Pelvic splanchnic nerves are the primary source for parasympathetic innervation. The parotid gland receives both sensory and autonomic innervation. The postganglionic sympathetic innervation arises from the superior cervical ganglia. Parasympathetic innervation to the ascending colon is supplied by the vagus nerve. Similarly, intestinal parasympathetic innervation and myelination also increases in later gestations. The pineal gland receives a sympathetic innervation from the superior cervical ganglion. These ganglia provide the postganglionic neurons from which innervation of target organs follows. A parasympathetic innervation from the pterygopalatine and otic ganglia is also present. These exceptions receive general somatic efferent innervation. The parasympathetic innervation of the ciliary body is the most clearly understood. There is no evidence for a parasympathetic pulpal innervation. It receives sympathetic innervation from the celiac ganglion. Somatic (conscious) innervation of the external urethral sphincter is supplied by the pudendal nerve. The primary factors that influence HR are autonomic innervation plus endocrine control. Retinal vessels lack a functional sympathetic innervation.