Opt - Lec1b - Physiology Flashcards
What glands are present in the outer lipid layer (tears)
Meibomian gland (mainly)
Glands of Zeis and Moll
Role is to retard evaporation and lubricate the occular surface
What glands are present in the middle aqueous layer (tears)
Lacrimal gland
Accessory lacrimal glands in conjunctiva
Provides oxygen and defends ocular surface
What is present in the inner mucin later (tears)
Mucus secretin cells in conjunctiva and cornea Lacrimal gland (little)
Wets and lubricates ocular surface
How is tear production controlled in…
Normal situations
Sympathetic to blood vessels supplying glands
Influenced by bright light and air pollution - maintains normal tear flow
How is tear production controlled in…
Emotional situations
Parasympathetic to myoepithelial cells
Via emotion sensors in brain
How is tear production controlled in…
Reflex - irritation
Parasympathetic to myoepithelial cells
When the cornea or conjunctiva is irritated
Via trigeminal (sensory) nerves
How is tear production controlled in…
Reflex - smell
Parasympathetic to myoepithelial cells
Via olfactory system
How is tear production controlled in…
Crocodile tears
Parasympathetic to myoepithelial cells
Eating - result of a faulty connection (lacrimal gland instead of salivary gland)
What muscle is involved as a tear drainage (pump)
Orbicularis oculi
Describe what happens during the contraction and relaxation of orbicularis oculi muscle fibres to facilitate tear drainage
Contraction
Closes eye - tears spread towards nose
Most evaporate - few spread into lacrimal puncta
Forces tears into lacrimal sac
May expand lacrimal sac so that tears are sucked in
Relaxation
Opens eye
Causes portions of canaliculi to expand so that tears are sucked in
May cause collapse of lacrimal sac so that tears are pushed into the nasolacrimal duct
What are the 3 tear layers of the adnexa
Outer Lipid layer
Middle aqueous layer
Inner mucin layer
What pupillary responses occur in near synkinesis?
accommodation
Convergence
MIOSIS
Choose the correct option
For ROD cells
High sensitivity/ high resolution
Good at contrast brightness and motion/ good at colour resolution
Dense at fovea/absent at fovea
Lease dense in peripherally/most dense at periphery
High sensitivity
Contrast brightness and motion
Absent at fovea
Most dense in mid-periphery
Choose the correct option
For CONE cells
High sensitivity/ high resolution
Good at contrast brightness and motion/ good at colour resolution
Dense at fovea/absent at fovea
Lease dense in peripherally/most dense at periphery
High resolution
Colour vision
Most dense at fovea
Numbers decrease in periphery
What is the function of having a low ratio of cone:bipolar cells and a high ratio of rod:bipolar cells?
Having a 1:1 ratio of cone:bipolar cells maximises resolution in the central retina
Having a 50-100 :1 ratio between rods and bipolar cells maximises sensitivity in peripheral retina
