why does our knee have a reflex to kick when you get hit in the kneecap? any other reflexes we have like this?
In: Biology
They exist to allow us to respond faster than we could if we had to stop to think about it. They work by essentially allowing the nerve that senses something, to fire a pre-programmed message to the muscles, without having to relay the information up to the central nervous system first. So, in the case of the knee one, the patellar reflex, it happens when the tendon is stretched, like in a way it might if your legs give out or something. So, you kick your foot out automatically to try to keep from falling.
There’s a few of them that we have – mostly to oppose forced movement (if your arm is forced in, it reflexes out), including one’s that make our toes curl with pressure to the sole – maybe a holdover from primate ancestry to try to grip a branch.
There are other ones that have to do with infancy to help us survive, that go away after your brain starts to mature. For instance, there’s a reflex that makes baby’s suckle when you tap their chins – which is almost certainly to help them latch on to a nipple so they can feed.
Yeah I learned a few places to do it in school. You just don’t normally test the other areas unless the patient brings something up specific.
Heres one, the inside of the thigh by the balls will make a testicle move up towards the body to protect it.
We are born with many Primitive Reflexes but most of them eventually integrate and no longer respond in the same way to the stimulus. A very well known one is when you put your finger in a baby’s palm and it curls its own fingers around it. But there are more – for example, if you simulate dropping a baby (don’t actually drop it), it will throw all of its limbs out and straighten its spine. Similarly, running your finger down the sole of a baby’s foot will make it curl its toes and spread them. Most of these seem to be leftover from evolution and most integrate by toddler/early childhood age. Google “Primitive Reflexes” to learn more 🙂
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