Question

Detail the complete reflex pathway involving parasympathetic signalling to the heart. Begin this at the carotid body baroreceptors.

Answer 1

Baroreceptors are receptors sensitive to the change in pressure in carotid body. When the blood pressure in ateries increases it causes increased firing from the baroreceptors. The baroreceptors sends sensory information to the nucleus tractus solitarius (NTS). NTS then releases glutamate sending excitatory signals to caudal ventrolateral medulla(CVM). The GABA released from CVM inhibits the rostral ventrolateral medulla. Inhibiting the rostral ventrolateral medulla inhibits the sympathetic activity to the heart. NTS also sends excitatory impulses to nucleus ambiguus. This activated the parasympathetic activity of heart. Parasympathetic stimulation and sympathetic inhibition of the heart results in decreased myocardial contraction, decreased heart rate, decreased stroke volume and cardiac output. It also causes vasodilation of blood vessels resulting in decreased peripheral resistance. All this causes decrease in blood pressure.
This reflex pathway elicited by the baroreceptors is known as barorefl