Re: Why don't paraplegics have reflex reactions?

While the pathways for the reflexes are still there (for example, the knee 
jerk reflex is done by just the nerves and spinal cord), the reflex is 
still influenced by the brain. In the case of the knee jerk reflex, the 
brain normally causes the muscles involved to have a certain amount of 
muscle tone, so that they are always contracting. This helps the reflex. 
With the brain out of the picture (because the brain is no longer 
connected to the spinal cord), the tone goes down, and the reflexes tend 
to be much weaker.

Another reason is called "spinal shock." This occurs soon after a spinal-
cord injury. Because the spinal cord normally has so much input from the 
brain and other parts of the spinal cord, when the spinal cord is injured, 
the spinal cord does not know how to respond. This causes the reflexes to 
go away for a while. They often return, although they are not nearly as 
strong as before.

However, the reflexes do recover to some extent. And they can be useful. 
If you have changed a lot of diapers, you know that babies have a tendency 
to get you with a stream of urine (pee) when you change their diapers. 
(Supposedly boys are better at this than girls.) The reason why is that 
there is a spinal-cord reflex causes them empty their urinary bladders 
(pee) when they are stroked or touched in the front of the legs near their 
diaper areas. They also tend to move their bowels (poop) about the same 
time. This is really the same reflex, affecting a slightly more posterior 
part of the body. As babies learn to pee and poop on their own, this 
reflex disappears. Some people who are paralyzed are able to stroke the 
inside upper part of their leg periodically, and thus empty their 
bladders. This makes taking care of this one activity much easier for 
paralyzed people.

So, paralyzed people do have reflexes, but they are weaker than in people 
who are not paralyzed. And people who are paralyzed are able to use the 
reflexes for their benefit.

(Warning: the following, while true, may be found to be disgusting by some 
people. Other animals also have the same reflex. For example, rat pups 
will not pee or poop unless their mother licks them in their groin area. 
If their mother gets killed or something, they will just continue filling 
their bladders until they die. After the mother licks the pups in the 
appropriate area, the pups pee and poop. Because the pups kidneys and 
intestines are not very good at conserving water, there is often too much 
water in the pee and poop. So the mother drinks and eats the pee and poop. 
The mother is able to get rid of the waste part of this, while at the same 
time absorbing the excess water. This way, the mother is able to regulate 
and conserve water for both herself and her pups.)