Quiz #2: The Senses

define sensory transduction.

the process of converting various forms of energy located outside of the body (e.g. light rays, sound waves, mechanical forces, or chemicals) into neural signals

explain how conformation change in retina is responsible for light detection.

rhodopsin molecules in outer segment of a photoreceptor undergoes conformational change when struck by a photon

activation of rhodopsin then activates G-protein transducin --> phototransduction cascade is initiated

classify rhodopsin, transducin, and hyperpolarization as either G-protein couples receptor, G-protein, or downstream effects of G-protein cascade.

G-protein: transducin

G-protein coupled receptor: rhodopsin

G-protein cascade: hyperpolarization

provide examples of how structure informs function in the visual system.

during the G-protein cascade, amplification allows sensitivity to a single photon

describe unequal distribution of rods and cones on the retina and how different photoreceptor densities affect vision.

cones: centralized where you look, low density throughout retina with sharp peak in center of fovea

rods: present at high density throughout retina with decline in fovea

blind spot: no photoreceptors (rods or cones)

trace how objects in visual space are represented in the retina, after the optic chiasm and in the visual cortex (V1).

objects are inverted (both upside down & right/left mirroring)

distinguish the function of the dorsal stream from the ventral stream. evaluate which stream is defective in akinetopsia, prosopagnosia, or a new medical condition.

dorsal stream: localization and action
- involves motor/premotor cortex & posterior parietal cortex
- damage to dorsal stream can lead to akinetopsia

ventral stream: object identification
- involves inferior temporal cortex
- damage to ventral stream can lead to prosopagnosia

determine which stimulus would best activate neurons in the fusiform face area.

stimulus with facial characteristics, especially eyes

not species dependent (neuronal activity doesn't differ for varying species)

distinguish how the grandmother cell coding scheme differs from the population coding scheme in use of neurons, efficiency, and accuracy.

grandmother cell coding scheme:
- each person has a cell dedicated to recognizing/coding their face
- uses more neurons since each person needs their own cell for facial recognition

population coding scheme:
- collection of neurons talk to feature detectors (use subsets of cells for different people)
- requires more ACTIVE neurons
- more efficient

identify what sensory transduction must be deciphered in the auditory system.

convert sounds (specifically pressure waves in the air) located outside of the body into neural signals

provide an example of how structure informs function in the auditory system.

different levels of stiffness along the cochlea make it differentially sensitive to different frequencies of sound

describe the tonotopic map in the cochlea and auditory cortex.

high sound frequencies cause maximal vibrations near the cochlea's base

low pitch sounds cause max vibrations in the cochlea's apex

the tonotopic map is preserved in the auditory cortex (rostral part corresponds to apex; caudal part corresponds to base).

describe the relationship between calcium carbonate crystals and vestibular hair cells to vertigo.

when head moves, calcium carbonate crystals collide with vestibular hair cells --> bends vestibular hair cells, causing cells to depolarize

dislodged calcium carbonate crystals overactivate hair cells

even when head is upright & stationary, calcium carbonate crystals collide w/ vestibular hair cells

the brain receives constant neural impulses that the body is upside down/falling when in actuality the body is stationary

Identify the five basic taste and example of each.

umami (MSG)

bitter (bitter melon)

salt (salt)

sour (lemon)

sweet (cake)

Describe differences, if any, between the expression patterns of taste buds responsible for different tastes.

different taste buds do not have discrete expression patterns (intermixed throughout tongue)

Classify T1R1, T1R2, T1R3, T2R, gustducin, TRP-M5, and TRP-M4 as either G-protein coupled receptor, G-protein, or TRP channel. Recall the order in which they are activated in the gustatory system.

G-protein coupled receptor: taste receptors

umami: T1R1 + T1R3

sweet: T1R2 + T1R3

bitter: T2R

G-protein: gustducin

TRP channel: TRP-M5, TRP-M4

order:
1. chemical compound (food) enters
2. molecule binds to G-protein coupled receptor --> initiates signal transduction pathway
3. at the end of G-protein cascade, TRP-M5 or TRP-M4 channels open

Describe characteristics of TRP channels.

when open, it produces a short depolarization (positive potential)

non-selective cation channels

activated through diverse mechanisms (chemicals, temperature, light, sound, touch)

w/o TRP-M4 or TRP-M5, you would not be able to taste sweet, bitter, or savory

Explain why anosmia is common after car accidents.

anosmia is common after whiplash

delicate olfactory nerves entering vertically though the cribriform plate are severed

Analyze patterns of odorant receptor activation involved in odor detection.

an odor activates a specific combo of receptors

ex: how does someone smell onion odor
1. a molecule in onions activates a combo of dif receptors
2. olfactory sensory neurons are activated when receptors on it are activated
3. olfactory sensory neurons activate a region of the olfactory bulb (responsible for detecting chemicals structurally similar to onion molecule)

Describe the chemotopic map and distinguish it from the retinotopic map, tonotopic map (and homunculus).

chemotopic map: structurally similar odorants stimulate overlapping but distinct domains in the olfactory bulb

retinotopic map = mapping of visual input from retina to neurons

tonotopic map = mapping of auditory input

homunculus = distorted representation of body

Define nociception.

the ability to feel pain, caused by stimulation of a nociceptor

Provide examples of where capsaicin can be found.

capsaicin is the active ingredient in chilli peppers & pepper spray

Classify capsaicin as either a polar or nonpolar substance and apply this knowledge to best extract capsaicin.

capsaicin = nonpolar (hydrocarbon chains)

nonpolar molecules do not dissolve well in polar solutions like water (like dissolves like)

dissolves better in nonpolar solutions like oil

Identify the receptor for capsaicin, classify the receptor under its receptor class, and identify other triggers of this receptor.

capsaicin binds TRPV1 (type of transient receptor potential ion channel)

TRPV1 receptors respond to heat & produce burning pain sensations

TRP channels are gated by temperature & various chemical ligands

Distinguish antagonists from agonists, and apply this knowledge to protection against capsaicin.

agonist: drug that mimics endogenous ligand and activates receptor

antagonist: drug that blocks endogenous ligand or agonists from activating receptor

capsaicin antagonist would be antidote to capsaicin (blocks capsaicin from binding to receptor)

Discern whether a particular input would or would not be able to activate touch receptors.

we detect touch through:
- finger position, lateral movement
- edges, fine details, points
- skin stretch
- pressure
- light touch
- itch
- vibration

Describe how touch receptors differ.

touch receptors differ from where they're located in the skin, what touch stimuli activate them, & in their receptive fields

Recall how receptive field size affects touch sensitivity (tactile acuity).

tactile acuity highest when receptive fields are small

Distinguish C fiber and A-delta sensory fibers in conduction speed, thickness, myelination, and usage.

slow C-fibers: thin, unmyelinated neurons; slow conduction velocity & duller pain

fast A-delta fibers: myelinated neurons; fast conduction velocity & sharp initial pain

Apply principles of topographic organization in order to predict body part representation in a homunculus of a novel organism.

spatially adjacent stimuli on sensory receptor surfaces are represented in adjacent positions in the cortex

there is larger representation for skin with smaller receptive fields