simple mechanisms in wildlife

In the skeleton of animals and humans, all bones that have some freedom of movement are leverage, for example, in humans - the bones of the limbs, the lower jaw, the skull (the fulcrum is the first vertebra), the phalanges of the fingers. In cats, movable claws are levers; many fish have spines on the dorsal fin; in arthropods, most segments of their external skeleton; bivalve mollusks have shell valves.

Skeletal linkages are usually designed to gain speed while losing power. This is essential for adaptability and survival. Especially large gains in speed are obtained in insects. The wings of some insects begin to vibrate according to electrical signals that are carried by the nerves. Each of these nerve signals results in a single contraction of a muscle, which in turn moves the wing. Two groups of opposing muscles, known as the "lifter" and "lowerer", help the wings rise and fall by pulling in opposite directions. Dragonflies can reach speeds of up to 40 km per hour in flight.

The ratio of the length of the arms of the lever element of the skeleton is closely dependent on the vital functions performed by this organ. For example, the long legs of a greyhound and a deer determine their ability to run fast; the short paws of the mole are designed for the development of large forces at low speed; the long jaws of the greyhound allow you to quickly grab the prey on the run, and the short jaws of the bulldog close slowly, but hold strongly (the chewing muscle is attached very close to the fangs, and the strength of the muscles is transmitted to the fangs almost without weakening).

In plants, lever elements are less common, which is explained by the low mobility of the plant organism. A typical lever is a tree trunk and its continuation, the main root. The root of a pine or oak that goes deep into the ground has great resistance to tipping over (the shoulder of resistance is large), so pines and oaks almost never turn upside down. On the contrary, spruce trees, which have a purely superficial root system, tip over very easily. Interesting linkage mechanisms can be found in some flowers (for example, sage stamens), as well as in some drop-down fruits. Consider the structure of meadow sage (Fig. 10).

The elongated stamen serves as a long arm BUT lever. Anther is located at its end. Short shoulder B the lever, as it were, guards the entrance to the flower. When an insect (most often a bumblebee) crawls into a flower, it presses on the short arm of the lever. At the same time, the long arm hits the back of the bumblebee with an anther and leaves pollen on it. Flying to another flower, the insect pollinates it with this pollen.

In nature, flexible organs are common that can change their curvature over a wide range (spine, tail, fingers, body of snakes and many fish). Their flexibility is due to either a combination a large number short levers with a system of rods, or a combination of elements that are relatively inflexible, with intermediate elements that are easily deformable (elephant trunk, caterpillar body, etc.). Bending control in the second case is achieved by a system of longitudinal or obliquely located rods.

Levers in the human body

Levers 2.jpg

In the skeleton of animals and humans, all bones that have some freedom of movement are levers. For example, in a person - the bones of the limbs, the lower jaw, the skull, the phalanges of the fingers. Skeletal linkages are usually designed to gain speed with a loss in strength. Consider the equilibrium conditions for a lever using the skull as an example. Here the rotation of the lever passes through the articulation of the skull with the first vertebra. In front of the fulcrum on a relatively short shoulder, the force of gravity of the head acts, behind it is the force of traction of the muscles and ligaments attached to the occipital bone. The hand is also a perfect lever, the fulcrum of which is in the elbow joint. acting force is the strength of the biceps muscle (biceps), which is attached to the tubercle of the radius, the resistance to be overcome is the load applied to the hand. Under the action of a force, a lever - a hand lifts a load that is in the palm of your hand. The point of application of the force is at a distance of =3 cm (i.e., the arm of the force =3 cm), and the arm of gravity =30 cm. Thus, in order to hold the load, a muscle force is needed that is ten times the size of the load. The fact that we lose here in strength does not matter much - the muscle has quite a lot of strength. But it is very important that, losing in strength, we win in other respects. A slight contraction in the length of the muscle allows, in this case, a significant movement of the palm with the load (we can even lift the load to the shoulder). In addition, we win in the speed of movement. Muscles cannot contract very quickly; fortunately, with such a lever, this is not required: the speed of movement of the palm with the load is 10 times the speed of muscle contraction. In other words, losing 10 times in strength, we gain in the same amount of time in the length and speed of the movement of the load. Another example of the operation of the lever is the action of the freedom of the foot when lifting on the toes. The support O of the lever, through which the axis of rotation passes, are the heads of the metatarsal bones. The overcome force - the weight of the whole body - is applied to the talus. The active muscle force that lifts the body is transmitted through the Achilles tendon and applied to the protrusion of the calcaneus. Why is it impossible to hold the same load with an outstretched arm as with a bent one? When the arm is extended, the direction of action of the muscle force makes a small angle with the longitudinal axis of rotation of the lever. In this case, to keep the load the same as with the bent arm, it is necessary to significantly increase the muscle effort. With the same muscular effort, a much smaller load can be held with an outstretched arm than with a bent one. Body links as levers and pendulums Bones as solid (inflexible) links, connecting movably, form the basis of biokinematic chains. The applied forces act on the links as on levers or pendulums. In many cases, the links keep moving under the action of applied forces like pendulums. Levers in biokinematic chains Bone levers - links of the body, movably connected in the joints under the action of applied forces - can either maintain their position or change it. They serve to transmit movement and work over a distance. All forces applied to a link as a lever can be combined into two groups: a) forces or their components lying in the plane of the lever axis (they cannot affect the movement around this axis) and b) forces or their components lying in a plane perpendicular to to the axis of the lever (they can affect movement around the axis in two opposite directions). Considering the action of forces on the lever, only forces directed in the direction of movement (moving) and against it (braking) are taken into account. When groups of forces are applied on either side of the axis (fulcrum) of the lever, it ...

Presentation of the group "Levers in wildlife and technology" Where do we meet with levers?

In the skeleton of animals, all bones that have some freedom of movement are levers: the bones of the legs and arms, the skull, the lower jaw

In felines, all movable bones are levers.

The spines of the dorsal fin are the levers of many fish.

Levers in arthropods - most segments of their external skeleton

Levers in bivalve molluscs - shell valves

Skeletal linkages are primarily designed to gain speed with a loss in strength. The gain in speed is especially great for insects.

Lever mechanisms can be found in some colors. For example: sage stamens.

LEVERAGE In the technique Wedge and screw - a variety inclined plane The wedge is intended for splitting of strong objects, for example, logs. It is also driven into the gaps between the parts in order to create a greater pressure force of one part on another and thereby increase the static friction force between them, which will ensure their reliable adhesion. With the enormous forces applied to the wedge, it must be very strong, made of the hardest material. The "piercing tools" of many animals and plants - claws, horns, teeth and thorns - are shaped like a wedge (a modified inclined plane); the pointed shape of the head of fast-moving fish is similar to a wedge. Many of these wedges have very smooth hard surfaces, which is what makes them so sharp.

The screw was invented by Archimedes. His screw was designed to raise water from a certain level to a higher one. Consider a screw as a device for obtaining a significant gain in strength. Imagine that an inclined plane of height h and length l is rolled up into a tube. By turning the nut on the bolt, you lift it up the inclined plane. Win in strength F1 / F2 = h / l, where h is the height of the inclined plane, or the pitch of the screw, l is the length of the inclined plane or the circumference l = ? D. When driving a screw into a wooden board or tightening a bolt (fastening parts with a bolt or nut), friction forces and elastic forces of the material have to be overcome so large that it is difficult and sometimes even impossible to do it with your fingers. In this case, the gain in strength obtained with the help of a screw is not enough, and levers must also be used: screwdrivers, wrenches. The screw is used as a device to gain strength. AT measuring instruments propeller properties are used - loss in distance. The screw is also used for its “intended purpose”, as its inventor once suggested: to move grain through a pipe or meat in a meat grinder. More accurately fitted screws carry out the movement of the cutter in the lathe.

Presentations can be used when studying the topic "Human Skeleton" in the lessons of the world around us in grade 4. Presentations were made according to the textbook "The World Around" in the 4th grade by N. Ya. Dmitrieva, A. N. Kazakov according to the system of developmental education by L. V. Zankov

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Support and protection of the body. Skeleton. Composition and properties of bones. 4th grade. (According to the textbook "The World Around" by N. Ya. Dmitrieva, A. N. Kazakova)

Significance of the skeleton The skeleton gives the body size and shape The skeleton protects and supports the internal organs The skeleton serves as a support for the muscles

Connection of bones The connection of bones in the skeleton is divided into three types: fixed semi-movable movable

Fixed connection of bones The fixed connection is represented by the bones of the skull.

Semi-movable connection of bones The semi-movable connection is represented by the connection of the vertebrae or ribs with the sternum. It occurs with the help of cartilage and ligaments.

Movable connection of bones The bones of the arms and legs are movably connected. Types of joints

Departments of the human skeleton

Skeleton of the head (skull) The skeleton of the head (skull) has a cavity in which the brain is located. In addition, there are cavities of the mouth, nose and receptacles for the organs of vision and hearing. Usually, the brain and facial sections of the skull are distinguished. In humans, the brain section predominates. All bones of the skull, with the exception of the lower jaw, are connected by sutures.

Skeleton of the trunk Consists of the spine and thorax

Spine The spine consists of 33-34 vertebrae and five sections: cervical - 7 p. Thoracic - 12p. lumbar - 5p. sacral - 5p. coccygeal - 4-5p.

Bends of the spine The main purpose of the bends is to weaken the concussion of the head and torso when walking, running, jumping.

There is a curvature of the spine to the side - scoliosis. Scoliosis is often the result of painful changes in the spine.

The vertebrae are interconnected through cartilage, joints and ligaments. The spine is able to bend and unbend, lean to the side and twist. The most mobile are the lumbar and cervical spine.

Thorax The thorax is formed by the thoracic vertebrae, twelve pairs of ribs, and the sternum.

The skeleton of the lower extremities Consists of the pelvic girdle and the skeleton of the limb itself

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Skeleton Live leverage 4th grade. (According to the textbook "The World Around" by N. Ya. Dmitrieva, A. N. Kazakova)

Number of bones in the human body NAME OF DEPARTMENT NUMBER OF BONES Spine Thorax Pelvic girdle with sacrum and coccyx Cerebral region of skull Facial region of skull Shoulder girdle together with upper limbs Lower limbs 24 25 4 8 15 64 60 TOTAL 200 THIS IS INTERESTING

TASK What are the functions of the skeleton: 1 - 2 - 3 -

TASK The functions of the skeleton: 1 - gives the body size and shape 2 - protects and supports the internal organs 3 - serves as a support for the muscles

5 TASK Name the parts of the skeleton and their composition: 1 - 2 - 3 - 4 - 5 - 1 3 2 4

5 TASK Parts of the skeleton and their composition: 1 - skull 2 ​​- spinal column 3 - rib cage 4 - upper limbs 5 - lower limbs 1 3 2 4

Upper Limbs The upper limb (arm) is made up of the humerus, forearm bones, and hand bones (carpus, metacarpus, and phalanges).

The skeleton of the upper limbs The skeleton of the upper limbs consists of the shoulder girdle and the skeleton of the free upper limbs.

Lower extremities The lower extremities consist of the femur, the bones of the lower leg (tibia and fibula), and the bones of the foot. The tibia is located on the lower leg on the inside and is much thicker than the fibula.

Departments of the human skeleton

TASK Names of the bones of the skeleton: 1 - brain region of the skull 2 ​​- facial region of the skull 3 - shoulder girdle 4 - shoulder 5 - forearm 6 - hand 7 - chest 8 - spine 9 - pelvis 10 - thigh 11 - lower leg 12 - foot

TASK Write down the names of the bones of the skeleton: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 -