Nervous System Overview

Importance in Human Performance

• Function: Coordinates body systems to facilitate meaningful activities.
  • Regulates emotions, sensations, and perceptions.
  • Determines responses through muscular or organ actions.

Main Components of the Nervous System

• Central Nervous System (CNS): Brain and spinal cord.
• Peripheral Nervous System (PNS): Nerves from the spinal cord, including 12 pairs of cranial nerves, spinal nerves, plexuses, and branches.
• Autonomic Nervous System (ANS): Regulates stress response and controls smooth muscles.

Sensory Information Processing

• Sensory Receptors: Three main types.
  • Mechanoreceptors: Sensitive to mechanical changes.
  • Thermoreceptors: Sensitive to temperature changes.
  • Nociceptors: Sensitive to pain or potentially harmful stimuli.
• Process: Sensory information is received and processed by sensory neurons, transmitted to the spinal cord, then to the brain for processing, and finally a motor output is generated and sent back through the spinal cord to the peripheral nervous system.

Structure of a Neuron

• Axon: Carries information; surrounded by myelin which protects and increases transmission speed.

Central Nervous System (CNS)

• Brain:
  • Protected by the skull with non-movable bone structures.
  • Cerebrum: Two hemispheres, each with four lobes (frontal, parietal, temporal, occipital).
    • Frontal Lobe: Personality, motor movement, speech.
    • Parietal Lobe: Touch, pressure, fine sensations (texture, weight, size, shape), reading skills.
    • Temporal Lobe: Behavior, hearing, language reception/understanding.
    • Occipital Lobe: Vision, recognition of size, shape, and color.
  • Deeper Structures:
    • Thalamus: Sensation perception, pain perception.
    • Hypothalamus: Behavioral center.
    • Basal Ganglia: Coordination of movement.
  • Brain Stem: Consists of midbrain, pons, and medulla; vital functions (heart rate, respiration).
  • Cerebellum: Muscle coordination, muscle tone, posture.
• Spinal Cord:
  • Transmits information between brain and body.
  • Protected by the spine; spinal cord ends at L2 in adults, beyond which is called cauda equina (L2 to S5).
  • Contains cerebrospinal fluid (CSF).
  • Spinal nerves named based on their exit points (e.g., C1 nerve exits above C1 vertebra).

Sensory and Motor Mapping

• Dermatomes: Sensory map; symmetrical on both sides; labeled by spinal cord level.
  • C spine: Upper extremity.
  • T spine: Trunk.
  • L spine: Anterior lower extremity.
  • S spine: Posterior lower extremity.
• Myotomes: Motor control map; key muscles associated with each spinal cord level.
  • C3-C5: Diaphragm.
  • C5: Biceps.
  • C8: Palmer interossei.
  • T levels: Trunk muscles.
  • L levels: Lower extremity.
  • S levels: Lower extremity.

Importance of Evaluation

• Sensory and motor areas are often innervated by multiple nerves, making detailed evaluation crucial to understand the extent and impact of injuries.