Endocrine System

The endocrine system is the body's hormone network - a collection of ductless glands that secrete hormones (chemical messengers) directly into the bloodstream. These hormones travel through blood to target organs and regulate major processes such as metabolism, growth, development, and homeostasis.

• Endocrine vs exocrine: Endocrine glands release hormones internally into blood (no ducts), whereas exocrine glands secrete substances through ducts to the outside or into cavities (e.g., sweat, digestive enzymes).
• Endocrine signaling is generally slower and longer-lasting than nervous system signaling. Hormones may take seconds to hours to exert effects, coordinating longer-term activities like growth, reproduction, and metabolic balance.
• Major endocrine glands include the pituitary, thyroid, parathyroids, adrenal glands, pancreas (endocrine portion), ovaries, and testes. (Pancreas has both endocrine functions - insulin/glucagon secretion - and exocrine functions for digestion.)

• Often tested via scenarios of hormonal imbalance. For example, a question might describe symptoms of a thyroid hormone deficiency or excess - understanding it's an endocrine issue involving the thyroid gland is key.
• Be prepared for questions asking about differences between endocrine and nervous regulation: e.g., recognizing that hormones (endocrine signals) generally maintain internal homeostasis and work more slowly compared to rapid nerve impulses.