What is the primary function of the hypothalamus?

Correct Answer: A

Rationale: The primary function of the hypothalamus is to regulate body balance and thermoregulation. It plays a crucial role in maintaining overall body equilibrium by controlling functions such as body temperature and water balance. While the hypothalamus is also involved in hunger and thirst regulation, its main role is to ensure homeostasis by monitoring and adjusting body balance and temperature. Choices B, C, and D are incorrect because hunger and thirst regulation, sleep and circadian rhythm regulation, and control of voluntary movements are secondary functions of the hypothalamus compared to its primary role in maintaining body balance and thermoregulation.

Correct Answer: A

Rationale: The primary function of the cardiovascular system is to pump blood throughout the body, ensuring that oxygen and nutrients are delivered to tissues while removing waste products. This circulation is essential for maintaining overall health and proper functioning of the body's cells and organs. Choices B, C, and D are incorrect because while the cardiovascular system does deliver nutrients to tissues indirectly by transporting them in the blood, regulating body temperature is primarily the role of the endocrine and nervous systems, and protecting the body from infection is the main function of the immune system.

Correct Answer: A

Rationale: The diaphragm is the primary muscle responsible for breathing. It is a large, dome-shaped muscle located at the base of the chest cavity. When it contracts, it flattens, increasing the volume of the chest cavity and causing inhalation. When it relaxes, it returns to its dome shape, decreasing the volume of the chest cavity and causing exhalation. The intercostal muscles, located between the ribs, assist the diaphragm in breathing by expanding and contracting the chest cavity. The rectus abdominis and pectoralis major are not directly involved in the process of breathing.

Correct Answer: B

Rationale: The correct answer is B: Detoxifying harmful substances. While the liver does produce bile for digestion and stores nutrients like glycogen, its primary function is to filter and detoxify blood coming from the digestive tract before passing it to the rest of the body. Therefore, choices A, C, and D are incorrect. Producing insulin is mainly done by the pancreas, digesting food is primarily the role of the stomach and intestines, and storing energy is a function of various organs like muscles and fat cells.

Correct Answer: B

Rationale: The correct answer is B: Hinge. A hinge joint, such as the one found at the elbow, allows for movement primarily in one plane, enabling flexion and extension similar to the movement of a door hinge. This joint structure permits bending and straightening of the arm, controlling the range of motion in a specific direction. Choices A, C, and D are incorrect. A ball and socket joint allows for multi-axial movement like the hip joint, a pivot joint allows for rotation around an axis like the joint between the first and second cervical vertebrae, and a saddle joint allows for movement in two planes at right angles to each other like the joint at the base of the thumb.