When vagus nerve stimulation was applied to the frog heart, .
a) the force of contraction increased and the heart rate slowed and eventually stopped
b) the force of contraction decreased the force of contraction decreased and the heart rate slowed and eventually stopped
c) the heart rate slowed and eventually stopped
d) the force of contraction increased

The correct answer is: c) the heart rate slowed and eventually stopped.

Explanation:

The vagus nerve (X) is a cranial nerve with the function to parasympathetically innervate the heart, the lungs and the digestive tract.

As a part of the Autonomic Nervous System (ANS), the vagus nerve regulates things such as heart rate and gastrointestinal peristalsis (things we cannot control).

Given that it is a component of the parasympathetic division of the ANS, it stimulates the organs when the individual is performing normal activities like resting and feeding (unlike the sympathetic division, responsible for the fight-or-flight response). For this specific reason, the vagus nerve slows the heart rate, so if it were to be stimulated in a frog, it would produce the same thing and ultimately lead to its heart stopping.

C. the heart rate slowed and eventually stopped.

Explanation:

Vagus nerve is the most complex and longest  of the 12 cranial  nerve fibres pairs. It major contributions is to the autonomic nervous system.Which contains the sympathetic and parasympathetic branches. The parasympathetic nervous system is concerned with slowing down of heart rate, relaxation of of sphincters, another functions which relaxes nerve stimulation to conserve energy.

Vagus nerves are made up of parasympathetic nerves as mixed nerves.Thus continuous  stimulation of the vagus nerve to the frog heart, relates to stimulation of   parasympathetic nervous system, thus slowdown of heart rate, and eventual stoppage.

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