C17 - Refractive media of the eye, optical accomodation and the visual pathways Flashcards

1
Q

Define refractive media of the eye

A
  • The structures of the eye that deflect light:
    • Cornea
    • Aqueous humor
      • In camera bulbi anterior and posterior
    • Lens
    • Corpus viterum
  • Light → cornea (transparent, bends light on retina) → camera bulbi anterior/posterior (filled with aqueous humor) → lenscorpus vitreumretina
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Refractive media of the eye

Draw

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Refractive media of the eye

Cornea

A
  • The transparent front part of the eye
  • Where light enters the eye
  • Covers:
    • Iris
    • Pupil
    • Anterior chamber
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Refractive media of the eye

Aqueous humor

A
  • Present in:
    • Camera bulbi anterior
    • Camera bulbi posterior
  • The camera bulbi anterior/posterior fills the space between cornea and lens
  • Role:
    • Refractive proeperties
    • Maintainance of intraocular pressure
  • Enters the system in the camera bulbi posterior → pupil → camera bulbi anterior
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Refractive media of the eye

Lens

A
  • Transparent
  • Biconvex:
    • Anterior pole
    • Posterior pole
    • Equator
    • Ventral axis (= optic axis)
  • Role: helps to refract light to be focused on the retina
    • Accommodation: By changing chape, functions to change the focal distance of the eye so that it can focus on objects at various distances

Suspension of the lens

  • Ciliary muscles
  • Iris: regulates diameter of the pupil, separates the anterior chamber from the posterior chamber
    • Pupil
      • Mm. sphinter
      • M. dialator
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Refractive media of the eye

Corpus vitreum

A
  • A transparent jellylike substance filling the interior of the eyeball behind the lens
  • Largest
  • Membrana vitera: dense surface of cells at the surface
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Give the division of the interior of the eyeball

General knowledge, not directly linked to the topic

A
  • The interior of the eyeball is divided into 3 chambers (camera bulbi):
    • Camera anteror (anterior chamber)
      • Between cornea and iris
      • Filled with aqueous humor
    • Camera posterior (posterior chamber)
      • Between iris, ciliary body and lens
      • Filled with aqueous humo
    • Camera viteria (viterous body)
      • Largest of the 3 chambers
      • Behind the lens
      • Surrounded by retina
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Optical accomodation

A
  • The ability of the eye to change its focus from distant to near opjects
  • Achived by the lens changing its shape
  • Infinite: tonus of m. ciliaris
    • Contraction of m. ciliaris → thicker lens → shorter focal length
  • Nearest point of focus: relaxation of eye
  • Central segments:
    • Optic radiation
    • Rostral colliculi
    • Geniculooccipital tract
    • Optic area of cerebral cortex
  • Peripheral segments:
    • Retinal neurons
    • N. opticus
    • Optic chiasm
    • Optic tract
    • Thalamus
    • Lateral geniculate bodies
  • Retinae
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Visual pathway

A
  • After decussation in the optic chiasm the axon of the retinal ganglion cells project to the lateral geniculate body, from where the next fibers reach the primary visual cortex
  • The primary visual area (Brodmann’s area 17) projects to further brain regions
  • Retina:
    • The temporal visual field and nasal visual field project to the opposite sides of the retina
    • The dorsal and ventral parts of visual field are reversed in the same way
    • The same mapping occurs in the visual cortex and retina
  • Optic nerve:
    • Fibers of n. opticus originating from the same quartes of retina run together
  • Optic tract:
    • Formed by medial and lateral bundle
      • Lateral branch:
        • Towards lateral geniculate body
        • Perception of visual information
      • Medial branch:
        • Towards pretectum, superior colliculus
        • Visual reflexes (pupil reflex, accommodation, convergence)
  • Pretectum:
    • Midbrain structure
    • Involved in mediating behavioral responses to acute changes in ambient light such as:
      • Pupillary light reflex
      • Optokinetic reflex
      • Temporal changest to the circadian rhythm
  • Superiro colliculus:
    • Innervated by tracts from the visual cortex
    • Integrator of accadical eye movement
    • Main function: localization of an object
  • Lateral Geniculate Nucleus (LGN)
    • Part of thalamus
    • Important relay station
    • Function: filter which, depending on the non-retinal afferents, does not let certain parts of the retinal stimuli pass to the higher cortical areas
    • Fibers of the LGN radiate to the primary visual cortex (Brodman’s area 17)
      • Location: medial and caudal regions of the occipital lobe
  • Optic radiation:
    • In the medial part of the occipital lobe, the information is transmitted to the visual cortex via radiation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly