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Neuroanatomy and Movement Control

Branching of Neurons

  • Axon Collaterals:
    • Branch off into the lateral corticospinal pathway, but not considered part of it.

Spinal Cord Structure

  • White and Gray Matter:
    • Outside of spinal cord: White Matter
    • Inside of spinal cord: Gray Matter (opposite of the brain)
    • Horns Configuration:
    • Two horns: anterior (ventral) and posterior horn.

Bell and Magendie's Law

  • Neural Entry and Exit:
    • Afferent neurons enter through the posterior horn (back side).
    • Efferent neurons exit through the anterior horn (front side).

Types of Neurons in Spinal Cord

  • Interneurons:
    • Project to efferent (motor) neurons.
    • Signal motor neurons on actions to take.
  • Motor Neurons:
    • Project to body muscles and are arranged according to body areas:
    • Lateral: fingers and hands
    • Middle: arms and shoulders
    • Medial: trunk muscles.

Types of Motor Control

  • Focus on Voluntary Motor Control:
    • Related to new behaviors.
  • Paths also include brainstem influences for balance and posture.
  • Efferent Neurons:
    • Not just to skeletal muscles but to autonomic systems (e.g., enteric nervous system for digestion).

Ozempic and Autonomic Nervous System

  • Ozempic:
    • Primarily affects enteric neurons, slowing down peristalsis by numbing enteric nervous system.

Muscle Control and Coordination

  • Motor Neurons' Role:
    • Innervate both extensor and flexor muscles.
    • Coordination is crucial; overstimulation leads to:
      • Twitching or convulsions (seizures)
      • Rigidity (hypertonicity) seen in conditions like Parkinson's and some types of schizophrenia.

Neuromuscular Junction

  • Neurotransmitter:
    • Acetylcholine is crucial at the junction between motor neuron and muscle.

Movements and Coordination

  • Muscles Arranged in Pairs:
    • Extensors extend away from the trunk; flexors pull towards the trunk.
  • Uncontrolled dual stimulation can cause:
    • Twitching, convulsions, rigidity.

Basal Ganglia

  • Location:
    • Subcortical nuclei, located beneath the cortex, wraps around thalamus.
  • Components:
    • Striatum (caudate nucleus and putamen).
    • Globus pallidus (internal and external).
    • Substantia nigra involved with dopamine regulation.

Functions of Basal Ganglia

  • Motor Pathways:
    • Two main pathways:
    • Direct Pathway: Increases movement.
    • Indirect Pathway: Decreases movement (inhibitory).
  • Motor Disorders:
    • Hyperkinetic: Too much movement (e.g., Huntington's chorea)
    • Hypokinetic: Not enough movement (e.g., Parkinson's).

Learning and Movement

  • Skill Acquisition:
    • Importance of practice and feedback for refining motor skills.
    • Visualization aids in motor learning.
  • Specific Examples:
    • Shooting basketball: Requires standard position, adjustments from feedback on performance.

Implications of Basal Ganglia Damage

  • Motor Symptoms:
    • Hyperkinetic disorders (excessive movement). e.g., Huntington's, Tourette syndrome.
    • Hypokinetic disorders (reduced movement): Parkinson's, tardive dyskinesia, catatonia.

Summary of Motor Control Pathways

  • Flow of information from motor cortex through basal