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Sensory Organs comparative study in vertebrates.
- 1. INDIRA GANDHI NATIONAL TRIBAL UNIVERSITY AMARKANTAK Department of ZOOLOGY Sensory Organs in higher vertebrates 2019
- 2. What are Sensory Organs? Sense organs are the specialized organs composed of sensory neurons, which help us to perceive and respond to our surroundings. There are five sense organs – eyes, ears, nose, tongue, and skin
- 3. External senses Taste Gustatoreceptors Sight Photoreceptors Smell Olfactoreceptors Touch Tangoreceptors Heat Thermoreceptors Cold Caloreceptors Pain Frigidoreceptors Hearing Phonoreceptors Pressure Mechanoreceptor
- 4. Internal Senses 1.in EYES 2. in EARS 3.in Brain
- 5. An Eye The main sensory organ of the visual system is the eye, which takes in the physical stimuli of light rays and transduces them into electrical and chemical signals that can be interpreted by the brain to construct physical images.
- 6. Fish eyes are similar to the eyes of terrestrial vertebrates like birds and mammals, but have a more spherical lens. ... Fish retinas generally have both rod cells and cone cells (for scotopic and photopic vision), and most species have colour vision. Some fish can see ultraviolet and some are sensitive to polarized light. Eyes of Fishes
- 7. Fish Eyes
- 8. Amphibians have eyes which are adjusted to seeing both on land and in water. Amphibians are unique in that they are capable of extra-ocular vision - sensing light energy using structures other than the eyes. For example, amphibian skin acts as a sense organ which often replaces the need for vision. Eyes of Amphibians
- 10. Reptiles active at night tend to have smaller eyes than those active during the day. The pupils of nocturnal species tend to be relatively large. This improves the reptile’s ability to gather light but reduces their visual acuity. Many nocturnal species have slit-shaped pupils. Species active during the day tend to have round pupils. Eyes of Reptiles
- 11. Reptilian Eye
- 12. Eyesight is a bird's most critical sense and the one it relies on the most for flight, evading predators, and finding food. ... They have much denser rods and cones, the "seeing" cells, packed on the retina, giving them superior vision in both black-and- white and color. Eyes Of Birds
- 13. The Avian Eye
- 14. Eyes Of Mammals (Marsupials and Placental mammals) • No bone or cartilage in sclera • No skeletal muscle • No photomechanical movement • Dichromatic Vision • No fovea • Most have blood vessles within the ratina • Accomodation limited by passive action of lens capsule on lens.
- 16. Ears ear is a delicate organ located in the temporal region of the skull. It is called membranous labyrinth, which evolved in primitive vertebrates for maintenance of balance and posture. Hearing function of this organ evolved for the first time in anurans when they started living in terrestrial environment, where sound waves travel faster and to longer distances.
- 17. Ears of Fishes fishes have developed sensory mechanisms for detecting, localizing, and interpreting sounds. Two independent but related sensory systems used by fish to detect sound are the inner ear(the auditory system) and, to a lesser extent, the mechanosensory lateral line system, which is generally used to detect vibration and water flow.
- 18. Fish Ear
- 19. As sense organs for hearing, the papillae, which appear for the first time in amphibians, have cells like those in lower vertebrates that serve the same purpose. There are two types of papillae: the amphibian papilla, which is found in all amphibians, and the basilar papilla, which is found in some amphibians. Ears of Amphibians
- 21. The reptile's senses of sight, smell, and hearing are similar to those of other vertebrates, though the levels of development of these senses vary among reptile groups. Snakes lack ears and can detect only ground vibrations or airborne vibrations of low frequency. Ears of Reptiles
- 23. Birds hear a smaller frequency range than humans, but they have much more acute sound recognition skills. Birds are especially sensitive to pitch, tone, and rhythm changes and use those variations to recognize other individual birds, even in a noisy flock. Birds also use different sounds, songs, and calls in different situations. Recognizing the different noises is essential to determine if a call is warning of a predator, advertising a territorial claim, or offering to share food. Many birders study those calls and birding by ear can be useful for not only identifying birds but also understanding their behavior. Ears of Birds
- 24. Avian Ear
- 25. Mammals possess the best developed hearing power among all Vertebrates. Langena elongates to form a spirally coiled cochlea. In middle ear cavity instead of one bone mammals have 3 ear ossicles namely incus mallus stapes.Which transmit sound vibrationsfrom tymphanic membrane to the fenestra ovalis that leads to scala vestibuli of cochlea.Mammals als have various size of ear pinna to collect sound wavesand diret them tothe auditory canal.Cloecha is a specialized and highly sensitive organ of hearing. Its cross section reveals three long chembers scala media and scalatympani the middle chamber is filled withendolymphwhile the other two are filled with perilymph.The organ of corti is attached to the bassilar membrane and carries sensory hair cells and supporting cells and the cochlear nerve at the base A tectorialmembrane floats in the Ears of Mammals
- 26. middle of scala mediaand touches the hairs of sensory cells when vibrates by the sound vibration resulting in the generation of a nerve impulse tha travels via cochlear nerve to the brain
- 27. A sensory system consists of sensory neurons (including the sensory receptor cells), neural pathways, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, touch, taste, smell, and balance. Brain
- 29. Brain of Fishes Fish typically have quite small brains relative to body size compared with other vertebrates, typically one-fifteenth the brain mass of a similarly sized bird or mammal.[6] However, some fish have relatively large brains, most notably mormyrids and sharks, which have brains about as massive relative to body weight as birds and marsupials.
- 30. The general structure and functional organization of the amphibian brain includes several apparently primitive features (such as a small size and relatively little cell migration and areal differentiation, these being less severe in anurans than in other amphibians) as well as the standard major brain areas and basic connectional patterns found in all vertebrates. Evolutionary specializations are also apparent, especially in anurans where expanded visual and auditory midbrain areas are present. The forebrain contains many of the basic vertebrate systems and general organization of connections, but the functional organization of sensory systems is quite different from the familiar pattern seen in mammals, birds and reptiles. Brain of Amphibians
- 31. The diversity of reptiles and their evolutionary relationship to mammals make reptilian brains great models to explore questions related to the structural and functional evolution of vertebrate neural circuits. To this end, comparative studies seek to identify homologies — structural or molecular similarities that are due to common ancestry — at a variety of levels, for example, brain regions, circuits or cell types. Homologies can be inferred from extant species by using a comparative approach within a phylogenetic framework. Vertebrate brains have been classically compared in terms of morphology, connectivity, and neurochemistry; however, adult neuroanatomy may not be sufficient to determine homologies without ambiguity. Brain of Reptiles
- 32. Brain of Birds Bird brain is characterized by enormous enlargement of cerebral hemisphere optic lobes and cerebellum. cerebral hemisphere become enlarges owing to enlargement of corpus straitum which is called hyperstraiatum but pallium is thin and surface has onliy white matter. Olfactory lobes are highly reduced attatched to the anterior end of the cerebral hemisphere. optic lobes are enormous as birds need good control over muscles and tendons which comes from trilobed highly enlarges cerebellum is called vermis as it has transverse folds and the lateral lobes are called floculi. Birds brain is instinctive brain that can carry out complex but sterotype fucntion such as nest building. spiral cord still has equal control over the body.
- 33. Urodele brain is primitive nd reflects their sluggish nature and underdeveloped sense organs. Olfactory lobes, optic lobes, and cerebellum are reduced and cerebral hemisphere are also small and smooth. pineal and parietal bodies are present but reduced. there is no saccus vacculosus and corpus straitum is weak. Urodele Brain
- 34. The most obvious difference between the brains of mammals and other vertebrates is in terms of size. On average, a mammal has a brain roughly twice as large as that of a bird of the same body size, and ten times as large as that of a reptile of the same body size Brain of Mammals
- 35. Size, however, is not the only difference: there are also substantial differences in shape. The hindbrain and midbrain of mammals are generally similar to those of other vertebrates, but dramatic differences appear in the forebrain,which is greatly enlarged and also altered in structure. The cerebral cortex is the part of the brain that most strongly distinguishes mammals. In non-mammalian vertebrates, the surface of the cerebrum is lined with a comparatively simple three-layered structure called the pallium. In mammals, the pallium evolves into a complex six-layered structure called neocortex or isocortex.Several areas at the edge of the neocortex, including the hippocampus and amygdala, are also much more extensively developed in mammals than in other vertebrates.
- 36. References