NeuroExplorer

Glycolysis can be divided into two phases: the energy investment phase and the energy payoff phase. The energy investment phase requires an input of two molecules of ATP. In the energy payoff phase (a continuation of the energy investment phase), four molecules of ATP are produced for a net total of two ATP during glycolysis.  The steps of the energy payoff phase are explained below. Notice that all of the steps are catalyzed by enzymes. The enzyme triose phosphate dehydrogenase  catalyzes the oxidation of G3P. Electrons are transferred from G3P to NAD+, forming NADH. Using the energy from this exergonic redox reaction, a phosphate group is attached to the oxidized product, forming 1, 3-biphosphoglycerate . The enzyme phosphoglycerokinase  catalyzes the transfer of a phosphate group from  1, 3-biphosphoglycerate  to ADP, forming ATP. This process is known as substrate-level phosphorylation. Phosphoglyceromutase  (an enzyme) relocates the remaining phosphate group, forming 2-phosphogly

Organic chemistry is the study of molecules containing the element carbon. Carbon is one of the most important elements in living things as it makes up the backbones of many molecules. There are some prefixes that you should know that indicate the number of carbons in a molecule. Meth- indicates one carbon, eth-  indicates two, prop-  indicates three, but-  is four, pent-  is five and hex-  is six. For example, methane has one carbon, ethane has two, propane has three, butane has four, a pentose sugar has five carbons and a hexose has six. A helpful mnemonic to remember these prefixes: meat eaters prefer buttered, peppered ham.                                                                                                                      ________ Image Credit: (1) Robson, Greg. “Carbon.” Wikimedia Commons, upload.wikimedia.org/wikipedia/commons/thumb/b/b3/Electron_shell_006_Carbon_-_no_label.svg/600px-Electron_shell_006_Carbon_-_no_label.svg.png.

Erwin Chargaff was a biochemist who analyzed the base compositions of DNA. His findings became known as Chargaff's rules, which will be explained later. To understand his rules, it is important to first understand DNA structure. DNA consists of units called nucleotides, which are made of three components: a nitrogen-containing (nitrogenous) base, a phosphate group, and the deoxyribose sugar. There are four types of bases: adenine (A), thymine (T), cytosine (C) and guanine (G). Erwin Chargaff made an interesting discovery about the ratio of nitrogenous bases; the number of adenines approximately equaled the number of thymines and the number of cytosines equaled the number of guanines. This discovery constitutes his first rule: 1) For each species, the percentages of A and T bases are equal, as are those of C and G bases. Chargaff also conducted research regarding the base concentrations among different species. His findings led to his second rule: 2) DNA base compositions vary betwe

Glycolysis is the first step of cellular respiration in which glucose, a six-carbon sugar, is split into two different three-carbon sugars. The three-carbon sugars are then oxidized and rearranged to form two molecules of pyruvate (an ionized form of pyruvic acid). There are two phases in glycolysis: the energy investment phase and the energy payoff phase. The energy investment phase requires an input of two molecules of ATP. In the energy payoff phase, four molecules of ATP are produced for a net total of two ATP during glycolysis. The steps of the energy investment phase are explained below. Notice that all of the steps are catalyzed by enzymes. The enzyme hexokinase  catalyzes the transfer of a phosphate group from ATP to glucose, releasing ADP in the process. Glucose becomes glucose 6-phosphate, which is more chemically reactive than glucose. It is trapped in the cell because its phosphate group carries a negative charge. The enzyme phosphoglucoisomerase  converts glucose 6-phospha

Linear electron flow produces ATP and NADPH through a series of reactions that occur in the photosystems embedded in the thylakoid membranes of chloroplasts. Cyclic electron flow is the alternative mechanism to linear electron flow that only produces ATP. Cyclic electron flow is a short circuit that only uses PSI, not PSII. Electrons cycle back from ferredoxin (in the second transport chain) to the cytochrome complex (in the first transport chain). They then travel via the plastocyanin molecule to the P700 chlorophyll in the PSI reaction center complex. By traveling along the 1st transport chain, an electrochemical gradient is produced, which then powers the production of ATP by chemiosmosis. However, there is no NADPH produced because electrons are not transferred to NADP+ via the enzyme NADP+ reductase.

Linear electron flow is the process that produces ATP and NADPH during the light reactions of photosynthesis. These products are then used for the next process, the Calvin cycle . Linear electron flow occurs in the photosystems that are embedded in the thylakoid membrane within a chloroplast. There are two photosystems (PSI and PSII), each made of a reaction-center complex surrounded by a light-harvesting complex , both of which will be discussed later. Photosystem II actually comes before photosystem I (they were named in order of discovery). The following steps describe linear electron flow in detail. A photon of light strikes the light-harvesting complex of photosystem II (PSII). The light-harvesting complex consists of various pigment molecules (e.g. chlorophyll a , chlorophyll b, and carotenoids) bound to proteins. The photon of light boosts an electron to a higher energy state. As it falls back to the ground state, it releases energy. This energy is then passed along to the ne

The Calvin cycle is a stage of photosynthesis that occurs during the light-independent reactions. This process allows autotrophs to convert carbon dioxide into sugar (an anabolic process). This sugar is not glucose; it is a three-carbon sugar known as glyceraldehyde 3-phosphate (G3P). Three turns of the cycle produce a net total of one molecule of G3P; therefore, three molecules of CO2 are required. The net synthesis of one G3P also requires nine ATP molecules and six NADPH molecules. The ATP and NADPH are produced during the light-dependent reactions. The Calvin cycle can be divided into three phases: carbon fixation, reduction and regeneration. Carbon Fixation A molecule of carbon dioxide is incorporated into a five-carbon sugar known as RuBP (ribulose bisphosphate). This step is catalyzed by the enzyme rubisco, short for RuBP carboxylase-oxygenase. It forms a six-carbon intermediate which is energetically unstable, so it splits in half to form two molecules of 3-phosphoglycerate. Re

The electron transport chain of cellular respiration is a series of molecules embedded within the inner mitochondrial membrane of a eukaryotic cell's mitochondria. Most of the molecules (electron carriers) are proteins with a tightly bound prosthetic group (a nonprotein component essential for enzymatic function). The molecules exist in multiprotein complexes numbered I to IV. The electron transport chain carries out a series of redox reactions that creates an electrochemical gradient, which then powers the production of ATP by chemiosmosis. A redox reaction occurs as the electron carriers transition from oxidized to reduced states by accepting electrons and then donating them to their neighbors. It is important to note that electronegativity (the measure of a molecule's attraction to electrons) increases as electrons progress through the chain. In other words, the first electron carrier is the least electronegative, and the last electron carrier is the most electronegative.

Biology is the only subject where multiplication is the same as division.

Huntington's Disease (HD) is a neurological disorder that impairs voluntary movement and cognition. Adult onset of the disease is usually in the 30s and 40s, but HD can occur in juveniles. Juvenile HD patients usually die 10 to 15 years after their symptoms appear. Huntington's Disease causes changes in mood, impaired cognition, and motor symptoms (such as chorea , small involuntary movements). Huntington's disease affects the basal ganglia and the cerebral cortex. Huntington's disease can be traced to genetics. It is caused by a dominant inheritance for a mutation of the  huntingtin (HTT) gene  located on chromosome 4, which codes for the huntingtin protein . The mutation involves an abnormal amount of repeats for a three-part snippet of DNA. Normally, people have 10 to 35 repeats of the sequence CAG (cytosine, adenine, guanine). HD patients, however, can have 36 to 120 of these repeats, known as a trinucleotide repeat . Potential HD biomarkers

Epilepsy is a condition characterized by seizures that result from irregular activity in brain cells. These seizures can last for five minutes or more. Most people associate seizures with collapsing, shaking, and losing consciousness. However, some seizures are milder and include staring spells or rapid blinking. Epileptic seizures are classified by their location in the brain.     Generalized seizures  affect both sides of the brain. They include: Absence or petit-mal   seizures cause rapid blinking or a few seconds of staring into space Tonic-clonic or grand-mal   seizures cause muscle spasms, loss of consciousness or suddenly crying out  Local or partial seizures  are localized to one area of the brain. They include Simple focal seizures  cause twitching or changes in sensation Complex focal seizures  can leave a person confused and unable to follow directions. There are also secondary generalized seizures , which begin as focal seizures and then spread to th

Deep brain stimulation (DBS) is a surgical procedure used for patients who do not respond to medication. This technique can be used for patients with neurological disorders, such as Parkinson's disease , to reduce symptoms such as tremors or muscular rigidity. DBS involves implanting a small device (an electrode) similar to a pacemaker that sends electrical signals to interfere with and block abnormal brain signals. The device is connected to a pulse stimulator attached to the back or the chest. Before beginning the procedure, the neurosurgeon determines where to implant the device by imaging the brain using MRI or CT scans. Since Parkinson's patients have damaged neurons in parts of the basal ganglia, (read more) the device is usually placed in the globus pallidus or the subthalamic nucleus (pictured below).                                                                                                                      ________ Image Credit: (1) “Basal Gangl

The cerebrum is the largest part of the human brain that is divided into two hemispheres. These hemispheres are connected by a bundle of nerve fibers known as the corpus callosum , which allows the hemisphere to communicate with each other. The cerebrum is divided into four lobes that each have a unique function (pictured below). The frontal lobe  is directly above the eyes at the front of the brain. It controls voluntary movement, speech, memory, emotion, and higher cognitive skills such as planning and problem-solving. The parietal lobe , located behind the frontal lobe, receives sensory signals and processes taste. The occipital lobe located at the back of the cerebrum processes visual information and the temporal lobe , located at the side of the brain, interprets auditory information.                                                                                                                      ________ Image Credit: (1)“Cerebrum Lobes.” Wikimedia Commons, uplo

Down syndrome is a neurological childhood disorder that is prevalent in about 250,000 people in the United States. Children with Down syndrome have distinctive facial features including a flattened face and bridge of the nose, eyes that slant upward, and small ears. They usually have low to moderate intellectual ability. Down syndrome is caused by an extra copy of the 21st chromosome in a person's cells, known as trisomy 21 . This means that, instead of having two copies of chromosome 21, they have three copies (pictured below). In rare cases, the extra copy may not be present in every cell — a condition known as mosaic down syndrome.  People with mosaic Down syndrome have milder symptoms and a longer life expectancy. There is no clear cause for trisomy 21, although maternal age can be a risk factor. People with Down syndrome are at a higher risk of developing early-onset Alzheimer's disease. Chromosome 21 contains the gene that codes for the amyloid precursor prot

Parkinson's disease (PD) is a neurodegenerative disease in which patients experience tremors, rigidity, and akinesia (the inability to move). After Alzheimer's, it is the second most common neurodegenerative disease (which involves progressive destruction of nerve cells). Parkinson's disease is characterized by the loss of dopaminergic neurons in the substantia nigra, a region of the basal ganglia in the brain (pictured below). As the name suggests, dopaminergic neurons produce dopamine, a critical neurotransmitter associated with motor control. This loss of dopamine leads to the hallmark symptoms of PD — tremors, muscular rigidity, and slow movement. Over time, the symptoms may worsen as patients begin to experience cognitive decline and develop emotional changes such as depression. The exact cause of Parkinson's is not entirely clear, but a combination of genetics and the environment appears to be the culprit. The disease is linked to a mutation in the PARK

The central dogma is a fundamental concept of biology. It describes the two step process of gene expression: transcription followed by translation. This allows a protein to be created from a gene. DNA  →   RNA   →  Protein During the first step, the genes in a DNA template are transcribed  to create a single strand of mRNA. Once the mRNA leaves the cell's nucleus, it is translated  into a protein at the ribosome in the cell's cytoplasm.

Paul Broca is one of the most influential neuroscientists best known for his patient, Tan. Well, his name wasn't really Tan. His name was Louis Victor Leborgne, and his incredibly unusual neurological disorder settled a debate about the location of language capabilities in the brain. In 1861, Leborgne approached Broca at the Bicetre Hospital to receive surgery for a leg infection. Leborgne had suffered from several medical conditions prior to his surgery; he had epilepsy at a young age and subsequently lost his ability to produce fluent speech. It was Leborgne's language disorder that really caught Broca's attention. Leborgne could think properly, but whenever he tried to communicate with Broca and verbalize his thoughts, all that came out of his mouth was the meaningless word "tan." For this reason, many scholars of neuroscience simply refer to Leborgne as "Tan". Broca realized that he could learn about our language capabilities by studying Leborg

Take a look at the image above. This is the chemical structure of caffeine, a widely consumed chemical that you are probably familiar with (it's in your coffee). Scientists use this as a shorthand depiction of chemical structures. While this image may be confusing at first, it's actually very simple to understand once you know the rules! And there are only two! The first rule is carbon at the corners . What does this mean? Well, at every corner where you do not see a letter (an atom), there is an implied carbon. This shorthand notation allows us to show the structure without writing in each single carbon. There is also an implied carbon at the end of every line. Using this rule, let's place carbons at the corners and the ends of the lines. Now that we have the carbons in place, let's move to the next rule: hydrogens bonded to carbons are implied.   To understand this rule, we must first understand the bonding properties of carbon. Carbon likes to make fou

Let's zoom into the synapse that makes neurotransmission possible. Action potentials travel in the direction from the dendrite to the axon. Therefore, in order to transmit signals from one neuron to another, the signal must leave the axon of one neuron and cross the synaptic cleft to reach the receiving dendrite of another neuron. The neuron that delivers the signal is known as the presynaptic neuron , as shown in the image below. The neuron receiving the signal is known as the postsynaptic neuron . The gap between both neurons is the synaptic cleft. Now, don't confuse the terms "synapse" and "synaptic cleft". The synapse includes the presynaptic neuron, the postsynaptic neuron, and the gap in between. The gap is known as the synaptic cleft . Electrical signals travel as action potentials through the axon. When they reach the axon terminal , which is the very end of the axon, neurotransmitters are released into the synaptic cleft. The neurotran

As we learned about in the blog post about the  Brain Box , the brain is protected by the skull, meninges, and cerebrospinal fluid (CSF). The meninges, which sit below the skull and vertebral column, is a series of three membranes that surround the brain and spinal cord. Its function is to protect and support the brain and spinal cord and contain cerebrospinal fluid (CSF). The three layers of the meninges (from outermost to innermost) are the dura mater, arachnoid mater and pia mater. The dura mater  is a thick, tough layer that adheres to the skull on one side and the arachnoid mater on the other. It is an extra protective layer that attaches the brain to the skull and the spinal cord to the vertebral column. Beneath the dura mater is the arachnoid mater. The arachnoid mater  is named after its appearance that resembles a cobweb. It is made of strands of connective tissue, known as arachnoid trabeculae , that suspend the brain in place. Between the arachnoid mater and t

The ventricles are cavities throughout the brain that produce and distribute cerebrospinal fluid. Cerebrospinal fluid (CSF) is a clear, colorless fluid that suspends the brain and protects it from strain. Check out this blog post to learn more about cerebrospinal fluid. The ventricles are lined with the choroid plexus , a membrane made of ependymal cells (a glial cell) that secrete CSF. There are four ventricles in the human brain. There are two C-shaped lateral ventricles ; one in each of the hemispheres. The lateral ventricles connect to the third ventricle via an opening known as the interventricular foramen . The third ventricle , which resembles a misshapen donut, is located along the midline of the diencephalon. It connects to the fourth ventricle via the cerebral aqueduct. The fourth ventricle is located between the cerebellum and brainstem. It has three openings that allow the CSF to enter the subarachnoid space (remember the meninges). Therefore, the CSF leaves the

Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less. — Marie Curie Physicist

We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special. — Stephen Hawking Physicist

Cells require many substances to ensure proper function — nutrients, oxygen, and more. But how does the cell acquire these substances? In other words, how are these substances transported? There are two main ways particles can be transported: active and passive transport. What is the difference? Well, to understand these two terms, we must first understand the ideas of particle concentrations and concentration gradients. The concentration of particles is simply the number of particles in that area. A gradient is uneven distribution, or concentration, of particles. Now, back to transport. Passive transport is the movement of particles without  energy. Particles move from a high to low concentration  along the concentration gradient. Active transport, however, is the movement of particles with  energy. The particles move from a low to high concentration   against the concentration gradient. Why does active transport require energy? Well, the cell prefers to be in a state of dynamic

To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge. — Nicolaus Copernicus Astronomer

As neuronal signals are constantly fired by the brain, they produce rhythmic electrical patterns known as brain waves that can be detected through a monitoring method known as electroencephalography (EEG). Electroencephalography is a noninvasive process during which electrodes (small metal conductors) placed on the scalp detect the brain waves. The EEG machine then amplifies and records the signals in a wave pattern. The human brain produces four types of brain waves that each create distinguishable shapes on EEG readings: alpha waves, beta waves, theta waves and delta waves. Alpha and beta waves are produced by the awake brain. Alpha waves, with frequencies of 8 to 13 Hz, originate mainly in the parietal and occipital lobes of the brain when the eyes are closed and the brain is relaxed. Beta waves are faster, with frequencies of 14 to 30 Hz, and originate in the frontal and parietal lobes when you are processing a sensory input or focusing on a task. Theta and delta waves are prod

Imagination will often carry us to worlds that never were. But without it we go nowhere. — Carl Sagan Astronomer  

The eyes are your windows to the external world. You are surrounded by different types of energy and molecules that must be translated into perceptions through a network of cells, fibers and electrical signals. Let's take a journey through the eye. In order to understand how vision works, we must first understand what light is. Light is an electromagnetic (EM) wave made of oscillating electric and magnetic fields. EM waves are able to travel without a medium, which is why light is able to travel to Earth through the vacuum of space. However, it is only a sliver of the entire electromagnetic spectrum (pictured below). The light that we are familiar with is visible light. However, there are also radio waves, microwaves, infrared light, ultraviolet light, X-rays and gamma rays  —  and all of them are invisible to us! This is because the human eye can only detect wavelengths from 400 to 700 nanometers (visible light). Visible light itself has a range of wavelengths that determines

The human nervous system is a complex and fascinating structure whose capabilities are far-reaching. How surprising is it that we know so much more about stars billions of light years away than our own brains? Why is the brain so mysterious? Well, studying the brain is a significant challenge. First of all, we cannot simply open the skull and observe the living brain, for obvious reasons. Second, the brain's many functions are at the molecular level, making them impossible to observe, even with the world's most powerful microscopes. According to the World Health Organization,  "N eurological disorders, ranging from epilepsy to Alzheimer disease, from stroke to headache, affect up to one billion people worldwide. An estimated 6.8 million people die every year as a result of neurological disorders."  Therefore, understanding the human brain is crucial.

The most beautiful thing we can experience is the mysterious. It is the source of all true art and all science. — Albert Einstein Physicist

Happiness can be found, even in the darkest of times, if one only remembers to turn on the light. — J.K. Rowling Author  

When you picture the brain, what do you see? Most of the brain is the cerebrum, which controls higher functions like thinking and speaking. The cerebrum is split down the middle by the longitudinal fissure (the red line in the picture) into the left and right hemispheres. These two halves are able to communicate through a bridge of nerve fibers known as the corpus callosum. Each half of the cerebrum is divided into four lobes: the frontal lobe, the temporal lobe, the parietal lobe and the occipital lobe. Therefore, the brain has eight lobes all together. Each lobe is associated with different functions. The top layer of the brain's wrinkly surface is the cortex. The cortex not only covers the surface of the brain but also the space between the hemispheres. The part of the cortex that covers the cerebrum is known as the cerebral cortex. The cortex is gray matter, which consists of unmyelinated axons, dendrites, cell bodies and glial cells. However, the gray matter act

Let's take a look at a cell. One thing that you will find common among all cells is the cell membrane - whether it's an animal cell, a plant cell or a bacterial cell. While this layer may only be ten nanometers thick, it has an intricate molecular structure designed for efficient transport of material into and out of the cell. This property is known as selective permeability , the control of the passage of materials across the cell membrane. The cell membrane is designed in a way that substances having certain properties are unable to enter or leave the cell (this movement across the cell boundary is known as transport ). The fluid mosaic model  describes how substances, mainly cholesterol, phospholipids and proteins, slide freely in the membrane. First, let's start with the phospholipid bilayer . A phospholipid a complex lipid with a "head" and a "tail". The head is made of one polar/hydrophilic phosphate group and a glycerol molecule. The ta

Life is like riding a bicycle. To keep your balance you must keep moving. —  Albert Einstein Physicist

The 3-pound mass of jelly sitting in between our ears is extremely  delicate. It lacks cartilage or bone to hold it together, and it isn't made of muscle tissue. To ensure its safety, the brain is enclosed within a thick, bony structure - the skull . Throughout your life, you will bump your head several times, but your brain will stay unharmed; the skull's purpose is to protect the brain. The cranium is the part of the skull enclosing the brain, but not including the face or jaws. The cranium is comprised of eight flat bones connected at sutures (immovable joints). These plate-like bones grow over time. A baby's skull is extremely fragile; you can even feel the sutures on a baby's head. The soft spot at the top of the head is where the sutures all meet. Eventually, this spot closes over and the cranium is sealed shut. In addition to the cranium, the fourteen facial bones also make up the skull. If you were to remove the skull (and doctors are able to do this

On September 13th of 1848, railroad worker Phineas Gage was working on a railroad construction project, tamping gunpowder into a blasting hole with an iron rod. Unfortunately, the gunpowder exploded, shooting the rod skyward. It penetrated Gage's left cheek, ripped into his brain, and exited through the back of his skull! Surprisingly, Gage walked away, fully conscious, and described what happened to the doctor. The accident left him blind in the left eye. But that wasn't the only consequence; people began to describe Gage as irritated and aggressive. He was no longer mild-mannered and soft-spoken; his personality had completely changed. Phineas later moved from the United States and died after a series of seizures at age 36. Phineas' odd case is a great yet extreme example of how functions of the brain are localized, and how this manifests itself through psychological behaviors. Today, Phineas Gage's skull and the tamping iron are on display at the Warr

The cell theory is a universally accepted principle of biology that sets the relationships between cell and livings things. The cell theory is composed of three basic principles that were established by three 19th-century German scientists – Matthias Schleiden, Theodor Schwann and Rudolph Virchow. The first principle of the cell theory is that all life is made of cells . All living organisms in the six kingdoms of life are made of cells. However, not all cells are alike. There are two categories of cells - prokaryotic and eukaryotic. Prokaryotic cells are simpler and lack a membrane-bound nucleus. In contrast, eukaryotes are larger and highly complex with a defined nucleus and several membrane-bound organelles. The second principle of the cell theory is that the cell is the basic unit of life . Some simpler organisms may by unicellular, meaning they only have one cell. However, these unicellular organisms still have remarkably complex structures – inside each cell are atoms

Neurons can transmit signals at astonishing speeds - some signals can travel as fast at 268 miles per hour! How are neurons capable of such speeds? Well, their axons, which transmit signals to other neurons, have a special covering known as the myelin sheath. Myelin, a lipid-rich substance, insulates the axon and increases the speed of signal transmission. As an action potential travels down the axon, some ions may cross the membrane and exit the cell. However, the presence of myelin prevents this escape. In the peripheral nervous system, myelin is found in the membranes of Schwann cells, a type of glial cell. Each Schwann cell forms one unit of myelin. In the central nervous system, oligodendrocytes, another type of glial cell, tightly wrap around the axon to form several layers of insulation. Each process of an oligodendrocyte can form one segment of myelin for several different cells. Myelin is not the only special feature of neurons that accelerates signal speeds. There are

You may be familiar with the branched out structure of the neuron - multiple, short dendrites and one long axon. But did you know that there are actually other neuron structures that differ in the number of processes? Processes are the project parts of an organic structure - in the case of the neuron, they are the dendrites and the axon. You are probably most familiar with the multipolar neuron , which has at least three processes extending from the soma - one axon and two or more dendrites. Multipolar neurons are the most abundant type of neurons and are usually motor neurons and interneurons. But did you know there are two other structures? Take a look at the picture below: The bipolar neurons  have two processes - one axon and one dendrite - that extend from opposite sides of the cell body. Bipolar neurons are rare and are only found in sensory organs - for example, the retina of the eye. Unipolar neurons  are sensory neurons that have one process extending from the soma. In

Neurons are highly specialized cells that respond to stimuli and transmit electrical and chemical signals to parts of the body. Their structure makes their function tremendously efficient. Take a look at the image below: Notice the branched out processes (projections). These processes, known as dendrites, receive electrical signals and transmit these signals down to the soma (cell body) and then the axon. Remember, electrical signals always travel from the dendrite end to the axon end . The soma contains organelles common to any other cell: the DNA-containing nucleus, cytoplasm, mitochondria, ribosomes, the endoplasmic reticulum, the Golgi Apparatus - just to name a few. Once the electrical signal is carried across the soma, it travels along the axon, a long fiber-like extension that transmits these impulses away from the cell body to other cells. The axon is covered in the myelin sheath, a special insulating envelope that increases the speed of signal transmissio