Question

Why do you think some animals have a myogenic heart (self-excitable found in Vertebrates and some Mollusks like cephalopods) while others have a neurogenic heart (controlled by nerve impulses from the brain found in Annelids, and Arthropods)? Explain your reasoning. Lungfishes have a rudimentary air sac they use when their environment temporarily becomes anaerobic. How do you think their circulatory system is different from other fish? Construct a drawing to emphasize your view. In giraffes, the head could be up to 6 feet (2 m) above the heart! This presents a problem in blood-flow and pressure. Calculations show that in order to pump enough oxygenated blood to the head to operate a giraffes' brain would require a heart weighing about 220 pounds (100 kg). A recent study revealed that the average heart found in giraffes only weighed about 22 pounds (10 kg). What structural modifications to the heart and circulatory system could help explain this discrepancy and compensate for such a small heart size?

Answer 1

Dear student as per HomeworkLib guideliness you are supposed to ask one question at a time so please ask other questions seperately. Thank you

3.) The circulatory system of the giraffe has several adaptations for its great height. Its heart, which can weigh more than 11 kg (25 lb) and measures about 60 cm (2 ft) long, must generate approximately double the blood pressure required for a human to maintain blood flow to the brain. As such, the wall of the heart can be as thick as 7.5 cm (3.0 in).Giraffes have unusually high heart rates for their size, at 150 beats per minute.The rete mirabile in the upper neck does not appear to prevent excess blood flow to the brain when the giraffe lowers its head as has often been believed. Instead the blood rushes to the head but when it raises again, the blood vessels constrict and direct the blood through a anastomosis between the occiput and vertebrae and into the brain so the animal doesn't faint.The jugular veins contain several (most commonly seven) valves to prevent blood flowing back into the head from the inferior vena cava and right atriumwhile the head is lowered.