Normal mice injected with high doses of LPS die of septic shock. Mice resistant to LPS-induced septic shock have a mutation in which receptor?

Correct Answer: A

Rationale: Step 1: TLR4 is the receptor for lipopolysaccharide (LPS), a component of gram-negative bacteria. Step 2: The question states that normal mice injected with high doses of LPS die, indicating TLR4 activation. Step 3: Mutations in TLR4 can confer resistance to LPS-induced septic shock. Step 4: Therefore, the correct answer is A: TLR4, as it is directly involved in recognizing LPS and triggering septic shock. Summary: B: TLR5 does not specifically bind LPS. C: NOD1 and D: NOD2 are involved in intracellular recognition of bacterial components, not LPS.

Correct Answer: A

Rationale: Step 1: Hypervariable regions are responsible for antigen binding specificity. Step 2: Complementary Determining Regions (CDRs) are the specific locations within the hypervariable regions. Step 3: As CDRs are part of the hypervariable regions, choice A is correct. Summary: Choices B, C, and D are incorrect because hypervariable regions are not in the constant region, are present in secreted antibodies, and are found in both heavy and light chains.

Correct Answer: D

Rationale: The correct answer is D because cardiac output refers to the amount of blood pumped by the heart into the systemic circulation per minute. It is a crucial measure of heart function. Option A, coronary insufficient circulation, specifically refers to inadequate blood flow to the heart muscle itself, not overall cardiac output. Option B, a defect in heart valves, would affect the efficiency of blood flow but not necessarily the total amount of blood pumped. Option C, a disorder in heart rhythm, relates to irregular heartbeat patterns rather than the volume of blood pumped. Therefore, D is the correct choice as it directly relates to the definition of cardiac output.

Correct Answer: A

Rationale: The correct answer is A: Red blood cell. Red blood cells, also known as erythrocytes, contain hemoglobin that binds to oxygen and carbon dioxide for transport in the bloodstream. They are specifically designed for gas exchange. White blood cells (B) are part of the immune system and fight infections. Platelets (C) are responsible for blood clotting. Hematocrit (D) refers to the proportion of red blood cells in the blood, not a specific type of cell responsible for gas transport.

Correct Answer: C

Rationale: The correct answer is C: Hemorrhage. Hemorrhage refers to excessive bleeding. Thrombosis (A) is the formation of blood clots, not excessive bleeding. Embolus (B) is a blood clot that travels through the bloodstream and blocks a blood vessel. Hemostasis (D) is the process of stopping bleeding, not the term for excessive bleeding. In summary, only choice C directly relates to the medical term for excessive bleeding.