Nokea
Which of the following neurotransmitters slows down the activity of neurons, preventing them from becoming overexcited?
- A. Acetylcholine
- B. Dopamine
- C. GABA
- D. Serotonin
Correct Answer: C
Rationale: The correct answer is C: GABA (gamma-aminobutyric acid). GABA acts as an inhibitory neurotransmitter that reduces neuronal activity, thus preventing overexcitation. Acetylcholine (choice A) is involved in muscle control and cognitive function, but it is not primarily responsible for slowing down neuronal activity. Dopamine (choice B) plays a role in reward-motivated behavior and motor control, rather than inhibiting neuronal firing. Serotonin (choice D) is involved in mood regulation, sleep, and appetite but does not primarily slow down neuronal activity to prevent overexcitation.
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What is hydroxyapatite?
- A. A mixture of minerals such as calcium and phosphorus that strengthen the collagen matrix of bone.
- B. The structural unit of a bone that runs the length of the bone.
- C. The covering of bones at the point of articulation to prevent grinding.
- D. The lightest portion of a long bone and concentrated at the ends.
Correct Answer: A
Rationale: Hydroxyapatite is a mineral compound composed of calcium and phosphorus that plays a crucial role in strengthening the collagen matrix of bones, contributing to their structural integrity and hardness. It is a key component of bone tissue and provides the mineralization necessary for bone strength and density. Choice B is incorrect because the structural unit of a bone is the osteon or Haversian system, not hydroxyapatite. Choice C is incorrect as it describes cartilage, not hydroxyapatite. Choice D is incorrect as it refers to the epiphysis, which is not synonymous with hydroxyapatite.
Which organelle in the cell is responsible for producing energy in the form of ATP?
- A. Nucleus
- B. Mitochondria
- C. Ribosome
- D. Golgi apparatus
Correct Answer: B
Rationale: The correct answer is B: Mitochondria. Mitochondria are known as the powerhouses of the cell and are responsible for producing energy in the form of ATP through cellular respiration. ATP is the primary energy currency of the cell, powering various cellular activities. The nucleus (choice A) is responsible for housing the cell's genetic material but is not involved in ATP production. Ribosomes (choice C) are involved in protein synthesis, not energy production. The Golgi apparatus (choice D) is responsible for modifying, sorting, and packaging proteins for secretion, not for ATP production.
Which of the following glands produces growth hormone?
- A. Pituitary
- B. Thyroid
- C. Adrenal
- D. Pancreas
Correct Answer: A
Rationale: The correct answer is A: Pituitary. The pituitary gland, also known as the master gland, produces growth hormone, which plays a crucial role in stimulating growth and cell reproduction. Choice B, the thyroid gland, primarily produces hormones that regulate metabolism, not growth hormone. Choice C, the adrenal glands, produce hormones like cortisol and adrenaline, but not growth hormone. Choice D, the pancreas, produces insulin and glucagon for regulating blood sugar levels, not growth hormone.
Which organ system is primarily responsible for transporting nutrients throughout the body?
- A. Respiratory
- B. Digestive
- C. Circulatory
- D. Nervous
Correct Answer: C
Rationale: The circulatory system, also known as the cardiovascular system, is primarily responsible for transporting nutrients and oxygen throughout the body. The heart pumps blood through blood vessels, delivering essential nutrients to cells and tissues. This system consists of the heart, blood vessels, and blood, working together to ensure the proper distribution of nutrients and removal of waste products. Choice A, the respiratory system, is responsible for gas exchange (oxygen and carbon dioxide) and not primarily involved in nutrient transportation. Choice B, the digestive system, is responsible for breaking down food and absorbing nutrients but does not transport nutrients throughout the body. Choice D, the nervous system, controls and coordinates body functions through electrical signals and is not directly involved in nutrient transportation.
Where does the maturation of T-cells and the production of T-cell receptors occur?
- A. Thymus
- B. Spleen
- C. Lymph nodes
- D. Bone marrow
Correct Answer: A
Rationale: The correct answer is the Thymus. T-cells mature and develop their receptors in the thymus gland, making it a vital organ for the immune system. The thymus provides the necessary environment for T-cells to differentiate and acquire their specific receptors and functions, which are essential for their role in the adaptive immune response. The spleen, lymph nodes, and bone marrow are all important components of the immune system, but they do not primarily serve as sites for T-cell maturation and T-cell receptor production.