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