Chapter 15 - Section 15.2 - Study Guide - Assess Your Learning Outcomes - Page 575: 9

The preganglionic fibers of the parasympathetic nervous system are carried by specific cranial nerves and sacral spinal nerves. Here are the names and numbers of the cranial and sacral nerves that carry these fibers: 1. **Cranial Nerves (Cranial Outflow)**: - **Cranial Nerve III**: Also known as the oculomotor nerve, Cranial Nerve III carries parasympathetic fibers to the ciliary ganglion, which is responsible for controlling the constriction of the pupil (miosis) and accommodation (focusing) of the lens in the eye. - **Cranial Nerve VII**: Also known as the facial nerve, Cranial Nerve VII carries parasympathetic fibers to various glands, including the submandibular and sublingual salivary glands, as well as the lacrimal (tear) glands. These fibers stimulate salivation and tear production. - **Cranial Nerve IX**: Also known as the glossopharyngeal nerve, Cranial Nerve IX carries parasympathetic fibers to the parotid salivary gland, promoting salivation. - **Cranial Nerve X**: Also known as the vagus nerve, Cranial Nerve X carries the largest percentage of parasympathetic fibers among the cranial nerves. It innervates a wide range of organs and tissues in the thoracic and abdominal cavities, including the heart, lungs, digestive organs, and various glands. The vagus nerve plays a significant role in regulating rest-and-digest functions, such as slowing the heart rate, promoting digestion, and facilitating relaxation. 2. **Sacral Spinal Nerves (Sacral Outflow)**: - The parasympathetic outflow from the sacral spinal cord segments (S2 to S4) is collectively known as the sacral outflow. Preganglionic parasympathetic fibers from these segments exit the spinal cord and travel to their target organs via the pelvic splanchnic nerves. - The sacral outflow is responsible for innervating the pelvic organs, including the bladder, rectum, and reproductive organs. It controls functions such as urination, defecation, and sexual arousal. Among these nerves, Cranial Nerve X, the vagus nerve, carries the largest percentage of parasympathetic fibers. It is often referred to as the "wandering nerve" because of its extensive distribution throughout the body and its role in regulating many vital functions, including heart rate, respiratory rate, and gastrointestinal activity.

The preganglionic fibers of the parasympathetic nervous system are carried by specific cranial nerves and sacral spinal nerves. Here are the names and numbers of the cranial and sacral nerves that carry these fibers: 1. **Cranial Nerves (Cranial Outflow)**: - **Cranial Nerve III**: Also known as the oculomotor nerve, Cranial Nerve III carries parasympathetic fibers to the ciliary ganglion, which is responsible for controlling the constriction of the pupil (miosis) and accommodation (focusing) of the lens in the eye. - **Cranial Nerve VII**: Also known as the facial nerve, Cranial Nerve VII carries parasympathetic fibers to various glands, including the submandibular and sublingual salivary glands, as well as the lacrimal (tear) glands. These fibers stimulate salivation and tear production. - **Cranial Nerve IX**: Also known as the glossopharyngeal nerve, Cranial Nerve IX carries parasympathetic fibers to the parotid salivary gland, promoting salivation. - **Cranial Nerve X**: Also known as the vagus nerve, Cranial Nerve X carries the largest percentage of parasympathetic fibers among the cranial nerves. It innervates a wide range of organs and tissues in the thoracic and abdominal cavities, including the heart, lungs, digestive organs, and various glands. The vagus nerve plays a significant role in regulating rest-and-digest functions, such as slowing the heart rate, promoting digestion, and facilitating relaxation. 2. **Sacral Spinal Nerves (Sacral Outflow)**: - The parasympathetic outflow from the sacral spinal cord segments (S2 to S4) is collectively known as the sacral outflow. Preganglionic parasympathetic fibers from these segments exit the spinal cord and travel to their target organs via the pelvic splanchnic nerves. - The sacral outflow is responsible for innervating the pelvic organs, including the bladder, rectum, and reproductive organs. It controls functions such as urination, defecation, and sexual arousal. Among these nerves, Cranial Nerve X, the vagus nerve, carries the largest percentage of parasympathetic fibers. It is often referred to as the "wandering nerve" because of its extensive distribution throughout the body and its role in regulating many vital functions, including heart rate, respiratory rate, and gastrointestinal activity.