What Are Polysynaptic and Monosynaptic Reflexes?

Springfield Technical Community College states that monosynaptic reflex is when a sensory neuron synapses, or a nerve impulse is transmitted, directly to a motor neuron, resulting in an automatic reflex. A polysynaptic reflex is when there are more than two synapses that connect the sensory neuron to the motor neuron.

A monosynaptic reflex, according to the Springfield Technical Community College, is also a knee-jerk reflex, or patellar reflex. For example, in order to test reflexes, a doctor taps above the knee on the patellar tendon and the leg kicks involuntarily. Another example is when arm muscles shift to keep an object upright. The muscles react without the person consciously doing it due to the brain’s awareness of the body in space.

A flexor reflex is an example of a polysynaptic reflex, says Austin Peay State University. The flexor reflex, or withdrawal reflex, is the body’s response to pain and takes slightly longer than monosynaptic reflexes. There is a polysynaptic reflex, called the plantar reflex, that has different results in babies and adults. In a baby, the bottom of the foot is stroked from the heel to the toes and the baby’s toes spread. Older persons do not normally have the same reaction. If they do, it is a sign of brain or spinal injury.