Chapter 10 - Chapter 10: Brain Damage and Neuroplasticity...

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Chapter 10: Brain Damage and Neuroplasticity The case of Prof. P Lets meet the man in person and listen to what he has to say. The case: was it hearing loss due to middle age or something a little more sinister? 10.1 Causes of Brain Damage Brain tumors Cerebrovascular disorders Closed-head injuries Infections of the brain Neurotoxins Genetic factors All the above can trigger apoptosis (programmed cell death) Brain Tumors A tumor (neoplasm) is a mass of cells that grows independently of the rest of the body – a cancer (can be benign or malignant) ~20% of brain tumors are meningiomas – encased in meninges - Encapsulated, growing within their own membranes - Usually benign (non-dangerous), surgically removable Most brain tumors are infiltrating - Grow diffusely through surrounding tissue - Malignant, difficult to remove or destroy About 10% of brain tumors are metastatic – they originate elsewhere, usually the lungs http://www.bio.davidson.edu/courses/Bio111/tumor.html Cerebrovascular Disorders Stroke – a sudden-onset cerebrovascular event that causes brain damage - Cerebral hemorrhage – bleeding in the brain/blood vessel ruptures o Aneurysm – a weakened point in a blood vessel that makes a stroke more likely, may be congenital (present at birth) or due to poison or infection - Cerebral ischemia – disruption of blood supply o Thrombosis – a plug forms in the brain o Embolism – a plug forms elsewhere and moves to the brain o Arteriosclerosis – wall of blood vessels thicken, usually due to fat deposits 3 rd leading cause of death in the U.S. and most common cause of adult disability
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Damage due to Cerebral Ischemia Does not develop immediately Most damage is a consequence of excess neurotransmitter release – especially glutamate Blood-deprived neurons become overactive and release glutamate to adjacent neurons Glutamate over-activates its receptors, especially NMDA receptors leading to an influx of Na + and Ca 2+ Influx of Na + and Ca 2+ triggers - The release of still more glutamate - A sequence of internal reactions that ultimately kill the neuron Ischemia-induced brain damage - Takes time - Does not occur equally in all parts of the brain - Mechanisms of damage vary with the brain structure affected Figure 10.5 – Stroke-induced release of glutamate Aneurysms: http://brainavm.uhnres.utoronto.ca/malformations/cerebral_aneurysms_index.htm Closed-Head Injuries Brain injuries due to blows that do not penetrate the skull – the brain collides with the skull - Contrecoup injuries – contusions are often on the side of the brain opposite to the blow Contusions – closed-head injuries that involve damage to the cerebral circulatory system; hematoma (bruise) forms Concussions – when there is disturbance of consciousness following a blow to the head and no evidence of structural damage - While there is no apparent brain damage with a single concussion, multiple concussions
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Chapter 10 - Chapter 10: Brain Damage and Neuroplasticity...

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