Chapter 10

• Brain Damage and Neuroplasticity

  Chapter 10
• Purposes of studying the human brain

  • Increases our understanding of healthy brain
  • Serves as basis for development of new treatments
• Professor P.


  Ironic case
• Causes of Brain Damage

  • Brain Tumors
  • Cerebrovascular Disorders: Strokes
  • Closed-Head Injuries
  • Infections of the Brain
  • Neurotoxins
  • Genetic Factors
  • Programmed Cell Death
• Tumor (Neoplasm)


  Mass of cells that grows independently from rest of body
• Meningiomas


  • Tumors that grow between meninges
  • All meningiomas are Encapsulated Tumors (Tumors that grow within their own membrane)
• Encapsulated tumors


  Easy to identify in a CT scan because they can influence function of brain only by pressure they exert on surrounding tissue, and almost always benign
• Infiltrating Tumors


  Tumors that grow diffusely through surrounding tissue, usually malignant
• Gliomas


  Tumors that develop from glial cells, are infiltrating, rapidly growing, and common
• Metastatic Tumors


  Tumors that don't originate in the brain but grow from infiltrating cells that are carried to the brain by the bloodstream from another part of the body
• Many metastatic brain tumors originate as cancer of the lungs
• Acoustic Neuromas


  Neuromas are tumors that grow on nerves or tracts
• Stroke


  Sudden-onset cerebrovascular disorder that causes brain damage
• In the U.S., stroke is the 5th leading cause of death, a major cause of neurological dysfunction, and the leading cause of adult disability
• Consequences of stroke


  • Amnesia
  • Aphasia
  • Paralysis
  • Coma
• Infarct


  Area of dead/dying tissue produced by a stroke
• Penumbra


  Dysfunctional area surrounding the infarct
• The primary goal of treatment after stroke is to save the penumbra
• Major types of strokes

  • Cerebral hemorrhage
  • Cerebral ischemia
• Cerebral Hemorrhage


  Bleeding in the brain that occurs when a cerebral blood vessel ruptures and blood seeps into the surrounding neural tissue, damaging it
• Aneurysm


  Pathological balloon-like dilation that forms in the wall of an artery at a point where the elasticity of the artery wall is defective, bursting aneurysms are a common cause of intracerebral hemorrhage
• Aneurysms can be congenital (present at birth) or can result from exposure to vascular poisons/infections
• Individuals at risk for aneurysms should make every effort to avoid cigarette smoking, alcohol consumption, and hypertension
• Cerebral Ischemia


  Disruption of blood supply to an area of the brain
• Main causes of cerebral ischemia

  • Thrombosis (a plug forms and blocks blood flow at the site of formation)
  • Embolism (a plug is carried by the blood from a larger vessel where it was formed to a smaller one where it becomes lodged)
  • Arteriosclerosis (the walls of blood vessels thicken and channels narrow, usually as a result of fat deposits, eventually leading to complete blockage of blood vessels)
• Ischemia-induced brain damage


  • Takes a while to develop (soon after a temporary cerebral ischemic episode, usually little or no evidence of brain damage, but substantial neuron loss can often be detected a day or two later)
  • Doesn't occur equally in all parts of the brain (neurons in certain areas of the hippocampus are more susceptible)
• Glutamate


  The brain's most prevalent excitatory neurotransmitter, plays a major role in ischemia-induced brain damage
• How ischemia-induced brain damage is thought to work

  1. After a blood vessel becomes blocked, many of the blood-deprived neurons become overactive and release excessive quantities of glutamate

  2. Glutamate in turn over-activates glutamate receptors in the membranes of postsynaptic neurons, with the NMDA (N-methyl-D-aspartate) receptors being most involved

  3. This results in large numbers of Na+ and Ca2+ ions entering the postsynaptic neurons

  4. The excessive internal concentrations of Na+ and Ca2+ ions in the postsynaptic neurons affect in two ways: 1) Trigger the release of excessive amounts of glutamate from neurons, therefore spreading the toxic cascade to other neurons, 2) Trigger a sequence of internal reactions that ultimately kill the postsynaptic neurons
• Tissue Plasminogen Activator


  A drug that breaks down blood clots, if administered soon after the onset of an ischemic stroke (within 3-4 hours) it leads to better recovery
• Closed-Head Injuries


  Brain injuries produced by blows that don't penetrate the skull
• Contusions


  Closed-head injuries that involve damage to the cerebral circulatory system, damaging produces internal hemorrhaging, resulting in a hematoma, occur when the brain slams against the inside of the skull
• Hematoma


  Localized collection of clotted blood in an organ or tissue (a bruise)
• Subdural Space


  The space between the dura mater and the arachnoid membrane
• Contrecoup Injuries


  Contusions that occur on the side of the brain opposite to the side struck by the blow, occur frequently because the blow causes the brain to strike the inside of the skull on the other side of the head
• Concussion


  A disturbance of consciousness following a blow to the head with no evidence of contusion or other structural damage, the effects can last many years and the effects of repeated concussions can accumulate
• Chronic Traumatic Encephalopathy (CTE)


  Dementia and cerebral scarring observed in boxers, rugby players, American football players, and others who have experienced repeated concussive or subconcussive blows to the head
• The case of Junior Seau
• Brain Infection


  Invasion of the brain by microorganisms
• Encephalitis


  Resulting inflammation from brain infections
• Common types of brain infection

  • Bacterial
  • Viral