Question

fill in the blank

The connective fibrous tissue between the atria and the ventricles is electrically nonconductive because it lacks ___________.

Increased sympathetic activity causes veins and arterioles to  _______________

When performing an EKG, a __________________________ is formed when all three leads are connected to the test subject.

Answer 1

1. gap junction

cardiac skeleton/ fibrous skeleton of the heart are made of collagen fibers, which lacks gap junctions that help in conducting the electrical impulse. these fibers have an important role in conducting the electrical signals to AV bundle by remaining itself as nonconductive.

2. constrict

sympathetic nerve fibers are cardio accelerator nerve fibers. neurotransmitter of the sympathetic system is nor-epinephrine, which mainly act through beta1 receptors of myocardium. it causes positive chronotropic and positive inotropic effect by constricting veins and arteries.

3. Einthoven's triangle

it is the triangle formed by the three lead systems with the heart at the center. according to this, Lead II = Lead I + Lead III