The Integumentary, Skeletal and Muscular Systems
At the neuromuscular junction of a skeletal muscle, neurotransmitters must contact receptors on the muscle fiber sarcolemma to transmit the signal for muscle contraction. That neurotransmitter must subsequently be enzymatically broken down, so that it is removed from the receptor, “resetting it” to receive another message. Mancy “chemical weapons” are in fact inhibitors of the enzyme necessary to break down the neurotransmitter in question, causing it to remain attached to the receptor indefinitely.
Which of the following would probably result after poisoning by one of the agents described in the passage?
|A||The heart would stop, since no messages from the nervous system could signal it to contract.|
|B||A person would begin to lose the ability to actively move, and would ultimately die from the failure of the diaphragm to contract, causing suffocation.|
|C||The person would suffer from mental confusion, as messages could not be sent within the brain itself.|
|D||All muscular functioning in the body would cease.|
Since only muscles stimulated by acetylcholine will be affected, choice D cannot be true. The heart requires no nervous stimulation to keep beating, and the brain uses different neurotransmitters than acetylcholine (choices A and C).