The Brain: Complexity and Fragility

Overview

• Role: The brain is the seat of intelligence, memory, sensory interpretation, and the director of movement.
• Structure: Weighs about three pounds, encased in bone, and cushioned by fluid.
• Consistency: Fragile, similar to gelatin.

Neurons

• Quantity: Over 100 billion nerve cells.
• Components:
  • Cell Body: Contains the nucleus and metabolic center.
  • Axon: Long nerve fiber for sending signals.
  • Dendrites: Branches that receive messages from other cells.
• Function: Neurons send electrical and chemical signals, connecting various brain areas.

Brain Injuries

• Fragility: Prone to damage from rapid head movements.
• Coup Contrecoup Injury:
  • Mechanism: Brain bounces against the skull, can cause swelling and bruising (contusion).
  • Severity: High-speed impacts cause visible damage; low-speed impacts may not show visible injury.
• Diffuse Axonal Injury (DAI):
  • Axonal Shearing: Axons experience shearing forces, leading to stretching and tearing.
  • Consequences: Breakdown of neuron communication, toxic neurotransmitter release, neuron death over 24-48 hours.

Symptoms of DAI

• Mild to Moderate Cases:
  • Brief loss of consciousness.
  • Impaired long-term memory and problem-solving.
  • Lower social inhibition and attention issues.
• Severe Cases:
  • Coma or persistent vegetative state.

Incidence and Diagnosis

• Statistics: Over 1 million mild traumatic brain injuries reported annually in the U.S.
  • 300,000 suffer long-term effects.
• Diagnosis:
  • CT and MRI tests often show normal results.
  • Diagnosis typically relies on patient history and clinical examination.