Question

What are the components of the central and peripheral nervous system that increase heart rate and blood pressure (include baroreceptors, and both sympathetic and parasympathetic systems)

Answer 1

Heart Rate:

The heart rate is controlled by the two branches of the autonomic nervous system. The ANS is under the control of the hypothalamus. The cardiac center in the medulla also governs the heart rate. The sympathetic nervous system releases the catecholamines hormones epinephrine and norepinephrine to accelerate the heart rate. The parasympathetic nervous system through the vagus controls the rate of firing of the SA node. By regulating the rate of firing of the SA node, the PSNS regulates the heart rate.

Blood Pressure:

Cardiac output = Heart rate x stroke volume

Through the above-mentioned pathways, an increase in heart rate can also increase the cardiac output and force of contraction of the heart. This also causes an increase in blood pressure.

Another mechanism through which the blood pressure can be increased is by vasoconstriction. The vasomotor center in the brain can cause an increase in sympathetic tone. This is mediated through the spinal cord and sympathetic chain of ganglia. Smooth muscles in the blood vessels receive innervation from the autonomic nervous system. These cause the vascular smooth muscles to contract. Widespread release of catecholamines also vasoconstriction causes an increase in blood pressure through the same mechanism.