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Chapter 10

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PSYC 370
Monica Valsangkar- Smyth

Chapter 10: Brain Damage and Neuroplasticity- Can the Brain Recover from Damage? - Six causes of brain damage: brain tumours, cerebrovascular disorders, closed-head injuries, infections of the brain, neurotoxins and genetic factors - Tumor (neoplasm): a mass of cells that grows independently of the rest of the body - About 20% of the tumors found in the human brain are meningiomas (grow between the meninges) - Encapsulated tumors: tumors that grow within their own membranes o Almost always benign - Benign tumors: tumors that are surgically removable with little risk of further growth in the body - Infiltrating tumors: tumors that grow diffusely through surrounding tissues - Malignant tumors: tumors that may continue to grow in the body even after attempted surgical removal - Metastatic tumors: tumors that originate in one organ and spread to another o About 10% of brain tumors originate this way - Neuromas are tumors that grow on nerves or tracts - Stokes: sudden-onset cerebrovascular disorders that cause brain damage o Common consequences of stroke are amnesia, aphasia (language difficulties), paralysis, and coma - Infarct is the area of dead or dying tissue produced by a stroke - Penumbra: the area of brain tissue around an infarct, in which the degree of damage can vary - Two major types of stroke: stroke due to cerebral hemorrhage and stroke due to cerebral ischemia - Bursting aneurysms are a common cause of intracerebral hemorrhage - Aneurysm: a pathological balloonlike dilation that forms in the wall of a blood vessel at a point where the elasticity of the vessel wall is defective o Can occur in any part of the body - Aneurysms can be congenital (present at birth) or can result from exposure to vascular poisons or infection - Cerebral ischemia: an interruption of the blood supply to an areas of the brain; a common cause of medial temporal lobe amnesia o Can be caused by thrombosis, embolism, and arteriosclerosis - Thrombosis: the blockage of blood flow by a plug (a thrombus) at the site of its formation - Embolism: the blockage of blood flow in a smaller blood vessel by a plug that was formed in a larger blood vessel and carried by the bloodstream to the smaller one - Arteriosclerosis: a condition in which blood vessels are blocked by the accumulation of fat deposits on their walls - Much of the brain damage associated with stroke is a consequence of excessive release of excitatory amino acid neurotransmitters (glutamate in particular) - After blood vessels become blocked many of the blood-deprived neurons become overactive and release excessive quantities of glutamate - Glutamate receptors that are involved in this reaction are the NMDA (N-methyl-D- aspartate) receptors - Large numbers of Na and Ca ions enter the postsynaptic neurons - This excessive internal concentration affects the postsynaptic neuron in two ways: o Trigger the release of excessive amounts of glutamate from the neurons; spreads the toxic cascade to other neurons o Trigger a sequence of internal reactions that ultimately kill the postsynaptic neurons - Ischemia-induced brain damage has three important properties: o Takes a while to develop o Does not occur equally in all parts of the brain ; particularly susceptible are neurons in certain areas of the hippocampus o Mechanisms of ischemia-induced damage vary somewhat from structure to structure within the brain - Search is on for a glutamate antagonist that is effective and safe for use in human stroke victims - Brain injuries produced by blows that do not penetrate the skill are called close-head injuries - Contusions: closed-head injuries involve damage to the cerebral circulatory system, which produces internal hemorrhaging - Hematoma: a bruise - Contusions from closed-head injuries occur when the brain slams against the inside of the skull - Blood from such injuries can accumulate in the subdural space (space between dura mater and arachnoid membrane) and severely distort the surrounding neural tissue - Contrecoup injuries: contusions that occur on the side of the brain opposite to the side of a blow - Concussion: disturbance of consciousness following a blow to the head with no cerebral bleeding or obvious structural damage - Substantial evidence that the cognitive, motor, and neurological effects of concussion can last many years - Punch-drunk syndrome: the dementia and cerebral scarring that results from repeated concussions o Observed in boxers - Dementia: general intellectual deterioration - Encephalitis: the inflammation associated with brain infection - Two common types of brain infections bacterial infections and viral infections - Bacterial infections in the brain often lead to the formation of cerebral abscesses (pockets of pus in the brain) - Bacteria is the major cause of meningitis (inflammation of the meninges, usually caused by bacterial infection; fatal in 25% of adults) - Penicillin and other antibiotics sometimes eliminate bacterial infections of the brain but cannot reverse brain damage - General paresis: the insanity and intellectual deterioration resulting from syphilitic infection - Two types of viral infections: those that attack neural tissue and have an affinity to it, and those that attack neural tissue and other kinds of tissue - The rabies virus is lethal once it has reached the brain but takes about a month after contraction to reach the brain and therefore allows some time for it to be treated - Mumps and herpes are another example of viruses that can attack the nervous system but have no affinity to it - Toxic psychosis: a chronic psychiatric disorder produced by exposure to a neurotoxin - Tardive dyskinesia (TD): a motor disorder that results from chronic use of certain antipsychotic drugs - Some neurotoxins are endogenous (produced by the patient’s own body) - Most neuropsychological diseases of genetic origin are caused by abnormal recessive genes that are passed from parent to offspring - Genetic accidents are another cause of neuropsychological diseases; i.e., Down syndrome - Some dying cells display signs of both necrosis and apoptosis - Five diseases that are associated with brain damage: epilepsy, Parkinson’s disease, Huntington’s disease, multiple sclerosis, and Alzheimer’s disease - Epilepsy: a neurological disorder characterized by spontaneously recurring seizures - A one-time convulsion (motor seizure) would not mean you have epilepsy; it can be triggered by high fever or exposure to a convulsive toxin - Not all seizures take the form of convulsions with tremors, rigidity, loss of balance and consciousness - Over 70 different faulty genes have been linked to epilepsy - Appears to be associated with faults at inhibitory synapses that cause many neurons in a particular area to fire in synchronous bursts - Diagnoses of epilepsy is usually made through the use of an electroencephalogram (EEG) o Epileptic seizures are associated with bursts of high-amplitude EEG spikes - Epileptic auras: psychological symptoms that precede the onset of a convulsion - The nature of the auras provides clues concerning the location of the epileptic focus and can warn the patient of an impending convulsion - Partial seizures: seizures that do not involve the entire brain o Not usually accompanied by a loss of balance or consciousness - Simple partial seizures: partial seizures in which the symptoms are primarily sensory or motor or both – sometimes called Jacksonian seizures - Complex partial seizures: seizures that are characterized by various complex psychological phenomena and are thought to result from temporal lobe discharges – temporal lobe epilepsy - During a complex partial seizure the person engages in compulsive, repetitive, simple behaviours called automatisms - After seizure, person has no recollection of what happened - Temporal loves are particularly susceptible to epileptic discharges - Generalized seizures: seizures that involve the entire brain - Grand mal seizure: a seizure whose symptoms are loss of consciousness, loss of equilibrium, and a violent tonic-clonic convulsion o Accompanied by hypoxia (shortage of oxyg
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