Usual? Why? Heart: rate is controlled 24/7 by ANS. Without ANS input, resting heart rate is mid-range, ~110-120 BPM, i.e. tachycardia. Common lower heart rates a result of dominant parasympathetic release of acetylcholine neurotransmitter ↓ing atrial heart muscle self-stimulation rate & intensity of contraction; opposite the response to sympathetic norepineprhine/epinephrine release onto atrial & ventricular cells.
Answered 2/19/2015
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