posture

  • position of the body w.r.t to gravity
  • the goal of posture is to keep the center of mass over the support surface of the feet
    • really it is the center of force over the support surface
    • i.e. the force of muscle contraction
  • the muscles have to be used to keep center of force above the support surface
    • by contracting different parts of the body muscles in symphony

posture control

  • posture control problem is a problem of the inverted pendulum
    • postural sway i.e. even when someone is standing straight, one is alway oscillating at \(0.5text{ }Hz\)
  • it is hard for the body to do, since the body is top heavy
    • it is a brain feat to maintain balance and posture
    • it is one of the first things a baby learns to do
  • we anticipate problems that arise out of shifts in balance due to forces from movement
    • there are postural adjustments before making movements
    • i.e. pulling something or pushing something, or holding up something
  • preventative control in posture

central pattern generator

  • most of things we do are stereotypical movements
    • these are done unconsciously
    • these are handles by the “central pattern generator”
    • CPG is a concept
  • CPG is a collection of neurons
    • that automate a movement pattern
      • that doesn’t depend on reflexes
      • also doesn’t depend on conscious decision
    • it happens automatically due to a group of neurons in the brain stem
    • the same circuits can be reconfigured to produce different patterns
  • it doesn’t require sensory f/b but is sensitive to it
    • one circuit gives multiple patterns
  • posture, walking, tight-rope etc are controlled by CPG
    • gait + balance = locomotion
    • gait handled by CPG

self-generate movements

  • movement that is initiated by the forebrain is self-generated
    • volitional movements (deliberate)
    • emotional movements

praxis

  • volitional/intentional/deliberate movement is called praxis
    • writing
    • turning a page
    • facial expression
    • playing music
    • speech
    • cleaning teeth
  • depends on descending info from neocortex
    • from primary motor cortex
    • to motor neurons that are either contained in the brain stem or spinal cord
  • i.e. for kicking when told to kick
    • work of right motor cortex
    • and corticospinal tract
    • and motor neurons in the lumbosacral spinal cord
  • i.e. tongue is extremely well controlled by the primary motor cortex
    • more finer motor control
    • less so axial movement

emotional movement

  • through posture and facial expressions

  • damage to corticobulbur tract damages volatile facial expression
    • so it is not possible to express voluntary expression on both sides of the face for instance
    • but involuntary is fine
  • extrapyramidal pathways
    • involuntary emotional expressions
    • emotional extrapyramidal
    • separate from volitional intentional pathways for emotions
  • emotions are approximated by pyramidal pathways