Final answer:
Vagal withdrawal leads to an increase in heart rate by reducing parasympathetic stimulation, while sympathetic stimulation further increases heart rate and the force of contraction. The correct response is that both vagal withdrawal and sympathetic stimulation result in an increased heart rate. option( 4) increase, increase.
Step-by-step explanation:
During exercise, vagal withdrawal produces an increase in heart rate and sympathetic stimulation produces an increase in heart rate. The correct answer is 4) increase, increase.
Parasympathetic stimulation (vagal tone) generally decreases heart rate and stroke volume. When this stimulation is reduced during vagal withdrawal, there is a corresponding increase in heart rate up to about 100 bpm. Any further increases in heart rate require sympathetic stimulation, which acts as a positive inotrope, increasing the heart rate and the force of contraction, leading to increased stroke volume and a reduced end-systolic volume (ESV) in the ventricles. During exercise, the cardiovascular center receives input indicating an increase in physical activity, which results in a decrease in parasympathetic stimulation and an increase in sympathetic stimulation to enhance blood flow to meet the body’s demands.