In an interview, Christopher Reeves and his wife announced that they were going to try to have children. Christopher Reeves is paralyzed from the neck down due to an accident. I wondered if the Reeves couple may have their hopes set a bit high. After all, all of the reproductive organs are located in the lower half of the body, and in Reeves' situation, the lower part of his body is disconnected from the brain. I began to think of the discussion in class about the accident victim with a broken neck. We concluded that if toe of such a victim is pinched, the leg will withdraw. We also concluded that the victim does not say ouch because the brain is not recieving the message that the toe has been pinched. What actually happens is that there are nerves that go into and come from the the caudal end of the spinal chord that control the legs. The nerve (axons) that run from the legs to the the dorsal horn of the spinal chord (sensory neurons that recieve message of the pinch) where they end and synapse with interneurons that in turn synapse with motor neurons that cause the leg to withdraw. The brain is not needed for this part of action. However, from the dorsal horn, signals also travel rostrally through the spine via white matter that in a normal nervous system would signal the brain that there is pain, and the "I-fuction" should say ouch, via the hypoglossal nerves in the medulla. The accident victin with the broken neck does not say ouch because nerves that run through the neck to the head have been severed and therefore the message does not reach the medulla. We also noted that if the victim is asked a question, he can answer, indicating that this action is not effected by the accident and funstions seperately from the spine.
With this bit of information, I think I can try to answer the question as to whether or not a person paralyzed from neck down has the ability to have sex. If in fact the male sex organs are controlled by sensory neurons running to the caudal end of the spine, and motor neurons running from the caudal end of the spine, with the brain playing no part, then stimulation of the sensory neurons should make it possible for the male to achieve an erection and have sex. However, there is a part of the brain that mediates arousal, and parts of the brain that would cause secretion of various hormones (the names of which I am not yet familiar), that may also need to be considered and we have already determined that the brain will not recieve any information, it is disconnected from information relayed fron the caudal nerves of the spinal chord. So it seems that the answer would be dependant on the role and how necessary of a role the brain plays. It is also apparent that having sex would be for the sake of reproduction only, because the rostral part of the nervous system, the brain, (where the I-function that we know of is located) will not know of any sensations transmitted because they will be cut off below the medulla.
It is also interesting to think about this: "If we do not need our brains, or to say, if we do not need the "I-function to reproduce", meaning to have sex only requires stimulation of sexual organs, than this should influence ones opinion in paternity suits, and other social functions. In other words cases of fatherhood and motherhood, and who has the rights to claim these titles.
An interesting, and highly germane set of concerns. Yes, indeed, some sexual function may be local to the spinal cord (though is possible, likely?, that in this case some kind of artifical insemination may be what is planned). And the fact that different parts of the nervous system can function to some extent independently of one another does indeed raise a host of legal/ethical issues that deserve some thought. PG