Motor Control, Involuntary Movement, & Voluntary Movement

Involuntary Movement & Receptors in Body

  • Involuntary (reflex)

    • subconscious

    • triggered response

    • predictable

    • simple (less modifiable)

    • “automatic”

  • Voluntary

    • conscious decision to move

    • self-generated

    • unpredictable

    • complex (highly modifiable)

    • non “automatic”

  • movements exist on a continuum/spectrum of involuntary to voluntary

  • reflexes exist to protect us & adjust posture at the most basic level

Motor Control Model

  • sensory input → triggered response → motor output

  • sensory input → planning → motor output

  • receptors are at the end of afferent neurons and sense the changes in the external environment (stimuli)

  • perception of a stimulus depends on the magnitude of the stimuli and the amount of receptors we have

Vision

  • rods: dim light

  • cones: bright light & colors

  • vision gets worse in the dark as we get older because we lose rods over time

Vestibular (balance & head orientation)

  • semicircular canals

    • hair cells detect movement of fluid within canals

Proprioception (knowing where we are in space)

  • specialized receptors in muscles, joints, & tendons

    • Muscle spindles

      • in muscle bellies, sensing changes in muscle length, firing rate increases with stretch

    • Golgi tendon organs (GTO)

      • in tendon, sensing changes in muscle force, firing rate increases with more tension, allow us to know how much force a muscle is outputting

    • Joint receptors

      • provide info about the joint at extreme joint positions

  • Cutaneous receptors

    • recieve info regarding temp., pain, & pressure

    • sensitivity changes depending on which area of the body the receptors are in (many in hands, less on torso)

  • the more complex a movement is the more it involves the CNS (brain)

  • Balance: the control of center of mass over base of support

    • CNS is constantly predicting or compensating for shifts in space (anticipatory/compensatory postural adjustments) (APA/CPA)

  • Posture is supported by vestibular, proprioceptors, and visual aids

    • cerebellum & brainstem

Voluntary Movement

  • Voluntary movement is a loop with sensory info, motor command processing, motor command feedforward, & movement

Dynamic Systems Theory

  • states that voluntary movement emerges from 3 factors:

    • Task

    • Individual

    • Environment

  • Task goals

    • accuracy

    • speed

    • stability

    • efficiency

    • etc.

  • Task nature

    • novelty (ex: 1st time riding bike vs 10th)

    • complexity

    • serial order of goal

    • continuous

  • Environment

    • location

    • predictability, open (changing environment) vs closed (unchanging)

    • context (kicking field goal in practice vs game)

    • geography (in CO vs sea level)

  • Individual

    • perception

    • cognition

    • anthropometrics (height, weight, muscle mass, etc)

    • motor ability, general skill in relating to potential

    • reaction time

    • motor skill, learned and developed specific motor skills