Children and Brain Development

Children and Brain Development: What We Know About How Children Learn

Like constructing a house, brains are built upon a strong foundation. This starts before birth, and is very important during the first three years of life. Brain cells are “raw” materials — much like lumber is a raw material in building a house, and a child’s experiences and interactions help build the structure, put in the wiring, and paint the walls. Heredity (nature) determines the basic number of “neurons” (brain nerve cells) children are born with, and their initial arrangement.

At birth, a baby’s brain contains 100 billion neurons, roughly as many nerve cells as there are stars in the Milky Way, and almost all the neurons the brain will ever have. The brain starts forming prenatally, about three weeks after conception. Before birth, the brain produces trillions more neurons and “synapses” (connections between the brain cells) than it needs. During the first years of life, the brain undergoes a series of extraordinary changes.

In the brain, the neurons are there at birth, as well as some synapses. As the neurons mature, more and more synapses are made. At birth, the number of synapses per neuron is 2,500, but by age two or three, it’s about 15,000 per neuron. The brain eliminates connections that are seldom or never used, which is a normal part of brain development.

“Windows of opportunity” are sensitive periods in children’s lives when specific types of learning take place. For instance, scientists have determined that the neurons for vision begin sending messages back and forth rapidly at 2 to 4 months of age, peaking in intensity at 8 months. It is no coincidence that babies begin to take notice of the world during this period.

 

illustration of a brain cell, showing cell body, axon, and dendrites

Brain Development

Scientists believe that language is acquired most easily during the first ten years of life. During these years, the circuits in children’s brains become wired for how their own language sounds. An infant’s repeated exposure to words clearly helps her brain build the neural connections that will enable her to learn more words later on. Language can be learned a multitude of ways, like casual conversation, songs, rhymes, reading, music, story telling and much more. Early stimulation sets the stage for how children will learn and interact with others throughout life. A child’s experiences, good or bad, influence the wiring of his brain and the connection in his nervous system. Loving interactions with caring adults strongly stimulate a child’s brain, causing synapses to grow and existing connections to get stronger. Connections that are used become permanent. If a child receives little stimulation early on, the synapses will not develop, and the brain will make fewer connections.

Stress can become toxic when a child has frequent or prolonged experiences like abuse, neglect or poverty without adult support. When adults are present to support a child’s experiences and help the child’s stress levels come down, stressors may be tolerable. Examples of tolerable stress include loss of a loved one, illness or injury, or poverty when a caring adult helps the child adapt. Some stresses are also thought of as positive stress, such as when there is a small amount of fear or sadness, or everyday challenges. In experiences of positive stress, the system can return to a calm state in a relatively short period of time. When children are faced with physical or emotional stress or trauma, the hormone cortisol is released when the brain sends a signal from the hypothalamus to the adrenal cortex, which is a gland above the kidney. High levels of cortisol can cause brain cells to die and reduces the connections between the cells in certain areas of the brain, harming the vital brain circuits. In other words, the wiring of the house can be severely damaged or miswired if a child is exposed to repeated and longtime stress with out the assistance of a caring adult. Babies with strong, positive emotional bonds to their caregivers show consistently lower levels of cortisol in their brains.

The Brain in Brief

Brain Structure

The brain is part of the central nervous system, and plays a decisive role in controlling many bodily functions, including both voluntary activities (such as walking or speaking) and involuntary ones (such as breathing or blinking).

The brain has two hemispheres, and each hemisphere has four lobes. Each of these lobes has numerous folds. These folds do not all mature at the same time. The chemicals that foster brain development are released in waves; as a result, different areas of the brain evolve in a predictable sequence. The timing of these developmental changes explains, in part, why there are “prime times” for certain kinds of learning and development.

Different parts of the brain control different kinds of functions. Most of the activities that we think of as “brain work,” like thinking, planning or remembering, are handled by the cerebral cortex, the uppermost, ridged portion of the brain. Other parts of the brain also play a role in memory and learning, including the thalamus, hippocampus, amygdala and basal forebrain. The hypothalamus and amygdala, as well as other parts of the brain, are also important in reacting to stress and controlling emotions.

The basic building blocks of the brain are specialized nerve cells that make up the central nervous system: neurons. The nerve cells proliferate before birth. In fact, a fetus’ brain produces roughly twice as many neurons as it will eventually need — a safety margin that gives newborns the best possible chance of coming into the world with healthy brains. Most of the excess neurons are shed in utero. At birth, an infant has roughly 100 billion brain cells.

Every neuron has an axon (usually only one). The axon is an “output” fiber that sends impulses to other neurons. Each neuron also has many dendrites — short, hair-like “input” fibers that receive impulses from other neurons. In this way, neurons are perfectly constructed to form connections.

As a child grows, the number of neurons remains relatively stable, but each cell grows, becoming bigger and heavier. The proliferation of dendrites accounts for some of this growth. The dendrites branch out, forming “dendrite trees” that can receive signals from many other neurons.

Connections among Brain Cells

At birth, the human brain is in a remarkably unfinished state. Most of its 100 billion neurons are not yet connected in networks. Forming and reinforcing these connections are the key tasks of early brain development. Connections among neurons are formed as the growing child experiences the surrounding world and forms attachments to parents, family members and other caregivers.

In the first decade of life, a child’s brain forms trillions of connections or synapses. Axons connect to dendrites, and chemicals called neurotransmitters help send messages (called “impulses”) across the resulting synapses. Each individual neuron may be connected to as many as 15,000 other neurons, forming a network of neural pathways that is immensely complex. This elaborate network is sometimes referred to as the brain’s “wiring” or “circuitry.” As the neurons mature, more and more synapses are made. At birth, the number of synapses per neuron is 2,500, but by age two or three, it’s about 15,000 synapses per neuron. This is like going from 100 to 600 friends on Facebook, and each of those friends in turn, is connected to 600 more people! The neural network expands exponentially. If they are not used repeatedly, or often enough, they are eliminated. In this way, experience plays a crucial role in “wiring” a young child’s brain. Brain development does not stop after early childhood, but it is the foundation upon which the brain continues developing. Early childhood is the time to build either a strong and supportive, or fragile and unreliable foundation. These early years are very important in the development that continues in childhood, adolescence, and adulthood.

Sources: Shonkoff, J.P., & Phillips, D.A. (Eds). (2000). From Neurons to Neighborhoods: The Science of Early Childhood Development National Academies’ Press. Retrieved from http://www.nap.edu/catalog/9824.html

Shore, R. (1997). Rethinking the Brain: New Insights into Early Development. New York, NY: Families and Work Institute, pp. 16-17.

Motor neuron disease

Motor Neuron Disease

Motor neuron diseases or motor neurone diseases (MNDs) are a group of rare neurodegenerative disorders that selectively affect motor neurons, the cells which control voluntary muscles of the body. They include amyotrophic lateral sclerosis (ALS), progressive bulbar palsy (PBP), pseudobulbar palsy, progressive muscular atrophy (PMA), primary lateral sclerosis (PLS), spinal muscular atrophy (SMA) and monomelic amyotrophy (MMA), as well as some rarer variants resembling ALS.

Motor neuron disease
Polio spinal diagram-en.svg
spinal diagram
Specialty Neurology

Motor neuron diseases affect both children and adults. While each motor neuron disease affects patients differently, they all cause movement-related symptoms, mainly muscle weakness.  Most of these diseases seem to occur randomly without known causes, but some forms are inherited. Studies into these inherited forms have led to discoveries of various genes (e.g. SOD1) that are thought to be important in understanding how the disease occurs.

Symptoms of motor neuron diseases can be first seen at birth or can come on slowly later in life. Most of these diseases worsen over time; while some, such as ALS, shorten one’s life expectancy, others do not. Currently, there are no approved treatments for the majority of motor neuron disorders, and care is mostly symptomatic.

Signs and symptoms depend on the specific disease, but motor neuron diseases typically manifest as a group of movement-related symptoms. They come on slowly, and worsen over the course of more than three months. Various patterns of muscle weakness are seen, and muscle cramps and spasms may occur. One can have difficulty breathing with climbing stairs (exertion), difficulty breathing when lying down (orthopnea), or even respiratory failure if breathing muscles become involved. Bulbar symptoms, including difficulty speaking (dysarthria), difficulty swallowing (dysphagia), and excessive saliva production (sialorrhea), can also occur. Sensation, or the ability to feel, is typically not affected. Emotional disturbance (e.g. pseudobulbar affect) and cognitive and behavioural changes (e.g. problems in word fluency, decision-making, and memory) are also seen. There can be lower motor neuron findings (e.g. muscle wasting, muscle twitching), upper motor neuron findings (e.g. brisk reflexes, Babinski reflexHoffman’s reflex, increased muscle tone), or both.

Motor neuron diseases are seen both in children and in adults. Those that affect children tend to be inherited or familial, and their symptoms are either present at birth or appear before learning to walk. Those that affect adults tend to appear after age 40. The clinical course depends on the specific disease, but most progress or worsen over the course of months. Some are fatal (e.g. ALS), while others are not (e.g. PLS).

Patterns of weakness

Various patterns of muscle weakness occur in different motor neuron diseases. Weakness can be symmetric or asymmetric, and it can occur in body parts that are distal, proximal, or both… According to Statland et al., there are three main weakness patterns that are seen in motor neuron diseases, which are:

  1. Asymmetric distal weakness without sensory loss (e.g. ALS, PLS, PMA, MMA)
  2. Symmetric weakness without sensory loss (e.g. PMA, PLS)
  3. Symmetric focal midline proximal weakness (neck, trunk, bulbar involvement; e.g. ALS, PBP, PLS)

Lower and upper motor neuron findings.

Motor neuron diseases are on a spectrum in terms of upper and lower motor neuron involvement. Some have just lower or upper motor neuron findings, while others have a mix of both. Lower motor neuron (LMN) findings include muscle atrophy and fasciculations, and upper motor neuron (UMN) findings include hyperreflexia, spasticity, muscle spasm, and abnormal reflexes.

Pure upper motor neuron diseases, or those with just UMN findings, include PLS.

Pure lower motor neuron diseases, or those with just LMN findings, include PMA.

Motor neuron diseases with both UMN and LMN findings include both familial and sporadic ALS.

6 Neurological Conditions

6 Neurological Conditions and Symptoms You Should Look Out For

people , health and stress concept – unhappy woman suffering from head ache at home

The nervous system is a complex, highly specialized network. From sight to smell and walking to speaking, our nervous system organizes, explains and connects us to the world around us.

When something goes wrong with a part of the nervous system, however, it can cause a neurological disorder. Neurological disorders affect millions of people each year, yet many people may be unaware they have one.

Understanding symptoms of neurological disorders is important, as it can lead you to an appropriate diagnosis and treatment. Here are six common neurological disorders and ways to identify each one.

1. Headaches

Headaches are one of the most common neurological disorders and can affect anyone at any age. While many times a headache shouldn’t be anything too serious to worry about, if your headache comes on suddenly and repeatedly, you should see a doctor, as these could be symptoms of an underlying condition.

“The sudden onset of severe headache as well as headache associated with a fever, light sensitivity and stiff neck are all red flags of something more serious such as intracranial bleeding or meningitis,” Dr. Chrisman said. “If your headaches are happening often and you find yourself taking over-the-counter pain medication frequently, this is also an indication you need medical attention.”

Although headache disorders like tension-type headaches and migraines aren’t life-threatening, dealing with chronic pain can be debilitating. There are many treatment options available today for headache disorders that can help you get back to a more normal life.

2. Epilepsy and Seizures

Epilepsy is a common neurological disorder involving abnormal electrical activity in the brain that makes you more susceptible to having recurrent, unprovoked seizures. “Unprovoked means the seizure cannot be explained by exposure to or withdrawal from drugs or alcohol, as well as not due to other medical issues such as severe electrolyte abnormalities or very high blood sugar,” Dr. Chrisman said.

The tricky part is that if you have one seizure in your life, it doesn’t necessarily mean you have epilepsy. But, if you have two or more, it may be epilepsy. Seizure symptoms can vary depending on where in the brain the seizure is coming from. After experiencing a seizure, it’s important to see your doctor. There are many effective treatments to manage epilepsy that can result in seizure-freedom, usually medication. “In the appropriate patient, treatment may include epilepsy surgery, which involves removing the seizure focus in the brain, and that can be curative,” Dr. Chrisman said.

3. Stroke

Strokes, which affect nearly 800,000 Americans each year, “are one of the most crucial neurological disorders to be aware of due to the severity of potential symptoms and resulting disability that can occur,” Dr. Chrisman cautioned.

A stroke is usually due to a lack of blood flow to the brain, oftentimes caused by a clot or blockage in an artery. Many interventions can be done to stop a stroke these days, but time is brain (not money) in this case. The B.E. F.A.S.T. mnemonic is helpful to remember to recognize the signs of a stroke: B: Balance difficulties; E: Eyesight changes; F: Face weakness; A: Arm weakness; S: Speech; and T: Time. These signs and symptoms don’t always mean someone is having a stroke, but it’s very important to call 911 and get help right away, just to be sure.

Identify your risk factors for stroke and ways to improve them by visiting our Stroke Risk Profiler.

4. ALS: Amyotrophic Lateral Sclerosis

ALS, also known as Lou Gehrig’s disease, is a somewhat rare neuromuscular condition that affects the nerve cells in the brain and spinal cord. Doctors are unsure what exactly causes ALS, but factors that may cause ALS include genetics and environmental factors.

Symptoms include muscle weakness and twitching, tight and stiff muscles, slurred speech, and difficulty breathing and swallowing. Unfortunately, this condition is difficult to diagnose and often requires the evaluation of a neuromuscular neurologist.

“There is usually a delay in diagnosis for this condition of about one year, on average, by the time the patient gets to the neuromuscular specialist and receives the correct diagnosis,” Dr. Chrisman said. “Although there is no cure, there are treatments, and it’s important to start these as early as possible.”

Read: 10 Foods for Brain

5. Alzheimer’s Disease and Dementia

Memory loss is a common complaint, especially in older adults. A certain degree of memory loss is a normal part of aging. For example, walking into a room and forgetting why may be totally normal.

However, there are signs that may indicate something more serious, such as dementia or Alzheimer’s disease. These symptoms may include getting lost, having difficulty managing finances, difficulties with activities of daily living, leaving the stove on, forgetting the names of close family and friends or problems with language. Behavioral changes along with these memory changes could also raise concerns.

Dementia is a slowly progressive condition and should be evaluated by a neurologist. While there is no cure, there are medications and therapies that can help manage symptoms.

6. Parkinson’s Disease

Parkinson’s disease is a progressive nervous system disorder that primarily affects coordination. Generally, it becomes more common as you age, impacting nearly one million Americans. Currently, there is no cure for Parkinson’s disease, but many treatment options are available.

Why do we Yawn

Why do we yawn and why is yawning contagious?

Just imagine: you’re driving down the highway at 2pm in the heat of the day, and you’re really looking forward to getting to your destination soon. You try to stay awake but drowsiness strikes.

As a result you yawn and then sit up straighter in the driver’s seat, perhaps you’re a little restless and act out in hopes of increasing your arousal.

Is this what people yawn for? Yawning is generally triggered by several things, including fatigue, fever, stress, medications and social and psychological reasons. From one person to another the causes are different.

The question of why we yawn raises a surprising amount of controversy over such a trivial matter. We have no evidence to point us to the exact reason why people yawn.

But there are several theories that explain why people yawn. These include increasing alertness, cooling the brain, and evolutionary theory explains that yawning is to remind others in your group that you are too tired to stay alert, and that someone else should take over.

1. Help us wake up

Yawning comes with increasing drowsiness. This is the hypothesis behind why people yawn. Yawning is also associated with increased activity and stretching movements. Increased body movement may help us stay alert when the pressure of drowsiness increases.

 

Also, certain muscles in the ear ( tensor tympani muscle ) are activated during yawning. This triggers a reset of the range of motion and sensitivity of the eardrum and hearing, which increases our ability to monitor the world around us after we may have lost consciousness before yawning.

Yawning is usually accompanied by stretching movements. from shutterstock.com

In addition, opening the eyeball and flushing the lens of the eye may result in increased visual alertness.

Read: Protect Your Mental Health from Social Media

2. Cools the brain

Another theory as to why we yawn is the thermoregulatory hypothesis which suggests that yawning cools the brain. Yawning draws cold air into the mouth, which then cools the blood to the brain.

Proponents of this theory claim the increase in brain temperature occurs before yawning, with the decrease in temperature occurring after yawning.

But the research that gave rise to this theory only shows that excessive yawning occurs when brain and body temperatures are increasing. The research doesn’t say that yawning has a cooling purpose.

People yawned more frequently when experiments created artificial fevers, which showed a correlation between warm body temperature and yawning. But there’s no evidence to suggest that yawning cools the body—only that a warm body temperature triggers yawning.

3. Guard duty

Yawn-like behavior has been observed in almost all vertebrates. These observations suggest that the yawning reflex is ancient. The behavioral hypothesis based on the theory of evolution refers to humans as social animals. When we are vulnerable to attacks from other species, the function of groups is to protect each other.

Watchkeeping is part of the deal within the group, and yawning and stretching are evidence when an individual’s alertness level is dropping. It is important to change activities to prevent negligence and indicate when to change people just in case.

Neuroscience explanation

The yawning reflex involves many structures in the brain.

A study that looked at the brains of people prone to yawning found activity in the ventromedial prefrontal cortex of the brain. This part of the brain is associated with decision-making activities. Damage to this area is also associated with a loss of empathy.

 

If a certain area around the hypothalamus , which is made up of neurons with oxytocin, is stimulated, in rodents this causes them to yawn. Oxytocin is a hormone associated with social bonding and mental health.

Injecting oxytocin into different regions of the brainstem also causes yawning. These include the hippocampus (associated with learning and memory), the ventral tegmental area (associated with the release of dopamine, the happy hormone) and the amygdala (associated with stress and emotions). Blocking the oxytocin receptors here prevents that effect.

Patients with Parkinson’s disease don’t yawn as often as others, which may be related to their low dopamine levels. Dopamine substitutes have been reported to increase yawning frequency .

Your dog may yawn on a long car trip because your dog is stressed. from shutterstock.com

The same is true of cortisol, a hormone that increases stress. Cortisol is known to trigger people to yawn , while removal of the adrenal glands (which produce the hormone cortisol) prevents people from yawning . This suggests that stress levels may play a role in triggering why people yawn, which could be why your dog may yawn so much on long car trips.

So, it seems that yawning is somehow linked to empathy, stress, and the release of dopamine.

Why is yawning contagious?

Chances are you’ve yawned at least once while reading this article. Yawning is a contagious behavior and seeing someone yawn often causes us to yawn too.

But the only theory offered here suggests that a person’s vulnerability to yawning is correlated with a person’s level of empathy.

It’s interesting to note that people on the autism spectrum are less likely to catch yawns than people with high psychopathic tendencies . And dogs, which are considered to be highly empathetic animals, can get infected when humans yawn .

 

Overall, neuroscientists have developed ideas that explain the various triggers why people yawn, and we have a very detailed picture of the mechanisms underlying yawning behavior. But the purpose of why people yawn remains elusive.

Back in our road trips, yawning may be a physiological cue when levels of self-awareness compete with intense drowsiness. But the important message here is that sleep may be a good choice and encourage drivers to stop and rest, and that should not be ignored.

Protect your Mental Health from Social Media

Six ways to protect your mental health from the dangers of social media

A  psychologist who studies the dangers of online interactions and observes the effects of (wrong) social media use on the lives of my clients , here are six suggestions for reducing the harm social media can do to mental health.

1. Limit the time and place you use social media

Using social media can affect direct communication with others . By turning off social media notifications or turning on airplane mode at a certain time each day, you can better relate to others. For example, not checking social media when eating with family and friends, when playing with children, to talking to a partner. Avoid social media so as not to interrupt work or distract from conversations with colleagues. Special advice, don’t keep your phone or computer in the bedroom, because it will disturb your sleep .

2. Schedule a ‘detox’ period

Several studies have shown that a social media ‘detox’ or a five-day to a week ‘pause’ from Facebook can reduce stress levels and increase life satisfaction . So start scheduling a daily break from social media for a few days.

Reduction doesn’t have to be so extreme that it makes you uncomfortable not being able to access social media, for example using Facebook, Instagram, and Snapchat for 10 minutes a day for three weeks can lead to less loneliness and depression . It may be difficult at first, but you can ask family and friends for support by saying you’re “detoxifying” on social media. Another thing that can be done is to delete your favorite social media apps.

3. Watch what you do and how you feel

Try using your favorite online platforms at different times and durations of the day to see how you feel then and after. You may find that using social media for a short amount of time will help you feel better than spending 45 minutes going through a site’s entire feed in depth.

If you feel like you’re wasting your energy on Facebook every midnight that leads to bad feelings about yourself, don’t go to the page after 10 p.m.

It should be noted that people who passively use social media, just looking at other people’s posts, feel worse than people who actively use social media , posting about themselves and interacting with others online. It’s better to focus on online interactions with people you know offline.

Read: Why Do We Yawn

4. Use social media mindfully: why am I doing this?

If opening Twitter has become the first thing you do in the morning, is it because you want to know the latest news or just a habit as an escape to face a new day? Do you prefer viewing posts on Instagram instead of doing a difficult task at work? Answer this question honestly with yourself. When reaching for the phone (or computer) to check social media, answer this question: why am I doing this now? Decide if this is indeed what you should do.

5. Crop

Over time, many people or organizations you follow on social media. Some of the content is interesting to look at, but there’s a lot that will be boring, annoying, annoying or it could be worse. It’s time to stop following (unfollow) , mute (mute) , or hide your contacts (hide) . They won’t notice if you ‘cut’ social media. As a result, your life will be better.

This is revealed in a recent study of how information about the lives of Facebook friends can affect people more negatively than any other content on Facebook. Meanwhile, content filled with inspirational stories actually creates feelings of gratitude, vitality, and admiration . Cutting out a few “friends” and adding a few motivating or funny sites tends to lessen the negative effects of social media.

6. Social media is not a substitute for real life

It’s good to use Facebook to find out how your cousin has just given birth, but don’t put off a visit after months. Tweeting with colleagues can be interesting and fun, as long as the interaction doesn’t replace direct communication with them.

When used with mindfulness and consideration, social media is a useful addition to your social life. However, only the person sitting across from you can satisfy the basic human need for a sense of connectedness and self-existence.

10 Foods for Healthy Brain

You are what you eat. While you may not literally transform into the things you eat, your nutritional choices certainly play an important role in your overall health. Not only that, but there are certain foods that can even help to maintain or improve the health of your brain. Eating the right foods to keep your brain healthy can dramatically decrease your risk of developing neurological problems later in life. Here are some of the best foods for your brain:

Blueberries

Blueberries contain a compound that has both anti-inflammatory and antioxidant effects. This means that blueberries can reduce inflammation, which reduces the risk of brain aging and neurodegenerative disease. Furthermore, antioxidants have also been found to aid in communication between brain cells.

hard boiled eggs against a grey wooden background

Eggs

Eggs are rich in B vitamins and a nutrient called choline. B vitamins help to slow cognitive decline and deficiencies in B vitamins have been associated with depression and dementia. The body uses choline to create the neurotransmitters responsible for mood and memory.

Fatty Fish

Fish such as trout, salmon, and sardines contain large amounts of omega-3 fatty acids. Not only is 60% of your brain composed of fat containing omega 3s, but it is also essential in the production of brain and nerve cells. Deficiencies in omega 3s can cause learning problems and depression.

Fruits

Certain fruits such as oranges, bell peppers, guava, kiwi, tomatoes, and strawberries, contain high amounts of vitamin C. Vitamin C helps prevent brain cells from becoming damaged and supports overall brain health. In fact, a study found that vitamin C can potentially prevent Alzheimer’s.

A variety of leafy greens such as brocolli, brussel sprouts, kale, parsley, lettuce, and spinach

Leafy Greens

Leafy greens such as broccoli, collards, spinach, and kale contain various nutrients such as vitamin K, lutein, folate, and beta carotene. Vitamin K helps with the formation of fat inside brain cells and has been seen to improve memory.

Nuts

Nuts contain healthy fats, antioxidants, and vitamin E, which have been found to be beneficial for both the brain and heart. Walnuts, in particular, also contain omega-3 fatty acids to further improve brain function essayswriting.org/. In fact, nuts have been linked to improved cognition, sharper memory, and slower mental decline.

Pumpkin Seeds

Pumpkin seeds contain antioxidants, as well as zinc, magnesium, copper, and iron. The brain uses zinc for nerve signaling, magnesium for learning and memory, copper for controlling nerve signals, and iron to prevent brain fog.

Tea and Coffee

Both tea and coffee contain caffeine, which boosts brain function and improves alertness, as well as antioxidants. Green tea also contains the amino acid L-theanine which can cross the blood-brain barrier and increase neurotransmitter activity.

Turmeric powder

Turmeric

Turmeric is a dark-yellow spice that is commonly found in curry powder. Not only is it a strong antioxidant and anti-inflammatory substance, but it can pass through the blood-brain barrier to enter the brain directly. Tumeric has been associated with improved memory, less depression, and the growth of new brain cells.

Whole Grains

Whole grains such as bread, pasta, barley, brown rice, oatmeal, and bulgur wheat contain vitamin E, which is used to protect and preserve healthy cells. In protecting these cells, vitamin E preserves brain function and prevents neurodegeneration.

Read: 6 Neurogical Conditions

Neurons & Neurotransmission

We have all experienced the reflex reaction when we accidentally touch something hot. But did you know how fast the nerve impulse that conducts this response is? It is estimated that the speed of a neural impulse can reach up to 120 meters/second or 268 miles/hour! That is much faster than the top speed of any of our cars, unless one of us is lucky enough to own a supercar like the one below. Impressive isn’t it?

 

Records of studying the nervous system dates back to Egyptian manuscripts from 1700 BC. However, major breakthrough discoveries were made in the field of Neuroscience in the late 19th century, and finally in 1906, Golgi and Ramón y Cajal shared the Nobel Prize in Physiology or Medicine in recognition of their work on the structure of the nervous system. A neuron, or a nerve cell, is one of the two main components of the central nervous system (glial cells are the other type).

Unlike other cells in the body, a neuron is a specialized cell (with great powers!) that is capable of conducting electrical and chemical signals in a process known as neurotransmission. A typical neuron is divided into three parts: the soma or cell body, dendrites and axon. While there are as many as 10,000 different types of neurons in the human brain, they can be broadly classified into three types: motor neurons (for conveying motor information), sensory neurons (for transmitting sensory information), and interneurons (which convey information between different types of neurons).

 

 

Synapses are the junctions where neurons pass signals to other neurons, muscle cells, or gland cells. Synaptic signals from other neurons can be received either by the soma, dendrite or axon, whereas signals to other neurons are transmitted only by the axon. The typical synaptic cleft (cell-to-cell distance) can vary between 3.5 nm to 40 nm (compare that to the thickness of your hair which is more than 250 times wider!). Thus the nervous system is wired by numerous neurons interconnected by synapses in a super-complicated neuronal circuit. It is estimated that the human brain alone contains around one hundred billion neurons and one hundred trillion synapses!
There are two main types of synapses, chemical and electrical. Electrical synapse is an electrical connection between neurons through structures known as gap junctions. Gap junctions are intercellular channels that allow ions and small molecules to pass directly from one cell to the other. On the other hand, in a chemical synapse, signals are transmitted via release of neurotransmitters (that are packed in synaptic vesicles in the presynaptic neuron) into the synaptic cleft. Binding of the neurotransmitters to receptors in the postsynaptic membrane causes activation of this cell through the post synaptic density (a protein dense signaling apparatus). Depending on the type of effect the neurotransmitter has on the postsynaptic cell, a chemical synapse can either be excitatory or inhibitory.

The fundamental process that triggers the release of neurotransmitters is the action potential, which is an electrochemical wave that travels along the axon of a neuron when there is a change in the membrane potential. Neurons maintain a steady resting voltage gradient (typically from –70 to –80 millivolts) across their membranes via ion channels and ion pumps.

In response to an external stimulus, when enough voltage-dependent positive ion channels such as sodium or calcium channels are activated, they allow a net inward sodium or calcium current which depolarizes the cell to a threshold potential above the resting potential and this triggers the neuron to fire. Eventually, the sodium/calcium channels inactivate and the potassium/chloride channels are activated which results in an outward current of positively charged potassium ions/inward current of negatively charged chloride ions causing the neuron to repolarize and hyperpolarize and ultimately return to the resting state.

Neuron Fun Fact

Neurons are cells within the nervous system that transfer info to other nerve cells, muscle, or gland cells. Most neurons have a cell body, an axon, and dendrites. The cell body includes the nucleus and cytoplasm. The axon extends from the cell body and often gives rise to many smaller branches before ending at nerve terminals. Dendrites extend from the neuron cell body and receive messages from other neurons. Synapses are the contact points where one neuron communicates with another. The dendrites are covered with synapses formed by the ends of axons from other neurons.

Read : Sensory Neuron

The brain is what it is because of the structural and functional properties of interconnected neurons. The mammalian brain consists of between 100 million and 100 billion neurons, depending on the species. Each mammalian neuron contains a cell body, dendrites, and an axon.

The cell body contains the nucleus and cytoplasm. The axon extends from the cell body and often gives rise to many smaller branches before ending at nerve terminals.

Dendrites extend from the neuron cell body and receive messages from other neurons. Synapses are the contact points where one neuron conveys with another. The dendrites are covered with synapses formed by the ends of axons from other neurons.

 

When neurons receive or send messages, they transmit electrical impulses along their axons, which can range in length from a tiny fraction of an inch (or centimeter) to three feet (about one meter) or more. Many axons are covered with a layered myelin sheath, which accelerates the transmission of electrical signals along the axon. This sheath is made by specialized cells called glia. In the brain, the glia that make the sheath are called oligodendrocytes, and in the peripheral nervous system, they are known as Schwann cells.

The brain consists of at least ten times more glia than neurons. Glia perform many jobs. Researchers have known for a while that glia transport nutrients to neurons, clean up brain debris, digest parts of dead neurons, and help hold neurons in place. Current research is uncovering important new roles for glia in brain function.

Sensory Neuron

Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The cell bodies of the sensory neurons are located in the dorsal ganglia of the spinal cord.

The sensory information travels along afferent nerve fibers in a sensory nerve, to the brain via the spinal cord. The stimulus can come from exteroreceptors outside the body, for example those that detect light and sound, or from interoreceptors inside the body, for example those that are responsive to blood pressure or the sense of body position.

Centra nervous syatem

Types and Function

Different types of sensory neurons have different sensory receptors that respond to different kinds of stimuli. There are at least six external and two internal sensory receptors:

  1. External receptors 

External receptors that respond to stimuli from outside the body are called exteroreceptors. Exteroreceptors include olfactory receptors (smell), taste receptorsphotoreceptors (vision), hair cells (hearing), thermoreceptors (temperature), and a number of different mechanoreceptors (stretch, distortion).

Smell

The sensory neurons involved in smell are called olfactory sensory neurons. These neurons contain receptors, called olfactory receptors, that are activated by odor molecules in the air. The molecules in the air are detected by enlarged cilia and microvilli.

These sensory neurons produce action potentials. Their axons form the olfactory nerve, and they synapse directly onto neurons in the cerebral cortex (olfactory bulb). They do not use the same route as other sensory systems, bypassing the brain stem and the thalamus. The neurons in the olfactory bulb that receive direct sensory nerve input, have connections to other parts of the olfactory system and many parts of the limbic system.

Taste

Similarly to olfactory receptorstaste receptors (gustatory receptors) in taste buds interact with chemicals in food to produce an action potential.

Vision

Photoreceptor cells are capable of phototransduction, a process which converts light (electromagnetic radiation) into electrical signals. These signals are refined and controlled by the interactions with other types of neurons in the retina. The five basic classes of neurons within the retina are photoreceptor cellsbipolar cellsganglion cellshorizontal cells, and amacrine cells.

The basic circuitry of the retina incorporates a three-neuron chain consisting of the photoreceptor (either a rod or cone), bipolar cell, and the ganglion cell. The first action potential occurs in the retinal ganglion cell. This pathway is the most direct way for transmitting visual information to the brain. There are three primary types of photoreceptors: Cones are photoreceptors that respond significantly to color. In humans the three different types of cones correspond with a primary response to short wavelength (blue), medium wavelength (green), and long wavelength (yellow/red). Rods are photoreceptors that are very sensitive to the intensity of light, allowing for vision in dim lighting.

The concentrations and ratio of rods to cones is strongly correlated with whether an animal is diurnal or nocturnal. In humans, rods outnumber cones by approximately 20:1, while in nocturnal animals, such as the tawny owl, the ratio is closer to 1000:1.  Retinal ganglion cells are involved in the sympathetic response. Of the ~1.3 million ganglion cells present in the retina, 1-2% are believed to be photosensitive.

Different kinds of neurons. structure of a typical neuron

Problems and decay of sensory neurons associated with vision lead to disorders such as:

  • Macular degeneration – degeneration of the central visual field due to either cellular debris or blood vessels accumulating between the retina and the choroid, thereby disturbing and/or destroying the complex interplay of neurons that are present there.
  • Glaucoma – loss of retinal ganglion cells which causes some loss of vision to blindness.
  • Diabetic retinopathy – poor blood sugar control due to diabetes damages the tiny blood vessels in the retina.

Auditory

The auditory system is responsible for converting pressure waves generated by vibrating air molecules or sound into signals that can be interpreted by the brain.

This mechanoelectrical transduction is mediated with hair cells within the ear. Depending on the movement, the hair cell can either hyperpolarize or depolarize. When the movement is towards the tallest stereocilia, the Na+ cation channels open allowing Na+ to flow into cell and the resulting depolarization causes the Ca++ channels to open, thus releasing its neurotransmitter into the afferent auditory nerve. There are two types of hair cells: inner and outer. The inner hair cells are the sensory receptors .

Problems with sensory neurons associated with the auditory system leads to disorders such as:

  • Auditory processing disorder – Auditory information in the brain is processed in an abnormal way. Patients with auditory processing disorder can usually gain the information normally, but their brain cannot process it properly, leading to hearing disability.
  • Auditory verbal agnosia – Comprehension of speech is lost but hearing, speaking, reading, and writing ability is retained. This is caused by damage to the posterior superior temporal lobes, again not allowing the brain to process auditory input correctly.

Temperature

Thermoreceptors are sensory receptors, which respond to varying [temperature]s. While the mechanisms through which these receptors operate is unclear, recent discoveries have shown that mammals have at least two distinct types of thermoreceptors. The bulboid corpuscle, is a cutaneous receptor a cold-sensitive receptor, that detects cold temperatures. The other type is a warmth-sensitive receptor.

Read; Neuron Fun Fact

Mechanoreceptors

Mechanoreceptors are sensory receptors which respond to mechanical forces, such as pressure or distortion.

Specialized sensory receptor cells called mechanoreceptors often encapsulate afferent fibers to help tune the afferent fibers to the different types of somatic stimulation. Mechanoreceptors also help lower thresholds for action potential generation in afferent fibers and thus make them more likely to fire in the presence of sensory stimulation.

Some types of mechanoreceptors fire action potentials when their membranes are physically stretched.

Proprioceptors are another type of mechanoreceptors which literally means “receptors for self”. These receptors provide spatial information about limbs and other body parts.

Nociceptors are responsible for processing pain and temperature changes. The burning pain and irritation experienced after eating a chili pepper (due to its main ingredient, capsaicin), the cold sensation experienced after ingesting a chemical such as menthol or icillin, as well as the common sensation of pain are all a result of neurons with these receptors.

Problems with mechanoreceptors lead to disorders such as:

  • Neuropathic pain – a severe pain condition resulting from a damaged sensory nerve 
  • Hyperalgesia – an increased sensitivity to pain caused by sensory ion channel, TRPM8, which is typically responds to temperatures between 23 and 26 degrees, and provides the cooling sensation associated with menthol and icillin.
  • Phantom limb syndrome – a sensory system disorder where pain or movement is experienced in a limb that does not exist.2. Internal receptorsInternal receptors that respond to changes inside the body are known as interoceptors.
  • Blood

    The aortic bodies and carotid bodies contain clusters of glomus cells – peripheral chemoreceptors that detect changes in chemical properties in the blood such as oxygen concentration. These receptors are polymodal responding to a number of different stimuli.

    Nociceptors

    Nociceptors respond to potentially damaging stimuli by sending signals to the spinal cord and brain. This process, called nociception, usually causes the perception of pain. They are found in internal organs as well as on the surface of the body to “detect and protect”. Nociceptors detect different kinds of noxious stimuli indicating potential for damage, then initiate neural responses to withdraw from the stimulus.

    • Thermal nociceptors are activated by noxious heat or cold at various temperatures.
    • Mechanical nociceptors respond to excess pressure or mechanical deformation, such as a pinch.
    • Chemical nociceptors respond to a wide variety of chemicals, some of which signal a response. They are involved in the detection of some spices in food, such as the pungent ingredients in Brassica and Allium plants, which target the sensory neural receptor to produce acute pain and subsequent pain hypersensitivity.

    Connection with the central nervous system

    Information coming from the sensory neurons in the head enters the central nervous system (CNS) through cranial nerves. Information from the sensory neurons below the head enters the spinal cord and passes towards the brain through the 31 spinal nerves. The sensory information traveling through the spinal cord follows well-defined pathways. The nervous system codes the differences among the sensations in terms of which cells are active.

Cholinergic Basal Forebrain Neurons

The integrity of cholinergic basal forebrain neurons depends on expression of Nkx2-1  categories:

The transcription factor Nkx2-1 belongs to the homeobox-encoding family of proteins that have essential functions in prenatal brain development. Nkx2-1 is required for the specification of cortical interneurons and several neuronal subtypes of the ventral forebrain. Moreover, this transcription factor is involved in migratory processes by regulating the expression of guidance molecules. Interestingly, Nkx2-1 expression was recently detected in the mouse brain at postnatal stages.

Using two transgenic mouse lines that allow prenatal or postnatal cell type-specific deletion of Nkx2-1, we show that continuous expression of the transcription factor is essential for the maturation and maintenance of cholinergic basal forebrain neurons in mice. Notably, prenatal deletion of Nkx2-1 in GAD67-expressing neurons leads to a nearly complete loss of cholinergic neurons and parvalbumin-containing GABAergic neurons in the basal forebrain.

We also show that postnatal mutation of Nkx2-1 in choline acetyltransferase-expressing cells causes a striking reduction in their number. These degenerative changes are accompanied by partial denervation of their target structures and results in a discrete impairment of spatial memory.

Article by: Lorenza Magno, Oliver Kretz, Bettina Bert, Sara Ersözlü, Johannes Vogt, Heidrun Fink, Shioko Kimura, Angelika Vogt, Hannah Monyer, Robert Nitsch and Thomas Naumann.

Read the full article on Wiley Online Library.