Final answer:
The part 'brady-' in 'bradycardia' signifies a slow condition, and '-cardia' relates to the heart, thus 'bradycardia' indicates a slower-than-normal heart rate. It can be caused by intrinsic heart node issues or external factors such as metabolic disorders or medication effects.
Step-by-step explanation:
The part of the word "bradycardia" that indicates a slow or deficient heartbeat is "brady-”. This prefix comes from Greek origin meaning 'slow'. The suffix '-cardia' pertains to the heart. Hence, bradycardia refers to a condition where the resting heart rate is slower than normal, specifically below 60 beats per minute (bpm) in adults. Trained athletes may naturally have lower heart rates due to higher cardiovascular efficiency, but in others, it may signify an underlying health issue.
Conditions related to bradycardia can be caused by inherent factors such as abnormalities of the sinoatrial (SA) or atrioventricular (AV) nodes, which are critical in maintaining normal heart rhythm. External factors can also lead to bradycardia, including metabolic disorders, endocrine system pathologies, especially involving the thyroid, or the over-prescription of beta blocker medications that reduce heart rate.