Endocrine System Lecture Notes

Overview

• The endocrine system interacts with the nervous system to regulate cellular activity in the body.
• Comprised primarily of glands that secrete hormones into the bloodstream.
• Hormones act as messengers, affecting cell function and communication.
• Different from exocrine glands (sweat and saliva production).

Key Components of the Endocrine System

• Pituitary Gland: Located in the brain, has two lobes (anterior and posterior).

  • Posterior Lobe: Releases oxytocin and antidiuretic hormone (ADH).
  • Anterior Lobe: Produces and secretes growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin.

• Thyroid Gland: Located in the neck.

  • Produces thyroid hormones (T3 and T4) which regulate metabolism, tissue growth, and blood pressure.

• Parathyroid Glands: Typically four in number.

  • Secrete parathyroid hormone which regulates calcium and phosphate levels in the blood.

• Adrenal Glands: Composed of an inner medulla and outer cortex.

  • Cortex: Produces corticosteroids like mineralocorticoids, glucocorticoids, and gonadocorticoids.
  • Medulla: Produces catecholamines (epinephrine and norepinephrine).

• Pineal Gland: Located in the brain.

  • Produces melatonin, which regulates sleep.

Other Important Organs

• Pancreas: Produces glucagon (increases blood glucose) and insulin (decreases blood glucose).

• Gonads:

  • Testes: Produce testosterone.
  • Ovaries: Produce estrogens and progesterone.

• Placenta (during pregnancy): Produces hormones to support fetal development.

• Other Organs: Heart, kidneys, bones, skin, and adipose tissue also produce various hormones.

Hormonal Stimuli

• Humoral Stimuli: Changes in blood composition trigger hormone release.
• Neural Stimuli: Nerve fibers stimulate hormone release.
• Hormonal Stimuli: Hormones from other glands trigger hormone release.

Hormone Categories

• Amino Acid-derived or small proteins
• Steroids

Hormonal Axes

• Hypothalamic-Pituitary-Adrenal Axis: Regulates cortisol.
• Renin-Angiotensin-Aldosterone Axis: Regulates sodium, potassium, and water balance.

Conclusion

• The endocrine system is a critical communication network for maintaining bodily functions.
• Hormones circulate through the bloodstream, highlighting the need to understand the circulatory system next.