B.Identify the internal structures of the heart. 13.Place the heart on its ventral side. You will cut the heart straight through in the frontal plane. Identify the left auricle and make a slicing cut with your scalpel all the way down to the apex of the heart. Continue the cut to all the way up to the right auricle. Make sure you cut through the intraventricular septum. Separate the two halves of the heart and identify the internal structures. a.Superior and inferior venae cavae b.Pulmonary trunk (left and right pulmonary arteries if those are present) c.Aorta and aortic arch d.Right and left pulmonary veins e.Left and right atria f.Left and right ventricles g.The intraventricular septum separating the two ventricles h.Papillary muscles i.Chordae tendineae j.Right and Left AV valves k.Aortic and pulmonary semilunar valves 14.Which chamber’s walls are the most muscular? ___________________________ 15.Which chamber reaches all the way down to the apex? _________________________________ 16.Which chamber pumps blood to the systemic circulation? ____________________________ 17.Which chamber receives blood from the pulmonary circulation? ______________________ 18.Once you are done please dispose of the tissue in thewhite pathological waste container and clean your dissecting equipment with powder soap and water. Exercise 4: Investigation of the effects of dopamine and serotonin on heart rate in ghost shrimp This exercise is adapted from Holsinger et al. Tested Studies for Laboratory Teaching, Proceedings of the Association for Biology Laboratory Education Vol. 33, 95–112, 2012. The purpose of this exercise is to investigate the effect of various environmental cues on the heart rate of the transparent ghost shrimp, Palaemonetes genus. Heart rate in crustaceans can be altered under many conditions. Neurotransmitters, temperature, and chemicals such as stimulants can all have an effect. Neurotransmitters act on the organism’s heart rate through the nervous system in a parasympathetic-like or sympathetic-like manner. This can either cause an increase or decrease in overall heart rate based on the properties of the neurotransmitter in question. The effects of temperature on heart rate are also variable. Lower temperatures tend to decrease the heart rate. Conversely, high temperatures tend to cause an increase in heart rate due to the increase in metabolic activity and higher rate of chemical reactions within the body. Chemical stimulants also increase the heart rate and blood flow. In this experiment, students will become familiar with these effects by subjecting a species of freshwater shrimp to varying environmental conditions – dopamine, serotonin, and cold water.