Brain Damage and Neurological Disorders Chapter 10 o Study Questions Chapter 10 Know the difference between ischemic and hemorrhagic strokes and A stroke is a disruption of blood flow Ischemic stroke is a blockage between a thrombus and an embolus Hemorrhagic stroke is bleeding Thrombus forms and blocks at same location Blood clot tumor cells plaque etc Embolus forms elsewhere travels through vasculature until it get stuck Types of strokes Ischemic stroke blockage Types of strokes Hemorrhagic stroke bleeding Ischemic strokes are more common and hemorrhagic strokes often lead to immediate death Ruptured blood vessel Aneurysm balloon like dilation in the wall of a blood vessel which could rupture Cerebrovascular Disorders Strokes Book definition Strokes are sudden onset cerebrovascular disorders that cause brain damage In the United States stroke is the third leading cause of death the major cause of neurological dysfunction and the most common cause of adult disability The symptoms of a stroke depend on the area of the brain affected but common consequences of stroke are amnesia aphasia language difficulties paralysis and coma There are two major types of strokes those resulting from cerebral hemorrhage and those resulting from cerebral ischemia Cerebral hemorrhage bleeding in the brain occurs when a cerebral blood vessel ruptures and blood seeps into the surrounding neural tissue and damages it Bursting aneurysms are a common cause of intracerebral hemorrhage An aneurysm is a pathological balloonlike dilation that forms in the wall of an artery at a point where the elasticity of the artery wall is defective Although Aneurysms of the brain are particularly problematic aneurysms 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 Individuals who have aneurysms should make every effort to avoid high blood pressure or strenuous activity Cerebral ischemia is a disruption of the blood supply to an area of the brain The three main causes of cerebral ischemia are thrombosis embolism and arteriosclerosis In thrombus a plug called a thrombus is formed and blocks blood flow at the site of its formation A thrombus may be composed of a blood clot fat oil an air bubble tumor cells or any combination thereof Embolism is similar except that the plug called an embolus in this case is carried by the blood from a larger vessel where it was formed to a smaller one where it becomes lodged in essence an embolus is just a thrombus that has taken a trip In arteriosclerosis the walls of the bloods vessels thicken and the channels narrow usually as the result of fat deposits this narrowing can eventually lead to complete blockage of the blood vessels What is the penumbra What is diaschisis Penumbra the region directly surrounding the epicenter of the stroke Most at risk in the immediate aftermath of a stroke Disaschisis to shock throughout Long term concerns about parts of brain distant from focal region Book definition The area of dead or dying tissue produced by a stroke is called an infarct Surrounding the infarct is a dysfunctional area called the penumbra The tissue in the penumbra may recover or die in the ensuing days depending on a variety of factors The primary goal of treatment following stroke is to save the penumbra Understand the series of events leading to cell death in stroke Neuron die from excitotoxicity Excess glutamate release Edema swelling also causes slowing of sodium potassium pump further depolarization Also disruption of BBB Book definition Ischemia induced brain damage has two important properties First it takes a while to develop Soon after a temporary cerebral ischemic episode there usually is little or no evidence brain damage however substantial neuron loss can often be detected a day or two later Second ischemia induced brain damage does not occur equally in all parts of the brain particularly susceptible are neurons in certain areas of the hippocampus Paradoxically glutamate the brain s most prevalent excitatory neurotransmitter plays a major role in stroke induced brain damage Here is how this mechanism is thought to work After a blood vessel becomes blocked many of the blood deprived neurons become overactive and release excessive quantities of glutamate The glutamate in turn over activates glutamate receptors in the membranes of postsynaptic neurons the glutamate receptors most involved in this reaction are the NMDA N methyl D aspartate receptors As a result large numbers of Na and Ca2 ions enter the postsynaptic neurons The excessive internal concentrations of Na and Ca2 ions in the postsynaptic neurons affect them in two ways They trigger the release of excessive amounts of glutamate from the neurons thus spreading the toxic cascade to yet other neurons and they trigger a sequence of internal reactions that ultimately kill the postsynaptic neurons An implication of the discovery that excessive glutamate release causes much of the brain damage associated with stroke is the possibility of preventing stroke related brain damage by blocking the glutaminergic cascade The search is on for a glutamate antagonist that is effective and safe for use in human stroke victims Several have proved to be effective in laboratory animals but so far none has been shown to limit brain damage from strokes in humans It may well be that if such treatments are to be effective they need to be initiated soon after the stroke as they are in animal studies Supporting this view is a recent report that neuroprotectant NA 1 blocks postsurgical strokes in human patients if given immediately after surgery How are concussions classified graded A Concussion is an injury to the brain that results in temporary loss of normal brain function Grades o Grade 1 symptoms last 15 minutes no loss of consciousness o Grade 2 symptoms last 15 minutes no loss of consciousness o Grade 3 loss of consciousness sometimes just for a few seconds When there is a disturbance of consciousness following a blow to the head or Book definition other structural damage the diagnosis is concussion It was once assumed that a concussion entails a temporary disruption of normal cerebral function with no long term damage However there is now substantial evidence that the effects of concussion can last many years and that the effects of repeated concussions can accumulate What sorts of physical damage can occur to the brain in a traumatic brain
View Full Document
Unlocking...