QWestions: Some disease, such as multiple sclerosis (MS), occur when the immune
ID: 134260 • Letter: Q
Question
QWestions: Some disease, such as multiple sclerosis (MS), occur when the immune system attacks and compromises the function of myelin. Use your understanding of myelinated axon conduction to explain the following symptoms of multiple sclerosis: muscle weakness problems maintaining balance while walking, and blurred vision. 2. A: A large quantity of K ions are ad is then stimulated to gen addition of phases of the action potential? Explain. ons are added to the extracellular fluid of a neuron. The neuron erate an action potential. During this action potential, how will the K" to the extracellular fluid influence the repolarization and hyperpolarization B: Following this action potential, how will the neuron's resting membrane potential compare to its resting membrane potential prior to the addition of K'? C: How will the addition of K' to the extracellular fluid affect the neuron's overall function? Why? (Hint: Injections of potassium chloridesolation are letha).Explanation / Answer
1. Muscle weakness: Myelin sheath occurs in the axon which is responsible for conduction of nerve impulses and generation of action potentials. When myelin sheath degenerates, the conduction of nerve impulses slow down and action potentials stop.New sodium channels are then replaced in place of the myelin sheath, which continues to function as the unyelinated one. Following this, the conduction velocity decreases due to the damage of the nerve fibres to the brain and spinal cord which then becomes unable to stimulate the muscles and hence cause muscle weakness.
Problems maintaing balance while walking: Walking requires a co-ordination of the various muscles. Damage to the myelinated sheath causes numbness in the feet, decreased activity of the muscle spindles to the joint receptor activity to fatigue in the legs.
Blurred vision: Blurred vision is caused due to the damage to the optic nerve fibres. The optical nerve fibres are demyelinated which causes inflammation of the nerve fibres. This further impairs visual co-ordination to occurence of a scotoma in the central region of the visual fiels which then causes improper vision. Lesions are formed in the white matter of the optic nerve which further aggravates the problem.