What is the primary action a healthcare professional should take when a patient with a suspected myocardial infarction (MI) arrives in the emergency department?

Correct Answer: B

Rationale: Administering oxygen and obtaining an ECG are crucial initial steps when managing a suspected myocardial infarction (MI). Oxygen helps improve oxygenation to the heart muscle, while an ECG is essential to diagnose an MI promptly. Applying a cold compress, encouraging the patient to walk, or providing a high-carbohydrate meal are not appropriate actions in the initial management of a suspected MI. Applying a cold compress can delay necessary interventions, encouraging the patient to walk may worsen the condition, and providing a high-carbohydrate meal is irrelevant to the immediate needs of a patient with a suspected MI.

Correct Answer: A

Rationale: The correct answer is A: Pacemaker of the heart. The SA node, known as the natural pacemaker, initiates the electrical impulses that set the rhythm for the heartbeat. It is responsible for coordinating the heart's contractions by generating electrical signals at regular intervals. Choice B is incorrect as the SA node's primary function is not related to blood pressure regulation. Choice C is incorrect as the SA node does not cause electrical conduction delay but rather initiates and conducts the electrical impulses. Choice D is incorrect as the SA node does not directly stimulate muscle contraction but rather initiates the electrical events that lead to muscle contraction.

Correct Answer: A

Rationale: The correct answer is A: Myasthenia gravis. Myasthenia gravis is characterized by muscle weakness caused by autoimmune attack on acetylcholine receptors at the neuromuscular junction. This results in impaired communication between nerves and muscles. Choice B, Multiple sclerosis, is a condition where the immune system attacks the protective myelin sheath covering the nerves in the central nervous system, leading to communication issues between the brain and the rest of the body. Choice C, Amyotrophic lateral sclerosis, is a progressive neurodegenerative disease affecting motor neurons in the brain and spinal cord, not involving acetylcholine receptors. Choice D, Guillain-Barr© syndrome, is an acute condition where the immune system attacks the peripheral nerves, causing muscle weakness and paralysis, but it does not target acetylcholine receptors.

Correct Answer: A

Rationale: The epiglottis is a flap of tissue that closes over the trachea during swallowing to prevent food and liquids from entering the airway. Choice A is correct because the primary function of the epiglottis is to act as a lid over the trachea, ensuring that food goes down the esophagus and not into the windpipe. Choices B, C, and D are incorrect as they do not describe the specific role of the epiglottis during swallowing.