Answer :
Final answer:
The AV node's intrinsic firing rate lies within the range of 30-40 BPM. This varies depending on the individual's health status and physical fitness. Norepinephrine and ACh affect the heart rate by interacting with different receptors.
Explanation:
The intrinsic firing rate of the AV node, or Atrioventricular node, is 30-40 beats per minute (BPM). This is important as the AV node regulates the contraction of the ventricles, ensuring efficient blood flow. The rate can vary depending on the individuals' health conditions or fitness levels. For instance, highly trained athletes can exhibit a resting heart rate of 30-40 BPM while a person with reduced cardiac function may have a much lower rate.
The intrinsic firing rate of the AV node is determined by the electrical impulses it generates to coordinate heart contractions. The AV node typically fires at a rate of approximately 40-60 beats per minute (BPM). This is slower than the firing rates of the sinoatrial (SA) node, bundle branches, and Purkinje fibers, which have higher intrinsic firing rates.
The SA node (sinoatrial node) also plays an essential role in regulating heart rate. When norepinephrine is released onto certain cells, it binds to an adrenergic receptor causing the heart rate to increase. Conversely, when ACh is released onto those cells, it binds to a muscarinic receptor, slowing the heart rate down.
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