The visual system, the sensibility of real

Synchronization cycle

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who are we, where are we from, where are we going. We are sentient beings who create every moment of our life from the past to a future that only exists in our imagination. To bring your imagination to life, the fewer intermediaries there are, the less possibility there is to go wrong. We can create a world of Peace, following the laws of Nature, dictated by our Humanity.

To learn to dominate nature, learns already to obey it.
« The name of the Rose »
by Jean-Jacques ANNAUD

The visual system, the importance of integration for a fresh start, and of covering as many directions as possible to increase the sharpness and accuracy of physical reality:

Multi-directional to capture everything

The light passes through the refractive media (cornea, aqueous humor, lens and vitreous body) of the eye to reach the nerve retina.

  • Sclera: Outer fibrous tunica of the eye bulb;
  • Cornea: Transparent part of the outer tunica: very sensitive to pain;
  • Choroid: Middle vascular tunic of the eyeball;
  • Ciliary body: Anterior vascular and muscular extension of the choroid;
  • Ciliary process: Radiant pigmented folds of the ciliary body: secreting the aqueous humor that occupies the anterior and posterior chambers;
  • Iris: Contractile diaphragm with a central opening (the pupil);
  • Lens: Transparent lens held in capsule form by consular fibers;
  • Retina: Photoreceptor tunica at the origin of the optic nerve (optic retina);
  • Macula (yellow spot): Retinal area of ​​maximum visual acuity;
  • Optic disc: The non-receptive area through which the axons of the optic nerve (Cranial Nerve II) leave the retina towards the brain.

A refractive medium changes the direction of the light rays, which means that the light will flood the bulb of the eye, and thus, the nerve retina will be fully illuminated.

From infinity small to infinity large

The ciliary body has smooth muscle organized in a circular fashion like a sphincter.

  • When this muscle is relaxed, traction is exerted on a set of zonular fibers attached to the elastic lens, which is then stretched and flattened, allowing objects to be seen at a distance far from the eyes;
  • When the gaze is focused on a nearby object, the ciliary muscle like a sphincter contracts, and approaches the lens, causing relaxation of the zonular fibers and allowing the faces of the lens to bulge for accommodation;
  • This accommodation reflex is controlled by the parasympathetic fibers of the oculomotor nerve (Cranial Nerve III).

The iris also has smooth muscle fibers.

  • The contraction of the circular pupillary sphincter muscle, under the control of the parasympathetic fibers of the NC III, leads to a reduction in the diameter of the pupil,
  • While fibers of the pupillary dilator muscle under sympathetic control increase the diameter of the pupil.

The part of the retina directly opposite the focal point of the lens at the posterior pole of the eyeball is specialized.

  • There is an area called the macula (yellow spot) with a small central pit called fovea centralis.
  • In the fovea, the retina is thinned and contains only cones and ganglion cells and is the region of greatest visual acuity.
  • The macula contains a lot of cones and a few rods, apart from the macula rods dominate.
  • Each human retina has about 7 million cones and about 120 million rods.

The bulb of the eye is attached to the orbital cavity by six extra-ocular muscles that move it, and it is cushioned by the fat that envelops the posterior two-thirds of the globe.

The need for the limits

The retina is a thin tunica that forms an expansion of the brain.

Most of the axons of its ganglion cells travel back through the optic nerve (NC II) and the central nervous system (CNS) to their synaptic region in the lateral geniculate body of the thalamus.

For this, the light must pass through the entire thickness of the retinal tunic:

  • To finally meet the photoreceptor cells located on the pigment epithelium;
  • Photoreceptors (rods and cones) synapse with bipolar cells,
  • The bipolar cells then establish a synapse with the ganglion cells,
  • while horizontal and amacrine cells make interconnections.
  • The cones are specialized in bright light vision (daytime),
  • The rods in twilight vision (night).

The pigment epithelium absorbs light, so only light rays that have passed through the eye bulb directly or by refraction will be transformed into nerve signals by the nerve retina, and sent to the brain.

The pigment epithelium also participates in immune modulation;

Let’s use the observation of feedback to readjust our actions:

If we considered Humanity as a human body,
where each of Us lives his own life;

If we considered Humanity as a human body,
where each of Us lives his own life;

Humanize the World,
we will free ourselves from our fears,
misery, violence, injustices, wars,
like the visual system let us observe the Earth in detail as a whole.

Bibliographic References:
– The information on the visual system is taken from the book « The Netter’s Anatomy Coloring Book », John T. HANSE, Elsevier Masson SAS, 2017 (the french version),
– The pictures are taken from the book « Atlas of Human Anatomy », Seventh edition, Franck H. NETTER, Elsevier Masson SAS, eBook.

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