Which human body system is correctly matched with its function?

Correct Answer: B

Rationale: The circulatory system is responsible for the transportation of oxygen from the lungs to all the body's cells and tissues, as well as removing carbon dioxide from the cells and transporting it back to the lungs to be exhaled. This process is crucial for cellular respiration and the exchange of gases necessary for bodily functions. Choice B accurately matches the role of the circulatory system by describing its function of transporting oxygen to cells and removing carbon dioxide, which is essential for maintaining proper cellular activities. Choices A, C, and D are incorrect because they do not accurately match the body system with its function. The respiratory system primarily involves the exchange of gases in the lungs, not transportation to cells; the lymphatic system deals with immunity through the production of antibodies, not gas exchange; and the endocrine system's main function is hormone regulation, not the transport of gases.

Correct Answer: D

Rationale: Endorphins are the class of hormones most likely to be released after a serious injury. Endorphins are the body's natural pain relievers and are produced in response to stress or pain, helping to alleviate discomfort and promote a sense of well-being. Acetylcholine is a neurotransmitter, not a hormone. Oxytocin is mainly involved in childbirth and lactation. Luteinizing hormone is involved in reproductive functions such as ovulation. Therefore, choices A, B, and C are incorrect in the context of a hormone release following a serious injury.

Correct Answer: C

Rationale: Hypertrophy refers to the enlargement of an organ or tissue, typically due to an increase in the size of individual cells. This can occur in response to increased workload, hormonal stimulation, or other factors. On the other hand, dystrophy refers to the degeneration and deterioration of tissue, atrophy describes the decrease in the size of an organ or tissue, and eutrophy denotes a state of normal nutrition or growth. Therefore, the correct answer is 'Hypertrophy' as it specifically relates to the increase in size or volume of an organ or tissue.

Correct Answer: A

Rationale: The triceps reflex causes the triceps muscle to contract, leading to the extension of the arm. This reflex is a protective response to sudden stretching of the triceps muscle, as seen when a physician taps the triceps tendon during a physical examination. Choice A is the correct answer as it accurately reflects the action of the triceps reflex. Choices B, C, and D are incorrect because they describe actions that are not associated with the triceps reflex. Biceps contraction, forearm supination, flexion, triceps relaxation, and pronation are not part of the triceps reflex arc.

Correct Answer: B

Rationale: The correct answer is the axon. The axon is the elongated, threadlike part of a neuron that carries nerve impulses away from the cell body towards other neurons or target cells, such as muscles or glands, in the direction of a synapse. Action potentials travel along the axon as electrical signals to communicate with neighboring cells. The cell body (choice A) contains the nucleus and organelles but does not transmit action potentials. Neuron (choice C) is a broad term that includes the entire nerve cell, not a specific structure. Myelin (choice D) is a fatty substance that surrounds and insulates axons, aiding in the conduction of nerve impulses, but it does not directly carry the action potential towards a synapse.