Central Nervous System Disorders and Structure

Glutamate and Brain Injury

• Glutamate is an excitatory neurotransmitter crucial for learning, memory, and other brain functions.
• After brain injury, oxygen deprivation causes neuron disintegration, leading to excessive release of glutamate.
  • Under such conditions, glutamate acts as an excitotoxin, killing surrounding cells.

Stroke Treatment

• Primary treatment for stroke includes tissue plasminogen activator (tPA), used to dissolve blood clots in the brain.
• Mechanical devices can also be used to extract clots mechanically.

Degenerative Brain Disorders

Alzheimer’s Disease (AD)

• Definition: Progressive degenerative disease leading to dementia, particularly common in individuals over 65.
• Symptoms include:
  • Memory loss, especially recent events.
  • Reduced attention span and disorientation.
  • Emotional changes, leading to irritability and confusion.
• Prevalence: Represent about 50% of nursing home residents; impacts up to 15% of over-65s and is a major cause of death for half of those over 85.
• Two key features:
  • Plaques: Aggregates of beta-amyloid peptide formed through the cleavage of amyloid precursor protein (APP). Excess beta-amyloid is believed to be toxic.
  • Neurofibrillary Tangles: Formed by misfolded tau protein; disrupt transport mechanisms within neurons leading to cell death.
• Misfolded proteins within plaques and tangles spread throughout the brain regions, contributing to varying dementia types and progression.
  • Areas particularly affected:
  • Hippocampus, basal forebrain, and cortical association regions.
• A decrease in acetylcholine production is noted, particularly affecting neural function; drugs that inhibit its breakdown can marginally improve cognitive function.

Parkinson’s Disease

• Definition: Degenerative disorder from the loss of dopamine-producing neurons in the substantia nigra.
• Characteristics:
  • Resting tremors (often presented as "pill-rolling"), stooped posture, shuffling gait, and slowed movement initiation.
• Risk increases with age; underlying cause remains unidentified but might involve mitochondrial dysfunction and other protein degradation issues.
• Treatments:
  • L-Dopa: Helps increase dopamine levels; however, efficacy diminishes as neurons die.
  • Combining L-Dopa with dopamine breakdown inhibitors can extend its effectiveness.
  • Deep brain stimulation can alleviate symptoms by shutting down abnormal activity in the brain.
  • Gene therapy and stem cell implantation present future treatment possibilities.

Huntington’s Disease

• Definition: Fatal hereditary disorder manifesting in middle age due to accumulation of mutant huntingtin protein in brain cells.
• Symptoms:
  • Characterized by chorea (wild, jerky movements) that appear voluntary but are not.
  • Severe mental decline occurs in late stages.
• The disease progresses rapidly, typically leading to death within 15 years.
• Treatment includes medications that block dopamine effects, contrasting with Parkinson’s disease treatments that enhance dopamine effects.

Diagnostic Procedures for CNS Dysfunction

• Reflex tests, like knee-jerk responses, assess neural function; abnormal responses may indicate severe conditions (e.g., intracranial hemorrhage, multiple sclerosis).
• Advanced imaging techniques, including CT, MRI, and PET scans, have improved the ability to identify brain lesions, tumors, plaques, and Alzheimer’s-related tissue.
• Transitional Ischemic Attack (TIA): A temporary reduction of blood flow to the brain that may present similarly to a stroke but does not cause permanent damage.

Anatomy of the Spinal Cord

• Extends from the foramen magnum to the L1 or L2 vertebra.
• Measures approximately 42 cm in length and 1.8 cm in thickness; acts as a conduit between the brain and the rest of the body.
• Surrounded by protective structures (bones, meninges, cerebrospinal fluid).
• Features:
  • Dorsal and ventral horns comprise gray matter; the white matter surrounds the gray matter and contains ascending and descending tracts.
• The spinal cord has enlargements at cervical and lumbar regions related to limb innervation.
• Consists of 31 pairs of spinal nerves; spinal nerve segments generally do not align perfectly with vertebrae due to differential growth rates during development.
• Cauda equina refers to the collection of nerve roots at the end of the vertebral column, resembling a horse’s tail.

Key Distinctions in Spinal Cord Structure:

1. Gray Matter:
   • Contains cell bodies (interneurons and motor neurons).
   • Dorsal and ventral horns serve different functional roles.
2. White Matter:
   • Organized into ascending and descending tracks, responsible for relaying information.