Endocrine System Overview

Study Notes

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.

Description

Explore the complex system of glands that secrete hormones, crucial for regulating various body functions such as metabolism, growth, and reproduction. This quiz covers the major endocrine glands, key hormones, their target cells, and feedback mechanisms that maintain balance within the body.