The correct answer is option A
A person that is having an allergy with pollen grains should take antihistamines.
When there is an allergic reaction in the body then the body releases histamines which evokes immune response.
As a result of this the person starts sneezing, runny nose, hives et cetera.
So, one should take antihistamines to prevent the action of histamines on the body.
Answer:
it results in 2 exact copies of the original dna strand
Explanation:
The dna is unzipped and the two strands are used as templates for the 2 new dna molecules
The sequence of impulse through the cardiac conduction system starts from SA node passes to AV node to atrioventricular bundle fibers and finally to Purkinje fibers.
Heart is an organ that receives oxygenated blood form lungs and deoxygenated blood from different parts of body. Oxygenated blood is transported to different organs and deoxygenated blood is transported to lungs for oxygenation.
Now, to perform this transportation, the auricles and ventricles of heart contract and relax. In order to contract and relax, impulse generation is required, which begins at SA node or Sinoatrial node. It is also referred to as pacemaker of the heart. SA node contracts the atria and the impulse transfers to AV node or Atrioventricular node.
This is followed by transfer of impulse to atrioventricular bundle fibers which further passes it on to Purkinje fibres for ventricular contraction. Now the blood is sent to lungs and aorta as per it's oxygen status.
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