Bio Help!!! Norepinephrine acts on heart muscle cells by:

Question

A. blocking the action of calcium B. causing a decrease in stroke volume C. decreasing heart contractility D. causing threshold to be reached more quickly

and....

If the vagal nerves to the heart were cut, the result would be that:

A. parasympathetic stimulation would increase, causing a decrease in heart rate B. the heart would stop, since the vagal nerves trigger the heart to contract C. the AV node would become the pacemaker of the heart D. the heart rate would increase by about 25 beats per minute

Answer 1

There is what you have in front of you as the answer.

Answer 2

Nor-epi is very similar to adrenalin. The effect on the heart will be that threshold will be reached sooner thus speeding up the heart and increasing the strength of contraction.

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If the vagus nerve was severed to the heart then the innervation of parasympathetic would be eliminated. The parasympathetic nervous system will slow the heart so in this case the answer is D, the heart rate likely would increase. Just a note, the heart does not need any nerves running to it in order to beat, even a heart taken out of the body will continue to beat as long as the tissues are alive.