Final answer:
The afferent branch consists of baroreceptors in the carotid sinuses that sense the stretch of the sinuses during an increase in blood volume or pressure, while the efferent branch involves the autonomic nervous system that modulates heart and blood vessel activity.
Step-by-step explanation:
The afferent branch for the carotid sinus reflex is the baroreceptors in the walls of the carotid sinuses. These baroreceptors sense the stretch of the carotid sinuses when blood volume or pressure increases. The baroreceptors send signals through the glossopharyngeal nerve into the central nervous system to initiate the reflex.
The efferent branch for the carotid sinus reflex is the autonomic nervous system. In response to the increase in blood pressure sensed by the baroreceptors, the autonomic nervous system modulates the activity of the heart and blood vessels to restore blood pressure to normal levels. The efferent signals are carried by the vagus nerve for the afferent branch.