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Ch 12.rtf - Ch. 12 INTRODUCTION: THE CENTRAL NERVOUS SYSTEM...

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Ch. 12INTRODUCTION: THE CENTRAL NERVOUS SYSTEMA. The central nervous system (CNS) comprises both the brain and the spinal cord and isthe principal integrator of sensory input and motor outputB. The CNS is capable of evaluating incoming information and formulating appropriateresponses to changes that may threaten our body's homeostatic balanceCOVERINGS OF THE BRAIN AND SPINAL CORDA. Two protective coverings of the brain and spinal cordBone—outer covering, cranium for brain and vertebrae for spinalcordMeninges—inner covering (membranes)Infection or inflammation of the meninges, calledmeningitisB.Meningeal layers:1. Dura mater—outer layer of the meninges; inner layer of the cranium'speriosteumContains many blood vessels and nerves2. Arachnoid—delicate, spiderweb-like layer, lying between the dura mater andthe innermost layerLacking blood vessels and nerves3. Pia mater—innermost layer; adheres tightly to the outer surface of the brainand spinal cordProvides the brain and spinal cord with many blood vessels andnervesThe pia mater forms a slender filament known as thefilumterminaleC.Dura materimportantinward extensions:1. Falx cerebri—projects downward into the longitudinal fissure (a “crack”) toform a tough partition between the two cerebral hemispheres2. Falx cerebelli—sickle-shaped extension that separates the two halves, orhemispheres, of the cerebellum
3. Tentorium cerebelli—separates the cerebellum from the cerebrum, tentlikecoveringD.Spaces between and around the meninges:1.Epidural space—above the dura mater and just below the bony coveringsof the spinal cord2.Subdural space—contains a small amount of lubricating (serous) fluid andlies between the dura mater and the arachnoid mater3.Subarachnoid space—lies underneath the arachnoid mater and outsidethe pia mater; contains a large amount ofcerebrospinal fluid (CSF)E. The meninges of the spinal cord continue down inside the spinal cavity1.Filum terminale—slender filament formed by the pia materF.Meningitis—infection or inflammation of the meningesIt most often involves the arachnoid and pia mater, or the leptomeninges(“thin meninges”)Caused by bacteria such as Neisseria meningitidis (meningococcus),Streptococcus pneumoniae, or Haemophilus influenzae
CEREBROSPINAL FLUIDA. Cerebrospinal fluid (CSF)—circulating serous fluid; protects by cushioning brain andspinal cordBody makes 500 mL of CSF, only 140 mL circulatesB. CSF has homeostatic functions; it is monitored by the brain for changes in the internalenvironment, such as the concentration of carbon dioxideC. Cerebrospinal fluid circulates within thesubarachnoid spacearound the brain andspinal cord; also circulates within the fluid-filled canals and cavities (ventricles) of thebrain and spinal cordD. Ventricles—four fluid-filled spaces within the brain1. Two large ventricles located in each hemisphere of the cerebrum2. A smaller third ventricle lying vertically between them3. Fourth diamond-shaped ventricle is attached to the brainstemE. Cerebrospinal fluid forms primarily byseparation of fluid from blood1.

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Term
Winter
Professor
Craig black
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