What is the function of the endocrine system?

Correct Answer: B

Rationale: The correct answer is B. The endocrine system releases hormones that regulate various functions, including metabolism and growth. It is responsible for producing and releasing hormones that control processes such as metabolism, growth, and development. The digestive enzymes are released by the digestive system, not the endocrine system. Choices A, C, and D are incorrect because protecting the body from infection is primarily the role of the immune system, breaking down food is the function of the digestive system, and regulating the sleep-wake cycle is controlled by the circadian rhythm which is mainly influenced by the brain's hypothalamus and not the endocrine system.

Correct Answer: C

Rationale: The correct answer is C: Skeletal muscle. Skeletal muscle is under voluntary control, allowing for conscious movement of the body. Smooth muscle and cardiac muscle are both types of involuntary muscles that are not under conscious control. Smooth muscle is found in the walls of internal organs and blood vessels, functioning involuntarily. Cardiac muscle makes up the heart and contracts involuntarily to pump blood. Involuntary muscle (choice D) is a general term that encompasses smooth muscle and cardiac muscle, which operate involuntarily throughout the body.

Correct Answer: B

Rationale: Smooth muscle is the correct type of muscle found in the walls of hollow organs like the intestines. It is responsible for movements such as peristalsis, aiding in the movement of food and other materials through the digestive system. Cardiac muscle (Choice A) is found in the heart and is responsible for the heart's contractions, not in hollow organs like the intestines. Skeletal muscle (Choice C) is attached to bones and responsible for voluntary movements, not in hollow organ walls. Voluntary muscle (Choice D) is another term for skeletal muscle, which is under conscious control, unlike smooth muscle in hollow organ walls.

Correct Answer: B

Rationale: The correct answer is B: White blood cell. White blood cells are the primary cells responsible for fighting infections and foreign invaders in the body. Red blood cells carry oxygen to tissues, platelets help in blood clotting to prevent excessive bleeding, and plasma is the liquid component of blood that carries cells and nutrients. White blood cells, also known as leukocytes, play a crucial role in the immune system by identifying and destroying pathogens, such as bacteria, viruses, and other harmful substances. Therefore, they are the key players in the body's defense against infections, making them the correct answer in this scenario. While red blood cells, platelets, and plasma have essential functions in the body, they are not primarily responsible for combating infections like white blood cells.

Correct Answer: B

Rationale: The correct answer is B: Neck. A pivot joint, as found in the neck, allows for rotational movement around a single axis. This type of joint is essential for movements like shaking your head 'no' or looking left and right. Choices A, C, and D are incorrect because the hip, shoulder, and elbow joints are examples of ball-and-socket joints, which allow for a wide range of motion in multiple directions, not just rotational movement around a single axis like a pivot joint.