Brain and Drugs

The brain is divided into two hemispheres. These hemispheres are connected by a structure called the corpus callosum. The corpus callosum is composed of white matter containing around 200 million myelinated fibers. The largest part of the brain is called the cerebrum. The cerebrum appears as a wrinkled surface because it is filled with gyri or the singular form gyrus. The gyri increases the surface area of the brian which increases the amount of neurons which can be associated with a higher level of intelligence. The cerebrum i divided into 4 lobes, Frontal, temporal, parietal, and occipital. Each lobe has different functions. The frontal lobe is located in the front of the cerebrum, It is associated with problem solving, decision making, and muscle movement. The parietal lobe is commonly associated with pain perception, pressure, touch and visual functions. The temporal lobe is associated with visual and auditory memory. The occipital lobe is important in recognizing visual stimuli and processing what we see. The next section of the brain is called the cerebellum and it is divided in half. Also called the small brain, and it is filled with neurons that control coordinated body movements and other essential functions. The cerebrum and the cerebellum make up the superficial portion of our brain. 

The brain also consists of the brian stem. The brainstem is the lower part of the brain and is composed of different parts. These are the midbrain, pons, and medulla oblongata. The brain stem has both gray and white matter. The gray matter is filled with neuron cell bodies and the white matter with the axons. Ten out of twelve cranial nerves originate in the brain stem all but the olfactory nerve and the optic nerve which are associated with smell and vision. There are many crucial functions that are controlled by the brain stem.These include heart rate, respiratory rate, circadian cycle for sleeping, and plays part in eating by interpreting when you are full or not. Due to the functions of the brain stem, death of the brain stem will result in actual death since there will be no longer independent respirations and the heart will eventually stop. It should be fairly simple declaring death of the brian stem but now with medical technology you can artificially keep the heart beating and oxygenating the body so it is much more complex to actually  declare brain death now regardless  that  tha patient will never regain those functions or their own. Due to the brain stem's role in consciousness after the brain stem dies a person will never regain consciousness again. 

As  previously stated the frontal lobe iss important in many roles. To highlight those again it is associated with voluntary movement, or movement of skeletal muscles, expressive language, and executive functions, such as decision making. The frontal lobe is very slowly developing. It is said that on average the frontal lobe is not fully developed till the age of 25. This is often why a lot of people essay not to make crazy life decisions before that age since your executive functions are not fully functional. There are some important structures in the frontal lobe. One of those being broca's area. Broca's area is associated with language development. There are cases such as phineas gage who had an injury to broca's area. Phineas gage was a railroad worker who had a railroad spike go through his head and he lived but he did have a big change in temperament and he had lost the ability to form words. He became much angrier and it was said before the injury he was pretty well mannered. It was very surprising he lived seeing the injury he took and how the railroad spike went fully through his skull. Broca's area is only associated with language formation though not language comprehension so people with what is called broca's aphasia can still understand other people they just can't form words on their own. The area that controls language comprehension is not in the frontal lobe. Damage to other areas of the frontal lobe can result in many things such as paralysis, sequencing or planning out movements, as already mentioned brocas aphasia, loss of spontaneity,  attention deficits, insatiable moods, inability to problem solve, disinhibition, lack of motivation, social behavior or personality changes.

These may also be associated with different diseases that affect the frontal lobe such as frontal lobe syndrome. 

The temporal lobe is often associated with auditory processing and encoding memories. As previously stated the temporal lobe is in the cerebrum and it is located by the ear. There is an important structure in the temporal lobe called Wernicke's area. I explained earlier how language comprehension was separated from language formation and language comprehension in the temporal lobe is Wernicke's area. Wernicke's aphasia looks very different from broca's aphasia. There is no issue with the formation of words so a patient will often speak words but they do not make any sense. They can't form sentences or understand sentences, they can just talk in random orders. The temporal lobe is also highly associated with long and short term encoding of memories so often Alzheimer's disease which is the buildup of plaques will be affecting the temporal lobes causing dementia or loss of memory. There are two types of amnesia, Anterograde and retrograde. Anterograde is where you can't form new memories after an event and retrograde is where you can't retrieve old memories before an event occurred. Damage in the temporal lobe may present itself as imparied verbal or nonverbal memory, wernicke's aphasia, impaired learning, direction troubles, impaired ability in recalling, difficulty recognizing people or stimuli, impulse control, deafness, amnesia, hallucination. 

One disease that may be associated with the temporal lobe is dyslexia. Patients with dyslexia commonly have decreased activity in their left temporal lobe. This usually presents as difficulty reading and understanding meanings of words or language. This can make learning and school very hard. The diagnosis usually occurs earlier on in life as children or young adults. Some symptoms of dyslexia may be not reaching developmental milestones, difficulty learning to speak and read, when learning to write they may reverse numbers and letters, difficulty processing sounds, and issues with coordination and concentration. Managing dyslexia is different for everyone but sometimes looks like adapting and using learning tools that work for them, guiding and supporting them, and continual evaluation. 

The function of the parietal lobe is to process somatosensory information. This information includes proprioception, touch, spatial perception, navigation, language processing, and pain. There are sometimes strokes in the parietal lobe. A stroke is when a blood clot travels to the brian and cuts off or reduces blood flow to parts of the brain preventing it from getting the appropriate amount of oxygen. A loos of blood flow to the parietal lobe can cause speech impairment, or deficits to thought coordination, and movement. There may also be symptoms such as abnormal sensations, inability to see out of the lower half of the eye, disorientation, loss of proprioception or not knowing how you are oriented, impulsive or inappropriate behaviors or cautious or hesitant behaviors( depending on what side of the brain is losing blood flow). There are some medical conditions associated with the parietal lobe such as gerstmann syndrome and apraxia. 

The occipital lobe is located in the back of the brain above the cerebellum. Its primary focus is auditory processing such as color, morphology, and motion. Vision is very complex and the occipital lobe plays a large role in processing it. There are some important structures in this slope including brodmann area 17, the ventral stream, the dorsomedial stream, the lateral geniculate bodies, and the lingula. Damage to this lobe may result in epilepsy, movement difficulties, perception difficulties, hallucinations, inability to detect movement, difficulty reading and writing, difficulty with fine motor skills. 

There are many types of disorders that are a result of something in the brain that is out of balance, The categories of these disorders are neurological disorders, storage disorders, personality disorders, mood disorders, developmental disorders, and prion diseases. All of these have different effects on everyone, some may be very minor and manageable and some may be fatal and incurable. They also may affect people at different stages of their life. They can also be onset from brian damage, or events or they may be genetic. 

There is something really interesting about our brain though. In some uncommon cases where a brian is damaged only in one hemisphere and it is discovered at a very young age there is a special procedure called a hemispherectomy. This entails removing the whole hemisphere of the brain that is damaged. This is usually only performed in very young patients and the younger they are the more likely they will live a relatively normal life. Most of the time this will only be performed in the first six years of life. After this procedure the cerebrum reorganizes its neurons to compensate for those lost in many cases there will be unequal capabilities between the sides of the body but it's truly amazing that people may live a relatively normal life with only half of their brain. This Procedure is commonly used for seizures that are localized to one side of the brain. 

Alzheimer's disease is a disease that is caused by the build up of beta-amyloid plaques in areas of the brain. It often results in memory loss or dementia. There is no definitive cause to what causes these plaques to build. There is a genetic predisposition to it in some patients. Many ad patients also have neurofibrillary tangles as well that may cause neuronal death. There is no cure to alzheimers but many treatments are tried to lessen or delay the symptoms.

There are many diseases that affect the brian and all present differently and affect different parts or multiple parts of the brain they range in severity as well as if they are treatable/curable or not. They also have different ages of onset. Some examples of diseases in the brain that have not previously been mentioned are multiple sclerosis, tay sachs, huntington's disease, parkinson's disease, schizophrenia, ocd, bi-polar disorder, autism, depression, and ALS. These are all very different from each other but thats why the brian is so unique because there are so many ways that even the tiniest but of damage can destroy the balance of your body. Ayurveda would describe each of these diseases as different imbalances for example, alzheimer's disease would be an imbalance in a misfolded protein, parkinsons would be an imbalance in dopamine concentration, alzheimers is also often associated with an imbalance in acetylcholine. This is a fraction of what we know about the brain and we know very little about it. Studying the brain is very challenging and there is still a lot more research to be done. 

There are many types of drugs, many ways drugs can be administered, and many effects of drugs. One thing all drugs must have in common is they must have the capability to pass the blood brain barrier. Drugs interfere with the brain by affecting the chemical signaling pathways in the brain. The brain uses neurons that generate action potentials that cause the release of neurotransmitters to enter the synapse between two neurons. These neurotransmitters are chemicals that can have different effects on the postsynaptic neuron. They can either send excitatory or inhibitory signals. To measure the effectiveness of a drug they test the ability to affect this chemical signaling process in a specific way at a certain point. So an SSRI or a serotonin reuptake inhibitor stops the brain's ability to reuptake the serotonin in the brain. Serotonin is an inhibitory neurotransmitter that is associated with mood and an imbalance in serotonin or a deficiency is often linked to depression. SSRI’s make us have higher levels of serotonin. Different drugs have different effects for different neurons and affect different points in the pathway.
Prodrugs are compounds that are inactive when they enter the body but by some natural body mechanism get activated inside the body. Prodrugs are often a good strategy to avoid unwanted side effects. There are two types of prodrugs type 1 and type 2. Type 1 prodrugs are activated inside the cells and type 2 are activated outside the cell usually in blood or other fluids such as lymph. There are two different designs for prodrugs as well, carrier-linked, and bioprecursor. Carrier-linked prodrugs are connected to another medication and this linkage is broken when entering the body. Bioprecursor prodrugs are chemically modified versions of an active form of the drug and different enzymes will activate them.  Prodrugs are generally used when they need to target a certain area of the body and will travel through the body inactivated until it gets to target. This is why it can help avoid side effects. 

Drugs can be very useful but can also be very dangerous. Recreational drugs such as fentanyl have led to many fatalities. Fentanyl poisoning/overdose has become the leading cause of death. Fentanyl can be used in a clinical setting though. Fentanyl can be used as a very stone painkiller about 50-100 times stronger than morphine. It is also very addictive and is commonly laced with recreational drugs which can often lead to fatalities. Fentanyl is a good example of how useful drugs can be and how dangerous they can be if not handled appropriately. 

Another aspect of drugs is when taking more than one type of drug combined with another. There are two types of drug interactions. Antagonism where the drugs cause opposite effects and essentially cancel eachother out. Or drug synergism where they interact and the effect becomes heightened due to the interaction. Naloxone is antagonistic to opioids which is why in case of an opioid overdose naloxone is often used to reverse the effects of the drugs. An example of synergism is opioids combined with analgesics, This heightens the effect of opioids. 

In conclusion, Many drugs have different effects on the brain. As previously discussed the brain is a very diverse organ that we are still learning about so it can be very difficult formulating drugs that do the correct thing and can pass through the blood brain barrier. There is a wider variety of types of drugs and sometimes they have unintended effects on other systems which can result in many outcomes. 

https://www.ncbi.nlm.nih.gov/books/NBK448209/

https://www.ncbi.nlm.nih.gov/books/NBK448209/ 

https://www.ncbi.nlm.nih.gov/books/NBK448209/ 

https://www.ncbi.nlm.nih.gov/books/NBK544297/

https://en.wikipedia.org/wiki/Phineas_Gage 

https://www.health.qld.gov.au/abios/asp/bfrontal 

https://www.medicalnewstoday.com/articles/temporal-lobe 

https://www.sciencedirect.com/topics/neuroscience/parietal-lobe https://www.verywellhealth.com/effects-of-a-parietal-lobe-stroke-3146435