PEX-06-02

Exercise 6: Cardiovascular Physiology: Activity 2: Examining the Effect of Vagus Nerve Stimulation Lab Report 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: a. decrease the heart rate. 2. The branch of the autonomic nervous system that dominates during exercise is You correctly answered: b. the sympathetic branch. 3. Parasympathetic stimulation reaches the heart through You correctly answered: d. vagus nerves, which are cranial nerves. 4. The usual usual pacemaker pacemaker of the heart You correctly answered: c. is the sinoatrial node.

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Experiment Results Predict Question: Predict Question: What do you think will happen if you apply apply multiple stimuli to the heart by indirectly stimulating the vagus nerve? Your answer : c. The heart rate will decrease and the heart will stop. 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) in the field below and then click l ab report. Submit to record your answer in the lab You answered: 60 beats/min The vagus nerve carries You correctly answered: a. signals that decrease the heart rate. 3. Enter the number of ventricular contractions per minute (from the heart rate display) in the field below and then click l ab report. Submit to record your answer in the lab You answered: 60 beats/min The response that resumed the heartbeat after the vagus nerve stimulation is called You correctly answered: b. vagal escape. Experiment Data:

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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: a. stopping the heart completely. 2. Vagal escape probably involves You correctly answered: c. sympathetic reflexes. 3. Research shows that, in the absence of neural and hormonal influences, the SA node generates action potentials 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: b. the parasympathetic nervous system has more control over heart rate. 4. The SA (sinoatrial) node in the human heart is located You correctly answered: c. in the right atrium

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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: My hypothesis was correct the heart rate surely decreased and as a result the heart stopped temporarily. 2. Explain two ways that the heart can overcome excessive vagal stimulation. Your answer: The heart can overcome excessive vegal stimulation by having sympathetic reflexes and initiating i nitiating the rhythm of the Purkinje Fibers. 3. Describe how the sympathetic sympathetic and parasympathetic parasympathetic nervous systems systems work together to regulate heart rate. Your answer: The Sympathetic nervous system increases heart rate and parasympathetic decreases heart rate, this is how they work together to regulate heart rate. 4. What do you think would happen to the heart rate rate if the vagus nerve was cut? Your answer: If the vagus nerve were cut then the heart rate would increase and return to 100 bpm.

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