Birds are the largest group among vertebrates. They are common in all ecosystems of our planet and inhabit even individual parts of Antarctica. What structure does the nervous system and sensory organs of birds have? What are their features? How is the nervous system of birds different from the nervous system of reptiles?
Bird Class
Birds are the most diverse and numerous group of vertebrates. In nature, they play an important role, being part of the food chain. The birds eat insects, and they, in turn, feed on mammals. In addition, they are important for human activities - they are bred for meat, eggs, feathers, fat.
More than 10,500 modern species of birds and about 20,300 subspecies are known. 789 species are common in Russia. The main feature of this class is the presence of wings and plumage, which covers the body of animals. The main mode of transportation for many species is to fly, although some wings do not perform this function.
The ability to fly was reflected in the external and internal attributes 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 various parts of the brain. All these structures interact closely 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 has common features with vertebrates, although some features significantly distinguish it.
The structure of the nervous system and sensory organs of birds is directly related to their vital functions. 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 eat mobile food. Whether it be insects, fish, rodents or reptiles, it is important for birds to navigate well in space and have excellent vision, hearing and quick reaction. 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 brain is made up 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.
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 spatial orientation, 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 functions important for the life of the bird: blood circulation, respiration, digestion, etc. The midbrain is well developed, it consists of two tubercles 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 cranial 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. It is divided conditionally from the brain. Inside it is a cavity or central channel. The spinal cord is protected from above by three membranes - soft, arachnoid and hard, and cerebrospinal fluid separates them from the central canal.
In the lumbar and brachial regions, the spinal cord of birds has small thickenings. Here, nerves diverge from him, which connect to the front and rear limbs. Thus, the pelvic and brachial plexus is formed.
In the region of the lower back, the central channel has an expanded rhombic fossa, which is covered by the membrane of connective tissue. The branches of the lumbar and brachial plexuses of the spinal cord are responsible for the work of the muscles of the corresponding limbs.
Difference from reptiles
Both classes belong to higher vertebrates, and birds are closest to reptiles in the structure of the nervous system. However, significant differences are observed between them. How is the nervous system of birds different from the nervous system 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 extending from the brain, and their spinal cord has thickenings in the lumbar and brachial regions.
The nervous system of birds is distinguished primarily by the size of the brain, which significantly exceeds the brain of reptiles. Its weight is 0.05-0.09% (of body weight) in ratites and 0.2-8% in flying representatives of birds. The cortex of the forebrain hemispheres in birds is a relic or vestige. In reptiles, it is better developed due to the occurrence of sexual smell.
In birds, there is no sexual sense of smell, and the sense of smell itself is extremely poorly developed, with the exception of species that eat meat. In both classes, a significant proportion of the forebrain is formed by striped bodies at its bottom. They are responsible for analyzing and responding to incoming information.
Sensory organs
The least developed feelings in birds are the sense of smell and taste. Most species can hardly distinguish smells, with the exception of predators, for example, American vultures. The taste of food is determined by taste buds located at the base of the tongue and on the palate. There is no special need for them, since food is basically just swallowed.
Tactile receptors are located in different places. They are represented by the bodies of Grandi, Herbst or Merkel. In some species, they are located near the bases of large feathers on the skin, as well as on the beak in the wax. For this, owls have special feathers on their beaks, sandpipers and ducks have receptors in the jaw apparatus, and parrots have their tongues.
Birds are best developed for vision and hearing. Their ears are covered with feathers and devoid of the auricle. They consist of the inner, middle and rudiments of the outer ear. In sound sensitivity, they are superior to many mammals. Owls, salagans, guaharos have the ability to echolocation. The developed labyrinth of the inner ear provides birds with an excellent sense of balance.
Birds have acute monocular vision (in sovinocular). Some are able to see at a distance of one kilometer. The eyes are flattened and have a wide view. They are inactive, so birds often have to turn their heads. In some species, the angle of view is 360 degrees. The retina reacts even to ultraviolet light, and a flexible lens allows you to see even under water.
Intelligence
Over their long history, birds have shown the ability to cope with difficult situations, make calculations and be creative. 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. The wood finch uses spines of cacti for these purposes, and some have learned how to make tools on their own.
Birds adapt pretty quickly to their environment. For example, tits learned to peck holes in caps of milk bottles, and sometimes even remove them. Species that feed on fish sometimes throw a false bait into a pond to attract prey.
Crows repeatedly throw a nut on the ground until it breaks. Eagles for the same purpose raise high into the air a turtle, which would seem to be securely hidden in a shell. Some birds, to break the shell of prey, throw stones at it.
Conclusion
Birds have a more developed nervous system compared to reptiles. The brain is much larger in size, which allows you to perform more complex tasks, develop complex forms of behavior and adapt to different situations.
The nervous system of birds consists of the brain, spinal cord and twelve pairs of nerves. The front and middle parts 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 smell are extremely poorly developed. The location of the tactile receptors is located in different parts of the body, depending on the species.