The blood flows from the dorsal arteries to capillaries and then into sinuses that function as veins. Blood flows into the heart through the dorsal ostia. The blood is then pumped into the body sinuses through arteries at the anterior and posterior ends of the ventricle (McCormack, 2012). Using a crayfish is ideal for monitoring heart rate due to the easy accessibility to the heart. The heart of the crayfish is located in the dorsal portion of the cephalothorax where two wires can be placed on either side to form a circuit enabling the measurement of heart …show more content…
Very early studies have noted a sympathetic-like response of an immediate and rapid response of defense posturing (Huxley, 2010). The central nervous system controls the beat and rhythm of the crayfish’s heart. The measurement of heart rate provides a direct measure of excitability and readiness of the internal environment. This shows that invertebrates have a sympathetic-like response to regulate the internal environment and ready the organism to act behaviorally to an external stimulus. Measurements of the physiological response can be directly related to internal and external stressors through changes in the central nervous system controlled coordination of the cardiovascular system. Monitoring heart rate provides a quantifiable measure of stress response that cannot always be behaviorally observed. This experiment will test the effects of neurotransmitters such as serotonin,