P/S: Sensation and Perception

Question 1

What binocular cue stems from our eyes being 2.5 inches apart?

Answer 1

Retinal Disparity

Question 2

How do our eyes focus on things far away vs. close to us? What term describes this phenomenon?

Answer 2

Things far away, eyes are relaxed. Things close to us, eyes contract.

This is known as convergence.

Question 3

What term describes a 2 vs. 2.05 lb weight feeling the same while a 2 vs. 2.2 lb weight difference feels different?

Answer 3

The threshold at which you’re able to notice a change in any sensation is the Just Noticeable Difference.

Question 4

If a person can barely detect a temperature change from 25°F to 27°F, will they be able to barely detect a temperature change from 70°F to 72°F. What term describes this?

Answer 4

No. A change of 2°F represents an 8% change from 25°F but only a 2.8% change from 70°F. A 5.6°F change from 70°F would be necessary to detect the change. Weber’s Law.

Question 5

Distinguish between the absolute threshold of sensation and the difference threshold or JND?

Answer 5

Absolute threshold of sensation = The minimum intensity of stimulus needed to detect a particular stimulus 50% of the time

Difference Threshold (JND) = smallest difference that can be detected 50% of the time.

Question 6

What term describes stimuli below the absolute threshold?

Answer 6

subliminal

Question 7

What are the semicircular canals filled with?

Answer 7

The semicircular canals are filled with endolymph, and causes it to shift – allows us to detect what direction our head is moving in, and the strength of rotation.

Question 8

Which structures allow us to detec linear acceleration and head positioning?

Answer 8

Otolithic organs (utricle and saccule) help us to detect linear acceleration and head positioning. In these are Ca²⁺ crystals attached to hair cells in viscous gel. If we go from lying down to standing up, they move, and pull on hair cells which triggers AP.

Question 9

Label the 3 ossicles (name them in order, from outside in), Vestibular Nerve (CN?), Cochlear Nerve (CN ?), Tympanic Membrane, Oval Window, Round Window, Cochlea, Semicircular Canals

Answer 9

Cochlear + Vestibular Nerves → CN 8

Question 10

Label the following cross section of the cochlea:

Answer 10

Question 11

Label below. Additionally, where is endolymph and where is perilymph?

Answer 11

Question 12

What are two difference between endolymph and perilymph?

Answer 12

Endolymph:

• intracellular
• ↑potassium

Perilymph:

• extracellular
• ↓low potassium

Question 13

Signal detection theory involves discerning between what two things?

Answer 13

ooks at how we make decision under conditions of uncertainty – discerning between important stimuli and unimportant “noise”

Question 14

In signal detection theory, what is the difference between conservative and liberal strategies for detecing important stimuli?

Answer 14

Conservative = always say no unless 100% sure signal is present. Lots of misses.

Liberal = always say yes, unless 100% sure signal is not present. Lots of false alarms.

Question 15

Gestalt Principles: What term describes similar items being grouped together?

Answer 15

Similarity

Question 16

Gestalt Principles: How does pragnanz differ from proximity?

Answer 16

Pragnanz – reality is often organized reduced to simplest form possible (Ex. Olympic rings)

Proximity – objects that are close are grouped together.

Question 17

Gestalt Principles: How does Continuity differ from Closure?

Answer 17

Continuity – lines are seen as following the smoothest path.

Closure – objects grouped together are seen as a whole.

Question 18

Label the cornea, lens, sclera, pupil, iris, aqueous humor, virteous humor, ciliary muscles, retina, optic nerve, optic disc and fovea. Describe the functions of the bolded items.

Answer 18

1) Cornea - the round, transparent area that allows light to pass into the eye.
2) Lens - the transparent structure that focuses light onto the retina.
3) Retina - inner membrane of the eye that receives information about light using rods and cones. The functioning of the retina is similar to the spinal cord - both act as a highway for information to travel on.
4) Iris - a circular muscle whose pigmentation gives the eye its colour and whose contraction lets the eye adapt continuously to changing light conditions
5) Pupil - opening at the center of the iris which controls the amount of light entering the eye. Dilates and Constricts.

Question 19

What is the wavelength of violet light? What is the wavelength of red light?

Answer 19

Violet (400nm) – Red (700nm)

Question 20

What happens when light hits a rod cell?

Answer 20

• There are 120 million rods, for night vision
  
  • Light comes in, goes through pupil, and hits rod. Normally rod is turned on, but when light hits turns off.
  • When rod is off, it turns on a bipolar cell, which turns on a retinal ganglion cell, which goes into the optic nerve and enters the brain.

Question 21

How many rods vs. cones are there in the eye?

Answer 21

There are 120 million rods, for night vision. There are 6-7 million cones (3 types: red, green, blue). Almost all cones are centered in fovea.

Question 22

What molecule is activated by light in a rod?

Answer 22

Rhodopsin, a multimeric protein with 7 discs, contains a small molecule called retinal (11-cis retinal). Photons cause it to change conformation from bent to straight. When retinal changes shape, rhodopsin changes shape.

Question 23

What does retinal do after being hit with photons?

Answer 23

Retinal dissociates from opsin and activates transducin.

Question 24

What does transducin do?

Answer 24

Transducin activates phosphodiesterase which decreases cGMP levels in cytosol.

Question 25

When are cGMP levels high in rods? What degrades cGMP?

Answer 25

cGMP levels in the cytosol are high in the dark. cGMP keeps sodium channels open so action potentials can occur onto bipolar cells.

Phosphodiesterase degrades cGMP, causing hyperpolarization.

Question 26

What are the three cells between the environment and the visual system?

Answer 26

1. Photoreceptor
2. Bipolar Cell
3. Retinal Ganglion cell

Question 27

While rods contain rhodopsin, what do cones have?

Answer 27

photopsin

Question 28

What visual feature does the parvocellular pathway and magnocellular pathway encode?

Answer 28

form - parvocelllular pathway

motion - magnocellular

Question 29

Compare the spatial and temporal resolution of the parvocellular pathway and magnocellular pathway.

Answer 29

parvocellular pathway – high spatial resolution, poor temporal resolution.

magnocellular pathway – high temporal resolution, poor spatial resolution.

Question 30

What is the stapes attatched to?

Answer 30

Oval Window

Question 31

Where along the basilar membrane is 20 Hz? 20,000 Hz? How is intensity coded?

Answer 31

Intensity is coded through the number of action potentials.

Base (near oval window): 20,000 Hz

Apex (near Helicotrema): 20 Hz

Question 32

What does the TRPV1 receptor do?

Answer 32

detects heat & pain

Question 33

Distinguish between A-delta fibres and C fibres

Answer 33

“Fast pain”, which goes away fairly quickly, comes from the stimulation and transmission of nerve impulses over A delta fibres, while “slow pain”, which persists longer, comes from stimulation and transmission over non-myelinated C fibres.

Question 34

Why can humans perceive pheromones?

Answer 34

While we have the vomeronasal organ (in the accessory olfactory epithelium), we do not have the acessory olfactory bulb.

Question 35

Which tastes rely on GPCR receptors?

Answer 35

Sweet, umami, and bitter cells GPCR receptors.

Sour and salty rely on ion channels. They bind to receptor directly, ex. NaCl binds to receptor and causes ion channel to open, and + ions outside flow in. Cell depolarizes and fires an AP.