Human Body Systems and Functions: Structure, Function, and Homeostasis
Core concepts
Expect questions that link an organ to its system, a system to its function, and a function to the mechanism that maintains balance. Build a mental map of the major systems:
- Integumentary: protection, temperature regulation, vitamin D synthesis, sensation.
- Skeletal: support, protection, mineral storage, blood cell production in marrow.
- Muscular: movement, posture, heat production.
- Nervous: rapid signaling, sensation, integration, control of other systems.
- Endocrine: slower, sustained regulation via hormones (insulin, thyroid hormone, cortisol, adrenaline).
- Cardiovascular: transport of oxygen, nutrients, hormones, wastes; includes heart, vessels, blood.
- Respiratory: gas exchange (oxygen in, carbon dioxide out) across alveoli.
- Digestive: mechanical and chemical breakdown, absorption, elimination.
- Urinary: filtration, fluid and electrolyte balance, waste removal.
- Lymphatic/immune: fluid return and defense.
- Reproductive: gamete production and reproduction.
Know homeostasis as maintenance of a stable internal environment through feedback. Negative feedback reverses a change (body temperature, blood glucose, blood pressure); positive feedback amplifies a change (childbirth contractions, blood clotting). Understand the anatomical position, and directional terms such as superior/inferior, anterior/posterior, proximal/distal, medial/lateral - these are frequent distractors.
Traps
Questions confuse the endocrine and nervous systems' speed and duration, or misassign an organ (the pancreas is both endocrine and digestive; the liver is not part of the urinary system). Another trap asks which system produces blood cells - marrow in the skeletal system, not the lymphatic system.
Worked example / rule of thumb
Rule of thumb: if the response opposes the original change, it is negative feedback. Example: blood glucose rises → insulin is released → glucose falls. That is negative feedback. If the response increases the change (labor contractions intensifying), it is positive feedback.
Exam strategy
Trace the pathway in the stem (stimulus → sensor → control center → effector → response) before choosing an answer.