Ethical / practical implication: When hormones malfunction, virtually every organ system is affected (e.g., infertility, dwarfism/gigantism, Addison/Cushing disease).
Metaphor used: The endocrine system is like hanging one poster in the hallway so every student eventually sees it; the nervous system is like calling one student directly on the phone.
Nervous System vs Endocrine System
Nervous system
Direct “phone-call” wiring (neurons → specific cell)
Millisecond speed; short-lived, very localized effects
Endocrine system
“Hallway flyer” or “mass e-mail” broadcast (hormone → bloodstream)
Slower onset; effects last seconds → days; 1 hormone can have many targets if they bear the matching receptor (e.g., testosterone acts on vocal cords, pelvis, skeletal muscle).
More energy-efficient for wide, coordinated changes (e.g., puberty, stress adaptation).
Hormones – Definition & Illustrative Examples
Chemical messengers released by specialized endocrine glands into blood/lymph; travel to distant targets.