cranial nerves and spinal nerves

 Cranial Nerves

• Overview: twelve pairs of cranial nerves connect to the brain, mostly the brainstem; identified by name (determined by either distribution or function) or number (order in which they emerge, anterior to posterior) or both
• Olfactory nerve (I): carries information about sense of smell
• Optic nerve (II): carries visual information from the eyes to the brain
• Oculomotor nerve (III): innervates the muscles of the eye and regulates amount of light entering the eye
• Trochlear nerve (IV): innervates the superior oblique muscles of the eye
• Trigeminal nerve (V): innervates the muscles of mastication and carries sensory information from the head and teeth
• Abducens nerve (VI): innervates the lateral rectus muscles of the eye
• Facial nerve (VII): innervates the muscles of the face and scalp and carries sensory information from taste buds of the anterior two thirds of the tongue
• Vestibulocochlear nerve (VIII): carries sensory information related to equilibrium and hearing
• Glossopharyngeal nerve (IX): innervates the pharynx and carries sensory information from taste buds of the posterior third of the tongue
• Vagus nerve (X): innervates various organs in the body and carries sensory information from the pharynx, larynx, trachea, heart, lungs, esophagus, stomach, small intestine, and gallbladder
• Accessory nerve (XI): innervates the trapezius and sternocleidomastoid muscles
• Hypoglossal nerve (XII): innervates the muscles of the tongue

 Spinal Nerves

• Overview: thirty-one pairs of spinal nerves are connected to the spinal cord; no special names; numbered by level of vertebral column at which they emerge from the spinal cavity
• Structure: each spinal nerve attaches to spinal cord by a ventral (anterior) root and a dorsal (posterior) root; dorsal root ganglion is a swelling in the dorsal root of each spinal nerve; all spinal nerves are mixed nerves
• Nerve Plexuses: complex networks formed by the ventral rami of most spinal nerves (not T2 through T12) subdividing and then joining together to form individual nerves; each individual nerve that emerges contains all the fibers that innervate a particular region of the body; in plexuses, spinal nerve fibers are rearranged according to their ultimate destination, reducing the number of nerves needed to supply each body part
• Dermatomes and Myotomes: dermatome is a region of skin surface area supplied by afferent (sensory) fibers of a given spinal nerve; myotome is a skeletal muscle or muscles supplied by efferent (motor) fibers of a given spinal nerve