Question

What is the first step in the myotatic stretch reflex

Answer 1

The first step in the myotatic stretch reflex is the activation of the muscle spindle when the muscle is rapidly stretched, such as by a tendon being struck with a mallet. This activation sends a signal to the spinal cord, which then directly stimulates the motor neuron, causing the muscle to contract in response.

Step-by-step explanation:

Myotatic Stretch Reflex First Step

The first step in the myotatic stretch reflex is the activation of the muscle spindle. This event begins when a muscle, such as those in the arm or leg, is quickly stretched. For example, during a neurological exam, a rubber mallet is used to strike the tendon at the insertion of muscles like the biceps, quadriceps, or gastrocnemius, resulting in a rapid stretch of the muscle. The stretching activates the muscle spindles, specialized receptors within the muscle, which then send a signal into the spinal cord through the dorsal root.

Upon reaching the spinal cord, the signal from the muscle spindle is relayed directly to the ventral horn motor neuron without any interneuronal delay. This mono-synaptic connection is what allows for the quick response of the reflex. The motor neuron is then activated and causes the muscle to contract. This contraction helps compensate for the change in muscle length and supports postural stability.

In this way, the myotatic stretch reflex provides a mechanism by which muscles can maintain constant length. When the muscle spindle detects a stretch, it immediately facilitates the contraction of the stretched muscle while simultaneously inhibiting the motor neurons of the antagonist muscle, helping to protect against over-stretching or muscle tearing.

Answer 2

The first step in the myotatic stretch reflex is the activation of muscle spindles by the rapid stretching of the muscle. This sends a signal through the spinal cord and results in the contraction of the muscle.

Step-by-step explanation:

The first step in the myotatic stretch reflex involves the rapid stretching of a muscle, which triggers the muscle spindles—specialized sensory receptors within the muscle. This stretching action causes the muscle spindles to send a signal into the spinal cord through the dorsal root.

The signal then synapses directly on the ventral horn motor neuron of the spinal cord that activates the muscle to contract. This reflexive contraction helps maintain stability and compensates for changes in muscle length, ensuring that muscles remain at a consistent length during activities.