Abstract of a lesson in biology on the topic: "Muscular and nervous tissues of animals." nervous tissue
A collection of cells that are similar in origin, structure, function and development is called cloth.
Cardiac muscles, although similar to striated muscles, have a more complex structure. They, like smooth muscles, work regardless of the will of the person.
Main Functions muscle tissue are motor-tion and contractile. Under the influence nerve impulses muscle tissue moves and responds with contraction.
nervous tissue
nervous tissue forms the spinal cord and brain. It controls the activity of all human tissues and organs. Nervous tissue is formed by cells of two types: nerve cell, or neuron, and neuroglia.
A nerve cell (neuron) is of two types: sensory and motor. The neuron has a different (round, star-shaped, oval, pear-shaped, etc.) shape. Its value is also different (from 4 to 130 microns). Unlike other cells, a nerve cell, in addition to the membrane, cytoplasm and nucleus, contains one long and several short processes. Its long process is called an axon, and its short process is called a dendrite. material from the site
The long processes of a sensitive neuron, leaving the spinal cord and brain, are sent to all tissues and organs and, perceiving from them irritation of the external and internal environment, transmit them to the central nervous system.
The long processes of the motor neuron also depart from the spinal cord and brain and, reaching the skeletal muscles of the body, smooth muscles internal organs and hearts govern their movement.
Short processes of nerve cells do not go beyond the spinal cord and brain; they connect some cells with other surrounding nerve cells. The main function of the nervous tissue is motor. Under external influence nerve cells are excited and transmit impulses to the corresponding organ.
Tissue is a collection of cells and intercellular substance that have the same structure, function and origin.
In the body of mammals and humans, 4 types of tissues are distinguished: epithelial, connective, in which bone, cartilage and adipose tissues can be distinguished; muscular and nervous.
Tissue - location in the body, types, functions, structure
Tissues are a system of cells and intercellular substance that have the same structure, origin and functions.
The intercellular substance is a product of the vital activity of cells. It provides communication between cells and creates a favorable environment for them. It may be liquid, such as blood plasma; amorphous - cartilage; structured - muscle fibers; solid - bone(as salt).
tissue cells have different shape, which defines their function. Fabrics are divided into four types:
- epithelial - border tissues: skin, mucous membrane;
- connective - the internal environment of our body;
- muscle;
- nervous tissue.
epithelial tissue
Epithelial (boundary) tissues - line the surface of the body, mucous membranes of all internal organs and cavities of the body, serous membranes, and also form the glands of the external and internal secretion. The epithelium lining the mucosa is located on the basement membrane, and inner surface directly facing the external environment. Its nutrition is accomplished by diffusion of substances and oxygen from blood vessels through the basement membrane.
Features: there are many cells, there is little intercellular substance and it is represented by a basement membrane.
epithelial tissues perform the following functions:
- protective;
- excretory;
- suction.
Classification of epithelium. According to the number of layers, single-layer and multi-layer are distinguished. The shape is distinguished: flat, cubic, cylindrical.
If all epithelial cells reach the basement membrane, this is a single-layer epithelium, and if only cells of one row are connected to the basement membrane, while others are free, it is multilayered. A single-layer epithelium can be single-row and multi-row, depending on the level of location of the nuclei. Sometimes mononuclear or multinuclear epithelium has ciliated cilia facing the external environment.
Stratified epithelium Epithelial (integumentary) tissue, or epithelium, is a boundary layer of cells that lines the integument of the body, the mucous membranes of all internal organs and cavities, and also forms the basis of many glands.
Glandular epithelium The epithelium separates the organism (internal environment) from external environment, but at the same time serves as an intermediary in the interaction of the organism with the environment. Epithelial cells are tightly connected to each other and form a mechanical barrier that prevents the penetration of microorganisms and foreign substances into the body. Epithelial tissue cells live for a short time and are quickly replaced by new ones (this process is called regeneration).
Epithelial tissue is also involved in many other functions: secretion (external and internal secretion glands), absorption (intestinal epithelium), gas exchange (lung epithelium).
The main feature of the epithelium is that it consists of a continuous layer of densely packed cells. The epithelium can be in the form of a layer of cells lining all surfaces of the body, and in the form of large clusters of cells - glands: liver, pancreas, thyroid, salivary glands etc. In the first case, it lies on the basement membrane, which separates the epithelium from the underlying connective tissue. However, there are exceptions: epithelial cells in the lymphatic tissue alternate with elements of connective tissue, such an epithelium is called atypical.
Epithelial cells located in a layer can lie in many layers (stratified epithelium) or in one layer (single layer epithelium). According to the height of the cells, the epithelium is divided into flat, cubic, prismatic, cylindrical.
Single layered squamous epithelium - lines the surface serous membranes: pleura, lungs, peritoneum, pericardium of the heart.
Single-layered cuboidal epithelium - forms the walls of the tubules of the kidneys and excretory ducts glands.
Single-layer cylindrical epithelium - forms the gastric mucosa.
The bordered epithelium - a single-layer cylindrical epithelium, on the outer surface of the cells of which there is a border formed by microvilli that provide absorption of nutrients - lines the mucous membrane of the small intestine.
Ciliated epithelium (ciliated epithelium) - a pseudo-stratified epithelium, consisting of cylindrical cells, the inner edge of which, that is, facing the cavity or channel, is equipped with constantly fluctuating hair-like formations (cilia) - cilia ensure the movement of the egg in the tubes; removes microbes and dust in the respiratory tract.
Stratified epithelium is located on the border of the organism and the external environment. If keratinization processes take place in the epithelium, i.e., the upper layers of cells turn into horny scales, then such a multilayer epithelium is called keratinizing (skin surface). Stratified epithelium lines the mucous membrane of the mouth, food cavity, horny eye.
The transitional epithelium lines the walls Bladder, renal pelvis, ureter. When filling these organs, the transitional epithelium is stretched, and cells can move from one row to another.
Glandular epithelium - forms glands and performs a secretory function (releasing substances - secrets that are either excreted into the external environment or enter the blood and lymph (hormones)). The ability of cells to produce and secrete substances necessary for the vital activity of the body is called secretion. In this regard, such an epithelium is also called the secretory epithelium.
Connective tissue
Connective tissue Consists of cells, intercellular substance and connective tissue fibers. It consists of bones, cartilage, tendons, ligaments, blood, fat, it is in all organs (loose connective tissue) in the form of the so-called stroma (skeleton) of organs.
In contrast to epithelial tissue, in all types of connective tissue (except adipose tissue), the intercellular substance predominates over the cells in volume, i.e., the intercellular substance is very well expressed. Chemical composition and physical properties intercellular substance are very diverse in various types connective tissue. For example, blood - the cells in it “float” and move freely, since the intercellular substance is well developed.
In general, connective tissue makes up what is called the internal environment of the body. It is very diverse and various types- from dense and loose forms to blood and lymph, the cells of which are in the liquid. The fundamental differences between the types of connective tissue are determined by the ratio of cellular components and the nature of the intercellular substance.
In dense fibrous connective tissue (tendons of muscles, ligaments of joints), fibrous structures predominate, it experiences significant mechanical loads.
Loose fibrous connective tissue is extremely common in the body. It is very rich, on the contrary, in cellular forms of different types. Some of them are involved in the formation of tissue fibers (fibroblasts), others, which is especially important, primarily provide protective and regulatory processes, including through immune mechanisms (macrophages, lymphocytes, tissue basophils, plasma cells).
Bone
Bone tissue The bone tissue that forms the bones of the skeleton is very strong. It maintains the shape of the body (constitution) and protects the organs located in the cranium, chest and pelvic cavities, participates in mineral metabolism. The tissue consists of cells (osteocytes) and an intercellular substance in which nutrient channels with vessels are located. The intercellular substance contains up to 70% mineral salts(calcium, phosphorus and magnesium).
In its development, bone tissue goes through fibrous and lamellar stages. In various parts of the bone, it is organized in the form of a compact or spongy bone substance.
cartilage tissue
Cartilage tissue consists of cells (chondrocytes) and intercellular substance (cartilaginous matrix), which is characterized by increased elasticity. It performs a supporting function, as it forms the bulk of the cartilage.
There are three types of cartilage tissue: hyaline, which is part of the cartilage of the trachea, bronchi, ends of the ribs, articular surfaces of bones; elastic, forming the auricle and epiglottis; fibrous, located in the intervertebral discs and joints of the pubic bones.
Adipose tissue
Adipose tissue is similar to loose connective tissue. The cells are large and filled with fat. Adipose tissue performs nutritional, shaping and thermoregulatory functions. Adipose tissue is divided into two types: white and brown. Humans are predominantly white adipose tissue, part of it surrounds the organs, maintaining their position in the human body and other functions. The amount of brown adipose tissue in humans is small (it is present mainly in a newborn child). Main function brown adipose tissue - heat production. Brown adipose tissue maintains the body temperature of animals during hibernation and the temperature of newborns.
Muscle
Muscle cells are called muscle fibers because they are constantly elongated in one direction.
The classification of muscle tissues is carried out on the basis of the structure of the tissue (histologically): by the presence or absence of transverse striation, and on the basis of the mechanism of contraction - voluntary (as in skeletal muscle) or involuntary (smooth or cardiac muscle).
Muscle tissue has excitability and the ability to actively contract under the influence of nervous system and some substances. Microscopic differences make it possible to distinguish two types of this tissue - smooth (non-striated) and striated (striated).
Smooth muscle tissue has a cellular structure. It forms the muscular membranes of the walls of internal organs (intestines, uterus, bladder, etc.), blood and lymphatic vessels; its contraction occurs involuntarily.
Striated muscle tissue consists of muscle fibers, each of which is represented by many thousands of cells, merged, in addition to their nuclei, into one structure. It forms skeletal muscles. We can shorten them as we wish.
A variety of striated muscle tissue is the heart muscle, which has unique abilities. During life (about 70 years), the heart muscle contracts more than 2.5 million times. No other fabric has such strength potential. Cardiac muscle tissue has a transverse striation. However, unlike skeletal muscle, there are special areas where the muscle fibers meet. Due to this structure, the contraction of one fiber is quickly transmitted to neighboring ones. This ensures the simultaneous contraction of large sections of the heart muscle.
Also, the structural features of muscle tissue are that its cells contain bundles of myofibrils formed by two proteins - actin and myosin.
nervous tissue
Nervous tissue consists of two types of cells: nervous (neurons) and glial. Glial cells are closely adjacent to the neuron, performing supporting, nutritional, secretory and protective functions.
The neuron is the main structural and functional unit nervous tissue. Its main feature is the ability to generate nerve impulses and transmit excitation to other neurons or muscle and glandular cells of the working organs. Neurons may consist of a body and processes. Nerve cells are designed to conduct nerve impulses. Having received information on one part of the surface, the neuron very quickly transmits it to another part of its surface. Since the processes of a neuron are very long, information is transmitted over long distances. Most neurons have processes of two types: short, thick, branching near the body - dendrites and long (up to 1.5 m), thin and branching only at the very end - axons. Axons form nerve fibers.
A nerve impulse is an electrical wave that travels high speed along the nerve fiber.
Depending on the functions performed and structural features, all nerve cells are divided into three types: sensory, motor (executive) and intercalary. motor fibers, which are part of the nerves, transmit signals to the muscles and glands, sensory fibers transmit information about the state of the organs to the central nervous system.
Now we can combine all the information received into a table.
Types of fabrics (table)
|
Fabric group |
Types of fabrics |
Fabric structure |
Location |
|
| Epithelium | Flat | The cell surface is smooth. Cells are tightly packed together | Skin surface, oral cavity, esophagus, alveoli, nephron capsules | Integumentary, protective, excretory (gas exchange, urine excretion) |
| Glandular | Glandular cells secrete | Skin glands, stomach, intestines, endocrine glands, salivary glands | Excretory (sweat, tears), secretory (formation of saliva, gastric and intestinal juice, hormones) | |
| Shimmery (ciliated) | Composed of cells with numerous hairs (cilia) | Airways | Protective (cilia trap and remove dust particles) | |
| Connective | dense fibrous | Groups of fibrous, densely packed cells without intercellular substance | Skin proper, tendons, ligaments, membranes of blood vessels, cornea of the eye | Integumentary, protective, motor |
| loose fibrous | Loosely arranged fibrous cells intertwined with each other. Intercellular substance structureless | Subcutaneous adipose tissue, pericardial sac, pathways of the nervous system | Connects the skin to the muscles, supports the organs in the body, fills the gaps between the organs. Carries out thermoregulation of the body | |
| cartilaginous | Living round or oval cells lying in capsules, intercellular substance is dense, elastic, transparent | Intervertebral discs, cartilages of the larynx, trachea, auricle, surface of the joints | Smoothing rubbing surfaces of bones. Warp protection respiratory tract, auricles | |
| Bone | Living cells with long processes, interconnected, intercellular substance - inorganic salts and ossein protein | Skeleton bones | Support, movement, protection | |
| Blood and lymph | Liquid connective tissue, composed of shaped elements(cells) and plasma (liquid with dissolved organic and minerals- serum and protein fibrinogen) | The circulatory system of the whole body | Carries O 2 and nutrients throughout the body. Collects CO 2 and dissimilation products. It ensures the constancy of the internal environment, the chemical and gas composition of the body. Protective (immunity). Regulatory (humoral) | |
| muscular | striated | Multinucleated cylindrical cells up to 10 cm long, striated with transverse stripes | Skeletal muscles, cardiac muscle | Arbitrary movements body and its parts, facial expressions, speech. Involuntary contractions (automatic) of the heart muscle to push blood through the chambers of the heart. Has properties of excitability and contractility |
| Smooth | Mononuclear cells up to 0.5 mm long with pointed ends | Walls digestive tract, blood and lymphatic vessels, skin muscles | Involuntary contractions of the walls of internal hollow organs. Raising hair on the skin | |
| nervous | Nerve cells (neurons) | The bodies of nerve cells, various in shape and size, up to 0.1 mm in diameter | Forms the gray matter of the brain and spinal cord | Higher nervous activity. The connection of the organism with the external environment. Centers of conditioned and unconditioned reflexes. Nervous tissue has the properties of excitability and conductivity |
| Short processes of neurons - tree-branching dendrites | Connect with processes of adjacent cells | They transmit the excitation of one neuron to another, establishing a connection between all organs of the body | ||
| Nerve fibers - axons (neurites) - long outgrowths of neurons up to 1.5 m in length. In organs, they end with branched nerve endings. | Nerves of the peripheral nervous system that innervate all organs of the body | Pathways of the nervous system. They transmit excitation from the nerve cell to the periphery along the centrifugal neurons; from receptors (innervated organs) - to the nerve cell along centripetal neurons. Intercalary neurons transmit excitation from centripetal (sensitive) neurons to centrifugal (motor) |
In humans and animals, four groups of basic tissues are distinguished: epithelial, connective, muscle and nervous. In muscles, for example, muscle tissue predominates, but connective and nervous tissue also occur along with it.
The intercellular substance can also be homogeneous, like that of cartilage, and can include various structural formations in the form of elastic bands, threads that give elasticity and resilience to tissues.
Students draw a table
"Tissues of animals and humans"
fabrics | Varieties | Functions | Structural features | Location |
epithelial | Single layer, multilayer, glandular, ciliary | Protective, secretory, absorbent | cells are closely adjacent to each other, forming a layer, there is very little intercellular substance; cells have the ability to repair (regenerate) | Shells of organs, endocrine glands, integuments of the body |
Connective | Bone cartilaginous Blood Adipose tissue Elastic connective tissue | Supporting, protective, hematopoietic Support, protective Respiratory, transport, protective storage, protective Support and protective | Have varied structure, but similar large quantity intercellular substance that determines the mechanical properties of tissues | Skeleton Respiratory organs, auricle, ligaments Cavity of the heart and blood vessels Subcutaneous tissue, between internal organs Ligaments, tendons, layers between organs, dermis |
muscular | smooth, striated, Cardiac | Contractile Contractile Contractile | Spindle cells with one rod-shaped nucleus Long multinucleated fibers Interconnected muscle fibers that have a small number of nuclei in the center of the fiber | Musculature of the digestive tract, bladder, lymphatic and blood vessels, and other internal organs Musculoskeletal system of the body and some internal organs Heart |
nervous | Ensuring coordinated activities various systems organs, ensuring the connection of the body with the external environment, adaptation of metabolism to changing conditions | Includes two types of cells - neurons and neuroglia | brain and spinal cord, ganglions and fibers |
- epithelial tissuesare borderline, as they cover the body from the outside and line the inside hollow organs and walls of body cavities. A special type of epithelial tissue - glandular epithelium- forms the majority of glands (thyroid, sweat, liver, etc.), the cells of which produce one or another secret. Epithelial tissues have the following features: their cells are closely adjacent to each other, forming a layer, there is very little intercellular substance; cells have the ability to recover (regenerate).
Epithelial cells in shape can be flat, cylindrical, cubic. According to the number of layers of the epithelium, there are single-layer and multilayer. Examples of epithelium: single-layered squamous lines the thoracic and abdominal cavity body; multilayer flat forms the outer layer of the skin (epidermis); single-layer cylindrical lines most of intestinal tract; multilayer cylindrical - the cavity of the upper respiratory tract); a single-layer cubic forms the tubules of the nephrons of the kidneys. Functions of epithelial tissues; protective, secretory, absorption.
- Connective tissues(tissues of the internal environment) unite groups of tissues of mesodermal origin, very different in structure and functions. Types of connective tissue: bone, cartilage, subcutaneous fatty tissue, ligaments, tendons, blood, lymph, etc. General feature the structure of these tissues isloose arrangement of cells separated from each other by a well-defined intercellular substance, which is formed by various fibers of protein nature (collagen, elastic) and the main amorphous substance.
Each type of connective tissue has a special structure of the intercellular substance, and, consequently, different functions due to it. For example, in the intercellular substance of the bone tissue there are salt crystals (mainly calcium salts), which give the bone tissue special strength. Therefore, bone tissue performs protective and supporting functions.
Blood is a type of connective tissue in which the intercellular substance is liquid (plasma), due to which one of the main functions of blood is transport (carries gases, nutrients, hormones, end products of cell vital activity, etc.).
The intercellular substance of loose fibrous connective tissue located in the layers between organs, as well as connecting the skin with muscles, consists of an amorphous substance and is freely located in different directions elastic fibres. Due to this structure of the intercellular substance, the skin is mobile. This tissue performs supporting, protective and nourishing functions.
- Muscle tissues determine all types of motor processes within the body, as well as the movement of the body and its parts in space. This is provided through special properties muscle cells - excitability and contractility. All muscle tissue cells contain the thinnest contractile fibers - myofibrils, formed by linear protein molecules - actin and myosin. When they slide relative to each other, the length of the muscle cells changes.
There are three types of muscle tissue: striated, smooth and cardiac. Striated (skeletal) muscle tissue is built from many multinucleated fiber-like cells 1-12 cm long. The presence of myofibrils with light and dark areas that refract light differently (when viewed under a microscope) gives the cell a characteristic transverse striation, which determined the name of this type of fabric. All skeletal muscles, muscles of the tongue, walls are built from it. oral cavity, pharynx, larynx, upper esophagus, mimic, diaphragm. Features of striated muscle tissue: speed and arbitrariness (i.e., dependence of contraction on the will, desire of a person), consumption a large number energy and oxygen, fatigue.Cardiac tissue consists of transversely striated mononuclear muscle cells, but has different properties. The cells are not arranged in a parallel bundle, like skeletal cells, but branch, forming a single network. Due to the many cellular contacts, the incoming nerve impulse is transmitted from one cell to another, providing simultaneous contraction and then relaxation of the heart muscle, which allows it to perform its pumping function.
Cells of smooth muscle tissue do not have transverse striation, they are fusiform, mononuclear, their length is about 0.1 mm. This type of tissue is involved in the formation of the walls of tube-shaped internal organs and vessels (digestive tract, uterus, bladder, blood and lymphatic vessels). Features of smooth muscle tissue: involuntariness and low force of contractions, the ability to long-term tonic contraction, less fatigue, a small need for energy and oxygen.
- nervous tissue , from which the brain and spinal cord, nerve nodes and plexuses are built, peripheral nerves, performs the functions of perception, processing, storage and transmission of information coming from both environment, and from the organs of the body itself. The activity of the nervous system provides the body's reactions to various stimuli, regulation and coordination of the work of all its organs.
The main properties of nerve cells - neurons that form the nervous tissue are excitability and conductivity. Excitability is the ability of the nervous tissue to enter a state of excitation in response to irritation, and conductivity is the ability to transmit excitation in the form of a nerve impulse to another cell (nerve, muscle, glandular). Due to these properties of the nervous tissue, the perception, conduction and formation of the body's response to the action of external and internal stimuli is carried out.
A nerve cell, or neuron, consists of a body and two types of processes. The body of a neuron is represented by the nucleus and the cytoplasm surrounding it. It is the metabolic center of the nerve cell; when it is destroyed, she dies. The bodies of neurons are located mainly in the brain and spinal cord, that is, in the central nervous system (CNS), where their accumulations form the gray matter of the brain. Clusters of nerve cell bodies outside the CNS form ganglia, or ganglia . Short, tree-like processes extending from the body of a neuron are called dendrites . They perform the functions of perceiving irritation and transmitting excitation to the body of the neuron.
3. Consolidation of new material.
Students must answer the following questions
What is fabric?
How many types of tissues are in the human body? Name them.
What types of connective tissue do you know?
« nervous tissue »
Biology lesson in grade 8
Lesson designed
biology teacher,
Kriulenko Nina Mikhailovna
Target. Explore features of the structure of the nervous tissue, conducting a nerve impulse, to find out the principle of interaction of nerve cells with each other and with other cells of the body. To develop the ability to analyze, compare and contrast data, the ability to work with a textbook, to isolate the main thing.
Equipment: presentation "Nervous tissue", a microscope with a video camera, a micropreparation "Nerve cells", a computer program "Biology Grade 9", an electronic library "Enlightenment" - (videos showing the resting potential and action potential, synapse work), video "Anatomy 1 part", interactive whiteboard.
During the classes.
Before the lesson, the presentation, videos and fragments of the film on the disk, as well as the output of the microscope with the camera, are loaded through the interactive whiteboard.
1 Learning new material
1. Display the image of the micropreparation "Nervous tissue" on the screen
2. Question: determine which tissue is under the microscope?
Exit on the topic of the lesson, work with the presentation. (slide number 1)
IN 1. What feature of nervous tissue?
IN 2. What mysteries of this tissue, these cells would be interesting to know?
(the problem is formulated by the students themselves)
Problem: How do nerve cells communicate with each other? How do they transmit information to other cells? (the problem is written out on the board (an interactive whiteboard is used) (slide No. 2)
3. Offer your versions. (versions are briefly written on the board) (slide No. 3)
4. Demonstration of the video fragment of the film "The structure of the nervous tissue"
5. Working with the presentation slide "Nervous tissue" (slide number 4)
The table is compiled by independently finding information in the textbook.
6. Demonstration of the video clip " The structure of a neuron»
7. During the film, sign the parts of the cage and draw it.
(Due to the board's capabilities, the movie stops at a close-up of the neuron, and parts of the neuron are labeled on the board.)
8. Classification of neurons Demonstration of the film "Types of Neurons" (the film is shown on TV using a video cassette, the teacher stops at key points. Simultaneously working with the board with the presentation slide "Types of Neurons" Students fill out a table in a notebook, answering the teacher's questions during the film. The presentation slide is used as a check for the correctness of the answer and design) (slide number 5)
10. Return to the problem: How do cells communicate with each other? Demonstration of the video film "Nerve circuits" The answer is with the help of nerve impulses. (output to videos via the List board function)
11. How does a cell behave at rest?
Demonstration of the video “Resting Potential” (access to the videos through the function of the board “List”)
12. What happens to the cell during excitation?
Demonstration of the video "Action Potential"
13. Why did the cell move from a state of rest to an excited state?
Synapses - Connection of neurons. (In the course of the lesson, all new words - terms are attached to a magnetic board. Students write them in a notebook on a separate sheet without definitions. By the end of the lesson, students write down: mediator, axon, dendrite, neuron, receptor, effector, glial cells, synapse).
Demonstration of the video fragment "Synapse", which explains the concept and necessity of synapses, and then the video "Synapse", which explains in detail the work of the synapse.
14. Work with slide No. 6 of the presentation. In the course of work, students make a diagram in a notebook using the information they find in the textbook.
15. Return to the problem. (slide number 7)
How do nerve cells communicate with each other? How do they transmit information to other cells?
16. Conclusion: Nerve cells communicate with each other and transmit information using electrical and chemical signals. (slide number 8) Students formulate the conclusion on their own, the presentation is used as confirmation.
The conclusion is written in a notebook.
2. Consolidation and primary verification of understanding.
1. Work with the test. Find matches for the term and definitions. The test is loaded as a document on the whiteboard, and opens on the test page, then shifts in peer review.
| A) base protective function |
|
| B) Transmission of a nerve impulse |
|
| 3 Glial cells | C) Connection of neurons |
| 4Plectrums | D) Substances formed in the synapse |
| 5 Norepinephrine | D) Brake mediator |
| 6 Dopamine | E) Excitatory mediator |
| 7 Motor neurons | G) Long process of a neuron |
| 8 Sensory neurons | H) They transmit a signal to the organs |
| 9 Interneurons | i) transmit signals to the brain |
| 10 Dendrites | C) Found in the brain and spinal cord |
| K) Short processes of a neuron |
2. Mutual verification. Evaluation criteria and test answers on the blackboard.
3. Reflection. (who, what received for the work. Only "5" and "4" are put in the class magazine)
Lecture 7. Hnerve tissue.
nervous tissue is a system of interconnected nerve cells and neuroglia that provide specific functions of perceiving irritation, excitation, generating an impulse and transmitting it. It is the basis of the structure of the organs of the nervous system, which ensure the regulation of all tissues and organs, their integration in the body and communication with the environment.
Nervous tissue is made up of:
Nerve cells (neurons, neurocytes)- the main structural components of the nervous tissue that perform a specific function.
neuroglia, which ensures the existence and functioning of nerve cells, carrying out supporting, trophic, delimiting, secretory and protective functions.
Development of nervous tissue
I - the formation of the neural groove, its immersion,
II - the formation of the neural tube, neural crest,
III - migration of neural crest cells;
1 - neural groove,
2 - neural crest,
3 - neural tube,
4 - ectoderm
Nervous tissue develops from dorsal ectoderm. The process of formation of the neural tube is called neurulation. On the 18th day, the ectoderm in the midline of the back differentiates, a longitudinal thickening is formed, called neural plate. Soon this plate bends along the center line and turns into groove bounded at the edges neural folds.
Subsequently, the groove closes in neural tube and separates from the cutaneous ectoderm. At the site of separation of the neural tube from the ectoderm, two strands of cells called neural crests (ganglion plates). The anterior part of the neural tube begins to thicken and turns into the brain.
The neural tube and ganglionic plate consist of poorly differentiated cells - meduloblasts, which are intensively divided by mitosis. Meduloblasts begin to differentiate very early and give rise to 2 differentons: neuroblastic differon (neuroblasts young neurocytes mature neurocytes); spongioblastic differon (spongioblasts glioblasts gliocytes).
From the neural tube further neurons and macroglia of the central nervous system are formed.
neural crest gives rise spinal ganglia and nodes of the autonomic NS, cells of the soft brain and arachnoid shells brain and some types of glia: neurolemmocytes (Schwann cells), ganglion satellite cells, adrenal medulla cells, skin melanocytes, etc.
Histogenesis
Reproduction of nerve cells occurs mainly during the period embryonic development. Initially, the neural tube consists of 1 layer of cells that multiply by mitosis, which leads to an increase in the number of layers.
The primary neural tube in the spinal region divides early into three layers:
1) innermost ependymal layer containing germ cells ependymocytes (line the spinal canal, cerebral ventricles).
2) intermediate zone ( mantle or mantle layer ), where proliferating cells migrate from the ependymal layer; Cells differentiate in two directions:
Neuroblasts lose their ability to divide and further differentiate into neurons (neurocytes).
Glioblasts continue to divide and give rise to astrocytes and oligodendrocytes. (See Macroglia, p. 5)
The ability to divide does not completely lose both mature astrocytes and oligodendrocytes. Neuronal neogenesis stops in the early postnatal period. From the cells of the mantle layer are formedGray matter dorsal and part of the gray matter of the brain.
3) the outer layer is the marginal veil, which in the mature brain contains myelin fibers- processes of 2 previous layers and macroglia and gives Startwhite matter .
Neurons
Neurons, or neurocytes, are specialized cells of the nervous system responsible for the reception, processing (processing) of stimuli, impulse conduction and influence on other neurons, muscle or secretory cells. Neurons release neurotransmitters and other substances that transmit information. A neuron is a morphologically and functionally independent unit, but with the help of its processes it makes synaptic contact with other neurons, forming reflex arcs- links of the chain from which the nervous system is built.
Neurons come in a wide variety of shapes and sizes. The diameter of the cell bodies-granules of the cerebellar cortex is 4-6 microns, and the giant pyramidal neurons of the motor zone of the cerebral cortex - 130-150 microns.
Usually neurons are from the body (perikaryon) and processes: axon and various number of branching dendrites.
Outgrowths of neurons
Axon (neurite)- the process along which the impulse travels from the bodies of neurons. The axon is always alone. It is formed before other processes.
Dendrites- processes along which the impulse goes to the body of the neuron. A cell may have several or even many dendrites. Usually dendrites branch, which is the reason for their name (Greek dendron - tree).
Types of neurons
By the number of processes are distinguished:
Different types of neurons:
a - unipolar,
b - bipolar,
c - pseudo-unipolar,
g - multipolar
Sometimes among bipolar neurons occurs pseudo-unipolar, from the body of which one common outgrowth departs - a process, which then divides into a dendrite and an axon. Pseudo-unipolar neurons are present in spinal ganglia.
multipolar having an axon and many dendrites. Most neurons are multipolar.
According to their function, neurocytes are divided into:
afferent (receptor, sensory, centripetal)- perceive and transmit impulses to the central nervous system under the influence of the internal or external environment;
associative (insert)- connect neurons of different types;
effector (efferent) - motor (motor) or secretory- transmit impulses from the central nervous system to the tissues of the working organs, prompting them to act.
Nucleus of the neurocyte - usually large, round, contains highly decondensed chromatin. The exception is the neurons of some ganglia of the autonomic nervous system; for example, in prostate and the cervix sometimes there are neurons containing up to 15 nuclei. The nucleus has 1, and sometimes 2-3 large nucleoli. Gain functional activity neurons is usually accompanied by an increase in the volume (and number) of nucleoli.
In the cytoplasm there is a well-defined granular EPS, ribosomes, a lamellar complex and mitochondria.
Special organelles:
Basophilic substance (chromatophilic substance or tigroid substance, or Nissl substance/substance/clumps). It is located in the perikaryon (body) and dendrites (in the axon (neurite) - absent). When staining the nervous tissue with aniline dyes, it is detected in the form of basophilic lumps and grains of various sizes and shapes. Electron microscopy showed that each lump of chromatophilic substance consists of cisterns of the granular endoplasmic reticulum, free ribosomes and polysomes. This substance actively synthesizes protein. It is active, is in a dynamic state, its amount depends on the state of the National Assembly. With the active activity of the neuron, the basophilia of the lump increases. With overvoltage or injury, the lumps break up and disappear, the process is called chromolysis (tigrolysis).
neurofibrils composed of neurofilaments and neurotubules. Neurofibrils are fibrillar structures of spirally twisted proteins; are detected by impregnation with silver in the form of fibers arranged randomly in the body of the neurocyte, and in parallel bundles in the processes; function: musculoskeletal (cytoskeleton) and are involved in the transport of substances along the nerve process.
Inclusions: glycogen, enzymes, pigments.
neuroglia
Glial cells provide the activity of neurons, playing an auxiliary role.
Performs the functions:
trophic,
delimiting,
maintaining the constancy of the environment around neurons,
protective
secretory.
Macroglia (gliocytes)
Macroglia develops from neural tube glioblasts. Gliocytes:
1. Epidymocytes.
2. Astrocytes:
a) protoplasmic astrocytes (synonym: short-beamed astrocytes);
b) fibrous astrocytes (synonym: long-beamed astrocytes).
3. Oligodendrocytes:
epindimocytes
Line the spinal canal, cerebral ventricles. They are similar in structure to epithelium. Cells have a low-prismatic shape, tightly adjacent to each other, forming a continuous layer. On the apical surface may have shimmering cilia, causing current cerebrospinal fluid. The other end of the cells continues into a long process penetrating the entire thickness of the brain and spinal cord. Functions : delimiting(boundary membrane: cerebrospinal fluid brain tissue), supporting, secretory- participates in the formation and regulation of the composition of the cerebrospinal fluid.
Astrocytes
Outgrowth ("radiant") cells form the backbone of the spinal cord and brain.
1) protoplasmic astrocytes- cells with short but thick processes, contained in gray matter. Functions: trophic, delimiting.
2) fibrous astrocytes- cells with thin long processes are located in the white matter of the CNS. Functions: support, participation in exchange processes.
Oligodendrocytes
Oligodendrogliocytes are present in both gray and white matter. In the gray matter, they are localized near the perikarya (the bodies of nerve cells). In the white matter, their processes form the myelin layer in the myelinated nerve fibers.
Oligodendrocytes adjacent to the perikaryon (in the periphery of the NS - satellite cells, mantle gliocytes, or ganglion gliocytes). They surround the bodies of neurons and thereby control the metabolism between neurons and the environment.
Oligodendrocytes of nerve fibers (in the periph. N.S. - lemmocytes, or Schwann cells). They surround the processes of neurons, forming sheaths of nerve fibers.
Functions : trophic, participation in metabolism, participation in regeneration processes, participation in the formation of a sheath around nerve processes, participation in impulse transmission.
microglia
Microglia are macrophages in the brain, they provide immunological processes in the central nervous system, phagocytosis, can affect the function of neurons. Kinds : - typical (branched, resting), - amoeboid, - reactive. (see textbook p. 283-4) Source of development : in embryonic period- from the mesenchyme; subsequently can be formed from blood cells of the monocytic series, i.e. from bone marrow. Function - protection against infection and damage and removal of products of destruction of nervous tissue.
NERVE FIBERS
They consist of a process of a nerve cell covered with a membrane, which is formed by oligodendrocytes. The process of a nerve cell (axon or dendrite) that is part of a nerve fiber is called axle cylinder.
Kinds:
non-myelinated (meelless) nerve fiber,
myelinated (pulp) nerve fiber.
unmyelinated nerve fibers
They are found predominantly in the autonomic nervous system. Neurolemmocytes of the sheaths of non-myelinated nerve fibers, being dense, form strands, in which oval nuclei are visible at a certain distance from each other. In the nerve fibers of the internal organs, as a rule, in such a strand there is not one, but several (10-20) axial cylinders belonging to different neurons. They can, leaving one fiber, move into an adjacent one. Such fibers containing several axial cylinders are called cable-type fibers. Electron microscopy of non-myelinated nerve fibers shows that as the axial cylinders are immersed in the strand of neurolemmocytes, the membranes of the latter sag, tightly cover the axial cylinders and, closing over them, form deep folds, at the bottom
which are located separate axial cylinders. The sections of the neurolemmocyte membrane close together in the fold area form a double membrane - mesaxon, on which, as it were, an axial cylinder is suspended. The membranes of neurolemmocytes are very thin, therefore, neither the mesaxon nor the boundaries of these cells can be seen under a light microscope, and the sheath of unmyelinated fibers under these conditions is revealed as a homogeneous strand of cytoplasm, "clothing" the axial cylinders. A nerve impulse along an unmyelinated nerve fiber is conducted as a wave of depolarization of the cytolemma of the axial cylinder at a speed of 1-2 m/sec.
myelinated nerve fibers
They are found in both the central and peripheral nervous systems. They are much thicker than unmyelinated nerve fibers. They also consist of an axial cylinder, "dressed" by a sheath of neurolemmocytes (Schwann cells), but the diameter of the axial cylinders of this type of fiber is much thicker, and the sheath is more complex. In the formed myelin fiber, it is customary to distinguish two layers of shell:
internal, thicker, - myelin layer,
outer, thin, consisting of cytoplasm, nuclei of neurolemmocytes and neurolemmas.
The myelin layer contains a significant amount of lipids, therefore, when treated with osmic acid, it stains in dark brown color. In the myelin layer, narrow light lines are periodically found - myelin notches, or Schmidt-Lanterman notches. At certain intervals, sections of the fiber devoid of the myelin layer are visible - knotted interceptions, or interceptions of Ranvier, i.e. boundaries between adjacent lemmocytes.
The segment of fiber between adjacent intercepts is called internodal segment.
During development, the axon sinks into a groove on the surface of the neurolemmocyte. The edges of the groove are closed. This creates double fold plasmolemma of the neurolemmocyte - mesaxon. Mesaxon elongates, concentrically layered on the axial cylinder and forms around it a dense layered zone - the myelin layer. The cytoplasm with nuclei is moved to the periphery - an outer shell or a light Schwann shell is formed (when stained with osmic acid).
The axial cylinder consists of neuroplasm, longitudinal parallel neurofilaments, mitochondria. From the surface covered with a membrane - axolemma that conducts a nerve impulse. The speed of impulse transmission by myelinated fibers is greater than by unmyelinated ones. The nerve impulse in the myelinated nerve fiber is conducted as a wave of depolarization of the cytolemma of the axial cylinder, "jumping" (salting) from interception to the next interception at a speed of up to 120 m/sec.
In case of damage only to the process of the neurocyte regeneration is possible and proceeds successfully in the presence of certain conditions for this. At the same time, distal to the site of damage, the axial cylinder of the nerve fiber undergoes destruction and resolves, but the lemmocytes remain viable. The free end of the axial cylinder thickens above the damage site - a " growth flask", and begins to grow at a rate of 1 mm / day along the surviving lemmocytes of the damaged nerve fiber, i.e. these lemmocytes play the role of a "guide" for the growing axial cylinder. Under favorable conditions, the growing axial cylinder reaches the former receptor or effector end apparatus and forms a new terminal apparatus.
Nerve endings
Nerve fibers end in terminal apparatus - nerve endings. There are 3 groups of nerve endings:
effector endings(effectors) that transmit a nerve impulse to the tissues of the working organ,
receptor(affectoral, or sensitive, sensory),
end devices, which form interneuronal synapses and carry out the connection of neurons with each other.
Effector nerve endings
There are two types of effector nerve endings:
motor,
secretory.
motor nerve endings
These are the end devices of the axons of the motor cells of the somatic, or autonomic, nervous system. With their participation, the nerve impulse is transmitted to the tissues of the working organs. Motor endings in striated muscles are called neuromuscular endings or motor plaques. neuromuscular ending consists of the terminal branching of the axial cylinder of the nerve fiber and a specialized section of the muscle fiber - the axo-muscular sinus.
The myelinated nerve fiber, approaching the muscle fiber, loses the myelin layer and sinks into it, involving its plasmolemma and basement membrane.
Neurolemmocytes covering the nerve terminals, in addition to their surface, which is in direct contact with the muscle fiber, turn into specialized flattened bodies of glial cells. Their basement membrane continues into the basement membrane of the muscle fiber. Connective tissue elements at the same time pass into the outer layer of the shell of the muscle fiber. The plasmalemma of the terminal branches of the axon and muscle fiber are separated by a synoptic slit about 50 nm wide. synaptic cleft filled with an amorphous substance rich in glycoproteins.
Sarcoplasm with mitochondria and nuclei together forms postsynaptic part of the synapse.
secretory nerve endings neuroglandular)
They are terminal thickenings of the terminal or thickening along the nerve fiber containing presynaptic vesicles, mainly cholinergic (contain acetylcholine).
Receptor (sensory) nerve endings
These nerve endings are receptors, terminal devices of dendrites sensory neurons, - are scattered throughout the body and perceive various irritations both from the external environment and from internal organs.
Accordingly, two large groups of receptors are distinguished: exteroreceptors and interoreceptors.
Depending on the perception of irritation: mechanoreceptors, chemoreceptors, baroreceptors, thermoreceptors.
According to the structural features, sensitive endings are divided into
free nerve endings, i.e. consisting only of the terminal branches of the axial cylinder,
not free, containing in its composition all the components of the nerve fiber, namely the branching of the axial cylinder and glial cells.
Non-free endings, in addition, can be covered with a connective tissue capsule, and then they are called encapsulated.
Non-free nerve endings that do not have a connective tissue capsule are called unencapsulated.
Encapsulated connective tissue receptors, with all their diversity, always consist of branching of the axial cylinder and glial cells. Outside, such receptors are covered with a connective tissue capsule. An example of such endings is the lamellar bodies that are very common in humans (Vater-Pacini bodies). In the center of such a body is an internal bulb, or flask (bulbus interims), formed by modified lemmocytes (Fig. 150). The myelinated sensitive nerve fiber loses its myelin layer near the lamellar body, penetrates into the inner bulb and branches. Outside, the body is surrounded by a layered capsule consisting of s / t plates connected by collagen fibers. Lamellar bodies perceive pressure and vibration. They are present in the deep layers of the dermis (especially in the skin of the fingers), in the mesentery and internal organs.
Sensitive encapsulated endings include tactile bodies - Meissner's bodies. These structures are ovoid in shape. They are located in the tops of the connective tissue papillae of the skin. Tactile bodies consist of modified neurolemmocytes (oligodendrocytes) - tactile cells located perpendicular to the long axis of the body. The body is surrounded by a thin capsule. Collagen microfibrils and fibers connect tactile cells with the capsule, and the capsule with the basal layer of the epidermis, so that any displacement of the epidermis is transmitted to the tactile body.
Encapsulated endings include genital bodies (in the genitals) and Krause end flasks.
To encapsulated nerve endings also include muscle and tendon receptors: neuromuscular spindles and neurotendinous spindles. Neuromuscular spindles are sensory organs in skeletal muscles, which function as a stretch receptor. The spindle consists of several striated muscle fibers enclosed in an extensible connective tissue capsule - intrafusal fibers. The rest of the muscle fibers lying outside the capsule are called extrafusal.
Intrafusal fibers have actin and myosin myofilaments only at the ends, which contract. The receptor part of the intrafusal muscle fiber is the central, non-contracting part. There are two types of intrafusal fibers: nuclear bag fibers(the central extended part they contain many nuclei) and nuclear chain fibers(the nuclei in them are located in a chain throughout the receptor area).
Interneuronal synapses
A synapse is the site of transmission of nerve impulses from one nerve cell to another nerve or non-nerve cell.
Depending on the localization of the endings of the terminal branches of the axon of the first neuron, there are:
axodendritic synapses (impulse passes from axon to dendrite),
axosomatic synapses (the impulse passes from the axon to the body of the nerve cell),
axoaxonal synapses (impulse passes from axon to axon).
According to the final effect, synapses are divided into:
Brake;
Exciting.
electrical synapse- is an accumulation of nexuses, the transmission is carried out without a neurotransmitter, the impulse can be transmitted both in the forward and in the opposite direction without any delay.
chemical synapse- transmission is carried out with the help of a neurotransmitter and only in one direction, to conduct an impulse through chemical synapse need time.
The axon terminal is presynaptic part, and the area of the second neuron, or other innervated cell with which it contacts, - postsynaptic part. In the presynaptic part are synaptic vesicles, numerous mitochondria and individual neurofilaments. Synaptic vesicles contain neurotransmitters: acetylcholine, norepinephrine, dopamine, serotonin, glycine, gamma-aminobutyric acid, serotonin, histamine, glutamate.
The area of synaptic contact between two neurons consists of the presynaptic membrane, the synaptic cleft, and the postsynaptic membrane.
presynaptic membrane- this is the membrane of the cell that transmits the impulse (axolemma). In this area are localized calcium channels, which contribute to the fusion of synaptic vesicles with the presynaptic membrane and the release of the mediator into the synaptic cleft.
fabrics, classification. As a result of evolution in higher multicellular organisms arose fabrics. fabrics It's historical...General characteristics of the curriculum in the specialty 5B071300 - "Transport, transport equipment and technology" Awarded degrees
Document2004 4. Zh. Dzhunusova Zh. Introduction into political science. - Almaty, ... directory in 2 parts. -Moscow: ... abstracts ... concepts ... classification. General patterns chemical processes. General ... : lecture, ... general and private embryology, the doctrine of tissues, private histology ...
Lectures on neuroanatomy
Tutorial... LECTURE O HISTOLOGY NERVOUS FABRICS 15 CELL THEORY 15 NEURON 18 CLASSIFICATION ... abstractslectures. ... preliminary introduction... pharyngeal, general
