Deep Tendon Reflexes: Nerve Roots and Spinal Levels
Save Time with a Video!
Save time by watching the video first, then supplement it with the lecture below!
Click below to view the EZmed video library. Subscribe to stay in the loop!
Become a Member!
Instant Access to All PDF Lectures, Study Guides, and Flashcards!
Instant access to a members-only page of ALL the flashcards, study guides, and PDF lectures. Cancel anytime.
Download the Lecture!
Get your copy of the lecture below today, and never forget reflexes and their nerve roots again!
Deep Tendon Reflexes: Nerve Roots
Assessment of the deep tendon reflexes, also known as muscle stretch reflexes, is an important component of the neurological exam.
Muscle stretch reflexes activate the reflex arc pathway between afferent sensory neurons and efferent motor neurons.
Common muscle stretch reflexes that are tested include the patella or knee, biceps, achilles or ankle, and triceps.
These reflexes can then be graded using a scale discussed below, and abnormal reflexes may indicate pathology to the musculoskeletal system, peripheral nervous system, or central nervous system.
It can be challenging to remember which nerve root or spinal level each deep tendon reflex assesses.
Fortunately, as with every EZmed lecture, you will learn a simple memory trick to remember it all!
The nerve roots or spinal levels can be remembered using 2 different tricks: the first with a nursery rhyme, and the second with a play on words.
What Are Reflexes?
Let’s first get a better understanding of reflexes.
A reflex is an unlearned, involuntary response.
Muscle stretch reflexes occur when stretch receptors within the muscle are activated.
When a deep tendon is struck, this will cause stretch of the muscle and activation of the stretch receptors.
When the stretch receptors are activated, they will generate an action potential through afferent neurons to the spinal cord.
At the spinal cord, the afferent neurons synapse on a motor neuron, which then generates an action potential through the efferent motor neuron back to the muscle which leads to contraction.
The connection between the afferent sensory neurons and efferent motor neuron is modulated by the descending corticospinal tract of the central nervous system.
Since the reflex arc has musculoskeletal, peripheral nervous system, and central nervous system components, abnormal reflexes could indicate a wide range of pathology.
Reflexes can be graded using a scale of 0-4+, with 0 being absent reflexes (areflexia), 1+ being a slight response (hyporeflexia), and 4+ being enhanced reflexes above the normal range (hyperreflexia).
The reflex grade can provide useful information about the nervous system, and any pathology that may be present.
For example, hyporeflexia may indicate a lower motor neuron lesion.
Whereas, hyperreflexia may suggest an upper motor neuron lesion.
Nursery Rhyme
The nerve root or spinal level involved with each reflex is commonly tested on healthcare board exams.
Below is a list of common muscle stretch reflexes that are tested and the nerve roots involved.
Achilles: S1 - S2
Patellar: L3 - L4
Biceps: C5 - C6
Triceps: C7 - C8
Take note how these reflexes count upward numerically.
A simple way to remember the spinal levels is with the following nursery rhyme:
1, 2 Buckle my Shoe (Achilles)
3, 4 Kick the Floor (Patellar)
5, 6 Pick up Sticks (Biceps)
7, 8 Lay them Straight (Triceps)
Play on Words
Another trick you can use to remember the spinal levels is with the following play on words.
Achilles: S1 - S2
Take the “S” in achilles which will help you remember sacral, and then take the 2 “Ls” in achilles and use them as the roman numeral II.
This will help you remember S2.
Patella: L3 - L4
Take the “L” in patella which will help you remember lumbar. Then turn the “A” into a “4”.
This will help you remember L4.
Biceps: C5 - C6
Take the “C” in biceps which will help you remember cervical. There are 6 letters in biceps.
This will help you remember C6.
Triceps: C7 - C8
Take the “C” in triceps which will help you remember cervical. There are 7 letters in triceps.
This will help you remember C7.
Summary
Hopefully this gave you 2 simple tricks to remember the muscle stretch reflexes and the spinal levels involved.
Simply remember the nursery rhyme or the play on words.
Before You Go, Make Your Learning Experience Even Easier!
If you enjoyed the content in this post, don’t forget to join the EZmed community for free on the bottom of the page or in the navigation bar so you don’t miss out on future medical topics made easy.
Boost your medical knowledge, perform well on exams, and keep up with your medical education throughout your career using:
High yield EZmed content on Instagram: @ezmedlearning
EZmed animations and videos on YouTube: Ezmed
EZmed Illustrations and flashcards on Pinterest: ezmedlearning
Feel free to use the contact button to reach out with any feedback or suggestions you may have for future topics. Thank you for using EZmed!
https://www.statpearls.com/kb/viewarticle/30581
https://www.ncbi.nlm.nih.gov/books/NBK396/