Nervous System Overview

Functions and Importance

• The nervous system enables us to receive, process, and respond to external stimuli, facilitating our performance in meaningful occupations.
• Regulates emotions, sensations, perceptions, and responses through muscular or organ actions.

Components of the Nervous System

• Central Nervous System (CNS): Includes the brain and spinal cord.
• Peripheral Nervous System (PNS): Includes nerves coming out from the spinal cord, 12 pairs of cranial nerves, spinal nerves, plexuses, and ganglionic branches.
• Autonomic Nervous System (ANS): Regulates responses to stress and controls smooth muscles.

Sensory Receptors

• Mechanoreceptors: Sensitive to mechanical changes.
• Thermoreceptors: Sensitive to temperature changes.
• Nociceptors: Sensitive to pain and potentially damaging stimuli.

Sensory Information Pathway

1. Sensory receptors receive information.
2. Sensory neurons transmit information to the spinal cord (dorsal root).
3. Information is processed in the brain.
4. Motor output is sent from the brain through the spinal cord (ventral root) to peripheral nerves.

Neuron Structure

• Axon: Nerve fiber that transmits information.
• Myelin: Surrounds the axon, protecting it and speeding up information transmission.

Central Nervous System Detailed

Brain Protection

• Skull: Frontal, parietal, occipital, and temporal bones protect the brain.

Brain Structure

• Cerebrum: Two hemispheres, each with four lobes.
  • Frontal Lobe: Personality, motor movement, speech.
  • Parietal Lobe: Sensation (touch, pressure, texture, weight, size, shape), reading skills.
  • Temporal Lobe: Behavior, hearing, language reception and understanding.
  • Occipital Lobe: Vision, recognizing size, shape, and color.
• Thalamus: Center for body sensation and pain perception.
• Hypothalamus: Behavior center.
• Basal Ganglia: Coordination of movement.
• Brainstem: Includes midbrain, pons, and medulla (regulates reflexes, heart rate, respiration).
• Cerebellum: Controls muscle coordination, muscle tone, and posture.

Spinal Cord

• Transmits information between the brain and the body.
• Protected by the spine, but the structure only extends to L2 in adults.
• Cauda Equina: Spinal nerves from L2 to S5, without bony protection.
• Cerebrospinal Fluid (CSF): Flows through the spinal cord.
• Spinal Nerve Levels: Named based on the corresponding vertebrae.
  • C1 to C7 nerves exit above the corresponding vertebrae, except for C8.
  • T1 downward nerves exit below the vertebrae.

Sensory and Motor Maps

• Dermatomes: Sensory map of the body, symmetrical and labeled according to spinal cord levels.
  • Upper extremities: C spine
  • Trunk: T spine
  • Anterior lower extremities: L spine
  • Posterior lower extremities: S spine
• Myotomes: Motor control map of the body, each spinal level has key muscles.
  • C3-C5: Diaphragm
  • C5: Biceps
  • C8: Palmar interossei
  • T levels: Trunk muscles
  • L and S levels: Lower extremity muscles

Injury and Evaluation

• Sensory and motor areas may not be completely covered by a single spinal nerve.
• Partial injuries (e.g., at C5) may still allow some function from nearby levels.
• Careful evaluation of clients' abilities is crucial.