Question

Describe the pathway/function that is tested with physical exam of deep tendon reflexes, including the location and role of the interneuron

Answer 1

The deep tendon reflexes are assesed from the tendons by creating a stretch in the muscle like biceps, triceps, supinator, knee (quadriceps)and in ankle jerk(Achilles tendon) to check Whether the corresponding nerve is intact. It is otherwise known as stretch reflex because of stretching a muscle causes a reflex.

It is a monosynaptic reflex which means that there will be only an one synapse in the reflex arc mechanism of the central nervous system.

In this deep tendon reflexes a gentle tap on the muscle using a reflex hammer done by the therapist. As a response there will be reflex contraction of the muscle producing a movement of the joint. The stretch of the muscle is a stimulus and receptor is the muscle spindle located inside the muscle. It senses the stretch of the muscle and sends a afferent fibres named as Type Ia and type IIb to the anterior horn cell of the spinal cord. There will be an interneuron has a role of relay station that transmitt information from the sensory afferent neuron to the motor efferent neuron in there a synapse takes place. Then a neurotransmitter named as glutamate is released. The motor or efferent neuron reaches the same muscle that is stretched and produces a contraction of the same muscle.