Research shows that, in the absence of neural and hormonal inﬂuences, the SA node generates action potentials at a frequency of approximately 100 times per minute. However, the resting heart rate is approximately 70 beats per minute, which suggests that 3
3/17/2020 PhysioEx Exercise 6 Activity 2 3/3 Review Sheet Results You correctly answered: the parasympathetic nervous system has more control over heart rate. The SA (sinoatrial) node in the human heart is located You correctly answered: in the right atrium. 4 Explain the effect that extreme vagus nerve stimulation had on the heart. How well did the results compare with your prediction? Your answer: The vagus nerve stimulation caused the heart to ﬂat line restart and react normally. The response after the stimulation that resumed the heart is called the vagal escape. 1 Explain two ways that the heart can overcome excessive vagal stimulation. Your answer: The heart can overcome excessive vagal stimulation through sympathetic reﬂexes and the initiation of a rhythm by the Purkinje fibers. 2 Describe how the sympathetic and parasympathetic nervous systems work together to regulate heart rate. Your answer: The sympathetic (fight or ﬂight), becomes more active when needed and will increase the heart rate and force of contractions. The parasympathetic (resting and digesting) this branch is more active and decreases the heart rate without directly changing force of contraction. 3 What do you think would happen to the heart rate if the vagus nerve was cut? Your answer: The heart rate would increase but the heart would be damaged. The vagus nerve carries important information to the heart from the parasympathetic nervous system. This information is the decrease of heart rate, contraction strength, and the rate of the electrical impulses conducted in the heart. The sympathetic does the opposite and raise heart rate, contraction force and electrical conduction. Both of these systems work together. 4
You've reached the end of your free preview.
Want to read all 3 pages?
- Fall '15
- Sinoatrial node, Electrical conduction system of the heart, session ID