Human Endocrine System Lecture Notes

Introduction

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• Endocrine System Overview:
  • Consists of glands throughout the body.
  • Secretes hormones to regulate body functions.

Historical Background

• Claude Bernard:
  • 20th-century French physiologist.
  • Observed the constant internal environment (milieu interior).
  • Contributions to understanding physiological regulation.

Body Systems Control

• Systems Involved in Body Control:
  • Nervous System: Fast processes (e.g., movement, breathing).
  • Immune System: Infection and damage response.
  • Endocrine System: Slow processes (e.g., growth, metabolic rate).

Major Endocrine Glands and Their Functions

1. Thyroid Gland:
   • Location: Neck.
   • Hormones: Thyroid hormones (T4, T3).
   • Functions: Metabolism regulation, affects nearly all cells.
2. Parathyroid Glands:
   • Location: Behind the thyroid.
   • Hormone: Parathormone.
   • Functions: Calcium and Vitamin D metabolism.
3. Adrenal Glands:
   • Location: Above kidneys.
   • Cortex Hormones:
     • Zona Glomerulosa: Aldosterone (mineralocorticoid for ion balance).
     • Zona Fasciculata: Cortisol (glucocorticoid for stress and metabolism).
     • Zona Reticularis: Androgens (secondary sexual characteristics).
   • Medulla Hormones: Catecholamines (epinephrine, norepinephrine).
4. Pancreas:
   • Hormone: Insulin.
   • Function: Glucose, fat, and protein metabolism.
5. Reproductive Glands:
   • Females: Ovaries (estrogen, progesterone).
   • Males: Testes (testosterone).
6. Pituitary and Thalamus:
   • Control secretion of other glands.

Hormone Types and Actions

• Protein vs. Steroid Hormones:
  • Protein: Most common.
  • Steroid: Includes testosterone, luteinizing hormone.
• Hormone Mechanisms:
  • Ion channel receptors: Regulate ion entry/exit.
  • Enzyme-linked/G-protein coupled: Activate enzymes.
  • Gene-linked: Affect transcription and protein synthesis.

Detailed Gland Functions

• Thyroid Gland:
  • Largest endocrine gland (15-20g).
  • Requires iodine for hormone synthesis.
  • Effects: Increased mitochondria, metabolism, cardiac output, CNS activity.
• Parathyroid Gland:
  • Maintains calcium and phosphate balance.
  • Acts on bones, intestines, kidneys.
• Adrenal Glands:
  • Cortex: Three layers (glomerulosa, fasciculata, reticularis).
  • Hormones for sodium balance, stress response, metabolism, sexual characteristics.
  • Medulla: Part of sympathetic nervous system, involved in fight or flight.

Conclusion

• This video is the first in a series on endocrinology.
• Next video will cover other glands, hypothalamus, and pituitary gland control.
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