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Knollenorgans
A Knollenorgan is an electroreceptor in the skin of weakly electric fish of the family Mormyridae (Elephantfish) from Africa. The structure was first described by Viktor Franz (1921), a German anatomist unaware of its function. They are named after "Knolle", German for "tuberous root" which describes their structure. Structure and function Knollenorgans contain modified epithelial cells that act as sensory transducers for electric fields. Besides these, there are supporting cells and a sensory neuron. The neuron projects to the fish's brain, specifically to the nucleus of the electrosensory lateral line lobe (nELL) of the medulla via the posterior branch of the lateral line nerve. The organs are embedded in the thickened epidermis. The receptor cells lie buried in the deeper layers of the epidermis, where they expand into a pocket in the superficial layers of the corium. The sense organ is surrounded by a basement membrane which separates corium from epidermis. Epithelial cel ...
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Knollenorgan By Viktor Franz 1921
A Knollenorgan is an electroreceptor in the skin of weakly electric fish of the family Mormyridae (Elephantfish) from Africa. The structure was first described by Viktor Franz (1921), a German anatomist unaware of its function. They are named after "Knolle", German for "tuberous root" which describes their structure. Structure and function Knollenorgans contain modified epithelial cells that act as sensory transducers for electric fields. Besides these, there are supporting cells and a sensory neuron. The neuron projects to the fish's brain, specifically to the nucleus of the electrosensory lateral line lobe (nELL) of the medulla via the posterior branch of the lateral line nerve. The organs are embedded in the thickened epidermis. The receptor cells lie buried in the deeper layers of the epidermis, where they expand into a pocket in the superficial layers of the corium. The sense organ is surrounded by a basement membrane which separates corium from epidermis. Epithelial c ...
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Electroreceptor
Electroreception and electrogenesis are the closely related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes, such as the electric eel, to stun prey. The capabilities are found almost exclusively in aquatic or amphibious animals, since water is a much better conductor of electricity than air. In passive electrolocation, objects such as prey are detected by sensing the electric fields they create. In active electrolocation, fish generate a weak electric field and sense the different distortions of that field created by objects that conduct or resist electricity. Active electrolocation is practised by two groups of weakly electric fish, the order Gymnotiformes (knifefishes) and family Mormyridae (elephantfishes), and by the monotypic genus '' Gymnarchus'' (African knifefish). An electric fish generates an electric field using an electric organ, modi ...
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Neuroethology
Neuroethology is the evolutionary and comparative approach to the study of animal behavior and its underlying mechanistic control by the nervous system. It is an interdisciplinary science that combines both neuroscience (study of the nervous system) and ethology (study of animal behavior in natural conditions). A central theme of neuroethology, which differentiates it from other branches of neuroscience, is its focus on behaviors that have been favored by natural selection (e.g., finding mates, navigation, locomotion, and predator avoidance) rather than on behaviors that are specific to a particular disease state or laboratory experiment. Neuroethologists hope to uncover general principles of the nervous system from the study of animals with exaggerated or specialized behaviors. They endeavor to understand how the nervous system translates biologically relevant stimuli into natural behavior. For example, many bats are capable of echolocation which is used for prey capture and ...
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Fish Physiology
Fish physiology is the scientific study of how the component parts of fish function together in the living fish. It can be contrasted with fish anatomy, which is the study of the form or Morphology (biology), morphology of fishes. In practice, fish anatomy and physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in the living fish. Respiration Most fish exchange gases using gills on either side of the pharynx (throat). Gills are tissues which consist of threadlike structures called Protein filament, filaments. These filaments have many functions and "are involved in ion and water transfer as well as oxygen, carbon dioxide, acid and ammonia exchange. Each filament contains a capillary network that provides a large surface area for exchanging ...
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Ampullae Of Lorenzini
Ampullae of Lorenzini (: ''ampulla'') are electroreceptors, sense organs able to detect electric fields. They form a network of mucus-filled pores in the skin of Chondrichthyes, cartilaginous fish (sharks, Ray (fish), rays, and chimaeras) and of basal Osteichthyes, bony fishes such as reedfish, sturgeon, and lungfish. They are associated with and evolved from the mechanosensory lateral line organs of early vertebrates. Most bony fishes and terrestrial vertebrates have lost their ampullae of Lorenzini. History Ampullae were initially described by Marcello Malpighi and later given an exact description by the Italian physician and ichthyologist Stefano Lorenzini in 1679, though their function was unknown. Electrophysiology, Electrophysiological experiments in the 20th century suggested a sensibility to temperature, mechanical pressure, and possibly salinity. In 1960 the ampullae were identified as specialized receptor organs for sensing electric fields. One of the first descriptio ...
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Volt
The volt (symbol: V) is the unit of electric potential, Voltage#Galvani potential vs. electrochemical potential, electric potential difference (voltage), and electromotive force in the International System of Units, International System of Units (SI). Definition One volt is defined as the electric potential between two points of a electrical conductor, conducting wire when an electric current of one ampere dissipates one watt of power (physics), power between those points. It can be expressed in terms of SI base units (metre, m, kilogram, kg, second, s, and ampere, A) as : \text = \frac = \frac = \frac = \text\text^2\text^. Equivalently, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can be expressed in terms of SI base units (metre, m, kilogram, kg, second, s, and ampere, A) as : \text = \frac = \frac = \frac = \text\text^2\text^. It can also be expressed as amperes times ohms (curre ...
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Hertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base units is 1/s or s−1, meaning that one hertz is one per second or the Inverse second, reciprocal of one second. It is used only in the case of periodic events. It is named after Heinrich Hertz, Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves. For high frequencies, the unit is commonly expressed in metric prefix, multiples: kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz). Some of the unit's most common uses are in the description of periodic waveforms and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics are driven. T ...
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Basal Group
In phylogenetics, basal is the direction of the ''base'' (or root) of a phylogenetic tree#Rooted tree, rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to the root. Note that extant taxa that lie on branches connecting directly to the root are not more closely related to the root than any other extant taxa. While there must always be two or more equally "basal" clades sprouting from the root of every cladogram, those clades may differ widely in taxonomic rank, Phylogenetic diversity, species diversity, or both. If ''C'' is a basal clade within ''D'' that has the lowest rank of all basal clades within ''D'', ''C'' may be described as ''the'' basal taxon of that rank within ''D''. The concept of a 'key innovation' implies some degree of correlation between evolutionary innovation and cladogenesis, diversification. However, such a correlation does not make a given ca ...
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Ampullae Of Lorenzini
Ampullae of Lorenzini (: ''ampulla'') are electroreceptors, sense organs able to detect electric fields. They form a network of mucus-filled pores in the skin of Chondrichthyes, cartilaginous fish (sharks, Ray (fish), rays, and chimaeras) and of basal Osteichthyes, bony fishes such as reedfish, sturgeon, and lungfish. They are associated with and evolved from the mechanosensory lateral line organs of early vertebrates. Most bony fishes and terrestrial vertebrates have lost their ampullae of Lorenzini. History Ampullae were initially described by Marcello Malpighi and later given an exact description by the Italian physician and ichthyologist Stefano Lorenzini in 1679, though their function was unknown. Electrophysiology, Electrophysiological experiments in the 20th century suggested a sensibility to temperature, mechanical pressure, and possibly salinity. In 1960 the ampullae were identified as specialized receptor organs for sensing electric fields. One of the first descriptio ...
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Sensory Receptor
Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded receptor potentials. This process is called sensory transduction. The cell bodies of the sensory neurons are located in the dorsal root ganglia of the spinal cord. The sensory information travels on the afferent nerve fibers in a sensory nerve, to the brain via the spinal cord. Spinal nerves transmit external sensations via sensory nerves to the brain through the spinal cord. The stimulus can come from exteroreceptors outside the body, for example those that detect light and sound, or from interoreceptors inside the body, for example those that are responsive to blood pressure or the sense of body position. Types and function Sensory neurons in vertebrates are predominantly pseudounipolar or bipolar, and different types of sensory neurons have different sensory receptors that respond to ...
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Dermis
The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided into two layers, the superficial area adjacent to the epidermis called the papillary region and a deep thicker area known as the reticular dermis.James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology'' (10th ed.). Saunders. Pages 1, 11–12. . The dermis is tightly connected to the epidermis through a basement membrane. Structural components of the dermis are collagen, elastic fibers, and Ground substance, extrafibrillar matrix.Marks, James G; Miller, Jeffery (2006). ''Lookingbill and Marks' Principles of Dermatology'' (4th ed.). Elsevier Inc. Page 8–9. . It also contains mechanoreceptors that provide the sense of touch and thermoreceptors that provide ...
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Epidermis (skin)
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss. The epidermis is composed of multiple layers of flattened cells that overlie a base layer ( stratum basale) composed of columnar cells arranged perpendicularly. The layers of cells develop from stem cells in the basal layer. The thickness of the epidermis varies from 31.2μm for the penis to 596.6μm for the sole of the foot with most being roughly 90μm. Thickness does not vary between the sexes but becomes thinner with age. The human epidermis is an example of epithelium, particularly a stratified squamous epithelium. The word epidermis is derived through Latin , itself and . Something related to or part of the epidermis is termed epidermal. Structure ...
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