Class 11 - Chemical coordination and Integration | Xylem NEET Tamil | Xylem NEET Tamil

Definition: The chapter focuses on the endocrine system, which consists of ductless glands that secrete hormones into the bloodstream, unlike exocrine glands which have ducts.
Hormones: Non-nutrient chemicals that act as intracellular messengers; hormones are released into the blood and do not contain any antigens.
Functions: Regulates various body functions, including blood sugar and calcium levels, in very low concentrations.

Action Speed: Hormones typically act quickly; however, some may require specific processes before they affect target organs.
Receptor Specificity: Hormones bind to specific receptors located on their target organs, indicating a highly specific interaction (e.g., thyroid hormone receptors).
Types of Hormones: Includes growth and development hormones, metabolic activity regulators, and inhibiting hormones like somatostatin, which inhibits growth hormone release from the hypothalamus.

Releasing and Inhibiting Hormones: The hypothalamus produces releasing hormones that stimulate the pituitary gland and inhibiting hormones that suppress hormone production.
Pituitary Gland Regulation: Pituitary hormones such as Thyroid-Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), and Growth Hormone (GH) play critical roles.

FLAT PG: Represents key anterior pituitary hormones:
- FSH - Follicle-Stimulating Hormone: Promotes growth of ovarian follicles in females and spermatogenesis in males.
- LH - Luteinizing Hormone: Involved in ovulation and testosterone production.
- ACTH - Adrenocorticotropic Hormone: Stimulates the adrenal cortex to release glucocorticoids.
- TSH - Thyroid-Stimulating Hormone: Stimulates the thyroid gland to produce thyroid hormones.
Growth Hormone: Impacts most tissues in the body, promoting growth and metabolism.

Adenohypophysis (Anterior Pituitary): Secretes hormones essential for growth and metabolism, including TSH and the growth hormone.
Neurohypophysis (Posterior Pituitary): Stores and releases hormones (e.g., oxytocin and vasopressin) synthesized in the hypothalamus.
Hormones from the Posterior Pituitary:
- Oxytocin: Stimulates uterine contractions and milk ejection during breastfeeding.
- Vasopressin (ADH): Regulates water retention in the kidneys.

Adrenal Gland:
- Cortex: Produces glucocorticoids and mineralocorticoids, involved in stress response and ion balance.
- Medulla: Secretes adrenaline (epinephrine) and noradrenaline (norepinephrine), important in the fight-or-flight response.
Thyroid Gland:
- Produces thyroxine (T4) and triiodothyronine (T3), crucial for metabolism and development.
Parathyroid Glands:
- Regulate calcium levels via parathyroid hormone.

Pineal Gland: Produces melatonin, which regulates sleep cycles.
Pancreas: Involved in hormonal balance and glucose metabolism.
Gonads (Ovaries and Testes): Produce sex hormones (estrogen, progesterone, testosterone) essential for reproductive functions.

Heart: Releases Atrial Natriuretic Factor (ANF), lowering blood pressure.
Kidneys: Produce erythropoietin, promoting red blood cell production.
Gastrointestinal Hormones:
- Gastrin: Stimulates gastric acid secretion.
- Secretin and Cholecystokinin (CCK): Stimulate digestive processes and enzyme release.

Types of Hormone Receptors:
- Nuclear Receptors: Bind to hormones that can penetrate the cell membrane, leading to direct changes in gene expression.
- Membrane-Bound Receptors: Utilize secondary messengers (e.g., cAMP) to mediate hormone effects inside the cell.
Hormone Types by Structure:
- Peptide Hormones: Includes insulin, glucagon, and all pituitary hormones; cannot cross lipid bilayers easily.
- Steroid Hormones: Includes cortisol, testosterone, and estrogen; can cross cell membranes due to their lipid-soluble nature.
- Amino Acid Derivatives: Includes adrenaline, which also demonstrates unique modes of action.