What Happens in Alzheimers Disease – Tens of billions of cells in the brain cells that receive and send information via electrical as well as chemical signals—are found in a normal human brain. They convey signals from the brain to the muscles as well as organs of the body, as well as between different sections of the brain. Alzheimer disease affects this connection between neurons, causing cell death as well as loss of function.
What Happens in Alzheimers Disease ?
A cell body, several dendrites, and an axon are the three basic components of most neurons.
The nucleus that houses the genetic code that controls and regulates the cell’s activity, is found in the cell body.
Dendrites are branch-like extensions that branch out from the cell body & collect data from other neurons.
The axon is a cord-like structure that delivers messages to other neurons and therefore is located at the end of the cell body against the dendrites.
Neuronal function and survival are dependent on a number of biological processes:
Neurons communicate with nearby brain cells all of the time. When a neuron gets a signal from another neuron, it produces an electrical charge that travels down its axon and distributes neurotransmitter molecules along a tiny gap known as a synapse. Each neurotransmitters molecule then attaches to specific receptor locations on a dendrite of a nearby neuron, similar to a key fitting into a lock.
This process sends chemical/electrical signals to the receiving neuron, which either stimulates or inhibits activity. Brain cell networks are frequently used to communicate. In fact, one neuron in the brain’s communication system may have as many as 7,000 synaptic neural connections, according to scientists.
Metabolism, or the breakdown of molecules as well as nutrients inside a cell, is essential for cell survival as well as function. A cell contains energy in the form of oxygen and glucose to conduct this function that is provided by blood moving through the brain. The brain has one of the most abundant blood supplies of any organ, and it uses up to 20% of the energy required by the human body, more than almost any other part of the body.
Regeneration, remodeling, as well as repair
Unlike many other cells in the body, neurons have developed to exist for an extended period of time—in humans, more than 100 years. As a consequence, neurons must maintain and repair themselves on a regular basis. Neurons also “remodel” their synaptic connections in response to the amount of input they receive from other neurons.
They could, for example, enhance or decrease synaptic connections, or even break down connections including one group of neurons while forming new ones with another. Neurogenesis is a process through which adult brains develop new neurons. Neurogenesis, as well as synaptic remodeling, are critical for learning, memory, and perhaps brain repair.
Although neurons play a prominent role in the central nervous system, other cell types are equally important for proper brain function. Glial cells are the most common cells, vastly outnumber neurons by a factor of ten to one. These cells surround as well as support the function and health of neurons in a variety of ways, including microglia, astrocytes, as well as oligodendrocytes.
Microglia, for example, is important for removing foreign substances as well as cellular waste from the brain as well as protecting neurons from physical and chemical injury. Glial cells frequently work with blood arteries in the brain to carry out these duties. Glial and blood vessel cells work together to maintain the delicate balance within the brain, ensuring that it operates optimally.
What Is the Impact of Alzheimer Disease on the Brain?
In healthy aging, the brain shrinks to some extent but, surprisingly, does not lose a substantial number of neurons. Meanwhile, with Alzheimer disease, the damage is widespread, with several neurons ceasing to function, losing connections with other neurons, and eventually dying. Alzheimer disease impairs communication, metabolism, and repair mechanisms in neurons as well as their networks.
Alzheimer disease damages neurons and their connections in memory-related areas of the brain, such as the entorhinal cortex and hippocampus, at first. It then has an effect on the parts of the cerebral cortex that control language, logic, and social behavior. Many other parts of the brain are eventually affected. Alzheimer disease causes a person’s ability to live and function independently to deteriorate over time. The sickness is lethal in the end.
What Are the Brain’s Main Characteristics in Alzheimer’s Disease?
A person with Alzheimer disease’s brain undergoes numerous molecular and cellular alterations. After death, these alterations can be seen under a microscope in brain tissue. There are currently studies being undertaken to find which changes may induce Alzheimer disease and that may be an outcome of the condition.
The Alzheimer protein beta-amyloid appears in a variety of molecular forms that aggregate between neurons. It’s made when a larger protein called amyloid precursor protein breaks down. One type, beta-amyloid 42, is known to be particularly dangerous. Abnormal levels of this normally occurring protein come together and form plaques in the Alzheimer brain, which gather between neurons and impede cell function. The study of how the different forms of beta-amyloid impact Alzheimer’s disease at whatever stage of the disease is continuous.
Inside neurons, neurofibrillary tangles are aberrant accumulations of a protein called tau. Internally, healthy neurons are sustained in part by microtubules, which assist transport nutrients and chemicals from the cell body to the axon and dendrites.
Tau binds to and stabilizes microtubules in healthy neurons. Meanwhile, abnormal chemical reactions in Alzheimer disease lead tau to separate from microtubules and attach to other tau molecules, generating threads that eventually unite to create tangles inside neurons. These tangles obstruct the transport mechanism of the cell, impairing synaptic contact between neurons.
According to research, chronic inflammation may be caused by the accumulation of glial cells, which are normally responsible for keeping the brain free of debris. In a healthy brain, one type of glial cell called microglia engulfs and eliminates trash and poisons. Microglia fail to sweep away waste, debris, as well as protein aggregates, particularly beta-amyloid plaques, in Alzheimer disease. Researchers are trying to figure out why microglia in Alzheimer disease fail to execute this critical job.
TREM2, a gene, is one of the genes being researched. TREM2 normally instructs microglia cells to eliminate beta-amyloid plaques from the brain as well as aids in the battle against inflammation. Plaques form between neurons in the brains of persons who do not have this gene working properly. Another kind of glial cell, astrocytes, are activated to assist in the removal of plaques and other cellular debris.
These microglia and astrocytes clump together around the neurons, but they don’t clear the trash. They also release substances that create persistent inflammation and inflict more damage to the neurons they are supposed to protect.
Alzheimer Disease and Vascular Contributions
Only Alzheimer-related alterations in the brains of persons with dementia are uncommon. A variety of vascular issues—problems involving blood vessels, such as beta-amyloid accumulation in brain arteries, atherosclerosis (artery hardening), and mini-strokes—could possibly be at play.
Vascular disorders can result in a reduction in blood flow and oxygen to the brain, as well as a disruption of the blood-brain barrier, which normally protects the brain from harmful agents while enabling glucose and other essential nutrients to pass through.
A defective blood-brain barrier inhibits glucose from reaching the brain and the clearance of harmful beta-amyloid and tau proteins in Alzheimer patients. This causes inflammation, which exacerbates vascular issues in the brain. Because Alzheimer disease appears to be both a cause and a result of vascular issues in the brain, researchers are looking for ways to break this complex and damaging loop.
As neurons in the brain are harmed and die, connections between neural circuits may break it down, as well as numerous regions of the brain begin to shrink in Alzheimer disease. This phenomenon, known as brain atrophy, is pervasive by the end stages of Alzheimer disease, resulting in considerable loss of brain volume.
People May Ask
Q- What causes Alzheimer’s disease in the brain?
A- The aberrant build-up of proteins in and around brain cells is assumed to be the origin of Alzheimer’s disease. Amyloid is one of the proteins involved, and deposits of it create plaques around brain cells. The other protein is tau, which forms tangles within brain cells as deposits.
Q- When a person has Alzheimer’s disease, what happens to their brain cells?
A- As neurons in the brain are harmed and die, connections between networks of neurons may break down, and numerous brain regions begin to shrink in Alzheimer’s disease. This process, known as brain atrophy, is pervasive by the end stages of Alzheimer’s disease, resulting in significant loss of brain volume.