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- Glossary
Red nucleus
The "red nucleus" owes its name to its high iron content. It can be seen with the naked eye as a large, round, reddish-colored nucleus in the midbrain. It belongs to the extrapyramidal motor system, and its central tasks are posture and muscle tone.
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- Glossary
Papilla
The optic nerve leaves the eye at the papilla, the optic disc. Since there are no photoreceptors at this point on the retina, the optic disc creates a blind spot.
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- Glossary
Pupil
The opening in the eye through which light enters. The size of the pupil is determined by the iris and changes reflexively (pupillary reflex). This process of adjusting to the brightness of the environment is called adaptation.
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- Glossary
Sleep phases
During sleep, we go through several non-REM/REM cycles, each lasting around 90 minutes. The non-REM phases consist of stages N1, N2, and N3, with slow delta waves with frequencies of 0.5–2 Hz dominating in N3 (deep sleep). REM sleep is characterized by rapid eye movements, low-amplitude, mixed-frequency brain activity, and greatly reduced muscle tone. Deep sleep predominates at the beginning of the night, while the proportion of REM sleep increases in later cycles.
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- Glossary
Visual pathway
The visual pathway refers to the network of nerve cells involved in visual perception. In mammals, it runs from the retinal ganglion cells in the eye – as the optic nerve to the optic chiasm, then as the visual tract – via the only switching point in the lateral geniculate nucleus to the primary visual cortex.
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- Glossary
Optic nerve
The axons (long fiber-like extensions) of the retinal ganglion cells form the optic nerve, which leaves the eye at the back of the optic disc. It comprises approximately one million axons and has a diameter of approximately seven millimeters.
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- Glossary
Vestibulo-ocular reflex
When we turn our head, our eyes automatically move in the opposite direction. This reflex ensures that a stable image is formed on the retina even when the head moves quickly. This is made possible by the connection between the semicircular canals of the vestibular system and the nerve nuclei of the eye muscles in the brain stem.
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- Glossary
Visual system
The visual system is the part of the nervous system that processes visual information. It primarily comprises the eye, the optic nerve, the optic chiasm, the optic tract, the lateral geniculate nucleus, the optic radiation, the primary visual cortex, and the visual association cortices.
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- Glossary
Zonules
The zonules are arranged in a radial pattern around the lens of the eye and connect it to the ciliary muscle.
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- Topic
animal thoughts
Some animals are more like us than we think
