Irritability is the general biological ability of cells and organisms to react (respond) to the influence of environmental factors. The most important element in the process of irritability are receptors. Receptor cells are called biological sensors or transducers, since they convert the energy of pressure, light, chemical and other factors into electrical impulses. Plants have receptors that are not as differentiated as animals. They are ectodesmas, starch statoliths, sensitive hairs, etc.

The main forms of manifestation of irritability in organisms are various types of motor reactions that are carried out by the whole organism or its individual parts. The most common motor reactions of living organisms to changes in environmental conditions are taxis, and in plants (except for taxis) - tropisms, nasties, nutations and autonomous movements.

Taxis are the movement of an organism, manifested in its spatial movement relative to the stimulus (amoeba, ciliate). If the movement of the organism is carried out in the direction of the acting factor, then such taxis is called positive; and negative when the movement occurs in the opposite direction.

Taxis are classified depending on the type of stimulus. Reaction to action: light - phototaxis, chemical compounds - chemotaxis, temperature - thermotaxis. An example of positive phototaxis is the oriented movement of flagellated unicellular algae (Chlamydomonas) to the zone of optimal lighting in an aquarium or pond, the appropriate orientation of chloroplasts in the mesophyll cells of a leaf; chemotaxis - accumulation of bacterial cells near a dead ciliate cell, movement of leukocytes towards the bacterium, etc.

Tropisms are a motor response of plant organs and parts to the unilateral influence of an environmental factor (light, gravity, water, chemicals, etc.).

Depending on the plant organism, tropisms can be positive when, due to uneven growth, an organ or part of the plant bends towards the active factor, and negative when growth processes cause deviations of the organ in the opposite direction. In plants, geotropism is best expressed - the reaction of its individual organs to the unilateral influence of the force of gravity.

There are three types of geotropism: positive - when the organ grows vertically downwards, negative - when the direction of movement is the opposite, and transverse, or diageotropism, when the organ tries to take a horizontal position. The main tap roots have, as a rule, positive geotropism; branches of the first order of woody plants, petioles of many leaves - negative; many rhizomes, lateral roots - transverse.

Phototropisms are growth movements of plants in response to unilateral exposure to light. With one-sided exposure to light (in a clearing, near buildings, in a room, etc.), the phototropism of individual shoots or even the entire above-ground part is especially clearly manifested. Plants seem to be drawn to the light (plants on the windowsill, sunflower inflorescences, leaves on the shoots).

Other physical and chemical factors can also have a one-sided effect on growing organs. Accordingly, chemotropisms, hydrotropisms, thermotropisms, and magnetotropisms are also distinguished (i.e., the classification of tropisms depends on the source of irritation).

Nastya. Nastic movements include movements that are a response of organs or parts of plants to the action of stimuli that do not have a specific direction, but affect diffusely and evenly from different directions. That is why it is impossible to establish any one-sided factor of the motor reaction.

Epinasty - when an organ (usually a leaf) bends downwards. This may be due to accelerated growth or turgor stretching of the upper side of the petiole (dropping of leaves of mimosa, vetch, white acacia).

Hyponasty - bending of an organ due to accelerated growth or stretching of cells on the lower side of the petiole and central vein (raising of leaf blades at night in quinoa, tobacco).

Nyctinasties are motor reactions caused by the onset of darkness, the so-called sleep in plants (closing flowers, lowering the inflorescences of carrots at night).

Photonasty - opening of flower petals when lighting increases (chicory, dandelion, potato inflorescences).

Thermonasty - opening of petals when the temperature rises (tulip, coltsfoot, garden poppy).

Seismonasty is the movement of plant organs that are a response to a shock or shock (mimosa, sorrel, purslane).

Nutations. Nutations are understood as the ability of plants to perform circular or pendulum movements due to periodically repeating changes in the values ​​of turgor pressure and the intensity of growth of opposite sides of a certain organ. This is best expressed at the tops and tendrils of climbing plants. In climbing plants, during growth, the apex makes uniform nutational movements and, upon contact with a support, begins to twine around it (hops, pumpkin, peas, beans).

IRRITABILITY IRRITABILITY

the ability of living cells, tissues or an entire organism to respond to external influences. or internal influences - irritants; underlies their adaptation to changing environmental conditions. R. manifests itself at all levels of life development and is accompanied by a nonspecific complex. changes, expressed in changes in metabolism, electrical. potential, the state of protoplasm, and in high-level organizations. animals is associated with the implementation of specific. functions (conduction of nerve impulses, muscle contraction, secretion of glandular tissue, etc.). In plants due to structural and functional changes in membranes and underlies their regulatory system. Naib, it is clearly manifested in reactions to light (phototropism, photoperiodism), to gravity. field (geotropism), in engine. reactions (nasty). In animals who do not have a nervous system, reactions to irritations cover the entire protoplasm and are expressed by ch. arr. in the form of an engine reactions (taxis). In multicellular animals, nervous and muscle tissues provide rapid and accurate responses to stimuli; forms of indirect reactive communication with the stimulus develop (reflexively) through higher nervous activity and consciousness. The ability of nerve and muscle cells to respond to stimulation is called. excitability. Sometimes local reactions of tissues or cells are called. reactivity, and the occurrence of a wave-like spreading process - excitability; often the term "R." used as a synonym for excitability.

.(Source: “Biological Encyclopedic Dictionary.” Editor-in-chief M. S. Gilyarov; Editorial Board: A. A. Babaev, G. G. Vinberg, G. A. Zavarzin and others - 2nd ed., corrected . - M.: Sov. Encyclopedia, 1986.)

irritability

The property of living organisms to respond to various influences (stimuli) with corresponding changes at the level of a cell, tissue or the entire organism. Irritability is associated with the body's adaptation to changing environmental conditions. In plants it manifests itself in reactions to light, gravity, and in motor (as in lower animals) reactions (see. Tropisms, Nastia). Multicellular animals and humans are characterized by more accurate, rapid and varied reactions in response to irritation. They are provided reflexes And higher nervous activity. The term “irritability” is often used as a synonym for “excitability.”

.(Source: “Biology. Modern illustrated encyclopedia.” Chief editor A. P. Gorkin; M.: Rosman, 2006.)

See what “IRRITABILITY” is in other dictionaries:

irritability- a change in the physiological state of the whole organism, its organs, tissues or cells under the influence of external influences called stimuli. The minimum magnitude of the stimulus sufficient to cause such a change is called... ... Great psychological encyclopedia

The ability of living cells, tissues or an entire organism to respond to the influence of factors (stimulants) of the external or internal environment by changing their state or activity. Underlies their adaptation to changing environmental conditions.... ... Ecological dictionary

1) excitability; 2) increasing susceptibility and counter-action in relation to irritation. The historian Lamprecht (“Zur jüngsten deutschen Vergangenheit”, 2 Bde., 1921 – 1922), drawing an analogy with the psychological in the spiritual historical field... ... Philosophical Encyclopedia

IRRITABILITY, irritability, many. no, female (book). distracted noun to irritable; property, ability to be irritated. Nerve irritability. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary

IRRITABILITY- IRRITABILITY, the property of living organisms or their parts to specifically change their states under the influence of changes in the environment or in other parts of the body. Very often the same definition is given to the concept of excitability. There is a big... ... Great Medical Encyclopedia

The property of organisms to respond to environmental influences by changes in their state or activity... Big Encyclopedic Dictionary Synonym dictionary

This article is about the properties of living organisms. For the human trait, see Irritability. Irritability (excitability) is the ability of a living organism to respond to external influences by changing its physicochemical and ... ... Wikipedia

Irritability is a universal property of all living things to respond to environmental influences.

From the textbook

§42.ANIMAL IRRITABILITY

Basic concepts: ANIMAL IRRITABILITY. SENSE ORGANS

Remember! What is irritability?

Think

The presence of irritability in plants is proven through research that demonstrates the growth movements of the root and shoot in the bean seedling. This is due to the fact that the shoot reacts to light by growing, and the root perceives the force of gravity and grows downward. How can you be sure that animals are irritable?

I l. 167. Plant growth movements

What are the characteristics of animal irritability?

Irritability in animals manifests itself in the ability to respond to environmental influences with active activity. For example, at morning sunrise, birds wake up and begin to sing, or touching a grape snail makes it hide in the plowing. In these examples, light or touch will be stimuli, the process of action of this force will be irritation, and the response of birds or snails to the action of factors will be a biological reaction. Irritants for animals can be light, mechanical stress, temperature, salt composition of water, food, humidity, water, sounds, chemicals and many other factors.

I l. 168. The finch is one of the most common songbirds

A sign of irritability at the cellular level is a positive electrical charge on the surface of the cell and a negative charge inside the cell. This charge difference can change under the influence of various factors, which is the beginning of intracellular processes. Changes in cellular metabolism determine the cell's response to the influence of the factor. Irritability is also characteristic of the cytoplasm of cells, which is capable of perceiving environmental influences and responding to them by the occurrence or cessation of movement. In multicellular animals, tissues that are characterized by excitability participate in the production of irritability. These are nervous, muscular and certain types of epithelial. The conduction of excitation to ensure movement, the release of secretions is associated with such organs as nerves, spinal cord and brain, muscles, and secretion glands. In shaping the animal’s response to environmental influences, the nervous and endocrine systems are of decisive importance.

Consequently, ANIMAL IRRITABILITY is the ability to move from a resting state to an active state in response to the action of environmental factors, realized at different levels of their organization.

What are the forms of irritability in animals?

Biological responses of animals to environmental influences manifest themselves in the form of taxis and reflexes. Unlike the growth or hygroscopic movements of plants and fungi, in animals these reactions are motor.

Taxis is a motor reaction in response to the directed influence of a factor, carried out by cells or organisms. For example, the ejection of a thread from a hydra stinging cell upon touching a sensitive outgrowth is mechanotaxis, and the movement of amebocytes towards nutrients or away from harmful substances is positive or negative chemotaxis. Taxis provide spatial orientation of animal movements to the action of favorable or unfavorable stimuli.

Reflexes are a motor response of the body to a specific trigger stimulus, carried out with the obligatory participation of the nervous system. For the first time, reflexes as forms of irritability appear in coelenterates due to the emergence of a diffuse nervous system in them. Reflexes can be innate unconditioned (compression of the hydra’s body into a lump after mechanical action) or acquired conditioned (food reflexes of fish that are formed when feeding at the same time).

Il. 169. Taxis of amebocytes

I l. 170. Unconditioned protective reflex of the hydra

Taxis and reflexes are constant components in animal behavior. If reflexes determine the occurrence and course of an animal’s biological reaction, then taxis provide its direction. For example, the appearance of a seagull with food triggers the reaction of the chicks (unconditioned food reflex), and the red spot on its beak directs the reaction of these chicks to its beak (positive phototaxis).

So, the biological reactions of animals to the influence of factors is the relationship between taxis and reflexes.

Il. 171. Forms of irritability in tern chicks

What is the sign of the senses for the animal body?

SENSE ORGANS are anatomical formations of the animal body that perceive information from the external or internal environment. This information comes in the form of effects of sound, light, chemicals and is important for turning on and off various biological reactions.

The main sense organs in animals are vision, hearing, smell, taste and touch. For mobile animals, the organs of balance are of great importance. Certain groups of animals may have specific sensory organs associated with their lifestyle. Thus, fish have a lateral line, pit snakes have organs for perceiving heat rays, and dolphins and sperm whales have organs for perceiving reflected sounds.

What is the importance of sense organs for animals?

The most primitive organs of vision, which are light-sensitive eyes (jellyfish, free-living flatworms), allow us to distinguish light from darkness. Simple eyes (spiders) allow one to distinguish the strength and direction of light and to detect the movements of objects. Compound eyes of insects, cephalopods and vertebrates. Such eyes already distinguish the shape, volume and color of objects. Thanks to their visual organs, animals navigate their environment, successfully obtain food during daylight hours, and protect themselves from enemies.

Sound - vibrations of the air or water environment or solid substrate - plays a dual role in the life of animals. On the one hand, it is a signal of danger, and on the other, it is a way of communication. Sound-receiving organs are already present in jellyfish. They perceive low-frequency vibrations and will allow you to “anticipate” a storm. The perception and reproduction of sounds is well developed in arthropods, in particular insects. their hearing organs can be located on the legs, abdomen, and antennae. The organ of hearing is most important for terrestrial vertebrates, so their auditory system is difficult: amphibians have an eardrum, reptiles have an external auditory canal, birds and some mammals have an external ear, mammals already have all three auditory ossicles.

Sensitivity to chemical stimuli is one of the oldest types of senses. In animals it is provided by the organs of smell and taste, which play an important role in searching for food, individuals of the opposite sex, recognizing individuals of their own species, avoiding predators and harmful influences. Among terrestrial invertebrates, the chemical sense organs reached their greatest development in arthropods, especially in insects, and among vertebrates - in mammals.

Mechanical influences of the environment (touch, pressure, vibration) in invertebrates are perceived by sensitive structures of the integument in the form of cilia, hairs, antennae, and in vertebrates - by skin receptors.

Consequently, environmental information is very diverse, and therefore the sense organs of animals are also diverse.

ACTIVITY

Laboratory research

ANIMAL SENSE ORGANS

Goal: to consolidate knowledge about the sense organs of animals; to develop the ability to characterize the sensory organs of various groups of animals using the example of specific representatives.

Equipment: drawings, insect collections, wet preparations of crayfish and fish.

Progress

1. Examine the body of the crayfish and determine the name, features and location of the organs of vision, touch, smell and taste.

2. Examine the body of the cockchafer and determine the name, features and location of the organs of vision, touch, smell and taste.

3. Examine the body of the river perch and determine the name, features and location of the organs of vision, smell, taste and lateral line.

4. Fill in the table.

Name of sense organs	Crayfish	Khrushchev May	River perch
Organs of vision
Olfactory organs
Organs of taste
Organs of touch

5. State your conclusion.

Learning to know

Mini-project “HOW DO ANIMALS SEE?”

For centuries, people had no idea how animals see the world. But today science gives us the opportunity to look into the wonderful world of diversity of animal visual organs. Use the guiding rule (see appendix) to create a mini-project and, using the example of the six proposed animals (cat, horse, dragonfly, pigeon, monkey, snake) or animals that you choose yourself, describe the capabilities of the animals’ visual organs.

RESULT

	Questions for self-control
	1. What is irritability? 2. What is the meaning of irritability? 3. Name the main forms of irritability in animals. 4. Give an example of the taxis and reflexes of animals. 5. What are sense organs? 6. Name the main sense organs of animals.
	7. What are the features of animal irritability? 8. What are the forms of irritability in animals? 9. What is the importance of sense organs for the animal body?
10-12	10. Describe the sensory organs of different groups of animals, using specific representatives.

The concept of irritability. Microorganisms, plants and animals respond to a wide variety of environmental influences: mechanical influences (puncture, pressure, shock, etc.), temperature changes, intensity and direction of light rays, sound, electrical stimulation, changes in the chemical composition of the air , water or soil, etc. This leads to certain fluctuations in the body between a stable and unstable state. Living organisms are capable, as they develop, of analyzing these states and reacting to them accordingly. Similar properties of all organisms are called irritability and excitability.

Irritability is the body’s ability to respond to external or internal influences.

Irritability arose in living organisms as an adaptation that provides better metabolism and protection from the effects of environmental conditions.

Excitability is the ability of living organisms to perceive the effects of stimuli and respond to them with an excitation reaction.

Environmental influences affect the state of the cell and its organelles, tissues, organs and the body as a whole. The body responds to this with appropriate reactions.

The simplest manifestation of irritability is movement. It is typical even for the simplest organisms. This can be observed in an experiment on an amoeba under a microscope. If small lumps of food or sugar crystals are placed next to the amoeba, it begins to actively move towards the nutrient. With the help of pseudopods, the amoeba envelops the lump, drawing it inside the cell. A digestive vacuole is immediately formed there, in which food is digested.

As the structure of the body becomes more complex, both metabolism and manifestations of irritability become more complex. Single-celled organisms and plants do not have special organs that provide the perception and transmission of irritations coming from the environment. Multicellular animals have sensory organs and a nervous system, thanks to which they perceive irritations, and responses to them achieve great accuracy and expediency.

Irritability in unicellular organisms. Taxis.

The simplest forms of irritability are observed in microorganisms (bacteria, unicellular fungi, algae, protozoa).

In the example with the amoeba, we observed the movement of the amoeba towards the stimulus (food). This motor reaction of unicellular organisms in response to irritation from the external environment is called taxis. Taxis is caused by chemical irritation, which is why it is also called chemotaxis(Fig. 51).

Rice. 51. Chemotaxis in ciliates

Taxis can be positive and negative. Let's place a test tube with a culture of ciliates-slippers in a closed cardboard box with a single hole located opposite the middle part of the test tube, and expose it to light.

After a few hours, all the ciliates will concentrate in the illuminated part of the test tube. This is positive phototaxis.

Taxis are characteristic of multicellular animals. For example, blood leukocytes exhibit positive chemotaxis towards substances secreted by bacteria, concentrate in places where these bacteria accumulate, capture and digest them.

Irritability in multicellular plants. Tropisms. Although multicellular plants do not have sensory organs or a nervous system, they nevertheless clearly exhibit various forms of irritability. They involve changing the direction of growth of a plant or its organs (root, stem, leaves). Such manifestations of irritability in multicellular plants are called tropisms.

Stem with leaves show positive phototropism and grow towards the light, and the root - negative phototropism(Fig. 52). Plants respond to the Earth's gravitational field. Pay attention to the trees growing along the mountainside. Although the soil surface has a slope, trees grow vertically. The response of plants to gravity is called geotropism(Fig. 53). The root that emerges from a germinating seed is always directed downwards towards the ground - positive geotropism. A shoot with leaves developing from a seed is always directed upward from the ground - negative geotropism.

Tropisms are very diverse and play a large role in plant life. They are clearly expressed in the direction of growth in various climbing and climbing plants, such as grapes and hops.

Rice. 52. Phototropism

Rice. 53. Geotropism: 1 – a flower pot with straight-growing radish seedlings; 2 – a flower pot placed on its side and kept in the dark to eliminate phototropism; 3 – the seedlings in the flower pot have bent in the direction opposite to the action of gravity (the stems have negative geotropism)

In addition to tropisms, plants exhibit other types of movements - nastia. They differ from tropisms in the absence of a specific orientation to the stimulus that caused them. For example, if you touch the leaves of a bashful mimosa, they quickly fold longitudinally and fall downwards. After some time, the leaves return to their previous position (Fig. 54).

Rice. 54. Nastia at the shy mimosa: 1 – in normal condition; 2 - when irritated

The flowers of many plants respond to light and humidity. For example, a tulip's flowers open in the light and close in the dark. The dandelion's inflorescence closes in cloudy weather and opens in clear weather.

Irritability in multicellular animals. Reflexes. Due to the development of the nervous system, sensory organs and organs of movement in multicellular animals, the forms of irritability become more complex and depend on the close interaction of these organs.

In its simplest form, such irritation occurs in coelenterates. If you prick a freshwater hydra with a needle, it will shrink into a ball. External irritation is perceived by a sensitive cell. The excitement that arises in it is transmitted to the nerve cell. The nerve cell transmits excitation to the skin-muscle cell, which reacts to irritation by contracting. This process is called reflex (reflection).

Reflex- This is the body’s response to irritation carried out by the nervous system.

The nervous system regulates the activity of the entire body and its reactions to external and internal changes. One of the functions of nerve cells is irritability.

What is irritability: concept

Irritability is the ability of a living organism to respond to external or internal stimuli. And irritability is a tendency to excessive, inadequate reactions to ordinary environmental stimuli. The causes of irritability may be:

• psychological (fears, anxiety, overwork, alcoholism, high-calorie foods),
• physiological (hormonal changes, lack of certain microelements in the body).

Irritability of organisms

Irritability can manifest itself at all levels of life development. In plants, irritants can be temperature, light, humidity, gravity, and the chemical composition of the environment. A plant, reacting to external or internal stimuli, can develop or die. People and animals are characterized by diverse reactions to different stimuli.

Irritability most often manifests itself in aggression and anger. Irritability is typical for teenagers with their mood swings. In young children, irritability is expressed in restlessness, tearfulness, and the slightest rejection of discomfort. Irritability appears in women during pregnancy due to sudden physiological changes.

Irritability and sensitivity

Sensitivity is the body's reflection of influences that may be necessary or dangerous. Depending on the location of irritation, superficial and deep sensitivity are distinguished.

Superficial sensitivity: pain, temperature (cold, hot), tactile (touch), hair, feeling of moisture, etc. Deep sensitivity: muscle-articular, vibration, sense of weight, sense of pressure.

Irritability and excitability

Excitability is the body's ability to respond with an excitation reaction to irritation. But not every irritation can cause arousal. If irritation occurs slowly and gradually, then excitation may not occur, but with rapid irritation, excitation occurs.

With tissue pathology, excitability can vary from a sharp increase to complete extinction. Sexual excitability is the body's reaction to environmental influences and is associated with pronounced sexual potency.

There is no need to turn irritability into a permanent state of your body. Be healthy!