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By tying a ligature as a constriction between the sinus venosus and the atrium in the frog and also one around the atrioventricular groove, Stannius was able to demonstrate that the muscle tissues of the atria and ventricles have independent and spontaneous rhythms. His observations also indicated that the sinus is the pacemaker of the heartbeat.
Diastolic dysfunction is associated with a reduced compliance, or increased stiffness, of the ventricle wall. This reduced compliance results in an inadequate filling of the ventricle and a decrease in the end-diastolic volume. The decreased end-diastolic volume then leads to a reduction in stroke volume because of the Frank-Starling mechanism. [1]
With the advent of lungs came a partitioning of the atrium into two parts divided by a septum. Among frogs, the oxygenated and deoxygenated blood is mixed in the ventricle before being pumped out to the body's organs; in turtles, the ventricle is almost entirely divided by a septum, but retains an opening through which some mixing of blood ...
When the ventricle starts contracting, ... Frogs can distinguish between low numbers (1 vs 2, 2 vs 3, but not 3 vs 4) and large numbers (3 vs 6, 4 vs 8, but not 4 vs ...
In 1852, H. F. Stannius used a frog's heart in a procedure called a Stannius ligature to demonstrate the ventricle and atria beat independently of each other and at different rates. [224] The African clawed frog or platanna ( Xenopus laevis ) was first widely used in laboratories in pregnancy tests in the first half of the 20th century.
The early bulbus cordis is formed by the fifth week of development. [4] The truncus arteriosus is derived from it later. [2]The adjacent walls of the bulbus cordis and ventricle approximate, fuse, and finally disappear, and the bulbus cordis now communicates freely with the right ventricle, while the junction of the bulbus with the truncus arteriosus is brought directly ventral to and applied ...
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The following are two lists of animals ordered by the size of their nervous system.The first list shows number of neurons in their entire nervous system. The second list shows the number of neurons in the structure that has been found to be representative of animal intelligence. [1]