1. Which part of the neuron receives incoming signals from other neurons and conducts them toward the cell body?

A. Axon
B. Dendrite
C. Synapse
D. Myelin sheath

Correct answer: b

Rationale: The correct answer is B: Dendrite. Dendrites are the part of the neuron that receive incoming signals from other neurons and conduct them toward the cell body. They play a crucial role in communication between neurons by receiving neurotransmitters released from neighboring neurons. Axons transmit signals away from the cell body, synapses are the junctions where neurons communicate with each other, and myelin sheath is a fatty insulation that surrounds and protects axons. Therefore, in this scenario, dendrites are specifically responsible for receiving and conducting incoming signals towards the cell body.

2. The microscopic units responsible for muscle contraction are called

A. Neurons
B. Myofibrils
C. Tendons
D. Sarcomeres

Correct answer: D

Rationale: The correct answer is D: Sarcomeres. Sarcomeres are the fundamental contractile units of skeletal muscle. They are composed of overlapping actin and myosin filaments that slide past each other during muscle contraction, resulting in muscle shortening. Neurons (A) are nerve cells that transmit signals to and from the brain. Myofibrils (B) are thread-like structures within muscle fibers that contain sarcomeres. Tendons (C) are fibrous connective tissues that attach muscles to bones, but they are not directly involved in muscle contraction like sarcomeres are.

3. Which of the following is an example of a decomposition reaction?

A. 2H2 + O2 â†’ 2H2O
B. CaCO3 â†’ CaO + CO2
C. 2Na + Cl2 â†’ 2NaCl
D. N2 + 3H2 â†’ 2NH3

Correct answer: b

Rationale: Decomposition reactions involve the breakdown of a compound into simpler substances.

4. What is the term for a solution that has a lower concentration of solute compared to another solution?

A. Saturated solution
B. Unsaturated solution
C. Dilute solution
D. Concentrated solution

Correct answer: C

Rationale: A dilute solution has a lower concentration of solute compared to another solution. The other choices do not accurately describe a dilute solution.

5. Which of the following blood vessels carries oxygenated blood from the lungs back to the left atrium of the heart?

A. Pulmonary artery
B. Pulmonary vein
C. Aorta
D. Inferior vena cava

Correct answer: B

Rationale: The correct answer is B: Pulmonary vein. The pulmonary vein is the blood vessel that carries oxygenated blood from the lungs back to the heart. Oxygenated blood flows from the lungs through the pulmonary veins to the left atrium of the heart, where it is then pumped out to the rest of the body through the aorta. The pulmonary artery, on the other hand, carries deoxygenated blood from the heart to the lungs for oxygenation. The aorta is the largest artery in the body and carries oxygenated blood from the heart to the rest of the body. The inferior vena cava carries deoxygenated blood from the lower body back to the right atrium of the heart. Therefore, the correct choice is B, the pulmonary vein, as it specifically carries oxygenated blood from the lungs back to the left atrium of the heart.

6. The innate immune system provides:

A. Nonspecific, immediate defense against pathogens
B. Specific, long-term immune response through memory cells
C. Both (a) and (b)
D. Neither (a) nor (b)

Correct answer: A

Rationale: The correct answer is A: 'Nonspecific, immediate defense against pathogens.' The innate immune system is the body's first line of defense against pathogens and provides a rapid, nonspecific response. It includes physical barriers like the skin, chemical barriers like stomach acid, and cellular responses like inflammation. This system does not involve memory cells or provide long-term immunity, which are characteristics of the adaptive immune system. Therefore, option A accurately describes the function of the innate immune system as a quick and nonspecific defense mechanism.