NCERT Solutions for Class 11 Biology Chapter 19 Chemical Coordination and Integration
NCERT Solutions for Class 11 Biology Chapter 19 Chemical Coordination and Integration covers the human endocrine system, the various endocrine glands and their hormones, and the mechanism of hormone action.
Overview of Topics & Subtopics (Click to Jump)
1. The Endocrine System
Short Note:
• Endocrine glands are ductless glands that secrete hormones directly into the bloodstream; hormones act as chemical messengers, regulating and coordinating physiological functions.
2. Major Endocrine Glands and Their Hormones
Short Note:
• Hypothalamus: releasing and inhibiting hormones, regulates the pituitary. Pituitary ('master gland'): secretes GH, TSH, ACTH, FSH, LH, prolactin (anterior); oxytocin, vasopressin (posterior, actually synthesised by hypothalamus).
• Thyroid: secretes thyroxine (T3, T4) — regulates basal metabolic rate; and calcitonin — regulates blood calcium. Parathyroid: secretes PTH — increases blood calcium.
• Adrenal Glands: cortex secretes corticosteroids (glucocorticoids like cortisol, mineralocorticoids like aldosterone); medulla secretes adrenaline and noradrenaline ('fight or flight' hormones).
• Pancreas: islets of Langerhans secrete insulin (lowers blood glucose) and glucagon (raises blood glucose). Gonads: testes secrete testosterone; ovaries secrete oestrogen and progesterone.
3. Mechanism of Hormone Action
Short Note:
• Hormones act via specific receptors, either on the cell membrane (for protein hormones, triggering a second messenger cascade like cAMP) or inside the cell (intracellular receptors, for steroid hormones, directly affecting gene expression).
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