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How many Types of Symmetry in Biology?
✍️ Symmetry in biology refers to the correspondence of body parts, in size, shape, and relative position, on opposite sides of a dividing line or distributed around a central point or axis.
There are 3️⃣ main types of symmetry in animals ⬆️
✅ Spherical, rare in animals and found mainly in Protozoa (e.g., Volvox, Heliozoa, and Radiolaria) and in eggs and early embryos of some animals.
✅ Radial, found in some sponges (Sycon), Coelenterates (Hydra, jellyfish), echinoderms (e.g.,starfish).
✅ Bilateral, found in many invertebrates, e.g., annelids arthropods, etc., and all vertebrates. It is strongly associated with cephalization.
Scientists also distinguish
✔️ Biradial Symmetry, found in organisms with morphological features (internal or external) of both bilateral and radial symmetry. e.g, sea anemones.
☘️🌱🌸🌻 Plants exhibit often both radial symmetry and bilateral symmetry, which has a lot to do with pollination strategy.
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Why temperature anomalies are so important?
📌A temperature anomaly is the difference from an average, or baseline, temperature.
📌The baseline temperature is typically computed by averaging 30 or more years of temperature data.
📌Anomalies are measured by the number of degrees that the temperature varies from the average and can be:
➕positive (the observed temperature is warmer than the baseline)
and
➖negative (the observed temperature is cooler than the baseline)
📌The anomalies are due to land-ocean-atmosphere processes that dynamically determine the weather and climate.
📌Anomalies are used to measure global surface temperature instead of absolute temperature because:
✔️absolute estimates are challenging to obtain and are uncertain
✔️anomalies describe how climate is changing over larger areas and over time more clearly.
❗️The world has been showing a frightening abundance of positive anomalies in the past decade, which means the world is getting warmer.
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What is at the heart of the SI standard?
The SI is defined in terms of a set of 7️⃣ defining constants:
1️⃣the caesium hyperfine frequency
2️⃣the speed of light in vacuum
3️⃣the Planck constant
4️⃣the elementary charge
5️⃣the Boltzmann constant
6️⃣the Avogadro constant
7️⃣the luminous efficacy of a defined visible radiation
The complete system of units can be derived from the fixed values of these defining constants, expressed in the units of the SI.
The 7️⃣ base units are:
1️⃣Second (s), unit of time
2️⃣Meter (m), unit of length
3️⃣Kilogram (kg), unit of mass
4️⃣Ampere (A), unit of electric current
5️⃣Kelvin (K), unit of thermodynamic temperature
6️⃣Mole (mol), unit of an amount of substance
7️⃣Candela (cd), unit of luminous intensity
The SI standard also includes units that are derived from the base units and are defined as products of powers of the base units. For example, one derived unit is the newton, which can be expressed in terms of base units as 1 kg m/s2.
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How does feeling lonely relate to spending time alone?
ℹ️ Loneliness - the subjective experience of social isolation - is a common experience that can become an enduring feature of everyday life.
Researchers have discerned the nuanced relationship between feeling lonely and actually being alone. The study involved over 400 participants with archival data collected in a series of studies completed over the last 20 years.
Key facts:
✔️ Loneliness becomes pronounced when individuals spend more than three-quarters of their time alone.
✔️ In older adults (above 67 years), the correlation between loneliness and time spent alone is particularly strong, with a 25% overlap.
✔️ In younger people, aloneness and loneliness are just two different things. Young persons may feel lonely in a crowd, or they may not feel lonely when they are by themselves.
To better quantify social behavior, the research team is developing a smartwatch app akin to fitness trackers.
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How many pets are in the world?
✍️According to different sources, there are over 1 billion pets in the world.
🇺🇸🇨🇳🇪🇺The USA, China and the EU alone, there are more than 500 mln 🐱 and 🐶.
Besides cats and dogs, the world pet population also includes animals like reptiles, fish, birds, rabbits, livestock, horses, hamsters, guinea pigs, mice, ferrets, iguanas, snakes, etc.
🐹After dogs and cats, hamsters are popular pets.
🇧🇷🥇Brazil ranks first in having the most small 🐶 per capita on the globe. In terms of exotic pets, it has the most unique number of animal pet species in the world.
🇷🇺🏆59% of Russian households have pet cats, making it the country with the highest overall share of cat owners.
🇬🇧🐢🐍🐊The highest pet reptile concentration - 1.45 mln reptiles - is in the United Kingdom.
🇮🇹🥇Italy takes first place in ornamental pet 🦜 in the world with 12.88 mln in households.
🇹🇷🥈Turkey takes second place with 11.2 mln ornamental birds in households.
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What were the first currencies?
💰 When, where and why money originated is uncertain and complicated. Because ancient civilizations developed at different times and recorded their history with a range of different approaches, archaeologists and historians can only make best guesses.
🐚🌾💎 Both shell money (comprised of shells or beads) and commodity money (comprised of objects that have a practical use, like grain) appear to have made up early forms of currency all around the world, from the Indigenous tribes of America to the villages of Africa to the populations of Asia and the South Pacific islands. Other objects likely used as early forms of currency vary immensely, from bricks of tea and livestock to gems and metal fragments.
ℹ️For example, shells ⬆️ were used as currency in ancient China and, about 5,000 years ago, Mesopotamians developed a banking system where people could "deposit" grains, livestock and other valuables for safekeeping or trade.
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What are some hydrogen bonding examples and applications?
I. Some examples of hydrogen bonding are as follows.
☑️ Ammonia
The hydrogen bonds in ammonia (NH3) are formed between nitrogen and hydrogen atoms. Nitrogen is a highly electronegative atom that is linked to hydrogen atoms in order to make hydrogen bonds.
☑️ Hydrogen Fluoride
❗️ Fluorine is an element that has the highest value of electronegativity, and it forms the strongest hydrogen bond.
☑️ Alcohols
Alcohols are organic compounds. It contains at least one -OH group. When any molecule containing the hydrogen atom is connected to either oxygen or nitrogen directly, it usually has the tendency to form hydrogen bonding.
☑️ Carboxylic Acid
Hydrogen bonding can occur in a pure carboxylic acid in between two molecules of acid in order to produce a dimer. The hydrogen bonding in carboxylic acid doubles the size of the molecule.
II. Some of the applications and effects of hydrogen bonds are given below.
🟢 Hydrogen Bonds in Plants
Water has the property to stick to itself (cohesion) and also with other molecules (adhesion). When water droplets fall on a leaf, the hydrogen bonds present between the molecules of water are more substantial than the intermolecular forces of adhesion between the water molecules and the leaf. The high surface tension of water is explained by this property.
⚪️ Hydrogen Bonds in Proteins
Intramolecular hydrogen bonding is responsible for different types of proteins such as secondary proteins, tertiary proteins, and quaternary proteins and as well as for the structure of the nucleic acids.
🧬 Hydrogen Bonds in DNA (Deoxyribonucleic Acid)
The double-helix model of DNA consists of two intertwined strands held together by a base pair. The hydrogen bonding present between the bases on adjacent strands is responsible for this. Because of different structure bases, adenine (A) always forms hydrogen bonds with thymine (T). Guanine (G) always forms hydrogen bonds with cytosine (C) in contrast.
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What is a new ultra-strong chemical bond lately discovered by scientists?
❗️Scientists have recently discovered a totally new type of chemical bond.
⚪️↔️⚪️ In the new study, the researchers dissolved a hydrogen-fluoride compound in water, and watched how the hydrogen and fluorine atoms interacted. What they found was a hydrogen bond with the strength of a covalent bond, binding atoms together into something resembling a molecule.
ℹ️ The new bonds had a strength of 45.8 kilocalories per mol (a unit of chemical bonding energy), greater than some covalent bonds. E.g., in nitrogen molecules two nitrogen atoms are bound together with a strength of about 40 kcal/mol. A hydrogen bond typically has an energy of about 1-3 kcal/mol, an ionic bond - between 5 and 10 kcal/mol.
✍️ According to scientists, this hybrid covalent-hydrogen bond not only challenges our current understanding of what a chemical bond exactly is, but also offers the opportunity to better understand chemical reactions.
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What is another way atoms can become more stable?
Rather than fully gaining or losing electrons, another way atoms can become more stable is by sharing them, thus forming covalent bonds, another intra-bond type.
They are more common than ionic bonds in the molecules of living organisms. E.g., they are key to the structure of carbon-based organic molecules like our DNA and proteins. Covalent bonds are also found in smaller inorganic molecules, such as H2O, CO2 and O2.
One, two, or three pairs of electrons may be shared between atoms, resulting in single, double, or triple bonds, respectively. The more electrons that are shared between two atoms, the stronger their bond will be.
Two basic types of covalent bonds are:
▫️ Polar bonds in which the electrons are unequally shared by the atoms.
▪️ Nonpolar bonds that form between atoms of the same element, or between atoms of different elements that share electrons more or less equally.
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What happens if atoms are gaining or losing electrons?
Some atoms become more stable by gaining or losing electrons.
When they do so, atoms form ions, or charged particles.
Ions come in 2️⃣ types:
➕Cations are positive ions formed by losing electrons. E.g., if a sodium atom loses an electron, it becomes a sodium cation, Na+.
➖Anions are negative ions formed by electron gain and named using the ending “-ide”: for example, the anion of chlorine (Cl-) is called chloride.
⚛️➡️⚛️The process itself is called electron transfer.
ℹ️The word ion comes from the Greek word ion or ienai, meaning “to go.” English scientist Michael Faraday coined the term in 1834.
ℹ️Certain ions are referred to in physiology as electrolytes (including sodium, potassium, and calcium). These ions are necessary for nerve impulse conduction, muscle contractions and water balance. Many sports drinks and dietary supplements provide these ions to replace those lost from the body via sweating during exercise.
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How many animals have ever existed on Earth?
📌Life appeared on Earth by 3.7 billion years ago. But those first organisms were very simple cells; it would be another 1.4 billion years before multicellular life showed up. Animals probably evolved even more recently, around 800 million years ago.
📌According to scientists, the total number of eukaryotic species on Earth was around 8.7 million, about 7.7 million of which were animals (roughly half were insects).
📌Researchers assume that 99.9% of species that have ever lived on Earth are extinct. So, 7.7 million could be multiplied by nearly 100 percent which puts the total number of animal species at roughly 770 million species.
📌Today, there are around 130 billion mammals, up to 428 billion birds, 3.5 trillion fish and an estimated 10 quintillion insects.
If we extrapolate out these figures using the proportions of the 7.7 million existing species, roughly, there have been approximately 4.5 x 10^27 animals ever on Earth.
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What science studies the nervous system?
Neuroscience, also known as Neural Science, is the study of how the nervous system develops, its structure, and what it does.
Neuroscientists focus on the brain and its impact on behavior and cognitive functions and study what happens to the nervous system when people have neurological, psychiatric and neurodevelopmental disorders.
Neuroscience is also often referred to in the plural, as neurosciences.
Neuroscience has traditionally been classed as a subdivision of biology, but today it’s an interdisciplinary science, which liaises closely with other disciplines, such as mathematics, linguistics, engineering, computer science, chemistry, philosophy, psychology, and medicine.
Some researchers say that neuroscience means the same as neurobiology. However, neurobiology looks at the biology of the nervous system, while neuroscience refers to anything to do with the nervous system.
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What are some amazing facts about the animals’ nervous system?
ℹ️Sponges are the only multicellular animals without a nervous system.
🪱🐘The size of the nervous system ranges from a few hundred cells in the simplest worms, to around 300 billion cells in elephants ⬆️.
🔰 The minuscule C. elegans nematode worm has just 302 neurons, but it’s able to carry out the same functions as the nervous systems of higher organisms.
🔰 The tiny Megaphragma mymaripenne wasp ⬆️ only lives for 5️⃣ days and has just 7️⃣4️⃣0️⃣0️⃣ neurons. As it changes from a larva into an adult, it destroys the majority or its neural nuclei until just a few hundred are left, because there’s not enough room in its head.
🔰 At a larval stage, sea squirts have the same anatomical characteristics as most vertebrates, but as they grow, they lose their minds – literally. They digest their own cerebral ganglia, which controls movement, because once they’re sedentary, they no longer need it.
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What are glial cells?
✔️The second main type in the nervous system are glial cells.
Glial cells (named from the Greek word for "glue") are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system.
Among the most important functions of glial cells are:
📍to support neurons and hold them in place
📍to supply nutrients to neurons
📍to insulate neurons electrically
📍to destroy pathogens and remove dead neurons
📍to provide guidance cues directing the axons of neurons to their targets.
✍️A very important set of glial cell generate layers of a fatty substance called myelin that wrap around axons and provide electrical insulation that allows them to transmit signals much more rapidly and efficiently.
✍️🧠In the human brain, it is currently estimated that the total number of glia roughly equals the number of neurons, although the proportions vary in different brain areas.
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What is the “command centre” of most animals?
📌The nervous system (NS) is the “command centre” of an animal's body that coordinates its behavior and transmits signals between different body areas.
📌The function of the NS is to control movement of the organism and to affect the environment (e.g. through pheromones) by sending signals from one cell to others, or from one part of the body to others.
📌At the cellular level, the NS is defined by the presence of neurons, also known as "nerve cells".
📌Nervous systems are found in almost all multicellular animals, but vary greatly in complexity.
📌The NS derives its name from nerves, which are cylindrical bundles of fibers that emanate from the brain and central cord, and branch repeatedly to innervate every part of the body. Nerves are large enough to have been recognized by the ancient Egyptians, Greeks, and Romans, but their internal structure was not understood until it became possible to examine them using a microscope.
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What are some interesting temperature highlights of October 2023?
According to climatologists,
🌡 🗓 October 2023 was the warmest October on record globally, with an average surface air temperature of 15.30°C, 0.85°C above the 1991-2020 average for October and 0.40°C above the previous warmest October, in 2019.
🌡🌏 The global temperature anomaly for October 2023 was the second highest across all months in the ERA5 dataset, behind September 2023.
🌡🌊 The average sea surface temperature for October over 60°S–60°N was 20.79°C, the highest on record for October.
🌡 The month as a whole was 1.7°C warmer than an estimate of the October average for 1850-1900, the designated pre-industrial reference period.
ℹ️ ERA5 is the latest climate reanalysis produced by European researchers. All the reported findings are based on computer-generated analyses, using billions of measurements from satellites, ships, aircraft and weather stations around the world.
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What tells us how much heat the object has?
🌡Temperature tells us the degree of hotness or coldness of an object.
🌡It is a measurable physical property like other measurable physical properties such as velocity, mass, and density.
🔬At a microscopic level, temperature describes the average kinetic energy of molecules within a material or system.
🌡Temperature is typically seen in units of degrees Celsius or °C (in some countries the Fahrenheit scale is used).
🌡Celsius is the standard unit of temperature in the metric system of units. Celsius is split up into degrees, with one degree being 1/100 of the temperature difference between the boiling and freezing points of water.
🌡Fahrenheit is equal to 9/5 degrees Celsius.
🌡Scientists use the Kelvin scale, which doesn’t measure temperature in degrees. Zero Kelvin is ‘absolute zero’, the coldest temperature and lowest energy level equal to about -273 degrees °C.
🌡A thermometer is a device used for measuring temperature.
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What is the International System of Units (SI)?
✍️ The International System of Units is a global standard for expressing the magnitudes or quantities of important natural phenomena.
📌 Also referred to as the Metric system, the System of Units is commonly abbreviated as SI, which comes from the original French name, Système international d'unités.
📌 The SI standard builds on an earlier system of measurement called the meter-kilogram-second (MKS) system.
📌 The Bureau international des poids et mesures (BIPM) ⬆️ is responsible for promoting and describing the SI standard. Known as the International Bureau of Weights and Measures in English, the organization was established in 1875 and operates under the supervision of the International Committee for Weights and Measures (CIPM).
ℹ️ The International Treaty of the Meter was signed in Paris on May 20, 1875 by seventeen countries and is now celebrated around the globe as World Metrology Day.
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How does the ‘Spanish Dancer Galaxy’ look like?
🔭🌀This vibrant and dynamic-looking image ⬆️, recently released by the ESA, features the spiral galaxy NGC 1566, which is sometimes informally referred to as the ‘Spanish Dancer Galaxy’.
💃🏻The galaxy owes its nickname to the vivid and dramatic swirling lines of its spiral arms, which could evoke the shapes and colours of a dancer’s moving form.
🌌NGC 1566 lies around 60 million light-years from Earth in the constellation Dorado, and is also a member of the Dorado galaxy group.
ℹ️In spite of more sophisticated observation techniques, it is rather challenging to pin down members of groups such as the Dorado group. When working out members of a galaxy group, astronomers are not necessarily equipped with the knowledge of the size of the individual galaxies, and so have to work out whether galaxies really are relatively close together in space, or whether some of them are actually much closer or much further away.
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What were the first coins?
The oldest known uses of coins as currency can be traced back to many archaic civilizations.
🪙 The Lydian stater ⬆️ is often considered the first minted — or state-produced — coin, issued by King Alyattes in the 7th century B.C. in a Greek kingdom of Lydia, located in modern-day Turkey.
These Lydian coins were made of electrum, a naturally occurring gold and silver alloy, and were supposed to conform to a specific standard of weight.
They weren’t very uniform compared to modern coins. Minted in the Lydian capital of Sardis, the coins generally featured a lion (known as the Lydian Lion) and bull facing each other.
🪙 Even before the Lydian stater, coins could be minted in ancient China.
According to scientists, clay molds ⬆️, discovered in a bronze foundry at Guanzhuang, in China’s Henan Province, were likely used as a mint for making standardized coins around 640 B.C. - the approximate birth year of Lydia’s King Alyattes.
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Why does paper tear more easily when it's wet?
📍The answer comes down to the paper's chemical structure.
📍At the heart of it, paper is just cellulose fibers — natural polymer molecules from wood — woven around each other to form a sheet. Within a normal sheet of paper, these fibers are interlocked with each other through little hook-like irregularities on the individual strands of cellulose and also bonded between each other by hydrogen bonds.
📍When you tear a piece of dry paper, you just need to overcome all the intermolecular forces, the friction, and the fiber entanglements.
📍On a chemical level, the water disrupts the vital hydrogen bonds. Because water contains oxygen-hydrogen bond, it begins to form its own hydrogen bonds with the cellulose, blocking the other fibers from binding. With fewer interactions between the individual cellulose polymers, it becomes easier to separate the fibers, so less force is needed to tear the paper.
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How does electronegativity affect chemical bonding?
✔️Electronegativity is the ability of an atom to attract a pair of electrons in a chemical bond.
✔️The higher the electronegativity of an element, the more strongly it attracts the shared electrons.
⬆️The difference in electronegativity between two bonded elements determines what type of bond they will form.
⤴️When atoms with an electronegativity difference of greater than 2️⃣ units are joined together, the bond that is formed is an ionic bond.
⤵️When atoms with an electronegativity difference of less than 2️⃣ units are joined together, the bond that is formed is a covalent bond.
ℹ️The concept of electronegativity was introduced by Linus Pauling in 1932; on the Pauling scale, fluorine is assigned an electronegativity of 3.98, and the other elements are scaled relative to that value.
In the periodic table ⬆️ electronegativity increases from bottom to top in groups, and increases from left to right across periods.
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What chemical bonds are considered weak?
Covalent and ionic bonds are both typically considered strong bonds.
However, more temporary and weak bonds can also form between atoms or molecules.
2️⃣ types of weak bonds are:
📍Hydrogen bond ⬆️, an intermolecular force (IMF) that behaving a bit like a magnet forms a special type of dipole-dipole attraction when a hydrogen atom bonded to a strongly electronegative atom, exists in the vicinity of another electronegative atom with a lone pair of electrons. For example, in water molecules (H2O), hydrogen is covalently bonded to the more electronegative oxygen atom.
Individual hydrogen bonds are easily broken, but many hydrogen bonds together can be very strong.
📍 London dispersion forces ⬆️ occur between atoms or molecules of any kind, and they depend on temporary imbalances in electron distribution.
ℹ️ These weak bonds are both often defined by a general term of van der Waals forces.
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How ionic bonds are formed?
Ionic bonds are bonds formed between ions with opposite charges. It’s an intra-bond type.
🫙 For instance, positively charged sodium ions and negatively charged chloride ions attract each other to make sodium chloride, or table salt. Like many ionic compounds, it doesn't consist of just one sodium and one chloride ion; instead, it contains many ions arranged in a crystal lattice (repeating, predictable 3D pattern) ⬆️.
Within sodium chloride all of the attractions between the ions are strong. A lot of energy is required to pull these ions apart. This trait means sodium chloride has a high melting point and a high boiling point. Those charges also mean that when salt is dissolved in water or melted, it becomes a good conductor of electricity.
ℹ️ Just a few grams of salt could contain more than a septillion ions. It’s a quadrillion times a billion (or 1,000,000,000,000,000,000,000,000).
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What is holding our universe together?
⚛️Our universe is made up of atoms, which in most cases are not just floating around individually, but usually interacting with other atoms (or groups of atoms).
Atoms might be connected by strong chemical bonds and organized into molecules or crystals. Or they might form temporary, weak chemical bonds with other atoms that they bump into or brush up against.
❗️Both the strong bonds that hold molecules together and the weaker bonds that create temporary connections are essential as they are literally holding our universe together.
Chemical bonds are formed because atoms are trying to reach the most stable (lowest-energy) state that they can.
Chemical bonds broadly fall into 2️⃣ categories:
🔄 intra-bonds that hold one building block to another inside a compound
➡️⬅️ inter-bonds that attract one compound to another
Intra- and inter-bonding are further divided into different types, but electrons control all types of bonds.
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What are the major branches of modern neuroscience?
According to researchers, the following branches of neuroscience, based on research areas and subjects of study can be broadly categorized in the following disciplines (neuroscientists usually cover several branches at the same time):
✔️ Affective neuroscience – in most cases, research is carried out on laboratory animals and looks at how neurons behave in relation to emotions.
✔️ Behavioral neuroscience – the study of the biological bases of behavior. Looking at how the brain affects behavior.
✔️ Cellular neuroscience – the study of neurons, including their form and physiological properties at cellular level.
✔️ Clinical neuroscience – looks at the disorders of the nervous system, while psychiatry, for example, looks at the disorders of the mind.
✔️ Cognitive neuroscience – the study of higher cognitive functions that exist in humans, and their underlying neural bases. Cognitive neuroscience draws from linguistics, neuroscience, psychology and cognitive science. Cognitive neuroscientists can take two broad directions; behavioral/experimental or computational/modeling, the aim being to understand the nature of cognition from a neural point of view.
✔️ Computational neuroscience – attempting to understand how brains compute, using computers to simulate and model brain functions, and applying techniques from mathematics, physics and other computational fields to study brain function.
✔️ Cultural neuroscience – looks at how beliefs, practices and cultural values are shaped by and shape the brain, minds and genes over different periods.
✔️ Developmental neuroscience – looks at how the nervous system develops on a cellular basis; what underlying mechanisms exist in neural development.
✔️ Molecular neuroscience – the study of the role of individual molecules in the nervous system.
✔️ Neuroengineering – using engineering techniques to better understand, replace, repair, or improve neural systems.
✔️ Neuroimaging – a branch of medical imaging that concentrates on the brain. Neuroimaging is used to diagnose disease and assess the health of the brain. It can also be useful in the study of the brain, how it works, and how different activities affect the brain.
✔️ Neuroinformatics – integrates data across all areas of neuroscience, to help understand the brain and treat diseases. Neuroinformatics involves acquiring data, sharing, publishing and storing information, analysis, modeling, and simulation.
✔️ Neurolinguistics – studying what neural mechanisms in the brain control the acquisition, comprehension and utterance of language.
✔️ Neurophysiology– looks at the relationship of the brain and its functions, and the sum of the body’s parts and how they interrelate. The study of how the nervous system functions, typically using physiological techniques, such as stimulation with electrodes, light-sensitive channels, or ion- or voltage-sensitive dyes.
✔️ Paleoneurology – the study of the brain using fossils.
✔️ Social neuroscience – this is an interdisciplinary field dedicated to understanding how biological systems implement social processes and behavior. Social neuroscience gathers biological concepts and methods to inform and refine theories of social behavior. It uses social and behavioral concepts and data to refine neural organization and function theories.
✔️ Systems neuroscience – follows the pathways of data flow within the CNS and tries to define the kinds of processing going on there. It uses that information to explain behavioral functions.
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What are some interesting features of the human nervous system?
🔴 The human nervous system can transmit signals at speeds of 100 meters per second.
🔴 The slowest signal transmission occurs inside the skin.
🔴 Every square cm of human skin contains around 200 pain receptors but only 15 receptors for pressure, 6 for cold and 1 for warmth.
🔴 In the human PNS, nerve cells can be threadlike—their width is microscopic, but their length can be measured in meters.
🔴 There are over millions of nerve cells in human CNS, 100 billion neurons in the human brain and around 13,500,000 neurons in the spinal cord.
🔴 Sciatic nerve is the longest and broadest single nerve in the human body.
🔴An optic (cranial) nerve is the fundamental part of the CNS, and the human eye's most significant sensory nerve.
🔴 B vitamins must be replenished daily as they are only stored in the body in a very small amount.
⬆️ Look at the human nervous system depicted using advanced computer modeling.
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What are the components of the nervous system?
✍️The nervous system of vertebrates has two components: the central nervous system (CNS) and the peripheral nervous system (PNS).
☑️The CNS is the largest part, and includes the brain and the spinal cord.
☑️Structures that do not lie within the CNS, are called the PNS.
The majority of nerves belong to the PNS, even when the cell bodies of the neurons to which they belong reside within the brain or spinal cord.
The PNS is divided into:
🔘the somatic part consisting of the nerves that innervate the skin, joints, and muscles.
🔘the visceral part, or the autonomic nervous system, that contains neurons that innervate the internal organs, blood vessels, and glands, and itself has two parts:
▪️the sympathetic nervous system
and
▪️the parasympathetic nervous system.
ℹ️Some authors also include sensory neurons whose cell bodies lie in the periphery (for senses such as hearing) as part of the PNS; others, however, omit them.
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What do we know about neurons?
✔️One of the two main types of cells in the nervous system are neurons.
🔬✍️They can be distinguished from other cells in a number of ways, but their most fundamental property is that they communicate with other cells via synapses, which are junctions containing molecular machinery allowing rapid transmission of electrical or chemical signals.
🔬✍️Many types of neuron possess an axon, a protoplasmic protrusion that can extend to distant parts of the body and make thousands of synaptic contacts.
✍️Even in the nervous system of a single species, hundreds of different types of neurons exist, with various morphologies and functions. For example, sensory neurons transmute physical stimuli such as light and sound into neural signals, and motor neurons transmute neural signals into activation of muscles or glands. In many species, though, the majority of neurons receive all of their input from other neurons and send their output to other neurons.
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How do CO2 emissions in Africa, Asia, Australia and Europe look like from space?
🌏The left view ⬆️ highlights CO2 sources and sinks over Asia and Australia. The notable feature is fossil fuel emissions from China. In contrast, drawdown from the land biosphere is visible over Australia for much of the year because emissions and population density are much lower. By the end of the animation, fossil fuel emissions which are released predominantly in the Northern Hemisphere are mixing southward obscuring Australia.
🌍The right view ⬆️ highlights Europe, the Middle East, and Africa. European fossil fuel emissions are visible as is red representing emissions from fires over central Africa that are used to clear crop residue.
ℹ️ Fires represent a much smaller source of CO2 to the atmosphere than fossil fuel emissions, but are monitored by scientists as they can alter the ability of an ecosystem to sequester carbon and in the future become more severe because of climate change.
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