Neurons are the cells in the nervous system that receive and send signals. They have the ability to convert various types of signals such as chemical or mechanical signals into an electrical signal. Neurons receive input from other neurons via their dendrites and then send a signal via their axon. Some neurons have myelin which wrap around their axon and allow the neuron to send the signal down their axon at a much faster speed.
The spinal cord is part of the central nervous system (brain and spinal cord). It receives sensory input from the body and sends it to the brain for processing. It also carries information from the brain to the body which consists of conscious control of muscle movement as well as other signals. It is protected by the bony vertebral segments. While the spinal cord contains gray matter (cell bodies) and white matter (axons), the gray matter ends between the first and second lumbar vertebrae and continues as only white matter fibers known as the cauda equina (horse tail in Latin as it looks like a horses tail).
The brain is the seat of consciousness and controls the functions of the body. There is still much that is not known of this mysterious organ.
Alzheimer's Disease is a neurodegenerative disease where there is a loss of neurons in the brain. This leads to a decrease in brain mass and function with one of the main symptoms being memory loss. While the exact mechanism of why these neurons die, it is thought that the buildup of toxic amyloid beta plaques and neurofibrillary tangles is the main cause.
SMA (Spinal Muscular Atrophy)
Spinal muscular atrophy is characterized by the death of motor neurons in the dorsal horn of the spinal cord. This is caused by a mutation in the SM1 gene which plays an important role in the survival of these neurons. Common symptoms include muscle weakness to muscle atrophy and in severe cases this can lead to the loss of muscle function. If this affects the diaphram muscle it can lead to the inability to breath and eventual death.
Parkinson disease is caused by a loss of neurons that regulate motor control. There is specific loss of dopamine releasing neurons in the region of the brainstem known at the substantia nigra (called this because the neurons appear black). Loss of these neurons leads to resting tremor and a slowing of the initiation of movement. Onset of the disease is commonly in the elderly population.
Alzheimer's Disease -> Neuron
The only medication approved to treat the underlying cause of Alzheimer's disease is aducanumab. It is an antibody that binds to the amyloid beta plaques and helps to remove them. It should be known that there is controversy over the efficacy of this drug.
SMA -> Spinal Cord
Nursinersen is an approved therapy for SMA. This drug regulates the expression of SM2, which can replace the mutated SM1 protein.
Parkinson Disease -> Brain
Levodopa is a common treatment for Parkinson disease. Levodopa is converted into dopamine and can replace the dopamine normally lost in this disease.