Nervous System CNS and Spinal PDF

The Nervous System Part 2 CNS Chapter 15 www.fanpop.com Outline Identify the anatomy of the spinal cord Describe the structure of a spinal nerve List the different plexuses and nerves that come from those and their functions. Explain reflexes Explain CSF and BBB Descr...

The Nervous System Part 2 CNS Chapter 15 www.fanpop.com Outline Identify the anatomy of the spinal cord Describe the structure of a spinal nerve List the different plexuses and nerves that come from those and their functions. Explain reflexes Explain CSF and BBB Describe the subdivisions of the brain. List the general functions of each. Identify the lobes of the cerebrum. List the general functions of each. List the 12 cranial nerves and their main function Protective Structures and Spinal Meninges Spinal cord Runs from the foramen magnum to vertebrae L1 and L2. Suspended within vertebral canal Protected by Vertebrae Adipose tissue Spinal meninges Three meninges (meninx = singular), Cover the spinal cord. Continuous with the cranial meninges (protect the brain) Cerebrospinal fluid Spinal Meninges Dura mater Outer meninx; Tough, single-layered membrane deep to the epidural space. Arachnoid mater Middle layer of the meninges; Collagen and elastic fibers resembles a spider's web.  Spinal Meninges Subarachnoid space A space between the arachnoid mater and pia mater; Filled with cerebrospinal fluid Pia mater Delicate, transparent inner layer; Adheres to the surface of the spinal cord. Arachnoid Pia mater Dura mater  Dura mater Arachnoid Pia mater Spinal Meninges Arachnoid Pia mater Dura mater  Dura mater Arachnoid Pia mater Spinal Cord Functions 1. Carry sensory and motor information Carries sensory information to brain and motor output to nerves 2. Spinal reflexes Process sensory input from spinal nerves Convey motor output to the spinal nerves Spinal Cord – Gross Anatomy The spinal cord is divided into right and left halves. White matter surrounds a centrally located H-shaped mass of gray matter. Central canal = contains CSF Spinal Cord – Gross Anatomy The gray matter of the spinal cord contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia. On each side of the spinal cord, the gray matter is subdivided into regions called horns. The white matter consists primarily of myelinated axons of neurons and is organized into white columns Spinal Cord – Gross Anatomy Dorsal horns (posterior) – cell bodies and axons of interneurons and axons of incoming sensory neurons (cell bodies of sensory neurons are located in dorsal root ganglia). Ventral horns (anterior) – cell bodies of motor neurons. Lateral horns – present only in thoracic and upper lumbar regions, contain cell bodies of ANS motor neurons (regulate activity of cardiac muscle, smooth muscle, and glands). White matter tracts – bundles of axons carrying similar information – sensory and motor tracts. Gray Matter Somatic Dorsal Sensory Horn Visceral Lateral Horn Somatic Ventral Motor Horn Spinal Cord – Gross Anatomy Spinal nerves serve as a path of communication between the spinal cord and specific regions of the body. Two bundles of axons, called roots, connect each spinal nerve to a segment of the cord. Spinal Cord – Gross Anatomy Dorsal Root – contains only sensory axons, which conduct nerve impulses from sensory receptors in the skin, muscles, and internal organs to the CNS. Dorsal Root Ganglion – contains sensory neuron cell bodies. Ventral Root – contains axons of motor neurons, which conduct nerve impulses from the CNS to the Spinal Nerves Because spinal nerves contain both sensory and motor functions, they are called mixed nerves. Spinal Nerves Spinal nerves and the nerves that branch from them are a part of the PNS. 31 pairs of nerves are named/numbered according to the region and level of the vertebral column from which they emerge. Spinal Cord - Gross Anatomy Spinal cord extends from: the medulla oblongata (part of brain stem), to the upper border of L2 (the conus medullaris). Cauda Equina = collection of spinal nerves that angle down the vertebral canal Enlargements Cervical – neurons innervate upper limbs Lumbar – neurons innervate lower limbs www.about.spine.com Spinal Nerves Spinal nerves pass through intervertebral foramen, then branch 8 Pairs of cervical spinal nerves 1st pair between the base of the skull (occipital bone), last pair after the C7 vertebrae 12 Pairs of thoracic spinal nerves 5 Pairs of lumbar spinal nerves 5 Pairs of sacral spinal nerves, 1 pair of coccygeal nerves Copyright © 2016 by Nelson Education Ltd. Spinal Nerves – General Branch off the spinal cord Leave the vertebral column through the intervertebral foramina Arranged much like muscles: neurons are grouped together in fascicles, a collection of fascicles make up a nerve Individual axons, fascicles and the whole nerve have protective connective tissue coverings. Spinal Nerves – Plexuses Some spinal nerves form a network of nerves called plexuses 1. Cervical plexus – innervates skin and muscles of head, neck, and upper shoulders, and diaphragm (C1-C5) 2. Brachial plexus – innervates upper limbs, neck and shoulder muscles (C5-T1) 3. Lumbar plexus – innervates abdominal wall, genitals, parts of lower limbs (L1-L4) 4. Sacral plexus – innervates buttocks, perineum, lower limbs (L4- S4) Spinal Nerves – Plexuses Copyright © 2016 by Nelson Education Ltd.