Physio Ex 6

Topics: Heart, Acetylcholine, Cardiac muscle Pages: 4 (937 words) Published: October 17, 2012
Nancy Yedanapalli physio ex

Activity 6

1. Explain why the larger waves seen on the oscilloscope represent ventricular contraction. a. The ventricular contraction is of greater force than the atrial contraction, since the ventricular contraction functions to send blood throughout the entire body (systemic circulation), where as the contraction of the atrium send blood only to the lungs and rest of the the heart (pulmonary circulation).

2. Explain why the amplitude of the wave did not change when you increased the frequency of the stimulation. a. The maximum threshold will not change in cardiac muscle cells (as with any other cells), which is determined by the X amount of voltage needed for calcium channels to open. After this point, no additional voltage can cause the channels to open more, or again, prior to depolarization.

3. Why is it only possible to induce an extrasystole during relaxation. a. 3. cardiac is able to depolarize only after repolarization

4. explain why wave summation and tetanus are not possible in the cardiac muscle tissue. a. Cardiac cells have long action potentials and long twitches, therefore do not show temporal summation.

Act 2

1. Explain the effect that extreme vagus nerve stimulation had on the heart. a. 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.

2. The SA node of the heart is located in the right arterial wall

3. Describe how the sympathetic and parasympathetic nervous systems work together to regulate the heart rate. a. The sympathetic and parasympathetic are two branches of the autonomic nervous system. Both supply nerve impulses to the heart. The sympathetic (fight or flight), becomes more active when needed. Stimulation will increase the heart rate and force of contractions....
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