Question

A(n) ______ in the SNS rate coupled with a(n) ______ in the vagal rate leads to a greater increase in MAP than would occur with either change alone.

decrease, increase

increase, decrease

decrease, decrease

increase, increase

Answer 1

Increased sympathetic stimulation along with decreased parasympathetic stimulation leads to a greater increase in mean arterial pressure (MAP) than either alone.

Step-by-step explanation:

The autonomic nervous system (ANS) regulates the heart rate through sympathetic and parasympathetic stimulation. An increase in sympathetic (SNS) stimulation coupled with a decrease in parasympathetic (vagal) stimulation leads to a greater increase in mean arterial pressure (MAP) than would occur with either change alone.

For example, when the body requires an increase in heart rate beyond the normal sinus rhythm of approximately 100 beats per minute, sympathetic stimulation becomes necessary. Figure 19.33 illustrates the effects of both parasympathetic and sympathetic stimulation on the heart rhythm.

Not surprisingly, sympathetic stimulation acts as a positive inotrope, increasing the force of contraction and cardiac output. On the other hand, parasympathetic stimulation acts as a negative inotrope, decreasing the force of contraction and stroke volume.