Is there a scientific reasen for the fact that the left arm and leg is connected to right hemisphere?
95547
This all comes down to the way that vertebrates evolved, and it is a classic example of evolution producing a workable though complicated design that no intelligent designer would ever produce unless she were on drugs.\n\nTo explain let’s go back to the very earliest chordates. We are going back here to a time before our ancestors were fish, before they even had backbones. These things existed as essentially free-swimming worms a few inches long. No fins, no jaws, not even a real mouth, no limbs of any sort, just a body and a head. Every body segment aside form the head was identical and had just 4 muscle blocks. \n\nThese things lived by swimming around in the water filtering plankton from the water through a hole in their front end. That hole wasn’t a mouth, it was just a hole lined with beating hairs that drew in water.\n\nWith such a simple body plan these creatures didn’t require much nervous control by the ‘brain’ to the body.  Each body segment was controlled by a simple reflex arc from those 4 muscle blocks to the spinal cord. The brain could make them more or less responsive to stimulation and so cause the animal to turn left or right, but direct control from the brain to the body was extremely limited and there were correspondingly few nerves running from the brain to the body.\n\nWhat I haven’t mentioned is that this creature had EYES, and therein lies the reason for the crossing over. The early chordate brain was excessively devoted to operating some rather complex eyes that allowed it to see both  food and predators. So why are the eyes so important? Because when light enters they eyes it… crosses over. It inverts. You can follow the link below to get a better idea of this, with diagrams. But for now simply remember that the eye has a lense, and a lense inverts an image left to right as well as up and down. So with a brain devoted to processing inverted images collected through a lense it makes sense for the left brain to control the right body.  After all the information that comes from the left eye will in large part be telling the brain about conditions on the right side of the body.\n\n And so that is exactly what happened. These earliest chordates had (and still have) a brain with massive visual centres and limited  control of the body itself but, and this is vital, the left visual centres are largely located in the right brain. To move towards food on the left side of the body for example the signal form the left eye is processed by the right brain, and the right brain then sends the appropriate signals to the left body. To move towards visually acquired stimuli the signal has to cross over from the side of the brain that processed the data to the OPPOSITE side of the body.\n\nAs chordates became larger and more complex one of the things they did was to grow paired fins. They ceased being wormlike and became fishlike. But paired limbs require far more fine and centralised control than can be provided by a reflex arc to the spinal cord. So the brain assumed control. \n\nThe same brain that had evolved a complex crossover so that visual data corresponded to the correct side of the body was now being asked to assume direct control of paired limbs. Of course evolution works with what it has, not with what is best. The brain had a complex crossover for controlling the muscles of the body, and it couldn’t re-wire that, so it simply built on it. Limb control also crossed over form the left to the right brain even though it was no longer under visual control.\n\nAnd as we became more and more complex we simply kept the same convoluted design. The reason the left brain control the right arm today is simply because hundreds of years ago information form the left eye was processed by the right brain, which was a very sensible solution at the time.
479875
If the stroke is on the left side of the brain, then it will be the opposite side that is effected..(ie the right).
712542
Not everyone is able to think in the abstract! Studies of left and right brain dominance\nshow some understand concepts, (left). Some people understand better when we "draw" a picture for them, (right)!
690865
Hello,\n\n    Simply, we're normally stronger in one arm!!! Hence, if your left one is stronger, the right arm will be tired first!!!\n\nBut don't worry, the more you train, the more that discrepancy will disappear!
347040
There are actually quite a few different medical terms for this, depending on the severity.\n\nBut what typically happens for most of us when we say that our leg "fell asleep" is simply the loss of blood circulation. Usually this will occur when we sit, sleep, or otherwise position ourselves in a particularly odd way...such as lying on one's arm for a lengthy period of time.\n\nOften, I have just referred to it called simply as "arm/leg numbness." But the more severe varieties have far more professional medical terms associated with them; for example, if one's arm nerves are the cause of the trouble.
1049855
actually, no. this has never happened to me, I actually died after I was born and revived, so not all my brain cells are functioning, that's probably why I am lefthanded too
428645
Approximately 10% of the population classify themselves as being left-handed, with the percentage slightly higher for males and lower for females (McManus, 2002). Faurie and Raymond (2004) reviewed handedness frequency over more than ten thousand years (the oldest evidence coming from Palaeolithic ‘negative hand’ paintings), and determined that there was no difference between the oldest sample and the proportions found in university students today.\n\nHope that helps!
429224
it depends on the damage to the left hemisphere. if the damage is extensive, the person would lose right side motor movement, meaning they cant really control their right arm and leg. their language will be impaired, and the right hemisphere will take over the laguage. \nif the left side is not extensively damaged, then the person will not really lose motor movement, but when they walk or grab things with their right side, it will look awkward. the language will be impaired, as with reading and writing and speaking. the left side can still control the language section, but with help from the right hemisphere
563801
there is a part of the brain that deals with that activity, the hand we use to pick up stuff or write, and from what i was told (i am left-handed by the way!)it is the side that is located that determines if you will be left-handed or right-handed. Left-handed people are no less intelligent then right-handed people OK?
107416
Ipsilateral in layman's term means 'same side'. I'm assuming you know what paralysis means. When there is a problem/lesion (upon investigation) on one side of the brain or nerve (e.g. right side), rendering a person paralysed on his right body part, it means, the person is affected on the same side of his lesion = Ipsilateral.\n\n Lesion on right/left side of brain/ nerve = Paralysis on right/left side of body = Ipsilateral Paralysis.\n\np/s: When a paralysis occurs on the opposite side (e.g left) of his lesion (e.g right), it is known as 'Contralateral' Paralysis.
19763
It's a very good question. But it would be even better if you asked other way around. \n\nBecause, people who are left-handed are right. cz left side of the brain controls the muscles and also it is a bit faster than left.\n\nBut if you ask the other way around, that why many of us do it wrong? I really don't know. But can guess that its more cultural thing than anything else.\n\nhttp://www.coolquiz.com/trivia/explain/docs/lefthand.asp
195572
I'm not sure but it's not just the arm or leg, that goes for evey part of the body.
1158573
No, this is a myth. A large part of our brain is used as proved by MRI's.
465972
What I learned is that the right is receiving and the left is giving out. Its not so important except in circle when holding hands. You want the energy in the circle to flow correctly so we all keep the left hand down sending to your "Neighbor" and the right hand up recieving from your other "neighbor".
302792
His left is your right isn't it? Perhaps you are righthanded and therefor your right eye dominates and stares at it's choice, the closer object to it (being the left eye of the other person). Try looking at a lefthanded or leftbrain dominant person and see if there's a difference. ^__^
700064
That depends which side.  The right hemisphere is more intuitive and creative, while the left side is more rational or mathematical and deals with language.
76862
Sounds like you need a DR.,opinion not a bunch of strangers on a computer.I know someone with the same prob. except it's the whole left arm and hand.I guessed a nerve pinched off or maybe poor circulation, but hey I'm no DR.