Bihar Board - Class 11 biology - Chapter 22: Chemical Coordination and Integration Handwritten Notes

Chemical coordination and integration involve the regulation of physiological processes through hormones secreted by endocrine glands. This chapter explains the endocrine system, types of hormones, their functions, and the mechanisms of hormonal control in the human body.

Key Points

1. Endocrine System

   • Comprises ductless glands that release hormones directly into the bloodstream.
   • Maintains homeostasis, regulates growth, development, metabolism, and reproduction.

2. Hormones

   • Definition: Chemical messengers secreted by endocrine glands, affecting target cells or organs.
   • Types of hormones:
     • Peptide Hormones: Insulin, glucagon.
     • Steroid Hormones: Testosterone, estrogen.
     • Amino Acid Derivatives: Thyroxine, adrenaline.

3. Major Endocrine Glands and Their Hormones

   • Hypothalamus: Regulates the pituitary gland by releasing and inhibiting hormones.
   • Pituitary Gland (Master Gland): Divided into anterior, intermediate, and posterior lobes.
     • Hormones: Growth hormone (GH), prolactin, oxytocin, ADH.
   • Pineal Gland: Produces melatonin, regulating sleep-wake cycles.
   • Thyroid Gland: Produces thyroxine and calcitonin, regulating metabolism and calcium levels.
   • Parathyroid Gland: Secretes parathyroid hormone (PTH), controlling calcium and phosphate balance.
   • Adrenal Glands:
     • Cortex: Produces cortisol, aldosterone.
     • Medulla: Produces adrenaline, noradrenaline.
   • Pancreas: Functions as both endocrine and exocrine.
     • Hormones: Insulin, glucagon for glucose regulation.
   • Gonads:
     • Testes produce testosterone for male characteristics.
     • Ovaries produce estrogen and progesterone for female characteristics and reproduction.
   • Thymus: Secretes thymosins, involved in immune response.

4. Mechanism of Hormonal Action

   • Hormones bind to specific receptors on target cells, initiating physiological changes.
   • Two types of mechanisms:
     • Surface Receptor Mechanism: For peptide hormones like insulin.
     • Intracellular Receptor Mechanism: For steroid hormones like cortisol.

5. Feedback Mechanisms

   • Positive Feedback: Reinforces the initial stimulus (e.g., oxytocin during childbirth).
   • Negative Feedback: Maintains homeostasis by counteracting the initial stimulus (e.g., insulin regulation of blood glucose).

6. Disorders Related to Hormones

   • Hypothyroidism: Deficiency of thyroid hormones, causing goiter and lethargy.
   • Hyperthyroidism: Excess thyroid hormones, causing weight loss and irritability.
   • Diabetes Mellitus: Insufficient insulin production leading to high blood sugar levels.
   • Addison’s Disease: Adrenal cortex insufficiency.
   • Cushing’s Syndrome: Overproduction of cortisol.

Conclusion

The endocrine system, through its network of glands and hormones, plays a pivotal role in maintaining the body's internal environment and regulating essential processes. Understanding chemical coordination is crucial for identifying and managing hormonal imbalances effectively.

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