Unit 7 - Functional Properties of Sensory Receptors

Question 1

overview

Answer 1

Question 2

Sensation =

Answer 2

ability to transduce, encode and perceive info from external and internal stimuli

Question 3

general sensory system

Answer 3

somatic sensation - mechanical, thermal and chemical stimulation

visceral sensation - internal organs (generally do not reach level of conscious awareness)

Question 4

special senses

Answer 4

vision

hearing

taste

smell

balance

Question 5

where is sensation perceived

Answer 5

in the cerebral cortex

Question 6

sensory pathway

Answer 6

from site of sensation to sensory cortex

periphery - 1st order - cell bodies in dorsal root ganglia

spinal cord or brainstem - 2nd order

brain (thalamus) - 3rd order - somatosensory cerebral cortex

Question 7

how are sensory receptors distinguished

Answer 7

form of peripheral terminal

sensitivity to particular stimuli (modality specific) - threshold e.g. nociceptors respond to pain

diameter of axon

presence of myelin sheath

Question 8

structure of nerves

Answer 8

Question 9

channels at nerves

Answer 9

Stimulate receptor - open ion channels - influx of Na+ ions into membrane - AP if reaches threshold

Question 10

categories of sensory afferents

Answer 10

Question 11

what is the receptive field

what does it determine

relationship between size of receptive field and no of afferents supplying the area

Answer 11

area over which stimulus results in change in rate of AP

determine spatial accuracy of sensory stimuli

different regions, different size of receptive fields

overlapping - summation at 2nd order neuron

inverse relationship between size of receptive field and no of afferents supplying the area ⇒ more receptors, smaller receptor fields

Question 12

2 point discrimination

Answer 12

minimum distance required to perceive 2 stimuli as distinct

Question 13

2 point discrimination - hand

Answer 13

Question 14

Answer 14

ANSWER IS ACTUALLY B

Question 15

Lateral Inhibition

Answer 15

enhances quality of sensory info

Enables us to finely tune our sensory input

Most activated receptor will transmit the most APs to somatosensory cortex

Question 16

adaptation =

Answer 16

code for stimulus duration

Question 17

rapidly adapting receptors

Answer 17

receptor potential decreases in response to sustained stimulus

on-off burst of AP

convey info on changes in ongoing stimulation

e.g. Pacinian corpuscle

(activated when you sat on the chair, no longer send signal, activate again if I stand up)

Question 18

slowly adapting receptors

Answer 18

sustained activity while stimulus present

convey info on spatial attribute of stimulus e.g. size, shape

e.g. nociceptors - painful stimulus - continuously fire

Question 19

Answer 19