Frog Heart Lab

Although human and frog hearts do not look the exact same, they do act very similar. Human hearts have four chambers: two atria and two ventricles. Contrarily, frog hearts have only three chambers: two atria and one ventricle. Frogs are helpful in scientific research of the heart and its many functions because human hearts can obviously not be used. In this case, the frog hearts are helpful in determining the effects of different chemicals on the heart. Certain chemicals and agents effect the heart's rate and contraction. Unlike skeletal muscle, the heart muscle depolarizes automatically when external stimuli are not present. This is called automaticity, which happens when the plasma membranes in heart muscle cells allow sodium to leak into the cell at a faster rate than potassium is moving across the membrane (book). The sodium moving inside the cell causes it to progressively …show more content…
Both controls can be seen in this lab. Intrinsic controls are within the heart while extrinsic controls are external to the heart (book). The nodal system is one intrinsic control example that has an effect on the heart's pumping activity. The nodal system occurs when the pacemaker places a depolarization rate on the rest of the heart (book). The pacemaker in a frog heart is positioned in the sinus venous, which is an enlarged area between the right atrium and the vena cava (pdf). If the impulse from the depolarization does not reach the ventricle(s) then the heart will beat at a much slower rate than what it usually beats at. The rate can be modified by extrinsic factors such as chemicals, hormones, ions, and metabolites (book). The chemicals and agents used in this lab to modify the frog's heart rate and contraction are extrinsic factors. They are cold water, warm water, pilocarpine, histamine, epinephrine, calcium chloride, sodium chloride, hydrochloric acid, and potassium