the cells that control the resting heart rate are found at sa node.
the cells that control the resting heart rate are found at sa node.
where are the cells that control the resting heart rate found?
sa node
section::::in different circumstances.









































heart rate is not a stable value and it increases or decreases in response to the body's need in a way to maintain an equilibrium (basal metabolic rate) between requirement and delivery of oxygen and nutrients. the normal sa node firing rate is affected by autonomic nervous system activity: sympathetic stimulation increases and parasympathetic stimulation decreases the firing rate. a number of different metrics are used to describe heart rate.









































section::::in different circumstances.:resting heart rate.









































normal pulse rates at rest, in beats per minute (bpm):
heart rate
the basal or resting heart rate (hr) is defined as the heart rate when a person is awake, in a neutrally temperate environment, and has not been subject to any recent exertion or stimulation, such as stress or surprise. a large body of evidence indicates that the normal range is 60-100 beats per minute. this resting heart rate is often correlated with mortality. for example, all-cause mortality is increased by 1.22 (hazard ratio) when heart rate exceeds 90 beats per minute. the mortality rate of patients with myocardial infarction increased from 15% to 41% if their admission heart rate was greater than 90 beats per minute. ecg of 46,129 individuals with low risk for cardiovascular disease revealed that 96% had resting heart rates ranging from 48-98 beats per minute. finally, expert consensus reveals that 98% of cardiologists believe that the "60 to 100" range is too high, with a vast majority of them agreeing that 50 to 90 beats per minute is more appropriate. the normal resting heart rate is based on the at-rest firing rate of the heart's sinoatrial node, where the faster pacemaker cells driving the self-generated rhythmic firing and responsible for the heart's autorhythmicity are located. for endurance athletes at the elite level, it is not unusual to have a resting heart rate between 33 and 50 bpm.
heart rate