Anatomy & Physiology I and II

Anatomy & Physiology Study Guide along the esophagus, respiratory tract, and abdominal viscera as distant as the last portions of the large intestine. This visceral sensory information is vital to the autonomic control of visceral function. The Accessory Nerves (XI) The accessory nerves (XI) are also known as the spinal accessory nerves, or the spinoaccessory nerves. The internal branch of nerve XI joins the vagus nerve and innervates the voluntary swallowing muscles of the soft palate and pharynx, and the intrinsic muscles that control the vocal cords. The sternocleidomastoid and trapezius muscles of the neck and back are controlled by the external branch of CN XI. The motor fibers of this branch originate in the lateral gray part of the anterior horns of cervical spinal nerves C1 to C5. The Hypoglossal Nerves (XII) Each hypoglossal nerve (XII) leaves the cranium through the hypoglossal canal. The nerve then curves to reach the skeletal muscles of the tongue. This cranial nerve provides voluntary motor control over movements of the tongue. 12.15 Chapter Twelve Review An introduction to the brain and cranial nerves: • The adult human brain contains almost 97 percent of the body’s neural tissue and averages 1.4 kg (3 lb.) in weight and 1200 cc (71 in3) in volume. The brain has several principal structures, each with specific functions: • The six regions in the adult brain are the cerebrum, cerebellum, diencephalon, mesencephalon (“midbrain”), pons, and medulla oblongata. • The brain contains extensive areas of neural cortex, a layer of gray matter on the surfaces of the cerebrum and cerebellum. • The brain forms from three swellings at the superior tip of the developing neural tube: the prosencephalon, the mesencephalon, and the rhombencephalon. The prosencephalon (“forebrain”) forms the telencephalon (which becomes the cerebrum) and diencephalon; the rhombencephalon (“hindbrain”) forms the metencephalon (cerebellum and pons) and myelencephalon (medulla oblongata). • The central passageway of the brain expands to form chambers called ventricles, which contain cerebrospinal fluid. The brain is protected and supported by the cranial meninges, cerebrospinal fluid, and the blood– brain barrier: • The cranial meninges (the dura mater, arachnoid mater, and pia mater) are continuous with those of the spinal cord. • Folds of dura mater, including the falx cerebri, tentorium cerebelli, and falx cerebelli, stabilize the position of the brain. ©2018 Achieve Test Prep Page 138 of 367