6.2 Receptors

Question 1

how many types of stimuli do receptors respond to

Answer 1

a receptor only responds to a specific stimulus

Question 2

when resting - is the inside of the cell negative or postive

Answer 2

négative

Question 3

what is the potential difference when a cell is at rest called

Answer 3

resting potential

Question 4

what is resting potential generated by

Answer 4

ion pumps and protein channels

Question 5

what is a generator potential

Answer 5

• change in potential difference due to stimulus

Question 6

what happens to a cell when a stimulus is detected

Answer 6

cell membrane becomes excited and becomes more permeable so more ions can move in ans out of the cell which alters the PD

Question 7

what is the generator potential

Answer 7

change in potential difference due to a stimulus

Question 8

how is a bigger generator potential produced

Answer 8

from a bigger stimulus
membrane is more excited so bigger ion movement and PD change

Question 9

what is potential difference measured in

Answer 9

millivolts

Question 10

how is an action potential produced

Answer 10

if a generator potential reaches threshold level

Question 11

what is an action potential

Answer 11

electrical impulse along a neurone

Question 12

what are pacinian corpuscle

Answer 12

mechanoreceptors so detect mechanical stimuli

Question 13

what do pacinian corpuscle contain

Answer 13

end of a sensory neuron called sensory nerve ending which is wrapped in lamellae

Question 14

what happens when pacinian corpuscle is stimulated

Answer 14

• lamellae are deformed and press on sensory nerve ending
• causes sensory neurones cell membrane to stretch
• stretch mediated NA+ channels are deformed
• NA+ diffuses into cell causing a generator potential
• triggers action potential if threshold is reached

Question 15

what do sodium ions move into the axon by

Answer 15

facilitated diffusion

Question 16

what happens when there’s a bigger stimulus

Answer 16

more sodium ion channels open

Question 17

what are photoreceptors

Answer 17

receptors in eye that detects light

Question 19

where does light enter the eye

Answer 19

pupil

Question 20

what controls the amount of light entering the eye

Answer 20

iris

Question 21

what are light rays focused on in the eye

Answer 21

onto the retina by the lens

Question 22

what does the retina contain

Answer 22

photoreceptors

Question 23

what is the fovea

Answer 23

area of retina with lots of photoreceptors

Question 24

what carries nerve impulses from the photoreceptors (from retina to brain)

Answer 24

optic nerve

Question 25

what is the optic nerve

Answer 25

bundle of neurones

Question 26

where does the optic nerve leave the eye

Answer 26

blind spot

Question 27

what does the blind spot not have

Answer 27

photoreceptors so it’s not sensitive to light

Question 28

how do photoreceptors work

Answer 28

- light enters eye, hits photoreceptors and is absorbed by light sensitive optical pigments - light bleaches pigments, causing chemical change - membrane permeability to NA+ is altered - generator potential > action potential sent along bipolar neurone - this connects photoreceptors to optic nerve which takes impilsss to brain

Question 29

two types of photoreceptors

Answer 29

rods and cones

Question 30

where are rods found

Answer 30

periphal of retina

Question 31

where are cones found

Answer 31

fovea

Question 32

what colour do rods give information

Answer 32

monochromatic

Question 33

what cooour do cones give info in

Answer 33

trichromatic - colours

Question 34

what are the 3 different types of cones

Answer 34

red sensitive blue sensitive green sensitive

Question 35

are rod cells sensitive to light

Answer 35

yes

Question 36

why are rod cells sensitive to light

Answer 36

many rods join to one bipolar neurone so many weak generator potentials combine to reach threshold to form an action potential

Question 37

are cones sensitive to light

Answer 37

no

Question 38

why aren’t cones sensitive to light

Answer 38

one cone joins to one bipolar neurone so more light is needed to reach threshold and trigger an action potential

Question 39

what is visual acuity

Answer 39

ability to tell apart points that are close together

Question 40

do rods give low or high visual acuity

Answer 40

low

Question 41

why do rods give low visual acuity

Answer 41

many rods join to one bipolar neurone so light from two points can’t be told apart

Question 42

do cones give low or high visual acuity

Answer 42

high

Question 43

why do cones give high visual acuity

Answer 43

cones are close together and one cone joins to one bipolar neurone - when light from two points hit two cones, two action potentials go to the brain so two points can be distinguished as seperate