which part of the eye is responsible for color vision
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HESI A2

HESI A2 Anatomy and Physiology 2023

1. Which part of the eye is responsible for color vision?

Correct answer: C

Rationale: The correct answer is option C: Retina. The retina contains photoreceptor cells, including cones that are responsible for color vision. Cones are sensitive to different wavelengths of light, allowing us to perceive and differentiate various colors. Choice A, Cornea, is the transparent outer layer of the eye that helps focus light. It does not play a direct role in color vision. Choice B, Iris, is the colored part of the eye that controls the size of the pupil and regulates the amount of light entering the eye. While it is essential for adjusting light levels, it is not directly involved in color vision. Choice D, Lens, is responsible for focusing light onto the retina. It helps to form clear images on the retina but does not play a role in color vision.

2. Which type of blood vessel carries blood back to the heart?

Correct answer: C

Rationale: Veins are the blood vessels that carry deoxygenated blood back to the heart, except for the pulmonary veins which carry oxygenated blood from the lungs. Arteries carry oxygenated blood away from the heart. Capillaries facilitate the exchange of nutrients and gases between the blood and tissues but do not specifically carry blood back to the heart. Lymphatic vessels are part of the lymphatic system responsible for immune function and do not directly carry blood back to the heart. Therefore, the correct answer is veins.

3. Which hormone is responsible for the regulation of calcium levels in the blood?

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.

4. What is the primary function of platelets?

Correct answer: B

Rationale: The primary function of platelets, or thrombocytes, is to clot blood. Platelets play a crucial role in hemostasis by forming clots to prevent excessive bleeding when injuries occur. They are not directly involved in fighting infections, carrying oxygen, or transporting nutrients. Therefore, the correct answer is B.

5. Which brain region is involved in memory formation?

Correct answer: B

Rationale: The hippocampus, located in the temporal lobe, is crucial for memory formation. It plays a vital role in converting short-term memories into long-term memories. Damage to the hippocampus can lead to significant memory deficits, highlighting its importance in the memory process. The cerebellum (Choice A) is primarily involved in coordination and balance, not memory. The brainstem (Choice C) is responsible for basic life functions such as breathing and heart rate, not memory. The frontal lobe (Choice D) is associated with functions like decision-making, problem-solving, and emotions, but not primarily memory formation.

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