Ch. 7 Thermo and Vision

Question 1

thermoreceptors in facial pits of rattlesnakes

Answer 1

infrared detectors that detect change in tissue temp

increase firing rate transiently when temp changes by .002 degrees C to modify behavior

helps snake hunt in poor light

Question 2

thermoreceptors

Answer 2

specialized nerve endings in the skin

Question 3

two types of thermoreceptors in the skin and tongue

Answer 3

some increase firing when hot

some increase firing when cold

both have less firing at sustained temp

Question 4

photoreceptors

Answer 4

transduce photons of light into electrical signals interpreted by the nervous system

Question 5

rhodopsin

Answer 5

visual pigment containing the light-absorbing retinal and protein opsin

Question 6

lens

Answer 6

structure that refracts (bends) light

Question 7

compound eyes of arthropods

Answer 7

image-forming containing many units called ommatidium aimed at a different part of the visual field

Question 8

each ommatidium of a compound eye contains several ____________ cells

Answer 8

photoreceptor

Question 9

rhabdomere

Answer 9

part of the cell where the plasmam membrane has densely packed microvilli

increases chance light will be captured b/c high surface area

Question 10

rhabdome

Answer 10

12 rhabdomeres that surround the dendrite of an afferent neuron

Question 11

how does vertebrate eye work

Answer 11

light is bent through the cornea and bent again to form an inverted image on the retina

Question 12

accomodation

Answer 12

adjusting the lens to see

ability decreases in old age

Question 13

the stimulud for all photoreceptor cells is __________ ________ that falls within a range of energy called visible light

Answer 13

electromagnetic radiation

violet (400nm) is highest energy light and red (650-700nm) is lowest energy

Question 14

where are the photoreceptors that transduce light energy found

Answer 14

retina

Question 15

rods vs cones

Answer 15

rods are blk/white and function in dim light

cones are color and function in bright light

Question 16

fovea

Answer 16

part of the retina that provides a lot of info - high visual acuity

only have cones

Question 17

vertebrate rods and cones _________ in response to light simuli, whereas invertebrate rhabdomeres ________

Answer 17

hyperpolarize, depolarize

Question 18

light for vertebrates ________ permeability of Na across the outer membrane

Answer 18

decreases

Question 19

in the dark, the Vrest of the vertebrate rod is…

Answer 19

much less inside-negative than normal neurons

Na channels are always open and Na is coming in but is being pumped out by the Na/K pump

Question 20

do rods and cones make APs

Answer 20

no, they release nt

Question 21

what does a light induced decrease in dark current do

Answer 21

makes Vm in outer segment hyperpol toward Ek which spreads to inner segment

this causes nt release

Question 22

________ of photoreceptors decreases amount of nt released

Answer 22

hyperpolarization

Question 23

all visual pigments contain 2 things

Answer 23

a protein opsin

a light absorbing molecule retinal

Question 24

retinal 2 different states

Answer 24

no light = linked to opsin in a cis

light captures = trans

Question 25

activated rhodopsin (light)

Answer 25

activates the G protein transducin –> activate phosphodiesterase (PDE) –> turn cGMP to GMP

this closes cGMP-gated channels and the cell hyperpolarizes

Question 26

when light stimulus ends, cGMP…

Answer 26

is regenerated by guanylate cyclate and dark-current channels reopen

Question 27

visual _______ is best when the image is focused onto rods and visual ______ is best when the image is focused onto the cones of the fovea

Answer 27

sensitivity, acuity

Question 28

thermal energy equation

Answer 28

Etherm = kT

k is boltzman’s constant

T in K

Question 29

what does thermal energy do to vision

Answer 29

lowers sensitivity of receptors b/c it produces a constant “background noise”

Question 30

equation for energy of a single photon

Answer 30

E = hv = hc/lamda

h = planck’s constant

v = frequency

c = speed of light

lamda = wavelength

Question 31

synesthesia

Answer 31

1 input generates multiple responses

ex. see a color and get taste

Question 32

optogenetics

Answer 32

light sensitive algae protein channel that opens to blue light

clone gene of channel proteins and transfect into a neuron

neuron becomes light sensitive and is activated by flashing light

Question 33

neuron specific promoters

Answer 33

promoter attached to a light-sensitive channel gene

Put into virus into brain so expressed in target neurons

target disease or memory

Question 34

advantages of light sensitive neurons

Answer 34

precise activation by illumination

cell-specific/region specific expression

speed of control is fast: speed of light

target specific pathways

No metabolic side effects