Which part of the neuron is responsible for transmitting signals away from the cell body and toward other neurons or muscles?

Correct Answer: A

Rationale: The axon is the part of the neuron responsible for transmitting signals away from the cell body and toward other neurons or muscles. It is a long, slender projection covered by the myelin sheath, which speeds up signal transmission. Dendrites, on the other hand, receive signals from other neurons and transmit them toward the cell body. The synapse is the junction between two neurons where communication occurs, but it is not responsible for transmitting signals away from the cell body.

Correct Answer: A

Rationale: Calcitonin, produced by the thyroid gland, is responsible for regulating calcium levels in the blood. It works by decreasing blood calcium levels through two main mechanisms: promoting calcium uptake by bones and decreasing calcium reabsorption in the kidneys. Parathyroid hormone (PTH), on the other hand, increases blood calcium levels by promoting calcium release from bones and increasing calcium absorption in the intestines. Thyroxine, another thyroid hormone, primarily regulates metabolism and has no direct influence on calcium levels. Insulin, produced by the pancreas, is involved in regulating blood sugar levels and is not related to calcium homeostasis.

Correct Answer: A

Rationale: The primary function of the coronary arteries is to carry oxygenated blood to the heart muscle. Oxygenated blood is crucial for providing nutrients and oxygen to the heart muscle cells, enabling the heart to work efficiently. Without this oxygenated blood supply, the heart muscle may not receive the required nutrients and oxygen, potentially resulting in heart damage or dysfunction. Choices B, C, and D are incorrect as coronary arteries do not carry deoxygenated blood from the heart muscle, pump blood to the lungs for oxygenation, or regulate blood pressure in the systemic circulation. The coronary arteries specifically supply oxygenated blood to the heart muscle to support its function and vitality.

Correct Answer: C

Rationale: The nasal passages are responsible for humidifying and warming inhaled air before it reaches the lungs. The mucous membranes in the nasal passages help add moisture to the air and warm it to body temperature. This process is crucial for protecting the lung tissues from potential damage caused by cold and dry air, ensuring optimal conditions for respiration. The trachea (Choice A) is responsible for conducting air to and from the lungs, the larynx (Choice B) is involved in sound production and protecting the airway during swallowing, and the bronchi (Choice D) are the branches of the trachea that further divide to deliver air to the lungs but are not primarily responsible for humidifying and warming inhaled air.

Correct Answer: A

Rationale: The main function of lysosomes is to break down and recycle cellular waste materials, such as old organelles, foreign substances, and cellular debris. This process is crucial for maintaining cellular homeostasis and proper functioning. Storing carbohydrates (B), synthesizing lipids (C), and transcribing DNA into mRNA (D) are not functions typically associated with lysosomes. Storing carbohydrates is primarily done by other organelles like vacuoles. Synthesizing lipids is a function usually associated with the endoplasmic reticulum and transcribing DNA into mRNA occurs in the nucleus by the process of transcription.