Vertebrate brain facts for kids

Kids Encyclopedia Facts

The vertebrate brain is the main part of the central nervous system. In vertebrates (and most other animals) the brain is at the front, in the head. It is protected by the skull and close to the main senses of vision, hearing, balance, taste, and smell. As an animal moves forward, its senses collect data about the surroundings, and that data goes directly to the brain.

Brains are extremely complex. The brain controls the other organs of the body, either by activating muscles or by causing secretion of chemicals such as hormones and neurotransmitters. Muscular action allows rapid and coordinated responses to changes in the environment; hormones and the autonomic nervous system make slower changes in the body.

In vertebrates, the spinal cord by itself can cause reflex responses as well as simple movement such as swimming or walking. However, sophisticated control of behaviour requires a centralized brain.

The structure of all vertebrate brains is basically the same. At the same time, during the course of evolution, the vertebrate brain has undergone changes, and become more effective. In so-called 'lower' animals, most or all of the brain structure is inherited, and therefore their behaviour is mostly instinctive. In mammals, and especially in man, the brain is developed further during life by learning. This has the benefit of helping them fit better into their environment. The capacity to learn is seen best in the cerebral cortex.

Three principles

  1. The brain and nervous system is essentially a system which makes connections. It has input from sense organs and output to muscles.
    It is connected in several ways with the endocrine system, which makes hormones, and the digestive system and sex system. Hormones work slowly, so those changes are gradual.
  2. The brain is a kind of department store. It has, all inter-connected, departments which do different things. They even look different from each other.
  3. Much of what the body does is not conscious. A person breathes, heart beats, intestines digest, hair grows, thoughts pop into their mind... Some of this can be noticed by a person, and some (like breathing) can be influenced to some extent. But, basically, much of the body runs on automatic, adjusted by the autonomic nervous system.
    The brain, too, does much of its work without a person noticing it. The unconscious mind refers to the brain activities which are seldom noticed.

Vertebrate brain regions

Vertebrate-brain-regions
Corresponding regions of human and shark brain are shown.
What is at the rear of the shark brain (the medulla) is at the bottom of the human brain.
The shark cerebrum (telenchephalon) is at the front, that of a human is at the top

Several brain areas have kept their identities across the whole range of vertebrates, from hagfishes to humans. Here is a list of some of the most important areas, with a brief description of their functions as currently understood. These functions may still be disputed to some degree. Starting from the back (or, in humans, the underneath part) the regions are:

  • The hypothalamus is a small region at the base of the forebrain. It is the central control station for sleep/wake cycles, control of eating and drinking, control of hormone release, and many other functions. It sits immediately above the pituitary gland, and secretes hormones into the gland. These hormones inhibit or stimulate the pituitary gland. The gland, in turn, makes hormones which affect the rest of the body.
  • The thalamus sits above the hypothalamus, and below the cerebral cortex. It is a collection of nuclei with various functions. It acts as a relay station, gathering sense information of all kinds (except olfactory) and passes it on to the cerebral cortex. Also, it has a role in consciousness and sleep.
    There are action systems for several types of behaviour, including eating, drinking, defecation, and copulation.
  • The cerebellum adjusts the output of other brain systems to make them more precise. Removal of the cerebellum does not prevent an animal from doing anything in particular, but it makes actions hesitant and clumsy. This precision is not built-in, but learned by trial and error. Learning how to ride a bicycle is an example of a type of neural plasticity that may take place largely within the cerebellum.ch 42
  • The tectum, often called 'optic tectum', directs actions to points in space. Its best studied function is to direct eye movements. It also directs reaching movements. It gets strong visual inputs, and inputs from other senses which are useful in directing actions, such as auditory input in owls, input from the thermosensitive pit organs in snakes, etc. In some fish, such as lampreys, it is the largest part of the brain.
  • The hippocampus is, strictly speaking, only in mammals, but it has counterparts in all vertebrates. It is involved in spatial memory and navigation in fishes, birds, reptiles, and mammals.
  • The basal ganglia are a group of structures in the forebrain, which are strongly connected to the cerebral cortex and the thalamus. The main function of the basal ganglia seems to be selecting actions. They send inhibitory signals to all parts of the brain that can generate actions. In the right circumstances they release the inhibition, so that the action-generating systems can execute their actions. Rewards and punishments exert most important neural effects on the basal ganglia.
  • The cerebral cortex is a layer of grey cells that is on the surface of the forebrain. It is involved in multiple functions, including olfaction and spatial memory. In mammals, where it dominates the brain, it controls functions from many subcortical areas.
  • The olfactory bulb is a special structure that processes olfactory sensory signals (smells), and sends its output to the olfactory part of the cerebral cortex. It is a major brain component in many vertebrates, but much reduced in primates.

Brain size

The relationship between brain size, body size and other variables has been studied in a wide range of vertebrate species. Brain size increases with body size but not proportionally.

Mammals

Averaging across all mammals, it follows a power law, with an exponent of about 0.75. This formula applies to the average brain of mammals but each family departs from it, reflecting their sophistication of behavior. For example, primates have brains 5 to 10 times as large as the formula predicts. Predators tend to have larger brains. When the mammalian brain increases in size, not all parts increase at the same rate. The larger the brain of a species, the greater the fraction taken up by the neocortex.

Images for kids

  • drawing showing a neuron with a fiber emanating from it labeled "axon" and making contact with another cell. An inset shows an enlargement of the contact zone.

    Neurons generate electrical signals that travel along their axons. When a pulse of electricity reaches a junction called a synapse, it causes a neurotransmitter chemical to be released, which binds to receptors on other cells and thereby alters their electrical activity.

  • A bright green cell is seen against a red and black background, with long, highly branched, green processes extending out from it in multiple directions.

    Neurons often have extensive networks of dendrites, which receive synaptic connections. Shown is a pyramidal neuron from the hippocampus, stained for green fluorescent protein.

  • Very simple drawing of the front end of a human embryo, showing each vesicle of the developing brain in a different color.

    Brain of a human embryo in the sixth week of development

  • Graph showing 16 voltage traces going across the page from left to right, each showing a different signal. At the middle of the page all of the traces abruptly begin to show sharp jerky spikes, which continue to the end of the plot.

    Brain electrical activity recorded from a human patient during an epileptic seizure

  • Model of Cerebellar Perceptron

    Model of a neural circuit in the cerebellum, as proposed by James S. Albus

  • Drawing showing the ear, inner ear, and brain areas involved in hearing. A series of light blue arrows shows the flow of signals through the system.

    Diagram of signal processing in the auditory system

  • LocationOfHypothalamus

    Cross-section of a human head, showing location of the hypothalamus

  • Henry Markram - Visualizing Synaptic Maps onto Neocrortical Neurons

    The Human Brain Project is a large scientific research project, starting in 2013, which aims to simulate the complete human brain.

  • Drawing showing a monkey in a restraint chair, a computer monitor, a rototic arm, and three pieces of computer equipment, with arrows between them to show the flow of information.

    Design of an experiment in which brain activity from a monkey was used to control a robotic arm

  • Descartes-reflex

    Illustration by René Descartes of how the brain implements a reflex response

  • 1543,AndreasVesalius'Fabrica,BaseOfTheBrain

    Andreas Vesalius' Fabrica, published in 1543, showing the base of the human brain, including optic chiasma, cerebellum, olfactory bulbs, etc.

  • A drawing on yellowing paper with an archiving stamp in the corner. A spidery tree branch structure connects to the top of a mass. A few narrow processes follow away from the bottom of the mass.

    Drawing by Santiago Ramón y Cajal of two types of Golgi-stained neurons from the cerebellum of a pigeon

  • A fly resting on a reflective surface. A large, red eye faces the camera. The body appears transparent, apart from black pigment at the end of its abdomen.

    Fruit flies (Drosophila) have been extensively studied to gain insight into the role of genes in brain development.

  • A T-shaped object is made up of the cord at the bottom which feeds into a lower central mass. This is topped by a larger central mass with an arm extending from either side.

    The brain of a shark

  • Corresponding regions of human and shark brain are shown. The shark brain is splayed out, while the human brain is more compact. The shark brain starts with the medulla, which is surrounded by various structures, and ends with the telencephalon. The cross-section of the human brain shows the medulla at the bottom surrounded by the same structures, with the telencephalon thickly coating the top of the brain.

    The main anatomical regions of the vertebrate brain, shown for shark and human. The same parts are present, but they differ greatly in size and shape.


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Vertebrate brain Facts for Kids. Kiddle Encyclopedia.