 Hi everybody, Dr. O here. In this video we're going to classify the different types of reflexes and I'm going to give you some examples of the most typically talked about or most famous reflexes. So first you can see that reflexes can be classified as innate or acquired. So innate means they are genetically determined, you're born with it. Acquired means they have to be learned. So an innate reflex is when you're born with an acquired reflex has to develop over time. Then we have somatic versus visceral reflexes. So somatic means body. Somatic reflexes control skeletal muscle. Visceral or your autonomic reflexes control cardiac muscle, smooth muscle, glands and fat. We'll talk about that more with the autonomic nervous system. Reflexes can be monosynaptic or polysynaptic. So like the name implies, a monosynaptic reflex has one synapse, which means it's a sensory nerve connected directly to a motor nerve. Those are going to be the fastest but least complex reflexes we have. Somatic reflexes can have hundreds of synapses and involve interneurons, which are going to allow for a lot more coordination of a response. So they're going to take a little longer, but the response is going to be much larger and more coordinated. And then we have spinal versus cranial reflexes. So spinal reflexes are ones that occur at the level of the spinal cord. Cranial reflexes occur at the brain. So something like, you know, response when I touch your eye, you know, is a different type of reflex than if I strike your patellar tendon with a reflex hammer. All right, so those are the eight different classifications of reflexes. Let's look at some examples. So here we see a stretch reflex, the patellar reflex here. A stretch reflex, its job is to regulate the muscle length. So if you strike that patellar tendon and quickly stretch that muscle, the response from the sensory information will be sent to the spinal cord, information will be processed. The response is going to be contraction of the knee extensors there and then inhibition or relaxation of the antagonist muscles there, the hamstrings, leading for that kick to regulate the muscle length. Now, just so you know, there's some confusion here. This is not the same as a tendon reflex. Those regulate muscle force, but those are not a big deal right now. There is a term you see up here which is reciprocal inhibition that I think is important. So you see that notice that we have interneurons. This is a very complex reflex because it's actually activating the agonist muscles to cause the quadriceps muscles to shorten. At the same time, it's inhibiting contractions of your knee flexors there. So that's what's known as reciprocal inhibition. For any movement to be smooth, you need the agonist, the prime movers to be stimulated while the opposing muscles, the antagonists are inhibited. Same thing, walking and everything else. All right. Let me see the withdrawal reflex. A flexor reflex would be an example of withdrawal reflex. So you have a painful stimulus here and the body is just using the muscle flexors to withdraw away from it. You'd also see that same level of reciprocal inhibition there because the last thing you'd want if you touch this flame is to rapidly pull your hand away, which is good, but that's also rapidly stretching your triceps. So what if that stretch reflex then kicked in, your triceps contracted and put your hand back in the fire? You wouldn't want that. So that's why reciprocal inhibition is so important. As agonist muscles contract, those antagonists are inhibited. So that's an example of a withdrawal reflex. The flexor reflex there. Then the most complex basic reflex that we talk about is called the cross extensor reflex. So the cross extensor reflex happens with a flexor reflex. So here you see someone stepping on the stimulus there. We'll pretend I'm a dad, so we'll pretend it's a Lego. So they stepped on a Lego and then the free nerve ending pain receptors in that foot are going to be triggered. That's going to lead to a flexor or withdrawal reflex. So you're going to pull that foot away from the painful stimulus. But if that's all that happened, you would topple over because your body weight would be redistributed and you'd fall over. So while there's a flexor or withdrawal reflex happening on one side, which this person's right side, you're going to see the cross extensor reflex is going to be involved, especially on the other side. So the cross extensor reflex is going to extend the muscles of the left leg to support the body weight that's being traveling to it. So this entire reflex you see here is not the cross extensor reflex. It is the flexor or withdrawal reflex happening along with this cross extensor reflex, which you can see there at the bottom. The withdrawal reflex is leading to flexion and withdrawal of that right foot. The cross extensor reflex is stabilizing the body to support the weight that's coming towards it. So that's a cross extensor reflex. All right. So those are the eight different classifications of reflexes and then a few examples for you. I hope this helps. Have a wonderful day. Be blessed.