Motor Control and Voluntary Movements

Voluntary Movements

• Initiated in the cerebral cortex, these movements involve complex planning and coordination.
• Purposeful and intentional actions enable interaction with the environment (e.g., walking, writing).
• Characterized by redundancy; the same muscles and joints are not always utilized for each movement task.
• Redundancy is significant for motor learning and compensatory mechanisms, aiding function despite movement impairments.

Reflex Movements

• Involuntary and rapid responses to stimuli, typically mediated by the spinal cord or lower brain centers.
• Serve protection and survival functions, occurring without conscious thought.
• Examples include knee-jerk reflex and withdrawal from heat; these are automatic and hardwired.
• Postural reflexes coordinate input from senses like vision and the vestibular system.

Lifespan of Reflexes

• Some reflexes persist throughout life, while developmental reflexes integrate into complex movements as the nervous system matures.
• Reflexes can re-emerge following nervous system injuries, indicating adaptability.

Motor Pathway Details

• Consists of two neurons and one synapse linking the cortex to skeletal muscle in the somatic nervous system.
• Upper motor neuron is part of the corticospinal or corticobulbar tract, facilitating skilled voluntary movement.
• Lower motor neuron, located in the spinal cord, synapses with the muscle at the neuromuscular junction.
• Lower motor neuron functions are always facilitatory; action potentials lead to muscle contraction.

Interneurons and Coordination

• Important interneurons within the spinal cord and connections to the cerebellum play a crucial role in smooth, coordinated movements.

Motor Effects and Nervous System Dysfunction

• Different motor impairments indicate damage or dysfunction within the nervous system and present clinically in various pathologies.
• Identifying the link between impairments and pathologies is essential for guiding intervention planning.
• Some impairments are treatable through physiotherapy or medical interventions, while others require a compensatory approach.

Clinical Reasoning and Measurement

• Objective measurement of impairments is crucial to assess:
  • Improvement in the client
  • Maintenance of functional capacity
  • Deterioration of condition
  • Effectiveness of interventions

Pathology and Impairments

• Consider how specific impairments relate to nervous system areas affected and common pathologies producing these signs and symptoms.

Types of Motor Impairments

• Damage in the central nervous system (CNS):
  • Affects voluntary motor pathways controlling motor planning (praxis) and voluntary actions.
• Non-voluntary control dysfunction in the CNS:
  • Results in altered tone (rigidity, spasticity, clonus), reflex movement issues, and tremors.
• Damage in the peripheral nervous system (PNS):
  • Causes deficits in strength, muscle endurance, motor fatigue, and sarcopenia (muscle wasting).

Influences from Other Systems

• Cardiovascular and hormonal systems can affect general capacity and contribute to fatigue.

Movement Control Pathways

• Movement involves a complex interaction between voluntary (pyramidal) and involuntary (extrapyramidal) pathways.
• Sensory input is integrated with experience, memory, and intentions to generate motor output through brain structures such as subcortical nuclei and brainstem motor centers.
• Feedback loops involving the cerebellum ensure smooth, coordinated movement by providing real-time spatial information.

Neural Mechanisms of Movement

• Upper motor neurons provide facilitatory and inhibitory impulses to modify tone and induce movement.
• Spinal cord nuclei are responsible for generating reflexive movement patterns, supporting activities like gait.
• Lower motor neuron damage leads to reduced or absent muscle tone, reflexes, and motor activity, demonstrating the importance of this neural level in movement control.