Physiology Flashcards
Does Anaemia increase bleeding time?
No
What does true auoofluoroscence on SLO a feature of?
SLO = scanning laser ophthalmoloscopy
Optic disc drusen
What are optic disc drusen?
Calcified deposits in optic nerve head
Are optic disc drusen symptomatic?
Usually not
What does off-centre on-surround mean for receptor fields of ganglion cells?
Off-centre: Centre of receptive field = inhibitory
aka
More light in centre: less firing
and vice versa
What does off-centre mean for receptor fields of ganglion cells?
On-surround: Surrounding area = excitatory
aka
More light in surrounding: more firing
and vice versa
When is IOP usually highest?
Morning
(peaks between 8am to 12pm)
In normal tension glaucoma, how are the fluctuations of IOP?
Same as normal eyes
What is the diurnal variation of IOP in normal eyes?
5mmHg
What has higher water content: Corneal stroma or sclera?
Corneal stroma
(got it wrong because I thought cornea is transparent so will have less but I was wrong)
What happens to the optic tract leaves the Optic chiasm?
Winds around the cerebral peduncles
What is nasal hemiretina? (easy)
Nasal half of retina
Where do the fibres of the nasal hemiretina decussate?
Optic chiasm
What does the Optic Tract divide into? (2 things)
- Larger lateral root
- Smaller medial root
What is the ratio of cones: bipolar cells : ganglion cells in Fovea?
1:1:1
What is ratio of rods : bipolar cells in peripheries?
50-100 : 1
How does the brain heal when its injured?
Gliosis
In head injury, where do countercoup lesions occur in relation to the site of impact?
Diagonal
What type of brain damage causes diffuse axonal injury?
PRIMARY brain damage
What layer of cornea uses the MOST energy?
Most > Least
Endothelium
Epithelium
Stroma
What concept aligns the eyes to correct small misalignments?
Vergence
What are the different types of vergence? (4 things)
- Vertical vergence
- Torsional fusional vergence
- Convergence fusional vergence
- Divergence fusional vergence
What is vertical vergence?
Aligns eyes up / down
What is Prism Dioptres (PD)?
Measures how much a prism bends light (up / down / left / right)
Explain prism dioptres using a real life example
Imagine you’re looking at an object 1 meter away (e.g., a letter on a Snellen chart).
If a 1 PD prism is placed in front of your eye, it shifts the image by 1 cm to the side (up, down, left, or right).
If a 10 PD prism is used, the image shifts by 10 cm at 1 meter.
So, higher PD values mean greater displacement of the image.
What is the normal vertical vergence range?
2-3 PD
What is Torsional vergence?
Rotates eyes to counter twisting
What is the normal Torsional vergence range?
2-3 degrees
What is Convergence vergence?
Moves eyes inwards (to focus on near objects)
What is the normal Convergence vergence range?
15-20 PD for distance
25 PD for near (stronger bc of accommodation)
What is Divergence vergence?
Moves eyes outwards (to align with distant objects)
What is the normal Divergence vergence?
6-10 PD for distance
9-12 PD for near (higher bc eye strain for near objects)
What part of visual pathway will Anterior Communicating Artery Aneurysm compress?
Upper part of Optic chiasm
What visual problem will Anterior Communicating Artery Aneurysm cause?
Bitemporal Lower Quadrantanopia
(because it will compress upper portion of optic chiasm)
Where does Corneal stroma get most of its glucose from?
(Recall)
Aqueous
What does the Anterior spinal nerve root connect?
Motor fibres to skeletal muscle
What fibres doest the Posterior spinal nerve root contain?
Sensory fibres
What fibres doest the Anterior spinal nerve root contain?
Autonomic nerve fibres
What is the rate of Aqueous production?
2-3 micro litres per minute
What is the Inner vs Outer part of Inner segment of Rod photoreceptor called?
Inner: Myoid
Outer: Ellipsoid
What does the Myoid part of Rod photoreceptor have a lot of? (2 things)
- Golgi apparatus
- Smooth ER
What does the Ellipsoid part of Rod photoreceptor have a lot of?
Mitochondria
