which muscle is responsible for the extension of the elbow
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HESI A2

HESI A2 Anatomy and Physiology Practice Test 2023

1. Which muscle is responsible for the extension of the elbow?

Correct answer: B

Rationale: The correct answer is B: Triceps brachii. The triceps brachii muscle is responsible for extending the elbow joint. It is located on the back of the upper arm and acts in opposition to the biceps brachii, which is responsible for elbow flexion. The deltoid muscle is primarily responsible for shoulder abduction, not elbow extension. The pectoralis major muscle is involved in movements of the shoulder joint, not the elbow.

2. Which part of the brain controls voluntary movement?

Correct answer: B

Rationale: The cerebrum, specifically the motor cortex located within it, is responsible for controlling voluntary movements such as walking, writing, and speaking. This region of the brain plays a crucial role in coordinating and executing voluntary muscle actions, making it the correct answer in this context. The cerebellum (Choice A) primarily coordinates balance, posture, and coordination of voluntary movements but does not control voluntary movement itself. The brainstem (Choice C) is responsible for basic life functions like breathing and heart rate, not voluntary movements. The medulla oblongata (Choice D) controls vital functions like blood pressure and breathing, not voluntary movement.

3. When the pulmonary valve and aortic valves are open, where can blood flow?

Correct answer: C

Rationale: When the pulmonary valve and aortic valves are open, blood can flow between the heart and the rest of the body. The pulmonary valve allows blood to flow from the right ventricle to the lungs for oxygenation, while the aortic valve permits blood to flow from the left ventricle to the rest of the body for distribution of oxygen and nutrients. This circulation pathway ensures that oxygen-rich blood is pumped to the body tissues. Choices A, B, and D are incorrect because when the pulmonary valve and aortic valves are open, blood is not flowing between the ventricles, from atrium to ventricle, or between the atria; instead, it is being pumped out of the heart to the lungs and the rest of the body.

4. Which gland is responsible for regulating metabolism and calcium levels?

Correct answer: C

Rationale: The correct answer is the thyroid gland (Choice C). The thyroid gland plays a crucial role in regulating metabolism by producing hormones like thyroxine, which control the body's metabolic rate. It also helps in controlling calcium levels in the blood through the release of calcitonin. The pituitary gland (Choice A) is known as the 'master gland' as it controls other glands but is not primarily responsible for regulating metabolism and calcium levels. The adrenal gland (Choice B) produces hormones like cortisol and adrenaline, which are involved in the stress response and metabolism, but they do not specifically regulate calcium levels. The pineal gland (Choice D) mainly produces melatonin, a hormone that helps in regulating sleep-wake cycles and has no direct role in metabolism or calcium level regulation.

5. What is the role of the spleen in the immune system?

Correct answer: A

Rationale: The spleen plays a crucial role in the immune system by filtering blood, specifically removing old or damaged red blood cells. It also stores lymphocytes, which are white blood cells that help fight infections. While the spleen does not produce white blood cells or antibodies, its main functions lie in blood filtration and storage of immune cells. Therefore, the correct answer is A. Choice B is incorrect because the spleen does not produce white blood cells. Choice C is incorrect as the spleen stores lymphocytes but does not primarily function to do so. Choice D is incorrect because the spleen does not produce antibodies.

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