PhysioEx Lab Report Exercise 6: Cardiovascular Physiology Activity 2: Examining the Effect of Vagus Nerve Stimulation Name: Date: 7 July 2020 Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 The effect of the parasympathetic nervous system on the heart is to You correctly answered: decrease the heart rate. 2 The branch of the autonomic nervous system that dominates during exercise is You correctly answered: the sympathetic branch. 3 Parasympathetic stimulation reaches the heart through You correctly answered: vagus nerves, which are cranial nerves. 4 The usual pacemaker of the heart You correctly answered: is the sinoatrial node. Experiment Results Predict Question 1 Predict Question: What do you think will happen if you apply multiple stimuli to the heart by indirectly stimulating the vagus nerve? Your answer: The heart rate will increase. Stop & Think Questions 1 Watch the contractile activity from the frog heart on the oscilloscope. Enter the number of ventricular contractions per minute (from the heart rate display). You answered: 62 beats/min. 2 The vagus nerve carries You correctly answered: signals that decrease the heart rate. 3 Enter the number of ventricular contractions per minute (from the heart rate display). You answered: 62 beats/min. 4 The response that resumed the heartbeat after the vagus nerve stimulation is called You correctly answered: vagal escape. Experiment Data Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 Extreme vagus nerve stimulation affects the heart by You correctly answered: stopping the heart completely. 2 Vagal escape probably involves You correctly answered: sympathetic reflexes. 3 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 You correctly answered: the parasympathetic nervous system has more control over heart rate. 4 The SA (sinoatrial) node in the human heart is located You correctly answered: in the right atrium. Review Sheet Results 1 Explain the effect that extreme vagus nerve stimulation had on the heart. How well did the results compare with your prediction? Your answer: The HR decreases and stopped the heart temporarily. 2 Explain two ways that the heart can overcome excessive vagal stimulation. Your answer: 1: Sympathetic reflexes 2: initiation of a rhythm by the Purkinje Fibers. 3 Describe how the sympathetic and parasympathetic nervous systems work together to regulate heart rate. Your answer: Sympathetic increases HR Parasympathetic decreases HR. 4 What do you think would happen to the heart rate if the vagus nerve was cut? Your answer: It would increase and go back to the 100bpm.