Lecture 15 part 1: intro to sensory system

Question 1

steps in sensory perception

Answer 1

reception, transduction/change to electrical signal+amplify, transmission (to brain), and perception/interpretation by brain

Question 2

sensory receptor cells contain ____

Answer 2

receptor proteins, to detect incoming stimulus

• all sensory receptors transduce incoming stimuli into changes in membrane potential
• ultimately stimuli are converted into APs in afferent neurons

Question 3

sensory receptors come in two forms

Answer 3

1. sensory receptor neuron

2. epithelial sensory receptor cell (AKA RECEPTOR PROTEINw/cell), which release neurotransmitters into afferent neurons

Question 4

senses other than big five

Answer 4

external:electroreception, magnetoreception, Internal: baroreceptors (blood pressure), body position, blood osmolarity

Question 5

classes of sensory receptors based on stim

Answer 5

telereceptors (distant stim: vision, hearing)
exteroceptors (stim outside the body: pressure, temp)
interoceptors (stim inside the body: blood pressure, temp, blood oxygen)

Question 6

class of receptors based on stim modality

Answer 6

chemoreceptors=chemicals
mechanoreceptors=pressure, movement, touch, hearing, balacnce, blood pressure
photoreceptors=light
electroreceptors=electrical fields
magnetoreceptors=magnetic fields
thermoreceptors=temperature
nociceptors=pain

Question 7

adequate stimulus

-polymodal receptors

Answer 7

• specific type of stimulus a receptor is sensitive to
• receptors that respond to several different stimuli with similar sensitivity (ie. ampullae of lorenzini in sharks detects electricity, pressure, and temp, or type C nociceptors in all animals, detecing noxious stimuli interpreted as pain

Question 8

sensory receptors encode four types of information

Answer 8

stimulus modality, location, intensity, and duration

Question 9

encoding modality and location of stim: labeled line theory

Answer 9

• each receptor connects to a specific sensory area of brain through one afferent neuron pathway
• brain interprets any signal coming from that receptor as being caused by a particular stim in that particular location (ie. sneezing when looking at the sun)

Question 10

stim location and receptive fields

Answer 10

• ie afferent neurons for touch sense have receptive field, which is the region of skin causing response in those neurons
• neurons with small receptive fields are more precise in location of stim
• large receptive fields detect stim across larger area, but with lower acuity
• acuity can be improved by overlapping receptive fields

Question 11

lateral inhibition

Answer 11

refines precision of stimulus by comparing signals coming from multiple receptor cells

Question 12

encoding stim intensity

Answer 12

-encoded by frequency of APs: high frequency=more intense stim

Question 13

limitations of stim intensity

Answer 13

-range of AP frequencies is limited, about 1000-fold range, whereas stimuli vary at a much greater range, about 1.4 million fold

Question 14

dynamic range:

Answer 14

range of stimulus intensities that a receptor cell can detect and encode (weakest stim produces response 50% of the time)

Question 15

the higher the dynamic range…

Answer 15

the less a receptor can discrimiate amongst small changes in intensity

Question 16

dynamic range vs discrimination: large dynamic range

Answer 16

-large change in stim causes a small change in AP frequency; therefore large dynamic range=poor sensory discrimination

Question 17

dynamic range vs discrimination: narrow dynamic range

Answer 17

-small change in stim causes large change in AP; therefore small dynamic range=good sensory discrimination

Question 18

stim intensity and range fractionation

Answer 18

-encoding high dynamic range and high discrimination requires groups of receptors working together to increase range without decreasing discrimination

Question 19

logarithmic encoding

Answer 19

allows a wide range of intensities to be encoded by a single receptor cell: fine discrimination at low intensities, and coarse at high

Question 20

encoding stimulus duration: tonic vs. phasic

Answer 20

tonic: produces APs as long as stimulus continues
phasic: produce APs only at the beginning (sometimes at the end) of the stimulus
(note: both are adapted to decrease frequency of APs if stim is maintained too long)

Question 21

Tonic receptors

Answer 21

tonic=slow adapting receptors:

• produce APs as long as stim occurs
• encode duratoin of stimulus
• adapted to decrease AP frequency if stim is prolonged

Question 22

Phasic receptors

Answer 22

phasic=rapidly adapting receptors

• produce APs at beginning
• encode when there is a change in stim, not the duration
• fast adaptation to change in stim
• encode both change and duration of the change of stim