Lab 4 Visual pathway and vestibular system overview Flashcards
What do sensory receptors do and how does this occur?
Convert a sensory stimulus into neurobiological activity. (transduction). A stimulus causes a change in membrane permeability Which leads to a receptor potential. This causes an action potential in a neuron which is carried to the CNS.
What is the retina?
A sheet of nerve and glial cells that lines the posterior globe .
Where does the retina terminate?
It terminates anteriorly at the ora Serrata.
Label these parts of the retina.
What are the two types of photoreceptors and what vision are they involved in?
Rods = Scotopic; low light level high sensitivity
Cones =Photopic; high acuity but low sensitivity
Where are visual pigments found in photoreceptors?
The outer segment of photoreceptors contain a disc in which the membranes contain visual pigments.
What are visual pigments made from?
Chromoproteins. - these comprise of chromophore and proetin.
The 4 visual pigments have retinal as their chromophore and opsin as their protein.
What determines the spectral nature of each visual pigment?
The protein determines the spectral nature of each visual pigment.
When adapted to the dark what happens to the photopigment?
The retinal is bent 11-cis configuration and is bound to the opsin within a ‘binding pocket’ formed by the opsin helices.
What is photoisomerisation?
The visual pigment chromophore can exist in a number of different isomeric forms.
When in dark-adapted form what happens when a visual pigment encounters a photon?
The absorption of a photon isomerises the chromophore to the ‘straight’ all trans form.
The all-trans isomer no longer fits into the opsin binding pocket and the opsin and retinal separate
The visual pigment bleaches.
Label this diagram
Via what, does the visual system reach the CNS?
Via the second cranial nerve which passes from the retina to the brain by the optic canal.
What is the vestibular system involved in?
balance and acceleration
Via what, does the V111 th nerve pass from the ear to the brain?
By the internal auditory meatus
label the cranial sections.
What are the 12 cranial nerves and their respective number?
Where does the II optic nerve of each eye cross over?
The optic chiasm
Where does the oculomotor nerve, trochlear nerve and abducens nerve enter the orbit from?
The superior orbital fissure.
