In Guillain-Barre syndrome, the immune system attacks and degrades the myelin sheath of PNS axons. Predict the effect this will have on nerve impulse and motor function.
A)Lost insulation from myelin will cause neurons of the PNS to be hyper-excitable and muscular spasms will result.
B)Motor signals will not be sent from the brain down the efferent pathway because the brain cannot generate them.
C)The brain will slowly degrade and various brain functions will be lost, including motor functions.
D)Lost insulation from myelin will cause neurons of the PNS to lose saltatory conduction, resulting in poor muscle function.

Question

Quizplus · Accepted Answer

The loss of myelin sheath will result in poor saltatory conduction, which is necessary for the efficient transmission of nerve impulses along the axon. This will result in poor muscle function and weakness since the motor signals will not be effectively transmitted to the muscles. Lost insulation from the myelin sheath will also result in an increased threshold for firing, so the neurons will require a higher amount of neurotransmitter stimulation to reach action potential. This will lead to reduced muscle activity rather than hyperactivity or spasms (choice A). The brain will not degrade in Guillain-Barre syndrome (choice C), but there may be some loss of sensation due to degradation of sensory neurons. Choice B is incorrect because the issue is with the PNS, which controls motor and sensory functions rather than the brain.

In Guillain-Barre Syndrome, the Immune System Attacks and Degrades the Myelin