Biology Questions and Answers
- Concerning the mixture of
arterial with venous blood
what is the difference
between the human fetal
circulation and the adult
circulation?
In the human fetal circulation there are
two command venous blood characterizing unications between arterialan
incomplete circulation. One of them is
the oval fthe right and the left atria of the fetaloramen, an opening between
heart. Tshort vessel conhe other is the arterialnecting the pulmonary duct, a (^)
artery to the aorta. These
communicationsbirth and so they are not present i close a few days aftern the (^)
adult heart.
- How is heart contraction
triggered?
Heart contraction is independent from
neuronal stimulus (althomodulated by the autonomous nugh it can bervouse (^)
system). In the heart there are
pacemaker themselves thcells that trige action potentials thatger by (^)
begin the muscle contraction. These
cells arpoints of e concethe heart: the sinoatrialntrated at two special node (^)
(SA node) located in the superior
portion atrioventricularof the right atrium a node (AV node) locatednd the (^)
near the interatrial septum.
The action potentials generated by
depolarization opropagate cell to cell throf the SA nughout thode cells (^) e
atria producing the atrial contraction.
The atrial depolarization also pto the AV node that then transmitsropagates the
electric impulse to the ventricles
through specialized of the interventricular seconduction buptum (thendles
bundle of His) and then to the Purkinje
fibers of the ventricle wallsventricular contraction. (The atrial causing
contraction precedes the ventricular
contractionbefore the ventricular co for blood to fill tntraction.)he ventricles
The repolarization othe atria relax and then the ventriclesf the SA node makes
relax too.
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