Flashcards in Physiology Deck (67):
Aqueous humour - where is it produced?
Aqueous humour - where is it secreted from?
Ciliary process (internal folds of ciliary body)
Aqueous humour pathway
Secreted into posterior chamber (nourishes lens)
Passes through the pupil to the anterior chamber (nourishes cornea)
Aqueous humour - where does it drain
Scleral venous sinus through the canal of schlemm
Aqueous humour is mainly found in the ANTERIOR/POSTERIOR segment of the eye?
Aqueous humour - function
Maintains intra-ocular pressure
- the IOP depends on the balance between the production and reabsorption of aqueous humour
Vitreous humour - definition
Clear fluid with a jelly like consistency
Vitreous humour is mainly found in the ANTERIOR/POSTERIOR segment of the eye?
Where are photoreceptors found
Posterior part of the retina
Photoreceptors - functions
Converts light into neural signals that can stimulate biological processes
2 types of photoreceptors
There is increased visual acuity if there are MORE/LESS photoreceptors present
There is increased visual acuity if the photoreceptors are spaced very close together. True or false?
Rods - light conditions
When light conditions are not good
Low levels of light
Night vision, peripheral vision
Rods - where are they located
Rods - photoreceptor spacing
Large spacing between photoreceptors
Rods - high/low light sensitivity
Rods - high/low visual acuity
Cones - light conditions
For seeing things in colour
Cones - where are they located
Cones - photoreceptor spacing
Minimal spacing between photoreceptors
Cones - high/low light sensitivity
Cones - high/low visual acuity
Colour vision - rods/cones
Short wave cone produces which colour?
Middle wave cone produces which colour?
Long wave cone produces which colour?
When exposed to light, Na+ levels increase/decrease ?
- due to the closure of cGMP gated Na+ channel
Decreased Na+ levels causes the membrane potential to become more positive/negative?
- Vm hyperpolarises
In the absence of light, Na+ levels increase/decrease?
- due to the opening of cGMP gated Na+ channel
Increased Na+ levels causes the membrane potential to become more positive/negative?
- Vm depolarises
What are the visual pigment molecules called?
2 components of rhodopsin
Retinal (vitamina A derivative)
Where in the retina is the fovea located?
In the centre of the retina, inside the macula
Infant presents with a visual problem in one eye. What is the initial management?
Put eye patch over GOOD eye.
Make the patient use their bad eye to force the brain to rely on signals from the bad eye. This helps the brain develop properly
Emmetropia - definition
No refractive error
The eye has no visual defects
Hyperopia - definition
Vision is better for distant than for near objects
Hyperopia - parallel rays are focussed in front of / behind the retina ?
Myopia - definition
Vision is bette for near than for far away objects
Myopia - visual images come in to focus in front of / behind the retina ?
In front of
Everything from the right visual field hits the eye at the ____ retina of the right eye and the ____ retina of the left eye
Nasal retina - right eye
Temporal retina - left eye
Light from objects in the right visual field is processed by the RIGHT/LEFT primary visual cortex
Light from objects in the lower visual field is processed by the UPPER/LOWER part of the primary visual cortex
What happens when we blink
Lacrimal fluid runs over the eye and this prevents the eye from drying out.
Helps remove foreign bodies from the eye
Which nerves (sympathetic/parasympathetic) cause dilation of the pupil?
How does light reach the retina?
It goes through the pupils
Dilated pupil allows more/less light to reach the retina?
Which muscle is responsible for pupillary dilation?
Dilator pupillae muscle
Location of the dilator pupillae muscle
Located around the external circumference of the iris
An abnormally sustained pupillary dilation
Mydratic pupil - causes
eye drops (drugs)
CNIII pathology (constrictors not working at all)
Constricted pupil allows more/less light to reach the retina?
Which nerves (sympathetic/parasympathetic) cause constriction of the pupil?
Which muscles is responsible for constriction of the pupil?
Sphincter pupillae muscle
Location of the sphincter pupillae muscle
It encircles the pupil
Around the internal circumference of the iris
Abnormally sustained pupillary constriction
Mitotic pupil - causes
Diseases (Horner's syndrome)
Pupillary light reflex (direct)
Shine a torch into one eye
Direct light reflex (constriction) in the stimulated eye
Pupillary light reflex (consensual)
Shine a torch into one eye
Constriction occurs in the non-stimulated eye
Which nerves (sympathetic/parasympathetic) are responsible for far (distant) vision
In far (distant) vision, the ciliary muscle contracts/relaxes ?
In far (distant) vision, the suspensory ligaments contract/relax
In far (distant) vision, the lens is flat/spherical
Which nerves (sympathetic/parasympathetic) are responsible for near vision
In near vision, the ciliary muscle contracts/relaxes?
In near vision, the suspensory ligaments contract/relax?