Lecture 9 Oligosynaptic and Polysynaptic Reflexes Oligosynaptic Reflexes

Lecture 9: Oligosynaptic and Polysynaptic Reflexes Oligosynaptic Reflexes: § Oligosynaptic Reflexes involves, by definition, more than one synapse which contained two to three central synapses. § Inhibitory between primary ending points of muscle spindle and α-motoneurons of antagonist muscle.

Oligosynaptic Reflexes

Oligosynaptic Reflexes • An other important group of Oligosynaptic Reflexes originate from Golgi tendon organs whose axons belongs to Іb-afferent which act oppositely of to Іa-afferent and inhibits homolateral α- motoneurons and exhibits contralateral α- motoneurons.

Oligosynaptic Reflexes

Key Elements Involved with Skeletal Muscle Reflexes Anterior Motor Neurons n Alpha motor neurons n n Motor unit Gamma motor neurons n Intrafusal fibers/Muscle spindle Other Neural Elements n n n Renshaw inhibitory cells Interneurons Golgi tendon organ

Spinal Reflex Pathways

Muscle Spindle Details

The Stretch Reflex

Spinal Reflex Pathways

Golgi Tendon Organ Details

Active Contraction

Active Contraction with Gamma Coactivation

Comparison Muscle Spindle Located Within the Muscle Belly (Intrafusal) Sensory & Motor Innervation Nuclear Bag Fibers Primary afferent only (fast stretch - dynamic) Chain Fibers Primary & Secondary afferents (slow stretch - static) Length & its Rate of Change Involuntary Muscular Contraction Golgi Tendon Organ Located Within the Muscle Tendon (Extrafusal) Sensory Innervation Only Tension & its Rate of Change Dynamic Response Static Response Involuntary Muscular Relaxation

Nociceptive Reflex Pathways (Flexor withdrawal reflex)