Vision Physiology Flashcards
This deck tests your knowledge of how vision works.
Draw out and label the general anatomy of the eye.
Refer to Notion.
Describe the anatomy and physiology of the cornea and lens.
- Both are the transparent media through which light is transmitted and focused
- Cornea is thick, and consists of regular layers of collagen (maintained by hydration); disruption of regular layers affects acuity
- Lens is biconvex and can change shape based on ciliary body contraction
Describe how the lens changes shape.
- Ciliary body relaxes, making it further from lens = pulls zonules taut = stretches lens and decreases refractory index for far vision
- Ciliary body contracts, making it closer to lens = zonules relax = lens becomes more globular and increases refractory index for near vision
Describe the basic anatomy of the retina’s layers.
The retina consists of various layers (pigment, photoreceptor, transmission, neurons)
What does the pigment layer of the retina do?
Contains melanin, which absorbs light and prevents scatter
What does the photoreceptor layer do?
- Contains rods and cones, which receive and transduce light energy into action potentials
- Rods: sensitive to dim light only
- Cones: sensitive to bright light, colour, and visual acuity
What are the limitations of rods?
- Many rods connected to one bipolar cell = poor acuity
- Only one type of rod = no colour vision
What are the strengths of cones?
- One cone connected to one bipolar cell = good acuity
- Three types of cones = RGB colour vision
What does the transmission layer do?
- Bipolar cells - transmit info to ganglion cells
- Ganglion cells - transmit info to thalamus and brainstem
- Horizontal and amacrine cells - integrate and modulate info
What is the macula and fovea?
- Macula is a yellow, oval-shaped spot at the center of the fovea with many cones
- Fovea is a small depression, and is the site where eyesight is sharpest
What is the optic disc?
The union of all the retinal ganglion cells into the optic nerve
What is the near triad?
Convergence, miosis, high refractive power from a globular lens
What are the intrinsic muscles of the eye, and what innervates them?
- Ciliary body muscles, dilator pupillae, sphincter pupillae
- Sympathetic: sup. cervical ganglion
- Parasympathetic: oculomotor nerve
Draw out the extraocular muscles of the eye.
Refer to Notion.
What is the function of the superior and inferior rectus?
- SR: upwards movement + slightly responsible for inward movement + slightly responsible for intorsion
- IR: downwards movement + slightly responsible for outward movement + slightly responsible for intorsion
What is the function of the medial and lateral rectus?
- MR: inward movement
- LR: outward movement
What is the function of the superior oblique?
Intorsion + downward movement in medial position + slightly responsible for outward movement
What is the function of the inferior oblique?
Extorsion + upward movement in medial position + slightly responsible for outward movement
What is the innervation of the extraocular muscles?
- A3 SO4 LR6
- All CN III, except SO (4) and LR (6)
What kind of hemidecussation occurs at the optic chiasma?
- The right nasal visual field info is transmitted to the left visual cortex (and inv.)
- The right temporal visual field info is transmitted to the right visual cortex (and inv.)
What collaterals are given off in the optic tract, and what function do they serve?
- Superior colliculus - for extraocular muscles
- Pretectal nucleus - for pupillary and lens accommodation reflex
What is the post-optic tract pathway for visual info?
lateral geniculate nucleus (thalamus) > optic radiation (sup. VF division is Meyer’s loop) > primary visual cortex (occipital lobe)
What is the optic radiation?
A collection of relay neuron axons
Visual field vs Retinal field?
VF: Area of external environment that is visible
RF: Regions on retina that receive image of VF; image is inverted and reversed by lens
