Which type of muscle tissue is voluntary?

Correct Answer: B

Rationale: The correct answer is B, Skeletal muscle. Skeletal muscle is a type of voluntary muscle tissue, allowing conscious control over its movement. Unlike smooth and cardiac muscle, which are involuntary, skeletal muscle is under direct voluntary control. Cardiac muscle (choice A) is involuntary and found in the heart. Smooth muscle (choice C) is also involuntary and found in the walls of internal organs. While skeletal muscle is striated (contains stripes), choice D is not the best answer as it does not specifically address the voluntary nature of skeletal muscle.

Correct Answer: B

Rationale: Parathyroid hormone, produced by the parathyroid glands, is responsible for regulating calcium levels in the blood. It achieves this by increasing calcium absorption in the intestines and kidneys, thus maintaining appropriate calcium levels in the bloodstream. Insulin is involved in glucose metabolism, not calcium regulation. Cortisol is a stress hormone that affects various body functions but not calcium levels. Melatonin is responsible for regulating the sleep-wake cycle, not calcium levels.

Correct Answer: B

Rationale: The correct answer is B: To produce bile. The liver's primary function in the digestive system is to produce bile. Bile is essential for the digestion and absorption of fats in the small intestine. It helps emulsify fats, making it easier for enzymes to break them down into smaller molecules for absorption. Choices A, C, and D are incorrect as storing glucose is primarily done in the liver for energy maintenance, detoxifying harmful substances is a function of the liver related to metabolism but not specifically in the digestive system, and absorbing nutrients is mainly done in the small intestine rather than the liver.

Correct Answer: A

Rationale: The correct answer is the cerebellum. Located at the back of the brain, the cerebellum plays a crucial role in controlling balance, coordination, and fine motor movements. It receives information from the sensory systems, the spinal cord, and other parts of the brain to coordinate voluntary movements and maintain posture. Damage to the cerebellum can result in issues with balance, coordination, and muscle tone. The cerebrum is responsible for higher brain functions like thinking and problem-solving, the medulla oblongata controls vital autonomic functions like breathing and heartbeat, and the brainstem serves as a pathway for neural fibers traveling to and from the brain.

Correct Answer: A

Rationale: The correct answer is the pancreas. The pancreas is responsible for producing insulin, a hormone crucial for regulating blood glucose levels. Insulin plays a key role in allowing cells to take in glucose, thereby helping to keep blood sugar levels in check. The liver (choice B), gallbladder (choice C), and kidneys (choice D) do not produce insulin. The liver is involved in glycogen storage and glucose regulation, the gallbladder stores bile, and the kidneys filter blood and regulate fluid balance.

Correct Answer: A

Rationale: The correct answer is the cerebellum. The cerebellum, situated at the back of the brain, is responsible for coordinating voluntary movements and maintaining balance and posture. It receives information from the sensory systems, the spinal cord, and other parts of the brain to regulate motor movements. The cerebrum (choice B) is responsible for higher brain functions such as thinking and decision-making, the medulla oblongata (choice C) controls vital autonomic functions like breathing and heart rate, and the hypothalamus (choice D) is involved in regulating basic biological needs like hunger, thirst, and body temperature.

Correct Answer: B

Rationale: White blood cells, also known as leukocytes, play a crucial role in the immune system by primarily combating infections. These cells can identify and destroy pathogens, such as bacteria and viruses, helping the body defend against illnesses and maintain overall health. Red blood cells are responsible for oxygen transport, platelets aid in blood clotting, and plasma carries various components throughout the circulatory system, but none of these functions involve fighting infections like white blood cells do.

Correct Answer: B

Rationale: The thyroid gland is responsible for producing hormones, such as thyroxine, that play a crucial role in regulating metabolism, energy production, and overall growth and development in the body. The pituitary gland, while important for hormone regulation, does not primarily regulate metabolism. The adrenal gland is responsible for producing hormones like cortisol and adrenaline, which are more related to stress response than direct metabolism regulation. The pineal gland mainly produces melatonin, which regulates sleep-wake cycles and not metabolism. Therefore, the correct answer is the thyroid gland.

Correct Answer: C

Rationale: The correct answer is C: Medulla oblongata. The medulla oblongata, situated in the brainstem, plays a crucial role in regulating vital functions such as heart rate, breathing, and blood pressure. It serves as the control center for involuntary actions, ensuring the body's automatic functions work properly. Choices A, B, and D are incorrect because the cerebrum is primarily responsible for functions such as thinking, voluntary movements, and sensory processing; the cerebellum is involved in coordination, balance, and muscle control; and the hypothalamus regulates body temperature, thirst, hunger, and some aspects of the autonomic nervous system but not specifically heart rate and breathing.