15.1.2—Nervous and endocrine systems

• Nervous system: CNS (brain and spinal cord) coordinates with the PNS (nerves); information is carried as electrical impulses along neurones to effectors such as muscles or glands.
• Endocrine system: endocrine glands release chemical hormones into the bloodstream; hormones travel to target cells with complementary receptors.

The nervous route is suited to rapid, localised control and usually ends when impulses stop. The endocrine route can reach distant target tissues through the blood and usually produces a slower response that lasts while the hormone remains active.

Both systems coordinate body functions by carrying information to cells that can respond. The route and signal type explain the main contrast: neurones provide a directed electrical pathway, whereas blood distributes a chemical signal and receptor distribution selects the target cells.

The nervous and endocrine systems are complementary, not interchangeable labels for every response. This card stops at the system-level comparison; detailed neurone structure, synapses, and muscle contraction are covered in later cards.