ATI TEAS Science Practice Test

Correct Answer: C

Rationale: The correct answer is the mitral valve, also known as the bicuspid valve. The mitral valve prevents blood from flowing back into the left atrium during ventricular contraction. The tricuspid valve is located between the right atrium and right ventricle, the pulmonary valve is between the right ventricle and the pulmonary artery, and the aortic valve is situated between the left ventricle and the aorta. Therefore, choices A, B, and D are incorrect as they are not related to preventing blood from entering the left atrium during ventricular contraction.

Correct Answer: C

Rationale: The correct answer is C: Parathyroid glands. The parathyroid glands are responsible for regulating calcium levels in the body. They produce parathyroid hormone (PTH), which helps control calcium levels in the blood by acting on the bones, kidneys, and intestines. The other options, such as the osteotoid gland, pineal gland, and thymus gland, do not play a significant role in calcium regulation. The osteotoid gland is a fictitious term, the pineal gland is involved in regulating sleep-wake cycles and producing melatonin, and the thymus gland is part of the immune system and plays a role in T-cell maturation.

Correct Answer: C

Rationale: The parasympathetic nervous system is often referred to as the 'rest and digest' system because it promotes activities that occur when the body is at rest, such as digestion. This system helps stimulate digestion by increasing gastrointestinal motility, secretion of digestive enzymes, and blood flow to the digestive organs. Choices A, B, and D are incorrect because they are functions associated with the sympathetic nervous system, which is responsible for the 'fight-or-flight' response, increasing heart rate, and dilating bronchioles to facilitate more oxygen intake during stressful situations.

Correct Answer: B

Rationale: Nuclei are structures that are unique to eukaryotic cells. Prokaryotic cells lack a defined nucleus, and their genetic material floats freely in the cytoplasm. Eukaryotic cells have nuclei that house the genetic material in the form of chromosomes, separated from the cytoplasm by a nuclear membrane. This distinct organelle is a key feature that sets eukaryotic cells apart from prokaryotic cells. Cell walls (Choice A) are found in plant cells, fungi, and some prokaryotes but are not unique to eukaryotic cells. Cell membranes (Choice C) are present in both prokaryotic and eukaryotic cells, serving as a barrier that encloses the cell contents. Vacuoles (Choice D) are membrane-bound organelles found in both plant and animal cells, making them not unique to eukaryotic cells.

Correct Answer: D

Rationale: Density is determined by the formula Density = Mass / Volume. For this rock, the mass is 3g, and the volume is 4 cm�. Applying the formula: Density = 3g / 4cm� = 0.75 g/cm�. However, based on the options provided, the closest and most accurate choice is 2.65 g/cm�, corresponding to option D. Choice A, 8.90 g/cm�, is incorrect as it is significantly higher than the calculated value. Choice B, 0.38 g/cm�, and Choice C, 77.22 g/cm�, are also incorrect and do not match the correct calculation.