Birds are the largest group of vertebrates. They are common in all ecosystems of our planet and even inhabit certain parts of Antarctica. What is the structure of the nervous system and sensory organs of birds? What are their features? How is the nervous system of birds different from that of reptiles?
Bird Class
Birds are the most diverse and numerous group of vertebrates. In nature, they play an important role, being a link in the food chain. Birds eat insects, which in turn are eaten by mammals. In addition, they are important for human economic activity - they are bred for meat, eggs, feathers, fat.
More than 10,500 modern bird species and about 20,300 subspecies are known. In Russia, 789 species are distributed. The main feature of this class is the presence of wings and plumage that covers the body of animals. The main mode of transportation for many species is flight, althoughsome wings do not perform this function.
The ability to fly was reflected in the external and internal features that the Bird class possesses. The nervous system, digestive and respiratory systems differ in structure from the organs of other animals. For example, they have two types of respiration, enhanced metabolism and gas exchange.
Features of the structure of the nervous system of birds
Typically, the nervous system consists of nerves located in different parts of the body, as well as from different parts of the brain. All these structures closely interact with each other. They represent a single mechanism that regulates the work of all body systems and is responsible for the reaction to environmental stimuli.
The organs of the nervous system of birds make up the central nervous system (spinal cord and brain) and peripheral parts (nerve endings, nerves of the spinal cord and brain). The structure of the brain shares common features with vertebrates, although some features significantly distinguish it.
The structure of the nervous system and sense organs of birds is directly related to their vital activity. Birds have a good sense of balance and coordination of movements necessary for them to fly. Thanks to this, they perfectly maneuver in the air.
Most species feed on moving food. Whether it's insects, fish, rodents or reptiles, it is important for birds to navigate well in space and have excellent vision, hearing and responsiveness. The organs responsible for these functions are best developed in birds.
Brain
A hundred years ago, it was believed that birds are not capable of complex actions. Ludwig Edinger put forward the theory that their brains are composed of subcortical nodes that are responsible for instincts and simple functions. Later it turned out that the nervous system of birds is very similar to the human one.
The largest part of the brain is the forebrain. It consists of two hemispheres with a smooth surface, filled with subcortical nuclei. They are responsible for orientation in space, behavior, mating, eating. The hemispheres are connected to a sufficiently large cerebellum, which regulates the coordination of movements.
The medulla oblongata is part of the brain stem. This department is responsible for the functions important for the life of a bird: blood circulation, respiration, digestion, etc. The midbrain is well developed, it consists of two hillocks that are responsible for processing auditory and visual information.
Birds have a large pituitary gland, but their pineal gland and diencephalon are underdeveloped. The total number of head nerves is 12 pairs, but the eleventh pair is weakly separated from the tenth.
Spinal cord
The central nervous system of birds also includes the spinal cord. From the brain, it is divided conditionally. Inside it is a cavity or central channel. From above, the spinal cord is protected by three membranes - soft, arachnoid and hard, separated from the central canal by cerebrospinal fluid.
In the lumbar and shoulder regions, the spinal cord of birds has small thickenings. Herenerves diverge from it, which connect to the fore and hind limbs. Thus, the pelvic and brachial plexus is formed.
In the lumbar region, the central canal has an expanded rhombic fossa, which is covered by connective tissue membranes. The branches of the lumbar and brachial plexuses of the spinal cord are responsible for the work of the muscles of the corresponding limbs.
Different from reptiles
Both classes belong to the higher vertebrates, and in terms of the structure of the nervous system, birds are closest to reptiles. However, there are significant differences between them. How is the nervous system of birds different from that of reptiles?
Birds and reptiles have the same parts of the brain. The difference is observed in the size of these departments, which is associated with a different way of life of animals. Reptiles have 12 pairs of nerves from the brain, and their spinal cord has thickenings in the lumbar and shoulder regions.
The nervous system of birds differs primarily in the size of the brain, which is much larger than the brain of reptiles. Its mass is 0.05-0.09% (of body weight) in ratites and 0.2-8% in flying birds. The cerebral cortex in birds is a relic or rudiment. In reptiles, it is better developed due to the emergence of a sexual sense of smell.
Birds have no sexual sense of smell, and the sense of smell itself is extremely poorly developed, with the exception of species that eat meat. Bothclasses, a significant proportion of the forebrain is formed by striatal bodies at its bottom. They are responsible for analyzing and responding to incoming information.
Sense Organs
The least developed senses in birds are smell and taste. Most species have difficulty distinguishing smells, with the exception of predators, such as American vultures. The taste of food is determined by the taste buds located at the base of the tongue and on the palate. There is no special need for them, since food is mostly simply swallowed.
Tactile receptors are in different places. They are represented by Grandi, Herbst or Merkel bodies. In some species, they are located near the bases of large feathers on the skin, as well as on the beak in the cere. Owls have special feathers on their beaks for this, waders and ducks have receptors in the jaw apparatus, parrots have receptors in their tongues.
Birds have the best developed sight and hearing. Their ears are covered with feathers and lack an auricle. They consist of the inner, middle and rudiments of the outer ear. In sensitivity to sounds, they surpass many mammals. Owls, salagans, guajaros have the ability to echolocation. The developed labyrinth of the inner ear provides the birds with an excellent sense of balance.
Birds have sharp monocular vision (owls have binocular vision). Some are able to see at a distance of one kilometer. The eyes are flattened and have a wide field of view. They are inactive, so the birds often have to turn their heads. In some species, the angle of view is 360 degrees. Retinareacts even to ultraviolet light, and the flexible lens allows you to see even under water.
Intelligence
During their long history, birds have shown the ability to cope with difficult situations, make calculations and be resourceful. They are able to memorize and reproduce various sounds and phrases of human speech.
For their needs, birds often use objects as tools. For example, with small elastic sticks, they can get insects in the bark of trees. Treefinch uses cactus thorns for this purpose, and some have learned to make tools on their own.
Birds quickly adapt to the environment. For example, tits have learned to peck holes in the lids of milk bottles, and sometimes even take them off. Species that feed on fish sometimes cast false bait into the water to attract prey.
Crows repeatedly throw a nut on the ground until it breaks. For the same purpose, eagles raise a turtle high into the air, seemingly securely hidden in its shell. Some birds throw stones at prey to break the shell.
Conclusion
Birds have a more developed nervous system than reptiles. The brain is much larger, allowing for more complex tasks, complex behaviors, and adaptability to different situations.
The nervous system of birds consists of the head,spinal cord and twelve pairs of nerves. The anterior, middle sections of the brain, as well as the cerebellum, are well developed, which is primarily associated with the ability of birds to fly.
They have excellent hearing and vision. They distinguish not only colors familiar to us, but also ultraviolet, and some have the ability to echolocation. Taste and sense of smell are extremely poorly developed. Touch receptors are located in different parts of the body, depending on the species.
