogenesis: The process by which insulin converts excess glucose into glycogen for storage in the liver and muscles.
Glucagon with Glycogen. Remember: Glucagon is the hormone that raises blood sugar; Glycogen is the stored form of glucose.
⚡ Quick Revision: Feedback & Summary
🔹 Negative Feedback Mechanism
- ✔ Process: The timing and amount of hormone released are controlled by feedback (e.g., high sugar levels trigger insulin; once sugar drops, insulin secretion stops).
- ✔ Importance: Ensures that hormones are not secreted in excess, maintaining Homeostasis.
🔹 Hormones & Their Deficiency Diseases
| Gland | Hormone | Hyposecretion Disease |
|---|---|---|
| Thyroid | Thyroxine | Myxoedema / Cretinism |
| Pancreas | Insulin | Diabetes Mellitus |
| Adrenal Cortex | Cortisones | Addison’s Disease |
| Pituitary | Vasopressin (ADH) | Diabetes Insipidus |
Target Organ: An organ on which a hormone acts specifically after being transported by the blood.
Nervous vs Endocrine control. Nervous control is electrical, rapid, and short-lived; Endocrine control is chemical, slow, and often long-lasting.