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Unformatted text preview: Teaching Experiment Physiology of the in situ Amphibian Heart and Human Electrocardiogram This experiment explores the basic principles of cardiac muscle physiology, including contraction force, electrocardiogram (ECG) and the effect of neurotransmitters on the heart. Background The heart is made up of specialized tissue called cardiac muscle. Cardiac muscle is similar to skeletal (striated) muscle, but exhibits some special properties, the most important of which is rhythmicity. Specialized heart muscle cells called pacemakers spontaneously depolarize and repolarize ; the depolarization spreads to the entire heart via electrical connections between cardiac muscle cells called gap junctions. This process occurs in rhythmic fashion, giving rise to an intrinsic, regular heartbeat. While no external stimulation is required to maintain the heartbeat, the heart receives continuous input from the sympathetic and parasympathetic nervous systems. Cardiac muscle responds to a variety of neurotransmitters , which can increase or decrease the heart rate. These molecules are able to influence heart rate by changing the rate of spontaneous depolarization of the heart’s “pacemaker” cells, located in the sinoatrial (SA) and atrioventricular (AV) nodes of the mammalian heart. In the frog, the sinus venosus is similar to the SA node. Required Equipment PowerLab Bridge Pod Force Transducer Mounting stand with micropositioner Thread Barb-less hook Pipettes Frog Ringer’s solution Bipolar stimulator Acetylcholine (0.1 mg/mL) Epinephrine (1% solution) TEB03cPage 1 of 12 7 May 2009 Figure 1. Mounting Stand and Micropositioner set up with Force Transducer. Teaching Experiment Procedures A. Setup and calibration of equipment 1. Set up your mounting stand with the Force Transducer mounted on the micropositioner (Figure 1). 2. Connect the force transducer cable to the back of the Bridge Pod. 3. Tie a piece of strong thread about 18 inches in length to the force transducer. Attach a bent straight pin to the other end of the thread. 4. Plug the Bridge Pod into the Pod Port on Input 1 of the PowerLab 5. Turn on the PowerLab using the power switch on the back of the unit. 6. Launch Chart 5 from your computer. 7. Open the settings file called Frog Heart Settings. 8. From the Force Channel Function pop-up menu, select Bridge Pod. 9. Turn the zeroing knob on the front of the Bridge Pod until you get a reading of zero in the dialog box....
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This note was uploaded on 04/09/2008 for the course BIO 3700 taught by Professor Mcclellan during the Spring '08 term at Missouri (Mizzou).
- Spring '08