- Human physiological development
- Egg, sperm, and fertilization
- Early embryogenesis - Cleavage, blastulation, gastrulation, and neurulation
- Germ layer derivatives
- Major motor milestones
- Motor development
- Neonatal reflexes
- Physical development in adolescence
- Brain changes during adolescence
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Brooke Miller.
Want to join the conversation?
- I thought the babinski reflex still occurs in adulthood?(10 votes)
- No, the toes should curl down when the sole of the foot is stimulated, the babinski reflex is when they curl up.(5 votes)
- Are there any differences between neonatal reflexes and instincts? Both seem to be involuntary responses to outside stimulus.(3 votes)
- Here's a paragraph straight from the Wikipedia article on instincts, but to paraphrase even more: instincts are complex behaviors compared to reflexes (for many of which you don't even need the brain's involvement at all, like pulling your hand away from a fire.)
"Instincts are inborn complex patterns of behavior that exist in most members of the species, and should be distinguished from reflexes, which are simple responses of an organism to a specific stimulus, such as the contraction of the pupil in response to bright light or the spasmodic movement of the lower leg when the knee is tapped."(4 votes)
- Is the parachute reflex the same as startle reflex?(1 vote)
- I think the Moro (startle) reflex and parachute reflex are similar, but not exactly the same.
For the Moro reflex, the baby will stretch out with their arms and then bring them back in while crying in response to sudden movement or sound. This may be important for holding onto one's mother when threatened or could be left over from evolution as an instinctive clutching reflex. As mentioned in the video, this reflex disappears around 4 months.
The parachute reflex is when an infant outstretches his/her arms when "falling" as if to break his/her fall. This reflex is said to persist into adulthood, as we usually outstretch our arms to minimize impact when we fall.(2 votes)
- would the swimming reflex possibly be a result of movement within the amniotic fluid?(1 vote)
- I am trying to cite this video for my Phycology assignment. When was this video published?(1 vote)
- Little late, but if anyone else is interested, it seems to have been published on YouTube on Jul 21, 2015.(1 vote)
- [Female Narrator] It might surprise you that there is an entire video devoted to the kinds of motor skills that newborns have. Because, maybe you've noticed that newborns don't have a lot of conscious control over their bodies. They flail their limbs, they can't pick up their heads, but, even so, humans are not blank slates, and we come into the world with certain motor skills already built in. Specifically, we have reflexes, or automatic involuntary motor responses that allow us to interact with the world. The first one that I want to talk about is the breathing reflex. The muscles required for inhalation and exhalation do their work on their own without any conscious awareness on the part of the newborn. Or the conscious awareness of adults, for that matter. There is also the eye blink reflex. So, that's the involuntary blinking of your eyes in the presence of a bright light or if something comes towards your head. Next we have the pupillary reflex, which constricts our pupils in the presence of bright light. And also the swallowing reflex. We aren't really ever taught how to swallow food, it just happens automatically. And one thing you may have noticed about all of these reflexes is that we still have them. And so we refer to these as the Permanent Reflexes. Because even though they're very important to newborns, they're also present throughout our entire life. Other reflexes which are known as the Neo-Natal Reflexes, or the Primitive Reflexes are only present for a short period of time. We typically only see them during the first year of life, and then they disappear as we age. We have the Rooting Reflex, which describes how if you stroke a baby's cheek they will involuntarily turn towards that stimulus. And this helps the infant to orient towards the mother's breast or a bottle. And this actually disappears over the first few weeks of life, and eventually the baby turns it's head voluntarily. We also have the Babinski Reflex, which describes how a baby will curl and uncurl his or her toes when the bottom of the foot is stroked. But unlike the Rooting Reflex, we really don't know why this might be. We don't know of any evolutionary or developmental advantage that this might have conferred. And this reflex disappears before 12 months, or before the baby is one year old. We also have the Moro Reflex, which is kind of a startle reaction. Things like a loud noise or a sudden change in the orientation of the baby's head will cause the baby to throw it's arms outward, arch it's back, and then bring it's arms back down towards each other. And the Moro reflex disappears at about 4-6 months of age. And obviously, we still have a startle reflex as adults, but it's different from the one that we see here. Next we have the Tonic Neck Reflex, which is a really subtle one, and this one describes how when a baby's head is turned to the side, the arm on that side tends to straighten, while the other one will bend. And I've also heard this referred to as "Fencing Posture". And this lasts until about 6 months of age. We also have the Galant Reflex, which describes how when the skin on one side of the baby's back is stroked, the baby will tend to move or swing to that side. And this also usually disappears around 6 months. And those might be a little hard to notice, because you kind of have to go looking for them. But one reflex you might have seen before is the Palmer Grasp Reflex, which describes how children will close their hands around any object that touches their palm. And they can actually grip pretty hard. And this lasts about 3-4 months, and after that, the child is able to grasp things voluntarily. You might also be aware of the Sucking Reflex, which describes how a baby will suck on any object that is placed in their mouth. And this one diminishes about 3-4 months as well. We also have the Stepping Reflex, which describes how when you hold an infant upright and let their feet touch a flat surface, they will start to step as if they're trying to walk. And this usually disappears in the first 2 months, but it always struck me as a really interesting one. And the Swimming Reflex is also one that I find to be very interesting, and that describes the behavior that infants show when they're put in water. They move their arms and legs around in a swimming motion, and they will involuntarily hold their breaths. And this actually does allow the infant to swim, or stay afloat for a short period of time. But before you get too carried away with this, and think that you can just throw a small child into a pool and that they'll be okay, and will miraculously know how to swim, know that this reflex disappears at about 6 months of age. Also, just so everyone is aware, you should never leave a child in water unattended. So why do we have these reflexes? Some of them, like breathing and swallowing and the Rooting Reflex are survival reflexes, they help us to live. But for other reflexes, it isn't exactly clear why they're there. One idea is that they're evolutionary holdovers, that things like the Grasping Reflex and the Swimming Reflex seem helpful if your ancestors were in situations where it was easy for them to be dropped. And things like the Stepping Reflex might be precursors to walking and crawling. Regardless of why they're there though, reflexes are really important today because they can help doctors assess if something is wrong. Because the absence of these reflexes in an infant can be an indicator that something might not be developing correctly. And the same is actually true of adults. The reappearance of Pre-Natal Reflexes in adulthood can signal doctors that there might be a serious medical problem.