Neurolgy RHS 344 Lecture 5 PDF

Neurology RHS 344 Lecture 5 The Cerebrum and the cerebrum function Lecture outline The protection and nourishment of the cerebrum The cerebrum Hemispheric specialization and connections Cerebral disorder Brain plasticity The cerebral cortex Brain Lobes ...

Neurology RHS 344 Lecture 5 The Cerebrum and the cerebrum function Lecture outline The protection and nourishment of the cerebrum The cerebrum Hemispheric specialization and connections Cerebral disorder Brain plasticity The cerebral cortex Brain Lobes  Protection: 1. The Meninges The inside of the skull can be a very inhospitable place for the delicate brain.  Protection: The Meninges Fortunately, a three-layered membrane called the meninges surrounds the delicate brain. Dura mater: most outer layer Arachnoid mater: middle layer Pia mater: inner layer Where there are layers, spaces result Potential spaces: Epidural space: between skull and dura mater Subdural space: between dura mater and arachnoid mater Actual space: Subarachnoid space: between arachnoid mater and pia mater  2. The Blood-Brain Barrier Located in the walls of CNS blood vessels The BBB protects the brain from foreign invaders, hormones, antibodies and other substances The BBB maintains a constant environment for the brain  Nourishment: The Cerebral Arteries Brain consumes 20% of body’s oxygen Blood enters brain through: – Carotid arteries – Vertebral arteries These feed the circle of Willis → promote equal blood pressure and blood flow to all brain areas  Nourishment: The Cerebral Arteries Circle of Willis feeds the brain oxygenated blood through: – Anterior cerebral artery – Middle cerebral artery – Posterior cerebral artery Nourishment: The Cerebral Arteries  Waste Removal: The Venous System Moves deoxygenated blood away from the brain and move used CSF away from the ventricular system Removed through 4 sinuses in meninges: – Superior sagittal – Transverse – Occipital – Sigmoid Superficial and deep cerebral veins  Overview of the Cerebrum Two cerebral hemispheres (left and right) Major layers from superficial to deep: – Surface gray matter (cerebral cortex; neuron somas) – White matter (axons) – Deep gray matter (e.g., thalamus, basal ganglia) – Ventricles (4 ventricles)  Cerebral Cortex Features Cortex means “bark” Features include: – Gyri (hills) – Sulci (shallow groove) – Fissures (deep sulci): Longitudinal Central Lateral Cerebral Cortex Gyri and Sulci  Brodmann Map Developed by Korbinian Brodmann (1868–1918) Developed cytoarchitectural maps based on the structure of the cortex Divides brain into 52 areas based on: Brain’s gross anatomy Cellular structure of brain Areas called Brodmann areas (BA)  Lobes of the Brain Frontal lobe: reasoning, planning, motor movement Parietal lobe: sensory perception and interpretation Occipital lobe: vision Temporal lobe: memory, receptive language  Frontal lobe Boundaries → Lateral sulcus anteriorly Central sulcus posteriorly Precentral gyrus → ✓located immediately anterior to the central gyrus ✓Comprise of the majority of the primary motor cortex PMC (motor strip) → responsible for voluntary control of skeletal muscles Premotor cortex & Supplementary motor area→ ✓Anterior to the PMC ✓Important for motor learning and performance of routine and less practice motor sequence Broca’s area (B 44 and 45) → b ✓Posterior to the inferior frontal gyrus ✓Important for the production of fluent well articulated speech  Parietal lobe Boundaries → Central sulcus anteriorly Posterior end of the lateral sulcus inferiorly Postcentral gyrus → ✓located immediately posterior to the central sulcus ✓Comprise of the majority of the Somatosensory cortex Supramarginal gyrus (B 40)→ ✓Curves around the posterior end of the sylvian fissure Angular gyrus (B 39) → ✓Lies directly posterior to the supramarginal gyrus  Temporal lobe Boundaries → sylvian fissure superiorly Superior temporal gyrus Middle temporal gyrus Inferior temporal gyrus Transverse gyrus→ ✓Heschl’s gyrus (B 41) ✓Auditory association area (B 42) Wernicke’s area (B 22) → ✓ In the posterior part of the STG in the left temporal lobe ✓ Important for the development and use of language  Occipital lobe Small area behind the parietal lobe Parieto-occipital sulcus Calcarine sulcus Concerned with vision Right vs. Left Hemisphere Function  Hemispheric Specialization: Language Dominance Most people are left hemisphere language dominant – 96% of right handers – 85% of ambidextrous – 73% of left handers  Interhemispheric Connections Corpus callosum is a band of fibers that connects the right and left hemispheres together.  Intrahemispheric Connections Numerous connections within the cerebral hemispheres Two examples: – Superior longitudinal fasciculus – Arcuate fasciculus  Cerebral disorder Cerebral Vascular Accident (CVA) Ischemic CVA – Thrombotic (cerebral thrombosis) → originate in the blood vessels – Embolic (cerebral embolism) – Transient