Physioex 6
Danielle Rollins
Cardiovascular Physiology
Activity 1 1) Explain why the larger waves seen on the oscilloscope represent ventricular contraction. The ventricular contraction is when the blood is sent through the whole body as opposed to the atrial contraction that sends the blood to the heart and lungs. 2) Explain why the amplitude of the wave did not change when you increased the frequency of the stimulation. (Hint: relate your response to the refractory period of the cardiac action potential) How well did the results compare with your prediction? The threshold doesn’t change because after the voltage was simulated the cardiac muscle cells Ca channels opened. You cannot open them anymore or reopen them before depolarization. This is due to the refractory period. 3) Why is it only possible to induce an extrasystole during relaxation? Because cardiac muscle is able to depolarize after repolarization takes place. 4) Explain why wave summation and tetanus are not possible in cardiac muscle tissue. How well did the results compare to your prediction? Cells do not show tetanus or summation because cardiac cells have both long action potentials and long twitches. Activity 2 1) Explain the effect that extreme vagus nerve stimulation had on the heart. How well did the results compare with your predictions? The heart rate decreases stopping the heart temporarily. 2) Explain two ways that the heart can overcome excessive vagal stimulation. Two ways to overcome excessive vagal stimulation are sympathetic reflexes and initiating the rhythm of the Purkinje Fibers. 3) Describe how the sympathetic and parasympathetic nervous systems work together to regulate heart rate. Sympathetic increases the heart rate whereas Parasympathetic decreases the heart rate. 4) What do you think would happen to the heart rate if the vagus nerve was cut? The heart rate will increase and return back to the 100 bpm.
Lab Questions: 1) Cardiac muscle does not
Cardiovascular Physiology
Activity 1 1) Explain why the larger waves seen on the oscilloscope represent ventricular contraction. The ventricular contraction is when the blood is sent through the whole body as opposed to the atrial contraction that sends the blood to the heart and lungs. 2) Explain why the amplitude of the wave did not change when you increased the frequency of the stimulation. (Hint: relate your response to the refractory period of the cardiac action potential) How well did the results compare with your prediction? The threshold doesn’t change because after the voltage was simulated the cardiac muscle cells Ca channels opened. You cannot open them anymore or reopen them before depolarization. This is due to the refractory period. 3) Why is it only possible to induce an extrasystole during relaxation? Because cardiac muscle is able to depolarize after repolarization takes place. 4) Explain why wave summation and tetanus are not possible in cardiac muscle tissue. How well did the results compare to your prediction? Cells do not show tetanus or summation because cardiac cells have both long action potentials and long twitches. Activity 2 1) Explain the effect that extreme vagus nerve stimulation had on the heart. How well did the results compare with your predictions? The heart rate decreases stopping the heart temporarily. 2) Explain two ways that the heart can overcome excessive vagal stimulation. Two ways to overcome excessive vagal stimulation are sympathetic reflexes and initiating the rhythm of the Purkinje Fibers. 3) Describe how the sympathetic and parasympathetic nervous systems work together to regulate heart rate. Sympathetic increases the heart rate whereas Parasympathetic decreases the heart rate. 4) What do you think would happen to the heart rate if the vagus nerve was cut? The heart rate will increase and return back to the 100 bpm.
Lab Questions: 1) Cardiac muscle does not