nervous system Best Guide in 2023

nervous system

The brain is a group of cells that specializes in processing electrochemical stimuli, from sensory receptors to a networked response center.

All living things can perceive changes in themselves and their environment. Changes in the external environment include changes in light, temperature, sound, movement and smell; changes in the internal environment include changes in the head, neck, and internal trunk. Once diagnosed, internal and external changes must be identified and acted upon for survival. As life on Earth evolves and the environment becomes more complex, the survival of organisms depends on their ability to respond to changes in their environment.

One thing necessary for survival is quick reflexes or reflexes. Because communication from one cell to another by chemical means was too slow to survive, the system evolved to allow for faster responses.

nervous system
nervous system

There are two types of nerves: distributed and centralized. The scattered-type systems found in lower invertebrates lack cells and neurons are distributed throughout the body in a reticular pattern.

In the central system of higher invertebrates and vertebrates, part of the brain is involved in coordinating information and directing responses. This centralization culminates in vertebrates with well-developed brains and spinal cords. The nerves that make up the peripheral nervous system carry impulses to the brain and spinal cord.


This article begins with a discussion of the properties of the nervous system, its functions in response to stimuli, and the similar electrochemical processes to which they respond. Below is a discussion of the different types of nerves, from the simplest to the most complex.

Form and function of the nervous system

Stimulus-response coordination

The simplest response is a direct one-on-one response. A change in environment is stimulating; the body’s reaction to it is a reaction. In single organisms, this response is triggered by a substance in the cell fluid called an irritant. In simple organisms such as algae, protozoa and fungi, the organism’s response to approach or move away from a stimulus is called tropism. In larger organisms, many organisms control processes or regulators, where the response involves the coordination and integration of events in different parts of the body Respect, support and sleep on responses.

Multicellular organisms have two basic mechanisms that provide this supervisory coordination: drug control and neuromodulation.

In drug administration, substances called hormones are produced by the right cell group and spread to other parts of the body where they act on target cells, or are transported through the blood and affect metabolism or support the synthesis of other drugs. Changes caused by hormonal activity manifest themselves as a result of changes in morphology, growth, development and behavior in the organism.

It uses hormones as regulators in the stimulus response of the body to various external stimuli. The directional response to motion is called tropism and is positive when the force moves towards the stimulus and negative when the force moves away from the stimulus.

When the seed germinates, the growing stem turns upward towards the light and the root turns downward, away from the light. Thus, stems show positive phototropism and negative geotropism, while roots show negative phototropism and positive geotropism. In this example, light and gravity are the stimulus and growth is the response. Regulators are some hormones produced by the cells in the shoot tips of the plant. These hormones, called auxin, diffuse from the tissue in the lower part of the shoot and concentrate on the shaded side, causing these cells to elongate and thus bending the shoot towards the light.

The result is to keep the plant in good light.

The nervous system can be defined as a group of cells called neurons that specialize in processing impulses (excited states) from sensory receptors through neural networks to effectors (affected area).

Organisms with a brain are capable of exhibiting more complex behaviors than organisms without a brain. The brain specializes in processing impulses and can respond quickly to environmental stimuli.

Many responses mediated by the nervous system are designed to maintain the status quo or homeostasis in animals. Stimuli that tend to move or destroy a part of the organism elicit a response that reduces side effects and restores them to a better state.Animals may go through periods of exploration or meditation, nesting and migration. While these activities are beneficial for the survival of animals, they are not always done by humans in response to personal needs or support.

Finally, behavioral learning may be based on the homeostatic and priming functions of the brain.


Intracellular systems

All living cells are sensitive to environmental stimuli that can affect the cell in many ways, such as electrical, chemical or changes. These changes occur as a response when glandular cells release secretions, muscle cells contract, plant stem cells twist, or strike the whip-like “arms” or cilia of ciliated cells. .

The functioning of a person’s brain can be explained by the behavior of simple amoebae. Unlike other protozoans, amoebas do not have structures that function to receive stimuli and produce or transmit responses.

However, the amoeba pretends to have a brain, as all the reactivity of its cytoplasm works for the brain. The excitement generated by the stimulus is transmitted to other parts of the cell and causes a response in the animal. The amoeba will move to areas where there is some kind of light. It is attracted to chemicals released by food and exhibits a nutritional response. It also leaves the area where it is poisoned and shows a protective reaction when it comes into contact with other substances.

Receptors include organelles of ciliates and photosensitive surfaces of flagellates. Cells include cilia (thin, hair-like projections on the brain), flagella (thin, flag-like cilia), and other organelles involved in feeding or movement. Protozoa also have subcellular cytoplasmic filaments that can contract like muscles. For example, the contraction of the protozoan vortex is the result of contraction of thread-like structures in the trunk called myofilaments.

Although protozoans clearly have specific receptors and effectors, it is unclear whether there is any variation between the two. In a ciliate such as Paramecium, the strokes of the cilia pushing it forward are not random but coordinated. The beating of the cilia begins at one end of the bacterium and moves to the other in regular waves, indicating that the relationship is long-term. The fibrillar system attached to the body, from which the eyelashes are rooted, can be replaced by waves, but without the system, the coordination of the eyelashes can also occur. Each cilium can respond to stimuli sent to the cell by neighboring cilia, if in cooperation, the connection between the cilia will be the result.

The best evidence that the structure is responsible for coordination by other ciliate species that have a specialized ciliated cell (membrane) array and widely separated cilia groups (cirri). By combining these structures, the vernier can perform various movements (such as sharp turns, backward movements, turns) in addition to swimming. The five furs on the back of the body are attached to an area on the front called the brain.

Motor fibers apparently coordinate between cilia and membranes. Membranes, cilia, and nerve cells make up the neuromotor system.


Nervous System

External stimuli are received by receptor cells, usually neurons. (In a few cases, the receptors are non-neurosensory epithelial cells such as hair cells or taste cells of the ear that stimulate neighboring cells.

) stimulation is changed or converted into electrical impulses in the receiving neuron. The incoming excitement or negative emotion then travels along the extensions or axons of the receptors to regulators called interneurons. (All neurons can make impulses that are short in electrical changes of the cell membrane. This impulse can be transmitted multiple times in the axon without loss of energy until the return (until the message or input reaches another axon). Interneuron regulators select, interpret, or modify input from receptors, and sends impulses that lead or lead to efferent neurons like the strong neurons of the body.

Inducing neurons make contact with an effector, such as a muscle or tumor, that causes a response.

In its simplest form, the receptor-regulatory-effector units form a functional group called the reflex arc. Sensory cells send impulses to central interneurons that make contact with motor neurons. Motor neurons transmit efferent impulses to responding effectors.

In two-neuron arcs, simple reflexes are fast, short, automatic, and only part of the body. Examples of simple reflexes include tensing muscles, blinking when the cornea is touched, and drooling when seeing food. This type of reflex is mainly involved in maintaining homeostasis.

The difference between a simple brain and a complex brain is not the basic units but their arrangement.

Sensory impulses from specific receptors reach the central nervous system via special neuronal pathways. However, in the central nervous system, impulses can go through many pathways generated by many neurons. Theoretically, impulses can be distributed to each motor neuron and produce a response in an effector. More than one stimulus can also produce the same response.

Thanks to the integration of interneurons, the body’s behavior does not equal its perception; It is a collective action that shows the coordination of many people’s reactions.

Reflections can occur in complex sequences that create complex behavioral patterns. In this case, the behavior is not a genetic trait, a stereotyped response, but is caused by adaptation and adaptation to the environment. Many automatic, intransitive processes can be modified or adapted to new perspectives. For example, experiments by the Russian physiologist Ivan Petrovich Pavlov showed that animals salivate when they see food, while other stimuli such as sound.

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