romikgosai/squad_modified_2 huggingface dataset:
Physiologically, the function of the brain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.

Q1: Hormones secreted are driven by what organ in the body?
A1: The brain
Q2: What type of responsiveness can be used without a brain?
A2: reflexes
Q3: Reflexes only require one of what two structures in a body?
A3: spinal cord or peripheral ganglia
The operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. Recent models in modern neuroscience treat the brain as a biological computer, very different in mechanism from an electronic computer, but similar in the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways, analogous to the central processing unit (CPU) in a computer.

Q1: Which part of a computer does the brain most resemble?
A1: central processing unit (CPU)
This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important is brain disease and the effects of brain damage, covered in the human brain article because the most common diseases of the human brain either do not show up in other species, or else manifest themselves in different ways.

Q1: Animals with a spine are called what?
A1: vertebrates
The shape and size of the brain varies greatly in different species, and identifying common features is often difficult. Nevertheless, there are a number of principles of brain architecture that apply across a wide range of species. Some aspects of brain structure are common to almost the entire range of animal species; others distinguish "advanced" brains from more primitive ones, or distinguish vertebrates from invertebrates.

Q1: Animals without a spine are called what?
A1: invertebrates
The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.

Q1: The easiest way to learn about brain anatomy is by what?
A1: visual inspection
Q2: Brain tissue is naturally soft, but can be stiffened with what liquid?
A2: alcohol
Q3: The two main areas of the brain are what colors?
A3: grey matter, with a dark color, separated by areas of white matter
Q4: What instrument can you use to examine the microstructure of the brain?
A4: microscope
Q5: Grey matter of the brain is what color?
A5: dark color
The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

Q1: Brains of organisms are made up mostly of what two classes of cells?
A1: neurons and glial cells
Q2: Glial cells are also referred to as what?
A2: glia or neuroglia
Q3: Which of the two broad classes of cells: neurons and glial cells send signals to other cells?
A3: neurons
Q4: Axons send signals that are named what?
A4: action potentials
Q5: What is the typical speed that axons send their electrical signals?
A5: 1–100 meters per second
Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell.

Q1: Axons send signals to other neurons by junctions known as what?
A1: synapses
Q2: The neurotansmitter binds to what of a target cell?
A2: receptor molecules
Q3: An axon can connect to how many other cells?
A3: several thousand
Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.

Q1: How many synapses does the human brain supposedly contain?
A1: 100 trillion synapses;
Q2: The fruit fly has a brain that has how many synapses?
A2: several million
Q3: A synapse whose purpose is to excite the target cell are called what?
A3: excitatory
Q4: The primary job of the brain is what?
A4: cell-to-cell communication
Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

Q1: Axons grouped together are known as what?
A1: nerve fiber tracts
Q2: An axon that can greatly increase speed of signals is wrapped in what?
A2: sheath of myelin
Q3: Myelin is what color in the brain?
A3: white
Q4: Most of the space in the brain is made up of what structures?
A4: axons
Q5: Grey matter of the brain consist of lots of what?
A5: neuron cell bodies
Except for a few primitive organisms such as sponges (which have no nervous system) and cnidarians (which have a nervous system consisting of a diffuse nerve net), all living multicellular animals are bilaterians, meaning animals with a bilaterally symmetric body shape (that is, left and right sides that are approximate mirror images of each other). All bilaterians are thought to have descended from a common ancestor that appeared early in the Cambrian period, 485-540 million years ago, and it has been hypothesized that this common ancestor had the shape of a simple tubeworm with a segmented body. At a schematic level, that basic worm-shape continues to be reflected in the body and nervous system architecture of all modern bilaterians, including vertebrates. The fundamental bilateral body form is a tube with a hollow gut cavity running from the mouth to the anus, and a nerve cord with an enlargement (a ganglion) for each body segment, with an especially large ganglion at the front, called the brain. The brain is small and simple in some species, such as nematode worms; in other species, including vertebrates, it is the most complex organ in the body. Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain".

Q1: Creatures that have a diffuse nerve net are called what?
A1: cnidarians
Q2: Bilaterians are animals that have what?
A2: symmetric body shape
Q3: The Cambrian period was how long ago?
A3: 485-540 million years ago
Q4: A nerve cord with an enlargement is called what?
A4: a ganglion
Q5: What type of creature has a ganglion at the back end of the nerve cord as well?
A5: leeches
There are a few types of existing bilaterians that lack a recognizable brain, including echinoderms, tunicates, and acoelomorphs (a group of primitive flatworms). It has not been definitively established whether the existence of these brainless species indicates that the earliest bilaterians lacked a brain, or whether their ancestors evolved in a way that led to the disappearance of a previously existing brain structure.

Q1: A name for a group of primitive flatworms is what?
A1: acoelomorphs
Q2: Some bilaterians without a brain are what?
A2: echinoderms, tunicates, and acoelomorphs
Two groups of invertebrates have notably complex brains: arthropods (insects, crustaceans, arachnids, and others), and cephalopods (octopuses, squids, and similar molluscs). The brains of arthropods and cephalopods arise from twin parallel nerve cords that extend through the body of the animal. Arthropods have a central brain with three divisions and large optical lobes behind each eye for visual processing. Cephalopods such as the octopus and squid have the largest brains of any invertebrates.

Q1: Which two groups of invertebrates have complex brains?
A1: arthropods (insects, crustaceans, arachnids, and others), and cephalopods
Q2: Arthropods and cephalopods have brains that come from a pair of what?
A2: parallel nerve cords
Q3: The invertebrates with the largest brain are what two animals?
A3: octopus and squid
There are several invertebrate species whose brains have been studied intensively because they have properties that make them convenient for experimental work:

Q1: Which brains are easier to work on, vertebrates or invertebrates?
A1: invertebrate
The first vertebrates appeared over 500 million years ago (Mya), during the Cambrian period, and may have resembled the modern hagfish in form. Sharks appeared about 450 Mya, amphibians about 400 Mya, reptiles about 350 Mya, and mammals about 200 Mya. Each species has an equally long evolutionary history, but the brains of modern hagfishes, lampreys, sharks, amphibians, reptiles, and mammals show a gradient of size and complexity that roughly follows the evolutionary sequence. All of these brains contain the same set of basic anatomical components, but many are rudimentary in the hagfish, whereas in mammals the foremost part (the telencephalon) is greatly elaborated and expanded.

Q1: How long ago did the first vertebrate organisms appear?
A1: over 500 million years ago
Q2: During which scientific period did vertebrates appear?
A2: Cambrian period
Q3: Sharks appeared at about how many Mya?
A3: 450 Mya
Q4: The foremost part of the brain in mammals is known as what?
A4: (the telencephalon
Q5: At how many mya did mammals first appear in time?
A5: 200 Mya
Brains are most simply compared in terms of their size. The relationship between brain size, body size and other variables has been studied across a wide range of vertebrate species. As a rule, brain size increases with body size, but not in a simple linear proportion. In general, smaller animals tend to have larger brains, measured as a fraction of body size. For mammals, the relationship between brain volume and body mass essentially follows a power law with an exponent of about 0.75. This formula describes the central tendency, but every family of mammals departs from it to some degree, in a way that reflects in part the complexity of their behavior. For example, primates have brains 5 to 10 times larger than the formula predicts. Predators tend to have larger brains than their prey, relative to body size.

Q1: Do predators have larger or smaller brains compared to their prey?
A1: larger
Q2: In mammals, brain volume and body mass follows a power law with an exponent of what?
A2: 0.75
Q3: Which group of animals have brains 5-10 times larger than the formula predicts?
A3: primates
All vertebrate brains share a common underlying form, which appears most clearly during early stages of embryonic development. In its earliest form, the brain appears as three swellings at the front end of the neural tube; these swellings eventually become the forebrain, midbrain, and hindbrain (the prosencephalon, mesencephalon, and rhombencephalon, respectively). At the earliest stages of brain development, the three areas are roughly equal in size. In many classes of vertebrates, such as fish and amphibians, the three parts remain similar in size in the adult, but in mammals the forebrain becomes much larger than the other parts, and the midbrain becomes very small.

Q1: The forebrain during development is known as what?
A1: prosencephalon
Q2: The midbrain during development is known as what?
A2: mesencephalon
Q3: The hindbrain during development is known as what?
A3: rhombencephalon
Q4: Which group of animals does the forebrain grow the largest?
A4: mammals
Q5: During development, the brain is made up of three swellings at the front of what?
A5: neural tube;
The brains of vertebrates are made of very soft tissue. Living brain tissue is pinkish on the outside and mostly white on the inside, with subtle variations in color. Vertebrate brains are surrounded by a system of connective tissue membranes called meninges that separate the skull from the brain. Blood vessels enter the central nervous system through holes in the meningeal layers. The cells in the blood vessel walls are joined tightly to one another, forming the blood–brain barrier, which blocks the passage of many toxins and pathogens (though at the same time blocking antibodies and some drugs, thereby presenting special challenges in treatment of diseases of the brain).

Q1: Brain tissue that is living is what color on the outside?
A1: pinkish
Q2: The color of the brain inside is what?
A2: white
Q3: Brains are surrounded by what system of tissues?
A3: meninges
Q4: Meninges separate what structure from the brain?
A4: the skull
Q5: The blood-brain barrier is made up of what?
A5: cells in the blood vessel walls
Neuroanatomists usually divide the vertebrate brain into six main regions: the telencephalon (cerebral hemispheres), diencephalon (thalamus and hypothalamus), mesencephalon (midbrain), cerebellum, pons, and medulla oblongata. Each of these areas has a complex internal structure. Some parts, such as the cerebral cortex and the cerebellar cortex, consist of layers that are folded or convoluted to fit within the available space. Other parts, such as the thalamus and hypothalamus, consist of clusters of many small nuclei. Thousands of distinguishable areas can be identified within the vertebrate brain based on fine distinctions of neural structure, chemistry, and connectivity.

Q1: People who study the anatomy of the central nervous system are known as what?
A1: Neuroanatomists
Q2: The cerebral hemispheres of the brain are called what?
A2: telencephalon
Q3: The thalamus and hypothalamus comprise what region of the brain?
A3: diencephalon
Q4: The midbrain region of the brain is known as what?
A4: mesencephalon
Q5: Clusters of small nuclei comprise what parts of the brain?
A5: thalamus and hypothalamus
Although the same basic components are present in all vertebrate brains, some branches of vertebrate evolution have led to substantial distortions of brain geometry, especially in the forebrain area. The brain of a shark shows the basic components in a straightforward way, but in teleost fishes (the great majority of existing fish species), the forebrain has become "everted", like a sock turned inside out. In birds, there are also major changes in forebrain structure. These distortions can make it difficult to match brain components from one species with those of another species.

Q1: The forebrain is everted in what type of fishes?
A1: teleost fishes
Q2: Which part of the brain has led to many distortions among different species?
A2: forebrain area
The most obvious difference between the brains of mammals and other vertebrates is in terms of size. On average, a mammal has a brain roughly twice as large as that of a bird of the same body size, and ten times as large as that of a reptile of the same body size.

Q1: A mammal's brain is how many times larger than a birds relative to body size?
A1: twice as large
Q2: A mammal's brain is how many times larger than a reptiles relative to body size?
A2: ten times
Q3: The biggest difference between brains of mammals and other vertebrates is what?
A3: size.
Size, however, is not the only difference: there are also substantial differences in shape. The hindbrain and midbrain of mammals are generally similar to those of other vertebrates, but dramatic differences appear in the forebrain, which is greatly enlarged and also altered in structure. The cerebral cortex is the part of the brain that most strongly distinguishes mammals. In non-mammalian vertebrates, the surface of the cerebrum is lined with a comparatively simple three-layered structure called the pallium. In mammals, the pallium evolves into a complex six-layered structure called neocortex or isocortex. Several areas at the edge of the neocortex, including the hippocampus and amygdala, are also much more extensively developed in mammals than in other vertebrates.

Q1: What part of the brain most strongly differentiates mammals from other vertebrates?
A1: The cerebral cortex
Q2: The three-layered structure covering the cerebrum in non-mammals is known as what?
A2: pallium
Q3: Mammals have a pallium that involved into what?
A3: neocortex or isocortex
Q4: The hippocampus and amygdala are ares inside what structure?
A4: neocortex
The elaboration of the cerebral cortex carries with it changes to other brain areas. The superior colliculus, which plays a major role in visual control of behavior in most vertebrates, shrinks to a small size in mammals, and many of its functions are taken over by visual areas of the cerebral cortex. The cerebellum of mammals contains a large portion (the neocerebellum) dedicated to supporting the cerebral cortex, which has no counterpart in other vertebrates.

Q1: The superior colliculus is related to what sensual control of vertebrates?
A1: visual
Q2: The larger part of the cerebellum in mammals is called what?
A2: (the neocerebellum
Q3: The Neocerebellum supports what other part of the brain?
A3: cerebral cortex
The brains of humans and other primates contain the same structures as the brains of other mammals, but are generally larger in proportion to body size. The most widely accepted way of comparing brain sizes across species is the so-called encephalization quotient (EQ), which takes into account the nonlinearity of the brain-to-body relationship. Humans have an average EQ in the 7-to-8 range, while most other primates have an EQ in the 2-to-3 range. Dolphins have values higher than those of primates other than humans, but nearly all other mammals have EQ values that are substantially lower.

Q1: Comparing brain sizes among different creatures is used most commonly by what?
A1: encephalization quotient (EQ)
Q2: What is the average EQ of a person?
A2: 7-to-8 range
Q3: Primates have an EQ in what range?
A3: 2-to-3
Most of the enlargement of the primate brain comes from a massive expansion of the cerebral cortex, especially the prefrontal cortex and the parts of the cortex involved in vision. The visual processing network of primates includes at least 30 distinguishable brain areas, with a complex web of interconnections. It has been estimated that visual processing areas occupy more than half of the total surface of the primate neocortex. The prefrontal cortex carries out functions that include planning, working memory, motivation, attention, and executive control. It takes up a much larger proportion of the brain for primates than for other species, and an especially large fraction of the human brain.

Q1: Primates have a visual processing network of how many brain areas?
A1: 30
Q2: The visual processing areas occupy how much of the surface of the neocortex or primates?
A2: more than half
Q3: Planning, motivation, and attention are controlled by what area?
A3: prefrontal cortex
Q4: The prefrontal cortex is the largest in what animals?
A4: primates
For vertebrates, the early stages of neural development are similar across all species. As the embryo transforms from a round blob of cells into a wormlike structure, a narrow strip of ectoderm running along the midline of the back is induced to become the neural plate, the precursor of the nervous system. The neural plate folds inward to form the neural groove, and then the lips that line the groove merge to enclose the neural tube, a hollow cord of cells with a fluid-filled ventricle at the center. At the front end, the ventricles and cord swell to form three vesicles that are the precursors of the forebrain, midbrain, and hindbrain. At the next stage, the forebrain splits into two vesicles called the telencephalon (which will contain the cerebral cortex, basal ganglia, and related structures) and the diencephalon (which will contain the thalamus and hypothalamus). At about the same time, the hindbrain splits into the metencephalon (which will contain the cerebellum and pons) and the myelencephalon (which will contain the medulla oblongata). Each of these areas contains proliferative zones where neurons and glial cells are generated; the resulting cells then migrate, sometimes for long distances, to their final positions.

Q1: The precursor of the nervous system is called what in vertebrates?
A1: the neural plate
Q2: The neural groove is a hollow cord of cells with what in the center?
A2: fluid-filled ventricle
Q3: The forebrain splits during development into vesicles called what?
A3: telencephalon (which will contain the cerebral cortex, basal ganglia, and related structures) and the diencephalon
Q4: The vesicle that contains the cerebral cortex is which one?
A4: telencephalon
Q5: The thalamus and hypothalamus are contained in which vesicle?
A5: the diencephalon