Physiologists speculate about cardiovascular adaptations in dinosaurs—some of which had necks almost 10 m (33 feet) long. Such animals would have required a systolic pressure of nearly 760 mm Hg to pump blood to the brain when the head was fully raised. Some analyses suggest that dinosaurs’ hearts were not powerful enough to generate such pressures, leading to the speculation that long-necked dinosaurs fed close to the ground rather than raising their heads to feed on high foliage. Scientists also debate whether dinosaurs had a “reptile-like” or “bird-like” heart. Most modern reptiles have a three-chambered heart with just one ventricle. Birds, which evolved from a lineage of dinosaurs, have a four-chambered heart. Some scientists believe that the circulatory needs of these long-necked dinosaurs provide evidence that dinosaurs must have had a four-chambered heart. Why might they conclude this?
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Pearson eText Campbell Biology: Concepts & Connections -- Access Card (9th Edition)
- Double-loop circulatory systems are found in adult amphibians, reptiles, birds, and mammals, In which characteristic do these systems differ from one another,arrow_forwardThe mammalian heart can beat without input from the brain. True Or false?arrow_forwardDescribe all the events (steps) that occur during a cardiac cycle for mammals (organisms with a double circulation). Please include in your description all the steps illustrated in slide #16 of the Cardiovascular System PowerPoint presentation (Lectures 5&6), as well as the opening and closing of all heart valves (refer to slide #21), and the signals arising from the SA and AV nodes (shown in slide #25). How does this cycle contribute to metabolic homeostasis for our cells, and what is the purpose of the valves?arrow_forward
- Construct a model for the relationship between the heart rate of mammals and theirweight. Also give all assumptions you make.You may assume the following:arrow_forwardWhat is the consequence of the prolonged plateau of depolarization in ventricular myocytes? a-it causes ventricular myocytes to contract for a longer time, allowing the ventricles time to empty b-it gives additional time for the atria to contract, filling the ventricles more completely c-it causes repolarization to be delayed which slows heart rate d-it allows the ventricles a moment to rest before completing contractionarrow_forwardThe mammalian circulatory system includes a four- chambered heart and a double-loop circulation. How do the four chambers of the heart relate to the two circulatory loops?arrow_forward
- Blood returning to the mammalian heart in a pulmonary veindrains first into the(A) left atrium.(B) right atrium.(C) left ventricle.(D) right ventricle.arrow_forwardList at least one reason why arteriole vasoconstriction helps mammals function and survive:arrow_forwardA large grasshopper and a small mouse may be similar in size. However, the total length of blood vessels is much greater in the mouse, and the mouse’s heart pumps at much higher pressure than the grasshopper’s hearts. Which statement is most useful for explaining these observations?arrow_forward
- A rhythmic beating of cardiac muscle in a mammalian heart is initiated by the _____. A.Atrioventricular node B.Parasympathetic nervous system C.Purkinje fibers D.Sinoatrial nodearrow_forwardDescribe how the four chambers of the fish heart function and the principal limitation of this design.arrow_forwardIn conditioned athletes, the resting Heart Rate is generally much lower than in non-athletes. Why? a-because long-term exercise reduces Cardiac Output at rest to conserve energy b-because athletes have a smaller Stroke Volume at rest, causing Heart Rate to decrease as well c-because long-term exercise leads to increased vagal tone which slows Heart Rate d-because athletes have stronger ventricles and therefore a larger Stroke Volume at rest, so they require fewer bpm to achieve the same Cardiac Outputarrow_forward
- Human Physiology: From Cells to Systems (MindTap ...BiologyISBN:9781285866932Author:Lauralee SherwoodPublisher:Cengage Learning