The answer is atrial depolarization. The P wave of a normal electrocardiogram specifies atrial depolarization. In addition, depolarization happens in the four compartments of the heart which is both atria first and in both ventricles. The sinoatrial or as called as SA node on the wall of the right atrium starts depolarization in the right and left atria that can cause the contraction in which it is symbolized by the P wave on an electrocardiogram.
This was Lamarck's idea. Here's an example: Suppose giraffes originally had short necks that they stretched to reach high-up leaves in the trees. This continuous stretching of the neck was passed onto offspring, who as a result had slightly longer necks. This continued for multiple generations until we get today's long-necked giraffe. Lamarck was on to something (that something being evolution by natural selection, which Darwin discovered), but his theory wasn't completely correct since organisms can only pass on genes (segments of DNA that code for a characteristic or function) to their offspring. Since "stretching" would not code into DNA, it wouldn't be passed onto offspring, proving Lamarck's theory incorrect.
Answer:
This is because fluids have a polar nature, so they couldn´t cross the lipidic bilayer that constitutes the plasma membrane
Explanation:
Plasma membranes are contituted by lipid bilayers. These kind of compounds are hidrophobic (they reject water) and don´t permit the freely passage of hidriphilic molecules that can disolve in water, constituing fluids. Because of that cells developed transport mechanism like endocytosis.
Pulmonary artery carry deoxygenated blood while are there arteries carry oxygenated blood.
pulmonary vein carries oxygenated blood while the other veins carry deoxygenated blood
