Final answer:
The term 'Dromotropic' refers to the increased speed of conduction, especially in the context of the heart's electrical conduction system.
Step-by-step explanation:
The term that refers to increased speed of conduction is A. Dromotropic. This term is often used in relation to heart function, where it refers specifically to the conduction velocity within the heart, increasing the rate at which the electrical impulse is passed along the heart's conduction system. This contrasts with chronotropic effects, which represent changes in heart rate, and inotropic effects, which are changes in the strength of the heart's contraction. Acetylcholine (ACh) is a neurotransmitter that generally has the opposite effect; it decreases heart rate by increasing parasympathetic stimulation and can decrease dromotropy.