Ch 6: remote sensing Flashcards
the ___ has a high density of photoreceptors, whereas the __ __ __ lacks them
the FOVEA has a high density of photoreceptors, whereas the OPTIC NERVE HEAD lacks them
the optic nerve head consists entirely of:
axons crossing through the retina
corollary discharge
- a copy of an eye movement command sent to the visual cortex
- it cancels the motion, producing a stabilizing image
- compensates for eye movement
smooth eye movement can only occur when:
tracking movement in the world (e.g., following a pencil with your eyes). Otherwise, saccadic eye movement
The unmyelinated axons turn inward at the ___ ___ ___ of the retina where there are no photoreceptors
OPTIC NERVE HEAD
why are rod photoreceptors unusual neurons?
because they do not fire APs and they have unusually short axons and posess a rod-shaped outer-segment rather than dendrites
each outer segment of rods contains disks filled with ____
rhodopsin
rhodopsin consists of:
2 linked molecules: retinal and opsin
Opsin has __ transmembrane domains and belongs to the family of __ ___ ___ receptors
7
G-protein coupled receptors
in the dark, retinal is ___, but becomes ___ after light activation
in the dark, retinal is BENT, but becomes STRAIGHT after light activation
absorption of a photon of light does what to retinal’s conformation
converts it from cis to trans (straight backbone). CHange in shape activates the rhodopsin molecule and retinal drifts away
Phototransduction cascade
- photon is absorbed and activates rhodopsin
- rhodopsin activawtes TRANSDUCIN (G protein) by exchanging GDP for GTP
- GTP binds to PHOSPHODIESTERASE (effector)
- phosphodiesterase generates GMP from cGMP
- GMP causes Na+/Ca2+ channel to CLOSE (it’s usually open). MEMBRANE BECOMES HYPERPOLARIZED.
- decrease in intracellular Ca2+ causes fewer glutamate-filled vesicles to be released
- this allows ROD BIPOLAR CELLS to become DEPOLARIZED, as their metabotropic glutamate receptors, which cause hyperpolarization of the cell, are no longer binding to glutamate. Cl- channels open. INCREASED NEUROTRANSMITTER RELEASE FROM BIPOLAR CELLS.
Rod bipolar cells synapse onto __ __, which synapse onto __ ___ ___
Rod bipolar cells synapse onto AMACRINE CELLS, which synapse onto CONE BIPOLAR CELLS
amacrine cells use ___ to communicate with OFF bipolar cells and __ __ to contact ON bipolar cells
amacrine cells use GLYCINE to communicate with OFF bipolar cells and ELECTRICAL SYNAPSES to contact ON bipolar cells
which photoreceptor do we use for daylight vision?
cones
___ predominate in the fovea. ____ in the periphery.
CONES predominate in the fovea, RODS in the periphery
3 types of cones tuned to different wavelengths of light:
S (short): dark blue
M (medium): green
L (long): yellow
OFF bipolar cells release ___ glu when the cone is exposed to light, and ___ when the light turns off
OFF bipolar cells release LESS glu when the cone is exposed to light, and MORE when the light turns off
all cone bipolar cells release glu directly onto ___ ___ ___
retinal ganglion cells
things that you taste are ___ soluble
things that you small are ___ soluble
things that you taste are WATER soluble
things that you small are LIPID soluble
Olfactory transduction cascade
- binding of olfactory receptor molecule to its preferred odorant activates G protein called Golf (changing GDP for GTP)
2.Golf then activates ADENYLATE CYCLASE, which raises cAMP levels within olfactory cilium - cAMP oens Na+/Ca2+ channel, allowing cation influx
4.rise in intracellular Ca2+ opens calcium-gated chloride channels - Cl- FLOWS OUT OF CILIA into the mucus along its concentration gradient
ODORANT BINDING DEPOLARIZES THE OLFACTORY SENSORY NEURON - once threshold is reached, an AP is sent to the olfactory bulb
