Physiology 3120 Lecture 10: Lecture 10 - Spinal Reflexes

• School: Western University
• Department: Physiology
• Course: Physiology 3120
• Professor: Tom Stavraky

Document Summary

These reflexes potentially occur in all skeletal muscles except eye muscles (there would be no purpose in having any reflex there). The tendon of the quadriceps muscle comes over the patellar and can be strike with a stimulus hammer. The striking produces a rapid stretch of quadriceps muscle. Diagram of the spinal reflex arc for the stretch (myotatic) reflex (e. g. knee jerk reflex) and sequence of events in this reflex including reciprocal inhibition. Stretch extensor muscle (quadriceps) result in receptor activation: Ions channels open >> na+ enters to depolarize >> if depolarization is large enough, the neuron reaches threshold and sends aps in the ia afferents. Ia afferents are largely responsible for the stretch reflex: the velocity component of the stretch gives most aps in afferent nerve. Action potentials in ia afferents from quadriceps muscle up the spinal cord and back down to the monosynaptic connection with quadriceps" alpha motoneuron: this monosynaptic connection is always excitatory.