Ch 6: remote sensing

Question 1

the ___ has a high density of photoreceptors, whereas the __ __ __ lacks them

Answer 1

the FOVEA has a high density of photoreceptors, whereas the OPTIC NERVE HEAD lacks them

Question 2

the optic nerve head consists entirely of:

Answer 2

axons crossing through the retina

Question 3

corollary discharge

Answer 3

• a copy of an eye movement command sent to the visual cortex
• it cancels the motion, producing a stabilizing image
• compensates for eye movement

Question 4

smooth eye movement can only occur when:

Answer 4

tracking movement in the world (e.g., following a pencil with your eyes). Otherwise, saccadic eye movement

Question 5

The unmyelinated axons turn inward at the ___ ___ ___ of the retina where there are no photoreceptors

Answer 5

OPTIC NERVE HEAD

Question 6

why are rod photoreceptors unusual neurons?

Answer 6

because they do not fire APs and they have unusually short axons and posess a rod-shaped outer-segment rather than dendrites

Question 7

each outer segment of rods contains disks filled with ____

Answer 7

rhodopsin

Question 8

rhodopsin consists of:

Answer 8

2 linked molecules: retinal and opsin

Question 9

Opsin has __ transmembrane domains and belongs to the family of __ ___ ___ receptors

Answer 9

7

G-protein coupled receptors

Question 10

in the dark, retinal is ___, but becomes ___ after light activation

Answer 10

in the dark, retinal is BENT, but becomes STRAIGHT after light activation

Question 11

absorption of a photon of light does what to retinal’s conformation

Answer 11

converts it from cis to trans (straight backbone). CHange in shape activates the rhodopsin molecule and retinal drifts away

Question 12

Phototransduction cascade

Answer 12

1. photon is absorbed and activates rhodopsin
2. rhodopsin activawtes TRANSDUCIN (G protein) by exchanging GDP for GTP
3. GTP binds to PHOSPHODIESTERASE (effector)
4. phosphodiesterase generates GMP from cGMP
5. GMP causes Na+/Ca2+ channel to CLOSE (it’s usually open). MEMBRANE BECOMES HYPERPOLARIZED.
6. decrease in intracellular Ca2+ causes fewer glutamate-filled vesicles to be released
7. 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.

Question 13

Rod bipolar cells synapse onto __ __, which synapse onto __ ___ ___

Answer 13

Rod bipolar cells synapse onto AMACRINE CELLS, which synapse onto CONE BIPOLAR CELLS

Question 14

amacrine cells use ___ to communicate with OFF bipolar cells and __ __ to contact ON bipolar cells

Answer 14

amacrine cells use GLYCINE to communicate with OFF bipolar cells and ELECTRICAL SYNAPSES to contact ON bipolar cells

Question 15

which photoreceptor do we use for daylight vision?

Answer 15

cones

Question 16

___ predominate in the fovea. ____ in the periphery.

Answer 16

CONES predominate in the fovea, RODS in the periphery

Question 17

3 types of cones tuned to different wavelengths of light:

Answer 17

S (short): dark blue
M (medium): green
L (long): yellow

Question 18

OFF bipolar cells release ___ glu when the cone is exposed to light, and ___ when the light turns off

Answer 18

OFF bipolar cells release LESS glu when the cone is exposed to light, and MORE when the light turns off

Question 19

all cone bipolar cells release glu directly onto ___ ___ ___

Answer 19

retinal ganglion cells

Question 20

things that you taste are ___ soluble

things that you small are ___ soluble

Answer 20

things that you taste are WATER soluble

things that you small are LIPID soluble

Question 21

Olfactory transduction cascade

Answer 21

1. 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
2. cAMP oens Na+/Ca2+ channel, allowing cation influx
   4.rise in intracellular Ca2+ opens calcium-gated chloride channels
3. Cl- FLOWS OUT OF CILIA into the mucus along its concentration gradient
   ODORANT BINDING DEPOLARIZES THE OLFACTORY SENSORY NEURON
4. once threshold is reached, an AP is sent to the olfactory bulb