An example of a stretch reflex is the blank______

General
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an example of a stretch reflex is the blank______.

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LectureNotes said an example of a stretch reflex is the blank______.

Answer:
The correct answer to fill in the blank is “knee-jerk reflex” or “patellar reflex”. Here is a comprehensive explanation:

Stretch Reflex

A stretch reflex, also known as a myotatic reflex, is a muscle contraction in response to stretching within the muscle. It serves as a protective mechanism that prevents muscle damage due to overstretching. When a muscle is stretched, sensory neurons detect this and send signals to the spinal cord. The spinal cord then sends an immediate response back to the muscle to contract, thereby resisting further stretching.

Example: The Knee-Jerk Reflex

  1. Stimulus and Sensory Detection

    • The knee-jerk reflex, or patellar reflex, is one of the most well-known stretch reflexes.
    • It is elicited by a light tap on the patellar tendon, located just below the kneecap.

  2. Neuronal Signal Pathway

    • The tap stretches the quadriceps muscle slightly.
    • Sensory receptors known as muscle spindles detect this stretch.
    • A signal travels via sensory neurons to the spinal cord.

  3. Motor Response

    • In the spinal cord, the signal is relayed to motor neurons without needing to go to the brain—a process known as a monosynaptic reflex arc.
    • Motor neurons then send a signal back to the quadriceps muscle.
    • This causes the muscle to contract and produces the characteristic ‘kick’ or jerk of the lower leg.

Significance

The knee-jerk reflex is often tested in clinical settings as it can provide valuable information about the nervous system. An abnormal response might indicate issues such as nerve damage, spinal cord injury, or even neurological conditions.

Final Answer:
An example of a stretch reflex is the knee-jerk reflex, also known as the patellar reflex.