7: Physiology - Vision Flashcards
What is strange about the cell arrangement of the retina?
Light passes THROUGH ganglia to reach photoreceptors
‘inside out’ arrangement
Photoreceptors (depolarise / hyperpolarise) in response to light.
hyperpolarise
unusual
Photoreceptors (depolarise / hyperpolarise) in the dark.
depolarise
What neurotransmitter is released when photoreceptors depolarise in the dark?
Glutamate
Which protein is converted to retinol when photoreceptors are struck by light?
Rhodopsin
When photoreceptors hyperpolarise by being exposed to light, what neurotransmitter is released?
No neurotransmitter is released
Not depolarised
Why do photoreceptors hyperpolarise when struck by light?
Rhodopsin activates G proteins (transducins)
Which indirectly CLOSE Na+ channels (causing hyperpolarisation)
(By activating PDE, which breaks cGMP (which is keeping Na+ channels open) to GMP. Na+ channels close, stopping Na+ influx. K+ efflux continues. Hyperpolarisation)
Describe some characteristics of cone cells.
Responsible for colour vision
High acuity
Low sensitivity
Low convergence
Found at the fovea
Describe some characteristics of rod cells.
Low-light vision, B&W
Low acuity
High sensitivity
High convergence
What process, by which excited neurons inhibit the neurons around them, also occurs in the eye?
Lateral inhibition
What is the point of lateral inhibition?
Reduces the excitation of other neurons, ‘drawing attention’ to a specific sitmulus
In the eyes: helps with localisation of specific stimuli
Lateral inhibition exaggerates the ___ between different stimuli.
contrast
What is
a) tonotopy
b) retinotopy?
a) Different frequencies of sound are processed by different areas of the auditory cortex in the temporal lobe
b) Visual information from different visual fields are processed by different areas of the visual cortex in the occipital lobe
Which anatomical feature divides the posterior occipital cortex into
a) superior and inferior
b) left and right
sections?
a) Calcarine sulcus
b) Falx cerebri
Which nucleus do the optic tracts synapse at?
Lateral geniculate nucleus
