A pulse is best described as

Step 1: Analyze the question We are asked to define a "pulse" in terms of what happens in the circulatory system.

Step 2: The concept When the left ventricle contracts, it forces blood into the aorta and arteries under high pressure. Artery walls are elastic, so they expand (dilate/stretch) to accommodate the surge of blood, then recoil as the pressure falls. This rhythmic expansion and recoil of the arterial wall is what you feel as the pulse when you press on the wrist (radial artery) or neck (carotid artery).

Step 3: Evaluate the options

• A. Contraction of arteries to let out blood: Wrong. Arteries have elastic walls that stretch and recoil. They do not actively contract to push blood out.
• B. Contraction of veins to allow blood into them: Wrong. Veins carry blood at low pressure and have no pulse.
• C. Dilation of arteries to accommodate blood rushing through: Correct. This is the arterial wall expanding with each surge of blood from the heart.
• D. Pumping action of the heart to move blood round the body: This describes the heartbeat. The heartbeat causes the pulse, but it is not the pulse itself.

Step 4: Answer The pulse is best described as the dilation of arteries to accommodate blood rushing through, which is option C.

Exam tip: Remember "Heart beats, arteries pulse." The heartbeat is the cause, and the pulse is the effect you feel in the artery. Also, veins have no pulse because the pressure in them is too low.