Which fibers distribute the electrical impulse to the ventricles, causing them to contract?

Correct Answer: A

Rationale: The correct answer is A: Purkinje fibers. Purkinje fibers are specialized cardiac muscle fibers that distribute the electrical impulse from the AV node to the ventricles, causing them to contract. They are located in the ventricles and ensure synchronized and efficient contraction. The SA node (B) is the pacemaker of the heart, initiating the electrical impulse. The AV node (C) delays the impulse to allow for atrial contraction before ventricular contraction. The Bundle of His (D) is a pathway for the electrical impulse from the AV node to the bundle branches, which then lead to the Purkinje fibers for ventricular contraction.

Correct Answer: A

Rationale: The correct answer is A: Ischemic stroke. This type of stroke is caused by a blockage in an artery supplying blood to the brain, leading to a lack of oxygen and nutrients to brain cells. This blockage can be due to a blood clot or plaque buildup. Ischemic strokes account for the majority of stroke cases. Incorrect choices: B: Hemorrhagic stroke - This type of stroke occurs when a blood vessel in the brain ruptures, leading to bleeding in the brain. C: Transient ischemic attack - Also known as a mini-stroke, it is caused by a temporary blockage of blood flow to the brain, often resolving on its own without permanent damage. D: Embolism - This refers to a condition where a blood clot or other foreign material travels through the bloodstream and blocks a blood vessel in the brain.

Correct Answer: A

Rationale: The correct answer is A: Paroxysmal nocturnal dyspnea. This condition is characterized by sudden, severe shortness of breath at night. It can be caused by heart failure or other cardiac conditions. Sleep apnea (B) is a disorder where breathing repeatedly stops and starts during sleep, not specifically related to acute shortness of breath. Orthopnea (C) is difficulty breathing while lying flat and is not specific to nighttime episodes. Dyspnea (D) is a general term for difficulty breathing and does not specifically refer to acute episodes at night.

Correct Answer: A

Rationale: Pulmonary edema is the correct answer because it is characterized by fluid accumulation in the lungs, leading to difficulty in breathing. This condition is often a result of heart failure, where the heart is unable to pump blood effectively, causing fluid to leak into the lungs. It can also be caused by lung infections or exposure to toxins. Pleurisy (B) is inflammation of the pleura, the lining around the lungs, leading to chest pain exacerbated by breathing. Pleural effusion (C) is fluid accumulation in the pleural space around the lungs, not within the lungs themselves. Pneumothorax (D) is characterized by air accumulation in the pleural space, causing lung collapse, but not fluid collection in the lungs.

Correct Answer: A

Rationale: The correct answer is A: Pneumothorax. Pneumothorax is the term used to describe a condition where the lung collapses due to air leaking into the pleural space. This causes pressure on the lung, leading to its collapse. Pleural effusion (B) is the accumulation of fluid in the pleural space, not air. Atelectasis (C) is the collapse of a portion or the entire lung due to various reasons but not air leakage. Pulmonary fibrosis (D) is a condition where lung tissue becomes scarred and thickened, not related to air leakage causing lung collapse.