1 9 3 Circulatory Systems Hearts BIO 361T Fall 2014 1 Why do hearts in animals with open circulatory systems need to exert little pressure on the blood Little resistance if tubes sinuses are open ended Heart is pumping against little resistance 2 In terms of circulatory system anatomy why are there no spiders the size of elephants Pressure from heart and in open circulatory system is too low to pump through a large system 3 What are two adaptive structures that have evolved in flying insects to compensate for their weak aortic hearts Respiratory pump and accessory hearts near wings and in tail 4 Through what structure does blood enter the heart of an arthropod during diastole Ostia 5 Looking to molluscs where chambered hearts first evolved what are the advantages of having a separate atrium and ventricle Which chamber receives blood and which one ejects blood Allows for continual return of blood via the veins The atrium can continually fill while the ventricle contracts and pumps blood out of the arteries It allows the ventricles to increase pressure without increasing mean venous pressure Atria receive blood and ventricles eject it 6 Hypothesize as to why hemolymph is 20 50 of an animal s body weight while blood is only 68 of an animal s body weight Open circulatory systems have less control over fluid and rely on more random motion so they have to have higher volumes that fill the body s sinuses 7 Choose either anterior posterior dorsal or ventral to answer the following questions a Into what side of the fish heart does blood flow Posterior caudal from tail b Which side of the fish heart is the conus arteriosus Anterior outflow c Into what side of the amphibian heart does blood flow Anterior head 8 Why do hearts with mostly compact myocardium exert higher pressure on the blood than those with trabeculated spongy myocardium In what animal groups does each predominate Cardiomyocytes are arranged tightly in organized bundles birds mammals vs loosely randomly distributed most fish amphibians About 50 50 in reptiles More active fish have more compact than others Compact myocardium has organized blood flow via coronary vessels Spongy myocardium receives O2 from less organized lacunae 9 When turtles dive the distribution of blood being pumped by the heart shifts from right to left a Does this divert more blood to the systemic or pulmonary circuit Systemic b What causes this shift Higher resistance in pulmonary capillaries c Why is this functionally adaptive Sends more blood to tissues instead of lungs d Why can t birds and mammals do this Circuits are completely separate 10 What is the adaptive function of the skin being wrapped tightly around the legs in giraffes 2 Increases resistance in the extremities distal veins to facilitate venous blood return to the heart against gravitational force and alleviate burden on the heart which still exerts systemic BP of 260 mmHg 11 In animals that have a systemic blood pressure over 50 mmHg a difference in heart anatomy has evolved multiple times a What is this difference Double circuitry b What is the adaptive advantage Different blood pressures in systemic vs pulmonary c How is pressure lower in the pulmonary circuit and why is this helpful Parallel capillary beds because tissues in lungs are too delicate for high pressure of systemic circuit d How is pressure higher in the systemic circuit and why is this helpful Many capillary beds in series and parallel to perfuse all tissues of large animal and travel long distances e f Which side of the heart muscle would you expect to be larger left What is another variable that differs widely between animals and roughly correlates with blood pressure Metabolic rate size terrestriality 12 Regulation a The smooth muscle cells in the tunica media of blood vessels express alphaadrenergic receptors These receptors bind norepinephrine also called noradrenaline Binding of this neurotransmitter causes the blood vessels to contract b Cardiomyocytes express beta adrenergic receptors These receptors bind epinephrine also called adrenaline and cause the heart muscle to contract Both classes of receptors are GPCRs that can bind epinephrine and norepinephrine to varying degrees Mammals have multiple variants in each class each of which has a different G coupled second messenger cascade e g cAMP in cardiomyocytes This allows different tissues to respond to the same neurotransmitter in different ways
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