Sinusal afferents supplying superior cervical ganglion.

Sinusal distension can evoke activity in nerves supplying the superior cervical ganglion. These nerves, which have been shown to have little depressor influence, may carry an inhibitory input from the carotid sinus to the superior cervical ganglion (SCG). They have the morphological characteristics of the nerve of Hering and show cardiac pulse-related activity that may reach a maximum of 50 impulses/s during distension of the sinus. Electrical stimulation of the ascending preganglionic sympathetic trunk supplying the SCG may evoke discreet bursts of activity in these fibers, which do not summate with continued stimulation.