Anatomy of the CNS.docx

CNS is well protected by 4 major components from injury Cranium and vertebral column Meninges Cerebrospinal fluid Blood-brain Barrier Meninges Consist of 3 membranes Dura matter- external membrane, tough Arachnoid matter- highly vascularised. Pia matter- internal layer and the most fragile Cer...

CNS is well protected by 4 major components from injury Cranium and vertebral column Meninges Cerebrospinal fluid Blood-brain Barrier Meninges Consist of 3 membranes Dura matter- external membrane, tough Arachnoid matter- highly vascularised. Pia matter- internal layer and the most fragile Cerebrospinal fluid (CFS) Surrounds the brain and spinal cord. Acts as a shock-absorber Exchange of materials between neuronal cells and interstitial fluid CFS is produced by choroid plexuses. There is 1 choroid plexuses in each lateral ventricle. One choroid plexuses in the third ventricle and one in the forth ventricle CFS circulates in the ventricle system and is able to exit from the base of the brain by the forth ventricle It then flows into the subarachnoid space. Finally reabsorbed from the subarachnoid space into the venous blood across the arachnoid villi. Choroid plexuses is a single layer of cuboidal to low cylindrical epithelial cells that reside on the basement membrane. Surface area is greatly enhanced due to presence of dense microvilli. What are ventricles in the brain? Cavities within the brain and there are 4 of them within the CNS. 1 ventricle for each lateral hemisphere All 4 ventricles are connected to each other. Continuous with narrow central canal of spinal cord Highly selective brain-blood barrier Protects brain from harmful pathogens and regulates exchanges between blood and brain. Endothelial cells are joined by tight junction therefore nothing can be exchanged across the wall by passing between cells but only through the cells. The only allows molecules are lipid soluble molecule. (O2, CO2) Structure of the brain Cerebral cortex Each half of the cortex can be divided into 4 major lobes. Frontal lone Parietal lobe- sensation of pain and touch Temporal lobe- language. Occipital lobe- vision Corpus collosum 300 million Myelinated neurones that connect both hemispheres of cerebrum together and allow them to communicate. CNS is made of grey and white matter. Grey matter= desnely packed neuronal cell bodies and dendrties, glial cells information processing part of the brain White matter= bundles of myelinated fibres (axons)