MVS 320- Spinal Control of Movement

What are the functions of spinal reflexes?

• adjust for unexpected disturbances (“perturbations”)

• provide rapid protection from painful stimuli

• provide basic motor patterns used in locomotion and voluntary movement

• Characteristics: involuntary, stereotyped, graded, rapid

Draw out the flexor withdrawal reflex?

What is reflex latency?

• Latency (period between stimulus onset to response but not reaction time)

• fixed latency for a given reflex pathway

What three things does latency depend on?

• length of the pathway

• # of synapses

• conduction velocity – (myelin, diameter)

Explain the spinal stretch reflex

• monosynaptic (25-30ms)

• also known as the tendon tap reflex or short latency stretch reflex

What is the function of the spinal stretch reflex?

• To maintain muscle length

  • Involves role of muscle spindles

  • Represents a negative pathway feedback

What is reflex gain control?

What is happening in this image

How does brainstem control locomotion?

• descending signals from brainstem activate spinal cord circuitry

• modulation of strength of spinal cord circuitry

• control of goal-directed locomotion

  • cerebellum

  • basal ganglia

  • motor cortex

What is happening in this image?

What are some cutaneous reflex responses affected by quality of stimulus?

• stroke foot - plantar flex. (plantar reflex)

• light pressure - extensor thrust

• pain - flexion withdrawal reflex