frog heart[1] - Kelly Lunt MCB 32L 12/2/07 Frog Heart Study...

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Kelly Lunt MCB 32L 12/2/07 Frog Heart Study I. Introduction Background: A frog heart is made up of four chambers, the sinus venosus, two atria and a ventricle. Because there is only one ventricle, there is mixing of oxygenated and deoxygenated blood. But the ventricle is built so that the blood is sufficiently separated by the spiral valve and the arterial cone. The heart is made up of myocardium which is a muscle layer. These myocardial cells are joined together by intercalated discs that are held together by desmosomes and have gap junctions that allow passage of molecules from one cell to another. The gap junctions in the heart spread the action potentials over the muscle cells. The heart has pacemaker cells that are spontaneously depolarized resulting in contraction of muscle cells in the atria and ventricles. One difference between an action potential along an axon in comparison to that in the heart is that in the heart it is spread by the gap junctions. Also in cardiac muscle, calcium rises because of calcium coming in from extracellular space as well as from the sarcoplasmic reticulum within the cell. Depolarization in cardiac muscle is longer than skeletal muscle which means that there is a longer absolute and relative refractory period which prevents tetanus from occurring. Hypothesis: The heart will create two ventricle pumps if the heart is stimulated at the right time by the electrodes. Warm ringers will speed up the heart while cold ringers will slow down the heart. Epinephrine will speed up the heart and acetylcholine will slow down the heart. KCl
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frog heart[1] - Kelly Lunt MCB 32L 12/2/07 Frog Heart Study...

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