Question

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease affecting adults (~30,000 in U.S.). It is a progressive, debilitating neuromuscular disorder that generally strikes in mid- to late-life (40-70 years) and can rapidly progress to death (3-5 years from onset). ALS is characterized by selective loss of motor neurons in spinal cord, which causes loss of skeletal muscle and weakness. Motor neurons in the largest motor units appear to be most vulnerable. Based on this, which type of motor neurons and muscle fibers would you expect to be most susceptible

Answer 1

Upper and Lower motor neurons, and Voluntary muscles.

Step-by-step explanation:

Structurally,the motor neurons in the Brain are called the upper motor neurons.While the motor neurons in the spinal cord and the brain Nuclei are called the lower motor motor neurons.

Therefore, transmission of sensory impulses from the brain through the upper motor neuron are sent to the spinal cord through the lower motor neurons. These are eventually sent to the muscles(voluntary muscles) the effectors to bring response.

However, in ALS both the upper and lower motor neurons degenerate and die.Therefore transmission of action potential is impeded.Thus the voluntary muscles are made redundant with no sensory information and therefore they twitch (this is called fasciculations) and progressively undergo waste away.

As this progress the ability of the brain to initiate action potential for sensory information and its propagation is lost.

Therefore weakness of muscles and stiffness results,followed by complete loss of sensory transmission and inability of the individual to respond to sensory stimulus of walking, standing, eating, and breathing.Slurred and nasal speech,and muscles cramps are other symptoms

At advanced stage loss of life usually results from the respiratory failure.

it occurs mostly in the Caucasians and non-Hispanics between the age of 55-75,and common in males than females.It causes are blend of genetic and environmental factors.

Medication,therapy-physical and speech therapy are some means of treatments.