Functions and Regulation of Human Body Cells

• Regulation Necessity: Continuous regulation of body cells is essential.
• Neural System Limitation: Nerve fibers do not innervate all body cells.
• Role of Endocrine System: Hormones secreted by endocrine system regulate body cells.

Neuro-Endocrine System

• Coordination with Neural System: Endocrine and neural systems function together.
• Study Field: Neural endocrinology is focused on these systems.
• Father of Endocrinology: Edison is credited as the father of endocrinology.

Human Endocrine System

• Components: Consists of various glands throughout the body.
• Main Glands:
  • Hypothalamus: Located in the forebrain, regulates hormone synthesis.
  • Pituitary Gland: Below hypothalamus, controls other glands.
  • Pineal Gland: In forebrain, regulates sleep cycles.
  • Thyroid Gland: Largest endocrine gland, in the neck.
  • Parathyroid Glands: Located on thyroid gland, regulate calcium.
  • Thymus: Above the heart, involved in immune function.
  • Pancreas: Both endocrine and exocrine functions.
  • Adrenal Glands: Above kidneys, release stress hormones.
  • Gonads (Testes and Ovaries): Reproductive hormone production.

Hormone Function and Secretion

• Characteristics:

  • Hormones are non-nutrient chemical messengers.
  • Released in trace amounts.
  • Affect specific target cells with receptors.

• Hormone Action:

  • Bind to receptors on target cells.
  • Induced by stimuli, affecting distant tissues.
  • Degraded by liver, excreted by kidneys.

• Types of Glands:

  • Endocrine Glands: Ductless, release hormones directly into blood.
  • Exocrine Glands: Use ducts to release secretions.
  • Heterocrine Glands: Both endocrine and exocrine functions.

Key Endocrine Glands and Hormones

• Brain Glands:

  • Hypothalamus: Produces neurohormones, regulates pituitary.
  • Pituitary:
    • Anterior Pituitary: Secretes growth hormone, prolactin, TSH, ACTH, LH, FSH.
    • Posterior Pituitary: Stores and releases oxytocin and vasopressin.
  • Pineal Gland: Secretes melatonin.

• Thyroid and Parathyroid:

  • Thyroid: Produces T3, T4 for metabolism regulation.
  • Parathyroid: Releases PTH for calcium regulation.

• Thymus: Secretes thymosin for immune development.

• Adrenal Glands:

  • Adrenal Cortex: Secretes glucocorticoids and mineralocorticoids.
  • Adrenal Medulla: Produces adrenaline and noradrenaline.

• Pancreas: Insulin and glucagon for blood sugar regulation.

• Gonads:

  • Testes: Produce testosterone.
  • Ovaries: Secrete estrogen and progesterone.

Hormone Mechanism

• Receptors:

  • Extracellular Receptors: For non-steroid hormones (e.g., proteins).
  • Intracellular Receptors: For steroid and thyroid hormones.

• Hormone-Receptor Interaction:

  • Non-steroid hormones use second messengers.
  • Steroid hormones directly influence gene expression.

Conclusion

• The endocrine system plays a crucial role in regulating physiological functions.
• Hormones provide critical signalling throughout the body to maintain homeostasis.