Endocrine System: Hypothalamus and Pituitary Gland

Endocrine System Overview

• A command center responsible for maintaining homeostasis in the body.
• Homeostasis involves keeping body temperature (98.6°F), blood pressure (120/80 mmHg), and glucose levels (70-100 mg/dL) stable.
• Uses hormones, which are chemical messengers, to control different body parts.

Hypothalamus

• The master controller of the endocrine system.
• Controls the pituitary gland and regulates temperature, hunger, emotions, and stress.
• Releases:
  • TRH, which stimulates the release of TSH
  • CRH, which stimulates the release of ACTH, activating stress hormones
  • GnRH, which stimulates the release of FSH & LH which in turn stimulate making babies
  • GHRH, which stimulates the release of GH
  • PIH (Dopamine) blocks prolactin
• Controls the fight-or-flight response by directly controlling the adrenal medulla.

Pituitary Gland

• An assistant to the hypothalamus, with two sections.
• Posterior Pituitary (Neurohypophysis):
  • Releases oxytocin (OT) for bonding, childbirth, and milk ejection.
  • Antidiuretic Hormone (ADH) promotes water retention in the kidneys.
• Anterior Pituitary (Adenohypophysis):
  • Releases TSH to stimulate the thyroid.
  • ACTH is a central stress hormone.
  • FSH & LH run the reproductive system.
  • PRL (Prolactin) stimulates milk production.
  • GH (Growth Hormone) is important for growth and repair; levels spike during sleep and exercise.

Thyroid Gland

• Involved in energy, metabolism, and mood regulation.
• Produces T3 & T4 to regulate metabolism.
  • Too little T3 & T4 can lead to hypothyroidism, causing sluggishness and weight gain.
  • Too much T3 & T4 can lead to hyperthyroidism, causing jitteriness and weight loss.
• Produces calcitonin, which promotes calcium deposition in bones.

Adrenal Glands

• Located on top of the kidneys.
• Cortex (Outer Layer):
  • Zona Glomerulosa releases aldosterone, which regulates sodium and blood pressure.
  • Zona Fasciculata releases cortisol, the stress hormone.
  • Zona Reticularis releases small amounts of testosterone and estrogen.
• Medulla (Inner Layer):
  • Releases epinephrine & norepinephrine, responsible for the fight-or-flight response.

Reproductive Glands

• Ovaries produce estrogen & progesterone, regulating menstrual cycles, pregnancy, and mood.
• Testes produce testosterone, building muscle, fueling libido, and supporting sperm production.
• Both ovaries and testes produce inhibin, which inhibits FSH release.

Pancreas

• Regulates blood sugar levels.
• Alpha cells release glucagon to increase blood sugar.
• Beta cells release insulin to decrease blood sugar.
• Delta cells release somatostatin to regulate hormone release.
• Problems with the pancreas can lead to diabetes.
  • Type 1 Diabetes: The pancreas stops producing insulin.
  • Type 2 Diabetes: The body becomes resistant to insulin.

Other Endocrine Players

• Pineal Gland: Secretes melatonin, regulating sleep.
• Heart: Produces ANP to lower blood pressure.
• Kidneys: Release EPO to make more red blood cells and activate vitamin D.
• Lungs: Convert angiotensin I into angiotensin II, which increases blood pressure.

Endocrine Disorders

• Hypothyroidism: Sluggishness, weight gain, and feeling cold.
• Hyperthyroidism: Jitteriness, weight loss, and rapid heart rate.
• Cushing’s Syndrome: Excess cortisol, leading to puffy face, weight gain, and weakened immune system.
• Addison’s Disease: Insufficient cortisol, leading to fatigue, low blood pressure, and salt cravings.
• Diabetes Mellitus: Disrupted sugar regulation.

Circulatory System Overview

• Transports oxygen, hormones, nutrients, and waste throughout the body.
• Blood flow is essential for survival.

Blood

• A mixture of plasma, cells, and other substances.
• Plasma (50-60%): Liquid component of blood, carries hormones, proteins, nutrients, and waste.
  • Albumin maintains blood thickness and carries hormones.
  • Globulins aid in immune defense.
  • Fibrinogen is involved in blood clotting.
• Red Blood Cells (RBCs): Transport oxygen from the lungs to the tissues.
  • Lack a nucleus and have a lifespan of 120 days.
  • Too many RBCs can increase the risk of stroke.
  • Too few RBCs can cause anemia, leading to exhaustion and dizziness.
• White Blood Cells (WBCs): Immune system cells that defend against bacteria, viruses, and parasites.
  • Granulocytes:
    • Neutrophils (60-70%): First responders that engulf bacteria.
    • Eosinophils (2-4%): Defend against allergies and parasites.
    • Basophils (

Overview of the endocrine system's command center for homeostasis. Covers the hypothalamus as the master controller, regulating temperature, hunger, and stress via hormone release. Details the pituitary gland's role, including hormone release from its posterior section.