Central Nervous System Part B PDF

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Central Nervous System Part B...

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Central Nervous System Part B 12 Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Protection of the Brain ▪ The brain is protected by bone, meninges, and cerebrospinal fluid (CSF) ▪ Harmful substances are shielded from the brain by the blood-brain barrier Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Meninges ▪ Three connective tissue membranes lie external to the CNS – dura mater, arachnoid mater, and pia mater ▪ Functions of the meninges ▪ Cover and protect the CNS ▪ Protect blood vessels and enclose venous sinuses ▪ Contain cerebrospinal fluid (CSF) ▪ Form partitions within the skull Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Meninges Figure 12.23a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Dura Mater ▪ Leathery, strong meninx composed of two fibrous connective tissue layers ▪ The two layers separate in certain areas and form dural sinuses Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Arachnoid Mater ▪ The middle meninx, which forms a loose brain covering ▪ It is separated from the dura mater by the subdural space ▪ Beneath the arachnoid is a wide subarachnoid space filled with CSF and large blood vessels ▪ Arachnoid villi protrude superiorly and permit CSF to be absorbed into venous blood Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Arachnoid Mater Figure 12.23a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Pia Mater ▪ Deep meninx composed of delicate connective tissue that clings tightly to the brain Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Cerebrospinal Fluid (CSF) ▪ Watery solution similar in composition to blood plasma ▪ Contains less protein and different ion concentrations than plasma ▪ Forms a liquid cushion that gives buoyancy to the CNS organs ▪ Prevents the brain from crushing under its own weight ▪ Protects the CNS from blows and other trauma ▪ Nourishes the brain and carries chemical signals throughout it Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Choroid Plexuses ▪ Clusters of capillaries that form tissue fluid filters, which hang from the roof of each ventricle ▪ Have ion pumps that allow them to alter ion concentrations of the CSF ▪ Help cleanse CSF by removing wastes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Choroid Plexuses Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.25a  Blood-Brain Barrier: Functions ▪ Protective mechanism that helps maintain a stable environment for the brain ▪ Bloodborne substances are separated from neurons ▪ Selective barrier that allows nutrients to pass freely ▪ Is ineffective against substances that can diffuse through plasma membranes ▪ Stress increases the ability of chemicals to pass through the blood-brain barrier Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Spinal Cord ▪ CNS tissue is enclosed within the vertebral column from the foramen magnum to L1 ▪ Provides two-way communication to and from the brain ▪ Protected by bone, meninges, and CSF ▪ Epidural space – space between the vertebrae and the dural sheath (dura mater) filled with fat and a network of veins Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Spinal Cord Figure 12.28a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Spinal Cord ▪ Conus medullaris – terminal portion of the spinal cord ▪ Filum terminale – fibrous extension of the pia mater; anchors the spinal cord to the coccyx ▪ Denticulate ligaments – delicate shelves of pia mater; attach the spinal cord to the vertebrae Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Spinal Cord ▪ Spinal nerves – 31 pairs attach to the cord by paired roots ▪ Cervical and lumbar enlargements – sites where nerves serving the upper and lower limbs emerge ▪ Cauda equina – collection of nerve roots at the inferior end of the vertebral canal Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Cross-Sectional Anatomy of the Spinal Cord ▪ Anterior median fissure – separates anterior funiculi ▪ Posterior median sulcus – divides posterior funiculi Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 12.30a  Gray Matter and Spinal Roots ▪ Gray matter consists of soma, unmyelinated processes, and neuroglia ▪ Posterior (dorsal) horns – interneurons ▪ Anterior (ventral) horns – interneurons and somatic motor neurons ▪ Lateral horns – contain sympathetic nerve fibers Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Gray Matter and Spinal Roots Figure 12.30b Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings