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Pupils
The pupil is a black hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil. The term "pupil" was coined by Gerard of Cremona. In humans, the pupil is round, but its shape varies between species; some cats, reptiles, and foxes have vertical slit pupils, goats have horizontally oriented pupils, and some catfish have annular types. In optical terms, the anatomical pupil is the eye's aperture and the iris is the aperture stop. The image of the pupil as seen from outside the eye is the entrance pupil, which does not exactly correspond to the location and size of the physical pupil because it is magnified by the cornea. On the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pupillary Light Reflex
The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity ( luminance) of light that falls on the retinal ganglion cells of the retina in the back of the eye, thereby assisting in adaptation of vision to various levels of lightness/darkness. A greater intensity of light causes the pupil to constrict ( miosis/myosis; thereby allowing less light in), whereas a lower intensity of light causes the pupil to dilate ( mydriasis, expansion; thereby allowing more light in). Thus, the pupillary light reflex regulates the intensity of light entering the eye. Light shone into one eye will cause both pupils to constrict. Terminology The pupil is the dark circular opening in the center of the iris and is where light enters the eye. By analogy with a camera, the pupil is equivalent to aperture, whereas the iris is equivalent to the diaphragm. It may be helpful to consider the ''Pupillary reflex'' as an Iris' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cat Eyes
Cat senses are adaptations that allow cats to be highly efficient predators. Cats are good at detecting movement in low light, have an acute sense of hearing and smell, and their sense of touch is enhanced by long whiskers that protrude from their heads and bodies. These senses evolved to allow cats to hunt effectively at dawn and dusk. Sight Cats have a ''tapetum lucidum'', which is a reflective layer behind the retina that sends light that passes through the retina back into the eye. While this improves the ability to see in darkness and enables cats to see using roughly one-sixth the amount of light that humans need, it appears to reduce net visual acuity, thus detracting when light is abundant. A cat's visual acuity is anywhere from 20/100 to 20/200, which means a cat has to be at 6 metres to see what an average human can see at 20 or 30 metres. Cats seem to be nearsighted, which means they cannot see far objects as well. The ability to see close objects would be well-su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Goats
The goat or domestic goat (''Capra hircus'') is a domesticated species of goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the animal family Bovidae and the tribe Caprini, meaning it is closely related to the sheep. There are over 300 distinct breeds of goat.Hirst, K. Kris"The History of the Domestication of Goats".''About.com''. Accessed August 18, 2008. It is one of the oldest domesticated species of animal, according to archaeological evidence that its earliest domestication occurred in Iran at 10,000 calibrated calendar years ago. Goats have been used for milk, meat, fur, and skins across much of the world. Milk from goats is often turned into goat cheese. Female goats are referred to as ''does'' or ''nannies'', intact males are called ''bucks'' or ''billies'', and juvenile goats of both sexes are called ''kids''. Castrated males are called ''wethers''. While ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oculomotor Nerve
The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of the eye and that raise the eyelid. The nerve also contains fibers that innervate the intrinsic eye muscles that enable pupillary constriction and accommodation (ability to focus on near objects as in reading). The oculomotor nerve is derived from the basal plate of the embryonic midbrain. Cranial nerves IV and VI also participate in control of eye movement. Structure The oculomotor nerve originates from the third nerve nucleus at the level of the superior colliculus in the midbrain. The third nerve nucleus is located ventral to the cerebral aqueduct, on the pre-aqueductal grey matter. The fibers from the two third nerve nuclei located laterally on either side of the cerebral aqueduct then pass through the red nucleus. From the r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brainstem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch, and sometimes the diencephalon is included in the brainstem. The brainstem is very small, making up around only 2.6 percent of the brain's total weight. It has the critical roles of regulating cardiac, and respiratory function, helping to control heart rate and breathing rate. It also provides the main motor and sensory nerve supply to the face and neck via the cranial nerves. Ten pairs of cranial nerves come from the brainstem. Other roles include the regulation of the central nervous system and the body's sleep cycle. It is also of prime importance in the conveyance of motor and sensory pathways from the rest of the brain to the body, and from the bod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hippus
Pupillary hippus, also known as pupillary athetosis, is spasmodic, rhythmic, but regular dilating and contracting pupillary movements between the sphincter and dilator muscles.Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company, 1990. Pupillary hippus comes from the Greek '' hippos'' meaning horse, perhaps due to the rhythm of the contractions representing a galloping horse.Beatty, J., & Lucero-Wagoner, B. (2000). The pupillary system. In J. T. Cacioppo, L. G. Tassinary & G. G. Bernston (Eds.), ''The handbook of psychophysiology'' (2nd ed.) (pp. 142-162). USA: Cambridge University Press. It is particularly noticeable when pupil function is tested with a light, but is independent of eye movements or changes in illumination. It is usually normal, however pathological hippus can occur. Pathologic hippus, the phenomenon of increased oscillation or their amplitude, is associated with aconite poisoning,Forensic and State Medici ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plural
The plural (sometimes list of glossing abbreviations, abbreviated pl., pl, or ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a quantity greater than the default quantity represented by that noun. This default quantity is most commonly one (a form that represents this default quantity of one is said to be of ''Grammatical number, singular'' number). Therefore, plurals most typically denote two or more of something, although they may also denote fractional, zero or negative amounts. An example of a plural is the English word ''cats'', which corresponds to the singular ''cat''. Words of other types, such as verbs, adjectives and pronouns, also frequently have distinct plural forms, which are used in agreement (linguistics), agreement with the number of their associated nouns. Some languages also have a dual (grammatical number), dual (denoting exactly two of something) or other systems of n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collarette (iris)
In humans and most mammals and birds, the iris (plural: ''irides'' or ''irises'') is a thin, annular structure in the eye, responsible for controlling the diameter and size of the pupil, and thus the amount of light reaching the retina. Eye color is defined by the iris. In optical terms, the pupil is the eye's aperture, while the iris is the diaphragm. Structure The iris consists of two layers: the front pigmented fibrovascular layer known as a stroma and, beneath the stroma, pigmented epithelial cells. The stroma is connected to a sphincter muscle ( sphincter pupillae), which contracts the pupil in a circular motion, and a set of dilator muscles (dilator pupillae), which pull the iris radially to enlarge the pupil, pulling it in folds. The sphincter pupillae is the opposing muscle of the dilator pupillae. The pupil's diameter, and thus the inner border of the iris, changes size when constricting or dilating. The outer border of the iris does not change size. The constricting ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redeye
Red eye, red-eye, redeye or variants may refer to: Related to the eye * Red-eye effect, in photographs * Red eye (medicine), an eye that appears red due to illness or injury * Red, an extremely rare eye color due to albinism * Red eyeshine in animals caused by '' tapetum lucidum'' Arts, entertainment and media Fictional characters * Red Eye, in video game '' Last Bronx'' * The Red Eye, in ''The Tick'' comics Film, television and radio * ''Red Eye'' (2005 American film), a psychological thriller * ''Red Eye'' (2005 South Korean film), a horror film * ''Red Eye'' (talk show), an American TV show * '' Red Eye Radio'', an American talk radio show Music * Redeye Distribution, an American record label * Red Eye Records (label), an Australian record label * Redeye (band), an American rock group * "Red Eye", a song by Ace Enders from ''The Secret Wars'', 2008 * "Red Eye", a song by Andy Grammer from ''Magazines or Novels'', 2014 * "Red Eye", a song by Big K.R.I.T. from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasympathetic
The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system. The autonomic nervous system is responsible for regulating the body's unconscious actions. The parasympathetic system is responsible for stimulation of "rest-and-digest" or "feed and breed" activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tears), urination, digestion, and defecation. Its action is described as being complementary to that of the sympathetic nervous system, which is responsible for stimulating activities associated with the fight-or-flight response. Nerve fibres of the parasympathetic nervous system arise from the central nervous system. Specific nerves include severa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinal Ganglion Cell
A retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the ganglion cell layer) of the retina of the eye. It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and retina amacrine cells. Retina amacrine cells, particularly narrow field cells, are important for creating functional subunits within the ganglion cell layer and making it so that ganglion cells can observe a small dot moving a small distance. Retinal ganglion cells collectively transmit image-forming and non-image forming visual information from the retina in the form of action potential to several regions in the thalamus, hypothalamus, and mesencephalon, or midbrain. Retinal ganglion cells vary significantly in terms of their size, connections, and responses to visual stimulation but they all share the defining property of having a long axon that extends into the brain. These axons form the optic nerve, optic chiasm, and optic tract. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
