Final answer:
The Korotkoff sounds, which denote turbulent blood flow in arteries, are heard at the beginning of systole for systolic pressure, and the cessation marks diastolic pressure.
Step-by-step explanation:
The sounds of Korotkoff occur in arteries at the beginning of systole. The Korotkoff sounds are noises created by turbulent blood flow in the vessels that can be heard when measuring blood pressure using a sphygmomanometer and a stethoscope. The first Korotkoff sound indicates systolic pressure, which is heard as the air pressure in the cuff drops and allows blood to begin flowing again. As the cuff is further deflated, allowing for unobstructed blood flow in the artery, the sounds will eventually cease, and the last Korotkoff sound heard is used to determine diastolic pressure.