CH11_KolbWhishaw_PPT

Nervous System and Movement Responses

• Hierarchy and Parallel Movement Control

  • Major components of the motor system:

    • Cerebrum (Forebrain): Responsible for conscious control of movement.

    • Brainstem: Directs movements; damage can disable conscious control.

    • Spinal Cord: Directly carries motor commands to muscles.

    • Basal Ganglia: Regulates force during tasks, aiding appropriate force for grasping.

    • Cerebellum: Involved in timing and accuracy of movements.

• Sequentially Organized Movement

  • Motor activity is a complex sequence: from visual information acquisition and planning in the brain to command execution by muscles, with feedback mechanisms incorporated.

    1. Visual input to locate target.

    2. Frontal lobe commands movement.

    3. Spinal cord transmits signals to the hand.

    4. Sensory cortex receives confirmation of grasp.

• Somatosensory System and Motor Coordination

  • Afferent pathways transport sensory input towards the CNS; Efferent pathways execute movement commands.

  • Connections:

    • Posterior Root: Carries sensory info from receptors to the spinal cord.

    • Anterior Root: Transmits outgoing motor commands to muscles.

  • Mapping of the body into dermatomes.

• Motor Sequence Planning

  • Frontal Lobe Functions:

    • Prefrontal Cortex: Plans movements.

    • Premotor Cortex: Organizes movement sequences.

    • Primary Motor Cortex: Executes planned movements.

• Motor Cortex Specialization

  • Produces skilled movements; damage to this area can impair abilities such as grasping.

  • Motor homunculus shows disproportionate representation for more dexterous regions like hands and face.

• Basal Ganglia's Role

  • Comprises nuclei (e.g., caudate, putamen) influences movement force.

  • Damage can lead to hyperkinetic symptoms (e.g., dyskinesias in Huntington's) and hypokinetic symptoms (e.g., rigidity in Parkinson's).

  • Volume Control Theory: Balances movement initiation and inhibition through pathways within the basal ganglia.

• Cerebellum and Movement Control

  • Regulates motor timing and accuracy; sends adjustments to the cortex based on movement discrepancies.

• Somatosensory System and Pain Perception

  • Involves nociception (pain detection), hapsis (fine touch), and proprioception (body position).

  • Pain signals travel through specific pathways (e.g., spinothalamic pathways).

  • Gate Control Theory: Explains interactions between nociceptive and non-nociceptive pathways controlling pain perception.

• Somatosensory Pathways

  • Dorsal Column Pathway: Carries haptic (touch) and proprioceptive information ipsilaterally.

  • Anterior Spinothalamic Tract: Carries nocioceptive information across to the contralateral side.

• Corticospinal Tracts and Movement Execution

  • The primary efferent pathways from motor areas of the cortex to the spinal cord, essential for limb movement.

  • Categorized into lateral (limb control) and ventral (trunk control) corticospinal tracts specializing in different areas of the body.

• Motor Neurons

  • Located in the spinal cord's anterior horns; categorized based on muscle control: laterally for hands, and medially for trunk and legs.

• Somatosensory Cortex and Motor Planning

  • Integrates sensory inputs for motor control; damage can lead to apraxia, impairing the sequence and execution of movements.

  • Adapting to damage is possible, leading to reorganization of neural representations in the cortex.

• Vestibular System

  • Facilitates balance and spatial orientation through structures in the inner ear.

  • Responds to head movement and body positioning changes.