MA High School Biology MCAS Module 4 anatomy and physiology: a complete overview of homeostasis, the nervous and endocrine systems, transport, digestion, immunity, and interacting systems

What Module 4 actually demands

Module 4 is anatomy and physiology, part of the From Molecules to Organisms reporting category (HS-LS1-2 and HS-LS1-3). It answers one question in many forms: how does the body keep its internal environment stable while supplying every cell? The MCAS tests it with feedback graphs, structure-to-function explanations (why a structure suits its job), and multi-system scenarios such as exercise. The crosscutting concepts are stability and change, structure and function, and systems and system models.

This guide ties together the matching dot-point pages, each with its own practice questions: homeostasis and feedback, the nervous and endocrine systems, transport and gas exchange, digestion and the immune system, and interacting body systems.

Homeostasis and feedback

Homeostasis is a stable internal environment, a dynamic equilibrium around a set point. It runs on negative feedback: a sensor detects a change, a control center processes it, and an effector produces a response that opposes the change. Body temperature is held by sweating and shivering; blood glucose by insulin (lowers) and glucagon (raises). The MCAS loves a temperature or glucose graph, asking you to name the feedback and explain the loop. When feedback fails, disease follows, as in diabetes.

The nervous and endocrine systems

Two systems coordinate the body. The nervous system uses fast electrical impulses along neurons: fast, short, and precise. The endocrine system uses hormones carried in the blood: slower, longer-lasting, and widespread. Both detect a stimulus and coordinate a response. The body needs both because some situations require speed (a reflex) and others require sustained, body-wide control (glucose balance, growth).

Transport and gas exchange

The respiratory system exchanges gases at the alveoli: oxygen diffuses into the blood, carbon dioxide diffuses out. Alveoli suit this with a large surface area, thin walls, and a rich blood supply. The circulatory system (heart, vessels, blood) then transports oxygen and nutrients to every cell and carries wastes away. The oxygen delivered is used in aerobic respiration. The two systems must work together: the respiratory system loads the blood, the circulatory system delivers it.

Digestion and immunity

The digestive system breaks large food molecules into small, absorbable ones using enzymes: starch to glucose, protein to amino acids, lipids to fatty acids and glycerol. The small molecules are absorbed into the blood and delivered to cells. The immune system defends against pathogens: white blood cells engulf pathogens or make antibodies that bind specifically to a pathogen and mark it for destruction. Memory cells make a second infection milder, which is immunity and the basis of vaccines.

Interacting body systems

The body is a system of interacting subsystems: no organ system works alone. During exercise, the nervous and endocrine systems speed up the heart and breathing, the respiratory system takes in more oxygen, the circulatory system delivers oxygen and glucose, and the digestive system supplies the glucose. They cooperate to meet demand and keep the internal environment stable. The MCAS rewards describing the cooperation, not just listing systems.

Check your knowledge

A mix of recall, data, and application questions covering Module 4. Attempt them under timed conditions, then check against the solutions.

1. State the three parts of a negative feedback loop. (2 marks)
2. Explain how negative feedback returns blood glucose to normal after a meal. (3 marks)
3. State the type of signal used by the nervous system and by the endocrine system. (2 marks)
4. Explain why an endocrine response lasts longer than a nervous response. (2 marks)
5. Name the process by which oxygen moves from the alveoli into the blood. (1 mark)
6. Explain how the structure of the alveoli suits gas exchange. (2 marks)
7. Explain why large food molecules must be broken down before absorption. (2 marks)
8. Explain how antibodies help defend the body against a pathogen. (2 marks)
9. Explain why a second infection by the same pathogen is usually milder. (2 marks)
10. Name two organ systems that cooperate to supply a muscle with oxygen during exercise, and state each one's role. (2 marks)