Endocrine System Overview

Endocrine System

• Definition: A system of glands that secrete hormones directly into the bloodstream to control body functions (metabolism, growth, reproduction).
• Hormones: Chemical messengers produced by endocrine glands.
• Target Cells & Receptors: Specific cells (target cells) have specific receptors for hormones; only those cells respond to those hormones.
• Feedback Mechanisms: Regulate hormone levels.
  • Negative Feedback: Response reduces the original stimulus (e.g., blood glucose regulation).
  • Positive Feedback: Response amplifies the original stimulus (e.g., oxytocin during childbirth).

Major Endocrine Glands & Functions

• Hypothalamus:

  • Location: Brain, below the thalamus.
  • Role: "Master control" of the endocrine system. Regulates pituitary, body temperature, thirst, hunger, and sleep.
  • Releasing and Inhibiting Hormones: Control hormone release from the anterior pituitary.

• Pituitary Gland:

  • Location: Base of the brain, connected to the hypothalamus.
  • Two Lobes:
    • Anterior Pituitary (Adenohypophysis)
      • Hormones: Growth Hormone (GH), Thyroid-Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), Luteinizing Hormone (LH), Follicle-Stimulating Hormone (FSH), Prolactin (PRL), Melanocyte-Stimulating Hormone (MSH)
      • Functions: Stimulate growth, thyroid function, adrenal function, sex hormone production, milk production, and skin pigmentation.
    • Posterior Pituitary (Neurohypophysis)
      • Hormones: Oxytocin, Antidiuretic Hormone (ADH)
      • Functions: Stimulate uterine contractions, milk ejection, and regulate water balance.

• Thyroid Gland:

  • Location: Neck, in front of trachea.
  • Role: Regulates metabolism.
  • Hormones: Thyroid hormones (T3 and T4), Calcitonin
  • Functions: Control metabolic rate, growth, development, and reduce blood calcium levels.

• Parathyroid Glands:

  • Location: On posterior surface of thyroid.
  • Role: Regulates blood calcium levels.
  • Hormone: Parathyroid Hormone (PTH)
  • Function: Increases blood calcium levels.

• Adrenal Glands:

  • Location: On top of each kidney.
  • Two Parts:
    • Adrenal Cortex:
      • Hormones: Cortisol, Aldosterone, Androgens
      • Functions: Regulate metabolism, stress response, sodium/potassium balance, and secondary sexual characteristics.
    • Adrenal Medulla:
      • Hormones: Epinephrine, Norepinephrine
      • Functions: Involved in the "fight or flight" response.

• Pancreas:

  • Location: Behind the stomach.
  • Endocrine Function: Islets of Langerhans
    • Hormones: Insulin (lower blood glucose), Glucagon (raise blood glucose)
  • Functions: Control blood sugar levels.

• Pineal Gland:

  • Location: Brain
  • Role: Regulates sleep-wake cycles.
  • Hormone: Melatonin

• Thymus:

  • Location: Behind sternum
  • Role: Develops T-cells for the immune system.
  • Hormone: Thymosin

Urinary System (Partial Section - Needs more details for full summary)

• Definition: Filters blood, removes waste, and excretes urine.
• Functions: Regulate blood volume and pressure, maintain electrolyte & pH balance, and excrete waste (urea, creatinine, drugs). Stimulates red blood cell production.
• Kidneys:
  • Location: On either side of the spine.
  • Structure: Bean-shaped, cortex, medulla, renal pelvis, hilum.
  • Nephrons: Functional unit of the kidney.
    • Renal Corpuscle: Glomerulus and Bowman's capsule.
    • Renal Tubule: Reabsorption of water/solutes, waste secretion.
    • Parts: Proximal Convoluted Tubule, Loop of Henle, Distal Convoluted Tubule.
• Ureters: Transport urine from kidneys to bladder.