2-Minute Neuroscience: Withdrawal Reflex

The withdrawal reflex is an automatic response that enables you to pull away from a painful stimulus (e.g., a hot stove, a tack you’ve stepped on) without having to consciously plan to do so. In this video, I explain the mechanism of the withdrawal reflex.

TRANSCRIPT:

The withdrawal reflex is an automatic response enacted to withdraw a limb from a painful stimulus. If, for example, you were to touch a hot stove or step on a tack, the withdrawal reflex would cause you to pull your arm or leg away from the painful stimulus without having to consciously plan to do so. The intensity of the reflex is proportional to the intensity of the painful stimulus, so a very hot stove would cause a more rapid and forceful withdrawal than a mildly hot stove.

The withdrawal reflex is a polysynaptic reflex, as it uses neurons called interneurons to pass signals from sensory to motor neurons, creating multiple synaptic connections. The reflex begins when a painful stimulus is detected by receptors called nociceptors, which are specialized to detect noxious stimuli. The activation of nociceptors leads to an action potential in a sensory neuron, which carries the signal to the spinal cord, where multiple reflex pathways are activated. One of those pathways excites a motor neuron that activates the flexor muscle in the limb, causing the limb to withdraw from the painful stimulus. Another pathway inhibits the motor neuron that normally activates the opposing extensor muscle in the limb. This will keep the extensor muscle from counteracting the attempt of the flexor muscle to pull the limb away. Another pathway crosses over to the other side of the spinal cord, and causes the opposite response to occur in the opposing limb. In other words, the extensor muscle in the opposing limb will be activated and the flexor muscle will be inhibited. This is sometimes called the crossed-extension reflex, and it is enacted for postural support. If, for example, you are withdrawing your foot from a painful stimulus, then the other leg needs to be prepared to hold your weight.

References:

Pearson KG, Gordon JE. 2013. Spinal Reflexes. In: Kandel ER, Schwartz JH, Jessell TM, Siegelbaum SA, Hudspeth AJ, eds. Principles of Neural Science, 5th ed. New York: McGraw-Hill.

[LanceMcCarthy]

I was not aware of the crossed extensor reflex, very cool

[justaguywithoutabeard]

Studied this last week. Good work dude!

[shitbag.]

I love a good "Woah" in the morning. Thanks.

[coach_rami]

one of the best videos iv'e seen, thanks

[udznpwg]

This will help me a lot in my studies. Thank you.

[BigTroubleD]

Thank you so much for explaining. Reading it only in words was very confusing.

[gagan.dee.p]

This video reminded me of inhibitory interneurons. Thanks, please do a video on inhibitory neurons, those which use GABA. What do they do? How do they work? What is their significance in the Brain and how they work with those that use excitatory neurotransmitters? Again...wrt higher brain functions maybe.

[absolutelyanele]

precise and informative. thank you so much. such a life saver!!

[florkiler]

ymm actually that was very interesting, this channel is so good

[dnein]

So, neurons can be thought of as the key interactors between consciousness and environment.
The pressure mediated action potential of nociceptors seems to signal the intensity of stimulus. Chronic interaction with an intense stimulus seems to be a driving force in raising tolerance, allowing a grown-up to have higher heat tolerance than a child. But, do you believe the neurons themselves become damaged by the stimulus? Or do we simply become desensitized towards their input... I think its difficult to differentiate between damage and decreased recruitment ability, unless the two are the same thing.

I just wanted to share my thoughts, thank you for the video sir! :)

[chandrug]

Your teachings are soo awesome
Can you make videos for some topics come from Guyton and hall of human physiology

[JamesonHuddle]

If you know the stove is going to be hot can you consciously change the reflex to not happen? Or maybe it happens briefly, but then you gain control again and force it back? Also, my little brother put his hand on a hot stove and I didn't see the reflex and he kept it there for a good few seconds (he later screamed so much because he gave himself a pretty bad burn on his whole hand). Is it possible the reflex is broken in him?

[SuperPipe]

A doctor said the stimulus must first go to the brain before the muscle contraction...is this true?

[champion]

So why isnt it triggered when we pick up a hot container filled with hot oil or water?

[MultiSamSami]

hey I watch a lot of your videos and I think their very helpful.. can you do one on heroïne?

[KA-bvzg]

What if your pain threshold is too high .Result no withdrawal and Injury👩‍⚕️ .So this very act of withdrawal from pain is God's protective mechanism from injury Him self

[n_alharbi]

Why you don’t consider to make videos more then 2 min ?