Behavioral Neuroscience Exam 2

transduction mechanisms

conductor cells convert energy into language the brain understands

thalamus

receives sensory information, relay center of the brain

taste & olfaction

what senses have chemical energy transduced

vision

what sense has electromagnetic energy transduced

hearing & somatosensory

what senses have mechanical energy transduced

chemoreceptors

receptors that receive the chemicals

flavor

dependent on smelling (ex: lemon)

afferent

messages arriving into the cell

efferent

messages exiting the cell

amygdala

emotional center & food aversions

hypothalamus

control feelings of hunger

1. receptor neurons
2. transduction
3. AP generation
4. propagation to the thalamus
5. sensation in the cortex

what are the steps for signal transduction for smell

1. each food activates a different combination of tase receptors
2. distinctive smell
3. other sensory modalities

what are the steps to distinguish the countless unique flavors of food

* salty
* sweet
* bitter
* sour
* umami

what are the five different tastes

taste cell

specific to 1 taste

taste bud

contains multiple taste cells

type 1 taste receptors

similar to astrocytes

type 2 taste receptors

g-coupled receptors for sweet, umami, and bitter

type 3 taste receptors

ionotropic receptors for salty and sour

type 4 taste receptors

immature cells

salty

Na+ flows directly into the ameloride-sensitive sodium channel

1. G protein dissociates
2. Activation of 2nd messenger
3. Ca2+ action
4. Amplification

standard steps for g-coupled protein receptors

sour

protons flow through the amelioride-sensitive Na+ channel and shut off a proton-sensitive K+ channel

Bitter

GPCRs activate PLC, IP3 releases Ca2+ from internal stores which activates a Na+ channel

sweet, umami

dimers of GPCRs activate PLC, IP3 releases Ca2+ from internal stores with activates a sodium channel

population coding

looking at many neurons simultaneously

NaCl

salt

quinine

bitter

HCl

sour

Sucrose

sweet

1. receptor cells in olfactory epithelium
2. transduction
3. AP generation in receptor cells themselves
4. direct or indirect pathway

\

what is the signal transduction/flow of olfaction

pyriform cortex

where does the direct pathway lead for olfaction

thalamus

where does the indirect pathway lead for olfaction

hippocampus

important for memories

basal cell

immature cell

1. each GPCR type responds to multiple odorants
2. each odorant can activate multiple GPCR types

why are olfactory GPCRs broadly tuned

glomerulus

contains 1 receptor type, connects to olfactory bulb

lateral inhibition of olfaction

stops other glomerulus from sending info to cortex, helps with specificity

* population coding
* sensory maps
* temporal coding

how does the olfactory system code for different scents

intensity

how high the peaks are, measured in dB

frequency

how many cycles, measured in Hz

tympanic membrane

first membrane that is hit by sound

cochlea

where signal transduction happens in the ear

amplification

what happens in the middle ear

turns weaker & large amplitude waves into stronger & smaller waves by concentrating force on a smaller surface area

how does the middle ear amplify sound

analyzes frequencies

what happens in the inner ear

tectorial membrane

in cochlea, very rigid, acts as a ceiling

organ of Corti

contains receptor cells

basilar membrane

in cochlea, very elastic

perilymph

fluid in scala vestibuli and scala tympani, similar to extracellular fluid

endolymph

fluid in scala media

apex

what part of the basilar membrane is wider

base

what part of the basilar membrane is stiffer

apex

what part of the basilar membrane detects lower frequencies

base

what part of the basilar membrane detects higher frequencies

inner hair cells in the organ of Corti

what is responsible for transduction in the inner ear

stereocilia goes right and tiplinks open, compressed air & depolarization

what happens when basilar membrane goes down

stereocilia goes left and tiplinks close, rarified & hyperpolarization

what happens when basilar membrane goes up

inner hair cells

what hair cells in the ear have the most output

function as a cochlear amplifier

what is the role of the outer hair cells in the ear

* frequency
* intensity
* location

what must the auditory system encode

phase locking

How does auditory system detect low frequencies

phase locking + population coding

how does the auditory system detect medium frequencies

labelled lines

how does the auditory system detect high frequencies

right superior olive

if the sound comes from the left, which superior olive activates first

left superior olive

if sound comes from the right, which superior olive activates first

interaural intensity difference

sound at high frequency is heard at different intensities in each ear

interaural time delay

time taken for sound to reach each ear

middle superior olive

if a sound comes from behind/ in front of you, which superior olive will activate first

ganglion cells

what are the only cells in the eye that can fire an action potential

ciliary muscle

helps the lens stretch or compress

lens

make the rays converge in the retina

the lens widens

what happens to the lens when it views something close

the lens compresses

what happens to the lens when it views something far away

located in the back of the retina, next to the pigmented epithelium, macula & fovea

where are photoreceptors located

optic disk (blind spot)

point where axons leave the sclera

fovea

area of maximum visual acuity

nasal retina

located closest to the nose

temporal retina

located farthest from nose

rods

what photoreceptor is the most numerous

rods

what photoreceptor is most sensitive to light

rods

what photoreceptor has high convergence

cones

what photoreceptor has high visual acuity

cones

what photoreceptor responds to color

cones

what photoreceptor is concentrated mostly in fovea

rods

what photoreceptor is concentrated mostly in the macular region

in the dark

when does the membrane depolarize in the visual system

* pupil constriction (closes)
* bleaching of rhodopsin
* lack of calcium disinhibits guanylate cyclase

what are the mechanisms of light adaptation

horizontal cell in the retina

inhibitory, releases GABA

* cell depolarizes
* glutamate releases

what happens to OFF-center bipolar cells in the dark

* mGLU-Rs) opens K channel
* cell hyperpolarizes
* no glutamate releases

what happens to ON-center bipolar cells in the dark

* glutamate turns off
* bipolar cell returns to resting potential (hyperpolarized)
* no glutamate releases

what happens to OFF-center bipolar cells in the light

* glutamate turns off (turning off inhibition)
* cells depolarize
* glutamate releases

what happens to ON-center bipolar cells in the light

small hyperpolarization

white light covering center and surround

small depolarization

black light covering center and surround

big hyperpolarization

white light covering center, black light covering surround

large depolarization

black light covering center, white light covering surround

* sharpens edges by enhancing contrast
* edges are enhanced to extract form
* focus most processing on edges, interpolate flat areas

what is lateral inhibition good for

peripheral vision of left side is lost

what happens when the optic nerve on the left is cut

vision lost in right visual field of each side

what happens when the optic tract on the left is cut