Question

What role do motor neurons play in A.L.S patients?

In what specific aspect are motor neurons useful for A.L.S patients?

What is the difference between motor neurons and astrocytes?

Answer 1

ALS or the Amyotrophic Lateral Sclerosis is a motor neuron degenerative disorder. The motor neurons signal impulses from the brain to parts of the body for movements like walking, swallowing, breathing, clenching of fists and almost every movement. The disease initiates with twitching and difficulty in basic movements and may progress to even paralysis.

The motor neurons are involved in transmitting impulses to and from the brain for most body movements. The gradually impaired activity of these neurons leads to difficulty in movements in the ALS patients. These motor neurons degenerate over time leading to up to 90% loss of movement in patients. The motor neurons are involved in the precise control of voluntary movements which become compromised in this disease.  The voluntary movements and motor control on activities are lost. Thus motor neurons have a pivotal role in the life of ALS patients.

Motor neurons have a selective vulnerability which is of great help to ALS patients. Some of the neurons are prone to degeneration during ALS while some are slow and some are resistant. One of the resistant motor neurons is the oculomotor neuron. This neuron is resistant to the effect of the disease till the last stage. This helps the patients to communicate through eye movements. Some digitally enabled aids can decipher these eye movements to ease communication in ALS patients.

Molecularly the muscle cells that rely on glycolysis fatigue fast and hence degenerate faster in ALS. While the muscle cells that employ oxidative metabolism are less prone to quick degeneration. Hence we find a degree of resistance and sustenance of motor neuron degeneration.

Difference between motor neurons and astrocytes:

Motor neurons carry nerve impulses directly while astrocytes are neuroglial cells that supportive and protective cells to them. The astrocytes modulate the amount of neurotransmitters and ions around the synapse and hence assist neurons in transmitting impulses. They do not directly conduct impulses but their role in the generation of impulse is very important. They also regulate nutrient supply to neurons. They do so by dilating blood vessels near active neurons to increase oxygen and carbohydrate supply. In addition, astrocytes give structural support to neurons. Also, they form the blood-brain barrier which screens what enters the brain from the bloodstream.

The astrocytes release growth factors for motor neuron survival. They are involved in glutamate clearance from synaptic clefts of motor neurons. It is believed that in ALS the altered activity of astrocytes leads to degeneration of motor neurons. They lose their ability to support motor neuron signal transduction. The environment they maintain for motor neuron function becomes unhealthy for survival due to glutamate accumulation. Hence motor neurons degenerate in ALS.