Final answer:
The normal rate for the SA node during rest is 60 to 100 beats per minute, which is the standard range for an adult's resting heart rate. This is established by the sinoatrial (SA) node, the heart's pacemaker. Rates below 60 bpm indicate bradycardia, and rates above 100 bpm indicate tachycardia.
Step-by-step explanation:
The normal rate for the SA node when the patient is at rest is 60 to 100 beats per minute. This range establishes the normal sinus rhythm dictated by the sinoatrial (SA) node, often referred to as the heart's natural pacemaker. The SA node's inherent rate of depolarization sets the pace for the heartbeat under resting conditions.
In the absence of nervous or endocrine influence, the SA node would naturally initiate a heart impulse approximately 80-100 times per minute. It is important to note that rates below 60 bpm are characterized as bradycardia, a condition that may or may not be clinically significant depending on the presence of symptoms like weakness or dizziness. Conversely, a resting rate above 100 bpm is known as tachycardia. Highly trained athletes may have resting heart rates lower than the general population, sometimes as low as 30-40 bpm, due to their enhanced cardiovascular efficiency.
Therefore, the correct answer to the question is b. 60 to 100 beats per minute.