In this video, we're going to be learning about 2 reflexes: the flexor reflex and the crossed extensor reflex. The flexor or the withdrawal reflex occurs when we have rapid withdrawal of a body part from a harmful or painful stimulus. What's happening here is that the flexor muscles in that limb are contracting. So, if I were to reach out and touch a hot pot, I would withdraw my hand. Right? That's a flexor reflex. And this is an ipsilateral reflex, which means that the motor activity will occur on the same side of the body as the painful or harmful stimulus. So if I were to step on a tack with my left foot, my left leg would exhibit that flexor reflex and it would withdraw.

Now, if the flexor reflex happens in a load or a weight-bearing limb, for example, in your legs, it's going to simultaneously happen with a crossed extensor reflex. In a load-bearing or weight-bearing limb, these will happen simultaneously, and this crossed extensor reflex will cause an extension of the opposite limb. This helps you maintain balance during the flexor reflex. This crossed extensor reflex is contralateral, which means it's going to occur on the opposite side of the body as the painful or harmful stimulus.

To give you an example, we have this situation here where this guy is stepping on some Legos. It's like the story of my life. Shout out to my children. But you can see he's stepping on the Legos here with his right foot. And so what's happening is that he got this sensory information coming in. This signal is traveling up the sensory neuron into the spinal cord. You can see we have a polysynaptic reflex. We have 2 interneurons there, and then the spinal cord sends this message via that motor neuron to have that flexor reflex withdraw the leg and pick up that leg. This one here in green is our flexor reflex, and then you can see simultaneously what's happening is this crossed extensor reflex where you can see the left leg is now extending and going down to kind of shift the weight so that he doesn't just fall over as he's withdrawing that limb. You can see that this is also a polysynaptic reflex. You've got 2 interneurons involved in this one as well.

Alright. So those are flexor and crossed extensor reflexes, and I will see you guys in our next video. Bye-bye.