Which brain part is responsible for regulating heart rate and blood pressure?

Correct Answer: B

Rationale: The medulla oblongata, situated in the brainstem, plays a crucial role in controlling essential functions like heart rate, blood pressure, and breathing. It contains vital cardiovascular and respiratory centers, making it the correct choice for the regulation of heart rate and blood pressure. The cerebellum is primarily involved in coordinating movement and balance, not in regulating heart rate and blood pressure. The hypothalamus is responsible for maintaining homeostasis, regulating body temperature, hunger, and thirst, but not specifically heart rate and blood pressure. The pons is involved in functions like sleep, respiration, and bladder control, not primarily in regulating heart rate and blood pressure.

Correct Answer: B

Rationale: The correct answer is B: To break down food. The stomach's primary function in digestion is to mechanically and chemically break down food. It achieves this by utilizing gastric acid and digestive enzymes to convert food into chyme, a semi-liquid mixture. The chyme is then passed to the small intestine for further processing and absorption of nutrients. Choices A, C, and D are incorrect because the stomach's main role is not to absorb nutrients, secrete digestive enzymes, or transport nutrients; instead, it primarily focuses on breaking down food.

Correct Answer: B

Rationale: The correct answer is B: To store urine. The urinary bladder's primary function is to store urine produced by the kidneys until it is ready to be excreted from the body. It acts as a reservoir that temporarily holds urine until an appropriate time for elimination. Choices A, C, and D are incorrect because the urinary bladder does not filter waste from the blood, regulate fluid balance, or directly remove waste from the body. These functions are primarily carried out by the kidneys and other organs in the excretory system.

Correct Answer: D

Rationale: The epiglottis is the structure that prevents food from entering the airway. It acts as a lid over the trachea during swallowing, directing food to the esophagus instead of the windpipe (trachea). The trachea (Choice A) is the windpipe that allows air to pass into the lungs, the esophagus (Choice B) is the tube that carries food from the mouth to the stomach, and the diaphragm (Choice C) is a muscle involved in breathing and not in preventing food passage.

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: B

Rationale: The adrenal cortex is the organ responsible for producing stress hormones like cortisol and aldosterone, which play a crucial role in the body's stress response. During stress, the adrenal cortex releases cortisol, a hormone that helps the body deal with stress by increasing blood sugar, suppressing the immune system, and aiding in metabolism. Parathyroid gland is responsible for calcium regulation, the posterior pituitary gland secretes hormones like oxytocin and vasopressin which are not directly related to the stress response, and the hypothalamus plays a role in regulating hormonal balance and various bodily functions but is not primarily responsible for producing stress hormones.

Correct Answer: B

Rationale: The correct answer is B. The thymus is not a principal organ of the nervous system; it is part of the immune system. The brain, spinal cord, and ganglia are principal organs of the nervous system. The brain is responsible for processing information, the spinal cord helps transmit signals between the brain and the rest of the body, and ganglia are clusters of nerve cells that support the nervous system's functions. Therefore, the thymus is the correct answer as it is not directly involved in nervous system functions.

Correct Answer: B

Rationale: Digestion begins in the mouth. Mechanical digestion through chewing and chemical digestion through saliva initiate the breakdown of food. Enzymes in saliva start breaking down carbohydrates, marking the beginning of the digestive process. The stomach primarily functions in further breaking down food and mixing it with gastric juices. The small intestine is where most of the digestion and absorption of nutrients occur. The esophagus is a muscular tube that helps move food from the mouth to the stomach, but digestion does not begin there.

Correct Answer: B

Rationale: The correct answer is B: Ribosome. Ribosomes, the cellular structures located in the cytoplasm or on the endoplasmic reticulum, are responsible for protein synthesis in the cell. They are the sites where mRNA is translated into proteins, making them essential for the synthesis of proteins in all living cells. The other choices, such as the nucleus (choice A), endoplasmic reticulum (choice C), and Golgi apparatus (choice D), are not directly involved in protein synthesis. The nucleus contains DNA and is responsible for housing the genetic material, the endoplasmic reticulum is involved in protein folding and transport, and the Golgi apparatus is responsible for modifying, sorting, and packaging proteins.