Lesson 5: Development and Plasticity of the Brain

• The Big Three (3) Layers

  Endoderm, Mesoderm, and Ectoderm.
• The Big Three layers give rise to every physiological system in your body, beginning at embryonic development.
• The nervous system stems from the outermost layer, the ectoderm.
• The growth and development of neurons


  1. Neural plate formation

  2. Neural groove formation

  3. Neural tube formation
• The neural tube later becomes cerebral ventricles of the brain and the central canal of the spinal cord
• Four (4) stages in the process of neuron development and the formation of the nervous system

  • Neurogenesis
  • Cell migration
  • Cellular differentiation
  • Outgrowth
• Neurogenesis


  The very first stage of the foundational process of neuronal development where cells undergo mitosis to produce stem cells or neuroblasts
• Neuroblasts and stem cells


  Precursors to what eventually becomes a neuron, with neuroblasts being more prominent in embryonic development and stem cells in adult neurogenesis
• The ventricular zone, intermediate zone, and marginal zone are formed due to the movement of cells during neurogenesis
• Cell migration


  The movement of cells formed during neurogenesis along the radial glia toward the marginal zone from the ventricular zone
• Cellular differentiation


  The process where the embryo's DNA dictates the nerve cells' specific physiology for their future core functions, determining what type of nerve cell they will become
• Outgrowth


  The stage where the axons and dendrites begin to form, and the proliferation of synapses begins
• Without the ongoing process of neurogenesis into adult life, intellectual and mental disorders and/or challenges are likely to emerge
• Lack of or low rates of neurogenesis in adults is directly associated with difficulty in differentiating stimuli and problems with long-term memory
• Factors that can decrease rates of neurogenesis

  • Stress
  • Sleep deprivation
  • Aging
• Axon


  A cytoplasmic process of a neuron that conducts electrochemical impulses or action potentials
• Axons most commonly attach to one side of a neuron cell body at a cone-shaped region called the axon hillock
• Electrochemical events in the cell body summate in the axon hillock, and the effect are directly passed to the attached axon
• If an action potential is generated, the axon conducts it away from the cell body
• Several types of proteins in the plasma membrane of an axon (axolemma) allow it to produce and conduct action potentials
• Brain damage


  An injury that causes the destruction or deterioration of the brain cells
• Two (2) types of brain injury

  • Traumatic brain injury (TBI)
  • Acquired brain injury (ABI)
• Traumatic brain injury (TBI)


  Caused by an external force such as a blow to the head that causes the brain to move inside the skull or damages the skull, which in turn damages the brain
• Acquired brain injury (ABI)


  Occurs at the cellular level, most often associated with pressure on the brain
• All traumatic brain injuries are head injuries, but head injury is not necessarily brain injury
• Focal or localized brain damage


  Damage confined to a small area, such as when a bullet enters the brain
• Closed head injuries


  Frequently cause diffuse brain damage, which means damage to several areas of the brain, including both sides and stretched nerves throughout the brain (Diffuse Axonal Injury)
• The severity of brain damage can vary with the type of brain injury

  • Mild brain injury
  • Moderate brain injury
• In both mild and moderate brain injury, most patients make a good recovery, although even in mild brain injury 15% of people will have persistent problems after one year
• Traumatic brain injury


  Caused by a blow, shaking, or strong rotational injury to the head that damages the brain
• Causes of traumatic brain injury

  • Blast injury
  • Blows to the head such as from a fistfight
  • Falls
  • Gunshot wound
  • Motor vehicle accident
  • Shaking an infant
• Severe brain injury


  • The person may suffer life-changing and debilitating problems
  • They will have cognitive, behavioral, and physical disabilities
  • May remain dependent on the care of others for the rest of their lives
• Coma or a minimally responsive state


  May remain dependent on the care of others for the rest of their lives
• Causes of non-traumatic brain injury

  • Choking
  • Drowning
  • Drug overdose
  • Exposure to poisons or pollutants such as carbon monoxide or lead
  • Infection such as encephalitis or meningitis
  • Seizure
• Traumatic brain injuries


  • Closed head injury
  • Concussion
  • Contusion
  • Penetrating injury
  • Shaken baby syndrome
• Symptoms of brain injury

  • Affected balance
  • Blurred vision
  • Confusion
  • Difficulty speaking clearly
  • Headache
  • Memory problems
  • Seizures
• Frontal lobe


  Responsible for speaking, personality, emotions and judgement
• Temporal lobe


  Responsible for memory, understanding spoken words and hearing
• Parietal lobe


  Responsible for the five senses including vision and sense of touch
• Occipital lobe


  Responsible for visuospatial coordination