21 Adaptations to Practice.docx

Adaptations to Practice

Practice – aimed at improving movement production and information processing used to perform motor skills

• Primarily involves neural adaptations (plasticity)

  • Working in two-walls, learning new footwork

• Can also induce muscular and metabolic adaptations

Training – aimed at improving physiological functioning and physical abilities involved in performing motor skills

• Primarily involves muscular and metabolic adaptations

  • Mel’s drill, getting up quickly to make a wall

• Can also induce neural adaptations (plasticity)

Neuron Structure

• Interneurons in the brain and spinal cord have a cell body, dendrites, and axons

• Neurotransmission – uses chemicals to transmit signals from axons to dendrites

  • Neurotransmitters – chemicals used for neurotransmission

• Synapses – spaces between axon terminals and dendrites

  • Presynaptic neurons – initially release neurotransmitters into synapses

    • Pitcher // Quarterback

  • Postsynaptic neurons – have receptors that bind neurotransmitters

    • Throwers // Receiver

Neurotransmission

• Involves a series of events that transmit signals between neurons

  • Action potentials travel down presynaptic axons to axon terminals

  • Neurotransmitters are released from vesicles located in axon terminals

  • Neurotransmitters diffuse across synapses to postsynaptic dendrites

  • Neurotransmitters bind to receptors located on postsynaptic dendrites

  • Ion channels open to allow electrical current to flow in postsynaptic dendrites

• Neurons have a resting potential of approximately –70mV

• Electrical potentials are altered by current flows during neurotransmission

  • Excitatory postsynaptic potentials (EPSPs): occur when currents produce depolarization (excitation)

  • Inhibitory postsynaptic potentials (IPSPs): occur when currents produce hyperpolarization (inhibition)

• Postsynaptic APs occur when the electrical potential of a neuron reaches an all-or-none threshold (around –50mV)

  • Firing of APs depends on COMBO action of EPSPs and IPSPs

• Individual neurons have thousands of excitatory synapses and inhibitory synapses – likelihood that a neuron will reach its all-or-none threshold is determined by summation of both EPSPs and IPSPs, which summate across space and time

  • Spatial summation – involves summation of both EPSPs and IPSPs that across at different synapses located close in space (one-time, multiple spots)

  • Temporal summation – involves summation of either EPSPs or IPSPs that occur close in time at the same synapse

Neural adaptations involve synaptic plasticity

• Plasticity – adaptations of neural structure and function due to experience

  • Adaptations induce transient and persistent changes in neurotransmission

    • Increased release of neurotransmitter by presynaptic neurons

    • Increased number of neurotransmitter receptors on postsynaptic neurons

    • Formation of new synapses between presynaptic and postsynaptic neurons

Neural Adaptations to practice – practicing motor skills induces cortical, subcortical, and spinal adaptations that improve motor skills

• Cortical regions – typically exhibit lower activity

  • Reflects greater efficiency of neural processing

• Subcortical regions – often exhibit greater activity

  • Reflects recruitment of additional resources

• Spinal regions – commonly exhibit lower activity

  • Reflects decreased reliance on hard-wired circuits that mediate stereotyped actions

• Neural adaptations following BALANCE PRACTICE – practicing balance tasks induces cortical, subcortical, and spinal adaptations that lead to greater autonomic control of posture

  • Lower cortical activity – reflects decreased use of voluntary postural control

  • Greater subcortical activity – reflects increased use of autonomic postural control

  • Lower spinal activity – reflects decreased use of reflexive postural control