Zoology - Body Fluids and Circulation Question with Solution | TestHub
Which of the following statements is CORRECT?
I. Heart, the mesodermally derived organ, is situated in the thoracic cavity, in between the two lungs, slightly tilted to the left.
II. During joint diastole, tricuspid and bicuspid valves are open and the semilunar valves are closed.
III. The first heart sound (lub) is associated with the closure of the tricuspid and bicuspid valves whereas the second heart sound (dub) is associated with the closure of the semilunar valves.
IV. Neural signals through the sympathetic nerves can increase the rate of heartbeat, the strength of ventricular contraction and thereby the cardiac output.
Options:
Answer:
Solution:
Heart is derived from mesoderm and it lies in the thoracic cavity between two lungs but slightly to the left. Joint diastole means both the auricles and ventricles are in relaxed state and so auriculoventricular valves are open while semilunar are closed. The heart sounds are lub and dub. Lub is the first heart sound and this is due to closure of AV valves while dub is due to closure of semilunar valves. Sympathetic nervous system works during stress situations and thus increase the heart beat.
