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.

Correct Answer: B

Rationale: Thyroxine, produced by the thyroid gland, is the hormone responsible for regulating metabolism. It plays a fundamental role in controlling the body's metabolic rate, affecting processes such as energy production and utilization. Thyroxine also influences growth and development in the body. Choice A, Insulin, is involved in regulating blood sugar levels and promoting the storage of glucose. While insulin has an impact on metabolism, it is not primarily responsible for regulating overall metabolic rate. Choice C, Glucagon, acts in opposition to insulin, stimulating the release of glucose from the liver to increase blood sugar levels. Glucagon primarily targets glucose regulation rather than overall metabolism. Choice D, Cortisol, is known as the stress hormone and plays a role in the body's response to stress, regulation of blood pressure, immune function, and anti-inflammatory actions. While cortisol can have some effects on metabolism during stress responses, it is not the primary hormone responsible for regulating overall metabolic rate.

Correct Answer: B

Rationale: The correct answer is B: Adrenaline. Adrenaline, also known as epinephrine, is the hormone involved in the fight or flight response. It is released by the adrenal glands, preparing the body for action by increasing heart rate, dilating airways, and mobilizing energy stores. Choice A, Cortisol, is a hormone released in response to stress but is not directly involved in the fight or flight response. Choice C, Thyroxine, is a hormone produced by the thyroid gland that regulates metabolism and growth, not specifically associated with the fight or flight response. Choice D, Melatonin, is a hormone that regulates sleep-wake cycles and is not involved in the fight or flight response.

Correct Answer: B

Rationale: The correct answer is B: Support and protection. The primary functions of the skeletal system include providing structural support to the body and protecting internal organs. While the skeletal system also plays a role in hematopoiesis (production of blood cells) and stores minerals, its main function is to support the body's framework and protect vital organs. Choices A, C, and D are incorrect as they do not directly relate to the primary functions of the skeletal system.

Correct Answer: A

Rationale: The biceps brachii muscle is the primary muscle responsible for flexing the forearm at the elbow joint. When the biceps brachii contracts, it causes the forearm to move towards the upper arm, resulting in flexion at the elbow. In contrast, the triceps brachii is responsible for extending the forearm, the deltoid muscle is primarily involved in shoulder movements, and the brachialis muscle also aids in flexion of the forearm but to a lesser extent compared to the biceps brachii.