Down Syndrome

First described by John Langdon Down in 1866, Down's Syndrome (DS) is the most commonly occurring chromosomal disorder in the world. DS effects an estimated 400,000 Americans. Meaning that 1 in 691 babies are born with DS and that 6,000 affected babies are born every year. 

DS is also known as trisomy 21 since the disorder occurs when the 21^st chromosome is repeated. Human body cells normally possess 46 chromosomes. Non-body cells, know as sex-cells or gametes (like sperm and eggs) contain 23 chromosomes. When egg and sperm fertilize, they produce a cell (known as a zygote) with 46 chromosomes.  When DS occurs, the 21^st chromosome from one of the parents is repeated. This in turn causes one parent to give 24 chromosomes while the other gives the normal 23 chromosomes. Consequently, there are an abnormal 47 chromosomes in the zygote.

Some physical signs of Down syndrome include…  

·         small chin,

·         slanted eyes,

·         a flattened nose,

·         only one crease in the palms

·         big gap between big toe and rest of the toes

·         low muscle tone, and more.

Note that affected individuals may express all/some of the characteristics listed

Those with Down's Syndrome are born with disabilities involving intellect. Depending on the severity of the Syndrome, the IQ of a patient ranges from 20-70. Additionally, language disabilities are common (stuttered, slurred or other irregular forms of speech), consequently; many victims will lose the ability to speak soon after age 30.  

Also, individuals with Down's Syndrome have a higher chance of getting

·         Epileptic seizures

·         Alzheimer’s

·         Sleep Apnea

·         Leukemia

·         Autism and more

The life of a person with Down's Syndrome is no doubt a tough one. However, many improvements have been made. For one, the lifespan of an individual with DS has gone from 25 up to 60 from 1983. Although most graduate successfully from high school, as of now, few receive paying jobs. But life for people with Down's Syndrome is improving with new programs in colleges that offer hope, and laws that have been passed to ensure that those with DS will be able to have a full and normal education.

Multiple Sclerosis

    Not as severe compared to other brain diseases, nor fatal, multiple sclerosis (MS) is a condition that primarily affects the central nervous system(CNS) by destroying Myelin and forming plaques in your brain's white matter.

    Myelin is a mixture of proteins that speeds up and carries out communication through nerves smoothly and effectively. In this disease, the immune system begins to destroy myelin. This not only makes communication rough between the CNS and the rest of your body, but may also deteriorates nerves.

    The first signs of MS often include; blurred/cross-eyed vision, red and green color frequency disturbances, balance + coordination problems, and can be the cause to total blindness in one eye. As the disease progresses, walking and standing becomes difficult. This could even lead to paralysis. 

    About 50% of those with MS may also develop optic neuritis, which is damage done to your optic nerve (nerve that connects eye to the brain) due to a lack of the protective cover myelin. And the same percentage of chance goes to having problems which are involved with: thinking, memory, concentration, or even impaired judgment. But these symptoms aren't often that destructive.

    In the USA alone there are over 200 cases of MS occurring every week and an estimated 250,000 people with the condition. Affecting people from ages 15-60 (most commonly), white people have a higher chance of developing this condition and women have 2 times the likability of developing this condition.

    There is no cure for this disease yet, and therapy isn’t very helpful, putting patients at risk (due to side effects). Nevertheless, some medications can slow down the development of the disease.

Dementia

    Dementia is NOT a type of disorder. Rather, a term given for people with certain symptoms caused by many different neural disorders. In dementia, major neurons and neural points may lose connection due to the lack of function (or a malfunction of fluids/proteins that the cells need) and an excess of neuron deaths. Among the types of dementia, Alzheimer’s disease (AD) is most commonly seen.

    Symptoms include drastically limited intellectual abilities, loss of memory, personality issues, a hard time controlling emotions, and/or cognitive disabilities. Some forms of dementia, like AD, do not have a cure and have progressive damage to the brain. Others may be halted, slowed down or reversed.

The different kinds of Dementia are

-          Cortical dementia – language loss, memory issues, social behavior problems, and thinking due to damage to the brain’s surface.

-          Subcortical dementia – emotions, memory, and movement problems come into play when parts below the surface are crippled.

-          Progressive Dementia – Like it suggests in the name, it a dementia which worsens (progresses).

-          Primary Dementia – A dementia which does not occur from any previous or currently possessed diseases

-          Secondary Dementia – Occurs from a physical injury or a disease.

Alzheimer’s disease (AD)

    As the most commonly occurring dementia, Alzheimer’s is a progressive disease which, unfortunately, does not have a reversible cure (yet). Taking its time to settle in and slowly beginning to emphasize certain symptoms, AD usually occurs in people who are 65+. Symptoms that people experience in this dementia include: memory loss, personality changes, a troubled time in decision making, and/or other cognitive issues. Memory problems may be so severe, that close people such as family and friends may not even be recognized.

    

    This mind altering disease begins when neurofibrillary tangles (clumps of filament-like structures found in neurons), composed mainly of a protein called tau, are affected. Specifically, this is when the tau is not manufactured like usual. Instead of helping the neural tangles, tau is changed to slow down/destroy sections of the communication paths and/or functions of neurons. As the disease progresses, more and more neurofibrillary clusters are affected causing an excess of neuron death and impairment.

    

     As the disease enters its final stages, the ability to recognize family members will seize to exist in addition to language skills and the ability to speak. Motor skills will begin to be executed less smoothly. Patients with AD will often live about 10 years after being diagnosed.

Traumatic Brain Injury

 Often resulting from damage to the head (blows, hits), mainly from transportation accidents, or even  violence, and taking poor care of babies, TBI’s effect the lives of about 6 million Americans every year.

    Fortunately not all TBI’s are major, for only 270,000 out of the colossal number of cases have a moderate or severe TBI. All other instances may just be mild concussions or a short blackout ranging from seconds to minutes. 

    After experiencing some form of damage to the brain, symptoms soon appear whether they are mild, or extreme. Symptoms of TBI’s include the patient not feeling like oneself, issues with memory, concentration, attention, senses and more. Those with a higher level of damage from TBI’s also experience these symptoms along with excruciating headaches, vomiting, nausea, or even seizures.

    There are many types of TBI’s but out of all of them, concussions have the least severity. Other TBI’s with a higher level of damage may come from different types of skull fractures. These occur whenever the skull cracks or breaks.

1.       Depressed skull fracture- this occurs when a piece of broken skull bone sinks into the brain causing damage of tissue.

2.       Penetrating skull fracture- as its name suggests, this is when an object penetrates the skull and plunges into the brain causing damage in a certain area/path.

    Skull fractures may cause swelling and could even break blood vessels and form blood clots. They will often cause bruising in a certain area of the tissue; these mixed with blood from broken blood vessels make up what are known as contusions. Contusions cause quite a bit of damage and often occur with the sudden back and forth movement of the head such as when a driver slams the brakes of a car after going 80 miles per hour. 

    Other conditions that skull fractures could lead to include hematoma (the heavy bleeding into or around the brain when major blood vessels break), Anoxia (the complete absence of oxygen through blood to the brain or any organ in the body), or hypoxia (a decrease in oxygen supply but not completely cut off from it).

  TBI’s may have a few consequences such as cognitive impairment (problems with thinking, deciding, and memory), problems with sensory information, a troubled time communicating, or even noticeable and major changes in behavior.

Credits: Brain Disorders Source Book - Judd, Sandra

Epilepsy

    Epilepsy is a brain disorder which effects the brain in many areas and different ways. Usually consisting of series of seizures, within the first few moments of the attack, you will lose consciousness and control of you. Twitching, falling to the floor, moving without control, drooling, and even loss of bladder control are symptoms that occur during tonic-clonic seizures, but there are many other different types of seizures which have shared and different symptoms. This disease was believed to be first described by the Babylonians some 3000 years ago, and the word epilepsy is the Greek word meaning- attack.

    Deep inside your brain are ganglia, which are clusters of interconnecting neurons and other neural cells.  When these begin to malfunction, seizures are sparked. Through the signaling, your average neuron will send 8 impulses per second, but a patient of seizure will have his/her neurons signaling 500x’s per second. And this occurs 100x’s a day for most epileptic patients. 

    Epilepsy, thankfully, is not contagious, nor caused by brain retardation. And again thankfully, most seizures do not damage the brain of those with epilepsy, and any changes to the brain caused by this disease are subtle. But there is no permanent cure for epilepsy at the moment. Many epileptics are normal people in terms of intellectuality. And 1 in 100 people will have epilepsy in their life time (2 million people in the USA). 20% of people who have epilepsy are immune to medication and suffer more than the rest 80% whose symptoms are controlled to some extent by modern medication.  Epilepsy, in most cases, is chronic; nevertheless, there is a high chance for children who spontaneously develop epilepsy, to get rid of it by the time they graduate into adulthood.

    The reason people get epilepsy are many- abnormal brain development or neural paths, to some brain diseases which cause neural cells to malfunction. Other reasons include an excessively large production of neurotransmitters, consequently, increasing neural activity to a point to where a seizure may start. And the same increase in activity of the brain occurs, in some cases, while trying to patch itself from a trauma, or a stroke. And in other cases, glia (glial cells), which affect neural processing while layering myelin (this substance speeds signaling), have known to cause epilepsy. Layering too much myelin can cause seizures. 

    Although half the occurrences of epilepsy have no known cause, researchers are looking into many different reasons trying to find solutions. Traumas, infection, and other threats to the brain.

Parkinson’s disease (PD)

    Both chronic and Progressive, Parkinson’s disease is a movement disorder which commences when dopamine producing cells, in the substantia nigra, begin to malfunction and die over time. Dopamine is a chemical messenger in your body which transmits signals to parts of the brain that coordinate and initiate movement. And in the course of one’s suffering of Parkinson’s disease, these dopamine cells are terminated for unexplained reasons. Their rate of death then picks up consequently stumping the quantity of dopamine production.

    It is estimated that 1 million or so Americans suffer from Parkinson’s, and more than 75% of those victims are diagnosed after reaching the age of 50.  Although the cause is unknown and no major cure is currently present, there are medicating and surgery options to reduce the effect of the symptoms.

    Although there are common symptoms shared by the diseased people, there are many more symptoms that vary and are different between people. The progression of the disease varies in speed between all. Some might suffer more, for their progression is rapid, while others will suffer at a lesser rate, but over a longer time when their symptom worsening is at a slow progression. Such commonly shared sympyoms consist of

1.       Constant shaking tremor of limbs, Face Muscles, and Jaw

    When the disease hasn’t developed as much in one’s brain, 7 out of 10 experience a constant tremor in their hands and legs (sometimes in the face and jaw). It is described as a “beating” movement. It is known as a resting tumor since it occurs more often when the muscle is relaxed.

This indicates that the tremor usually is present after a loss of activity. As the disease progresses more and more, so does the tremor. It will even spread to different parts of the body.

2.       Slowness of movement (Bradykinesia)

    In this symptom, your voluntary muscle movements are slowed down, and they begin to slow down drastically as the disease progresses and worsens. Many will have problems, even with having the ability to start movements. When this is added to stiffening limbs (also a symptom of Parkinson’s) the amount of times a patient stumbles or falls increases. They might even find themselves getting stuck, this is when they cannot begin or stop walking/moving.

3.       Loss of balance and coordination

4.       Stiffness in limbs and trunk

    This is a symptom that includes the stiffness of muscles or inflexibility of them. Because of  the “rigityness” of the muscles, it decreases the rate and length your muscles can stretch to, for it decreases muscle contraction and relaxation. It will even cause cramps in addition to searing pains.

    But often in PD, there are secondary symptoms that are soon to follow. Speech issues such as slurred or stuttering talking habits, a stooped posture (such as leaning forward or backwards) are all caused by a lack of muscle control. There are many more symptoms to follow. More speech changes, loss of facial expression, difficulty in swallowing/drooling, pain, dementia/confusion, constipation, skin problems, depression, fear/anxiety, memory losses/hard time thinking, loss of energy, fatigue, and even urinary problems.

    The cause of Parkinson’s is yet to be solved, chemicals, and mechanisms have been suggested to cause an increasing amount of cell death.  These include…

Oxidative damage (due to stress)

Unstable molecules whose toxic effects are believed to be caused by oxidation are theorized to contribute to cell death, consequently leading to Parkinson’s. Oxidation, in the brain, is hypothesized to cause death and increase damage in tissues. As a result, antioxidants are now to be used as an attempt to slow down the disease.

Mitochondial dysfunction

In our cells, we have small organelles known as mitochondria which break down food suplements and convert it to energy for cell usage. An increasing dysfunction of the mitochondria were found in scientific research to cause cell death to accelerate. So in this theory, scientisits are now investigating if this plays a role in Parkinson’s disease.

Excitotoxicity

Excitotoxicity is the result of an over production of neurotransmitters leading to an increase of cell death. This cause has already been found in Parkinsons’s. Finding a way to now balance the production of neurotransmitants may be able to cause less cases of the disease and slow it down.

There are also genetic factors in which it has been found that 15%-25% of all patients have relatives who have had Parkinson’s . Again, after scientific study, it has been found that there is a defective gene, uncommonly found in families to which Parkinson’s disease may be inherited. 

Other causes include environmental factors which include rural living toxins such as MPTP which cause death to dopmaine and slow down its production.

Credits: Brain disorders source book.

The Organization of the Human Nervous System

    I think of it this way. Cells. Multiple cells make up tissues. Multiple tissues make up organs and organ systems consist of multiple organs. Similarly, the nervous system is organized in the same way. Neurons and axons make up nerves, nerves make up neural circuits, and neural circuits create neural systems. Neural circuits which share similar tasks, come together to make neural systems.

  

    Such neural systems include sensory systems (observe and process information about the environments like the visual system, auditory system etc.) and the motor systems (reactions to certain input information. They include reflexes and counter balancing some moves).  Associational systems are composed of large numbers of cells and circuits which are located between both motor and sensory systems. Associational systems also carry out some of the most intricate processes and brain functions.

    As you know, the Central Nervous System (CNS) is composed of the brain (all 4 regions), and the spinal cord. And then, there is also the peripheral nervous system (PNS) which is all the cranial nerves which branch off the brain, and the many nerves which branch off the spinal cord. The PNS also includes sensory neurons which link sensory receptors (parts of sensory neurons which receive sensory information) to circuits in the CNS (missed information about neural circuits? Click here to view my previous post about them).

    The movement (motor) portion of the PNS is divided into 2 branches which both rely on one another in various ways. There is the somatic motor division which consists of nerves and axons which connect the brain and spinal cord to skeletal muscles. And, an autonomic nervous system which controls smooth muscles (which are muscles that move with conscious control ex: Biceps) and involuntary muscles. Both are crucial for survival, as they provide you, your muscle controls and gland controls to live. Without the somatic motor system, the autonomic system cannot move arms and legs, and without your autonomic system, you will need to keep remembering to execute many of your involuntary muscle movements!

    The neurons which lie within the PNS are located in ganglia which are lumps of nerve cells and supporting cells. Bundles of peripheral axons come together to make nerves, just like how thread is made of many thin fibers bundled and twisted. Those fibers are like axons. In nerves, all-around the body, lie glia. The only glia in the periphery though, are Schwann cells which lie layers of Myelin to help speed up neural messages.

In the PNS it is ganglia but in the CNS it is known as nuclei. Local accumulations of cells in the CNS are known as nuclei (not to get confused with the other meaning of nuclei – control center in most cells. Nuclei are found throughout the CNS, including the Spinal cord and division of the main area of the brain. In addition, there are cortices (cortex-singular) which are flat sheets of nerve cells. 

Tracts in the CNS consist of axons, just like those in the PNS. And those tracts that cross the midline division of the brain are called commissures. The area that contains axons, tracts, and commissures is known as white matter (named so because of its color due to its heavy content of myelin). On the other hand, gray matter is the large clumps of cell bodies and neuropil (click here for more info about neuropil). It is located in the brain and spinal cord.

Neural Circuits

Neural Circuits

  Neural Circuits have different and unique tasks that process different information and are organized and arranged in specific ways. In addition, they control our senses, moods, movement, etc. The connection format is what distinguishes the circuits. These connections are made of thick lumps of dendrites and axons and glia, which are known as neuropil.

    
    Although different, many have the same characteristics and similar ways processes are carried out. Preeminent is the direction and way that information travels in all circuits. The direction information flows is key to the distinction of the circuit.The 2 types of preeminent is afferent and efferent. Neurons that carry information from the Peripheral nervous system (PNS)(check my post about peripheral nervous system and central nervous system here for more information here) to the central nervous system are called afferent neurons, but those who carry information away from the CNS to the PNS branches, are classified as  efferent neurons. And there are 

    Interneurons (local circuit neurons) which only participate in short-distance routes which their axons extend.

    An example of a neural circuit is the myotatic spinal reflex, also known as knee-jerk reflex. Afferent and efferent play the role of the reflex. When you get your reflexes tested, you get a hammer tap test. This is what, if you have normal reflexes, triggers the knee-jerk reflex.

    So, here is how it works. The process begins after the hammer has tapped your knee. This stretches your tendon which then stretches the sensory receptors in your extensor muscles (the sensory receptor is the pink little dot on the extensor muscles in this diagram). You can see a blue line, a sensory axon, which is afferent. This axon carries the message of the hammer tap to the purple interneuron and the red motor axon. Now, the interneuron stops the yellow flexor muscle motor axon from moving the flexor muscle. Instead, the flexor muscle relaxes.

    Now, the red extensor muscles axon carries the message to the extensor muscles, which then contracts the muscle. Finally, the leg extends.
Credits: Neuroscience 4th edition