Receptors

Question 1

Sensory reception function

Answer 1

responding to a different and specific type of stimulus

Question 2

What do receptors act as

Answer 2

-transducer, producing generator potential

Question 3

define generator potential

Answer 3

depolarisation of the membrane of receptor cell as the result of the stimulus

Question 4

function of sensory perception

Answer 4

involves making sense of information from the receptors

Question 5

function of pacinian corpuscle

Answer 5

transduces the mechanical energy of the stimulus into a generator potential

Question 6

how does pacinian corpuscle produces a generator potential

Answer 6

by acting as a transducer

Question 7

features of pacinian corpusle

Answer 7

-specific to a single type of stimulus > mechanical pressure only
-produces a generator potential by acting as a transducer

Question 8

what does transducer do

Answer 8

convert change in form of energy by stimulus into nerve impulses

Question 9

where do pacinian corpuscle occur

Answer 9

-deep skin
-most abundant on fingers, soles of feet and genitalia
-occur in joins like ligaments and tendons too

Question 10

why is it important for pacinian corpuscle to occur in join

Answer 10

enable organisms to know which joints are changing directions

Question 11

where is the single sensory neurone of a pacinian corpuscle

Answer 11

centre of layers of tissue , each separated by gel

Question 12

what does the sensory neurone ending of pacinian corpuscle have

Answer 12

sodium channel in its plasma membrane (known as stretch-mediated sodium channel)

Question 13

why are they called stretch-mediated sodium channel

Answer 13

their permeability to sodium changes when they’re deformed eg stretching

Question 14

how pacinian corpuscle functions

Answer 14

-resting state = stretch mediated sodium channels pf membrane around neurone are too narrow to allow Na+ to pass along them > pacinian corpuscle has a resting potential

-pressure applied > PC is deformed and membrane around its neurone becomes stretched

-stretching widens the sodium channels in membrane and Na+ diffuses into neurone

-generator potential in turn creates an action potential (nerve impulse) that passes along neurone and then via other neurones to CNS

Question 15

establishment of generator potential

Answer 15

-pressure applied > layers distorted > causing stretch-mediated Na channels to open > Na+ enter axon of sensory neurone
-generator potential established, excess Na+ insiden end of axon which causes depolarisation of membrane
-if enough generator potential are produced then an action potential will be established and a nerve impulse move along axon

Question 16

where are light receptors on mammalian eye found

Answer 16

retina

Question 17

two types of receptor cells found in eye and what do they both do

Answer 17

-rod cells
-clone cells
-both act as transducers by conserving light energy into electrical energy of a nerve impulse

Question 18

what can’t rod cells distinguish

Answer 18

different wavelengths of light so images are only seen black and white

Question 19

What are rods?

Answer 19

cells which cannot distinguish between the different wavelengths of light and processes images in black and white

Question 20

what are many rod cells connected to

Answer 20

single sensory neurone in optic nerve

Question 21

what are rod cells used to detect

Answer 21

light of very low intensity

Question 22

why do rod cells respond to low-intensity light

Answer 22

-to create a generator potential the pigment (rhodopsin) must be broken down
-energy from low intensity light causes breakdown

Question 23

Why can rods detect light at very low intensities?

Answer 23

-certain value has to be exceeded before generator potential
-created in bipolar cells to which rod cells are connected to a single bipolar cell retinal convergence

Question 24

why is there a greater chance that threshold value will exceed than if only a single rod cell were connected to each bipolar cell

Answer 24

-summation

Question 25

consequence of many rod cells linking to single bipolar cell

Answer 25

-light received by rod cells sharing same neurone will only generate a single impulse travelling to brain regardless of how many neurones are stimulated
-so brain cannot distinguish between seperate sources of light that stimulated them
-so rod cells give low visual acuity
-so get low resolution to the image produced by brain

Question 26

how many cone cells are there

Answer 26

3 that respond to a different range of wavelengths of light
-depending on proportion of each type that is stimulated, we can perceive images in full colour

Question 27

how many cone cell is attached to
a bipolar cell

Answer 27

1

Question 28

problem of 1 cone cell being attached to a bipolar cell that is connected to a sensory neurone

Answer 28

-stimulation of a number of cone cells cannot be combined to help exceed threshold value and so create a generator potential
-so cone cells only respond to high light intensity

Question 29

what does it mean if cone cells contain different types of pigment (iodopsin)

Answer 29

-iodopsin requires a higher light intensity for its breakdown
-high intensity light will provide energy for break it down and create generator potential

Question 30

what does it mean if there are 3 different types of cone cells

Answer 30

-each contain specific iodopsin so each cone cell is sensitive to a different specific range of wavelengths

Question 31

what does it mean if 2 adjacent cone cells are stimulated

Answer 31

-brain receives 2 separate impulses
-so brain can distinguish between the two separate sources of light that stimulated the 2 cone cells
-giving accurate vision as they have good visual acuity

Question 32

what’s the distribution of rod and cone cells on retina like

Answer 32

uneven

Question 33

where are cone cells found and why

Answer 33

-fovea
-as they receive the highest intensity of light because light is focused by lens on part of retina opposite pupil
-conc of cone cells diminishes further away from fovea