14.4- RECEPTORS

Question 1

How does the CNS receive sensory info?

Answer 1

from its internal + external environment through variety of receptors, each type responding to different + specific type of stimulus

Question 2

What is the function of receptors?

Answer 2

sensory reception

Question 3

What does sensory perception involve?

Answer 3

making sense of information from receptors

Question 4

What is sensory perception largely a function of?

Answer 4

the brain

Question 5

What does the Pacinian corpuscle respond to?

Answer 5

changes in mechanical pressure

Question 6

What is the Pacinian corpuscle specific to?

Answer 6

specific to single type of stimulus

Question 7

What stimulus is the Pacinian corpuscle specific to?

Answer 7

responds only to mechanical pressure

Question 8

What does the Pacinian corpuscle produce?

Answer 8

generator potential by acting as transducer

Question 9

What do all stimuli involve a change in?

Answer 9

change in some form of energy

Question 10

What is the role of the transducer?

Answer 10

convert change in form of energy by stimulus into form, namely nerve impulses that can be understood by body

Question 11

What does the stimulus always involve?

Answer 11

change in some form of energy, e.g. heat, light, sound, or mechanical energy

Question 12

What do receptors transduce?

Answer 12

one form of energy into another

Question 13

What do receptors in the nervous system convert energy of the stimulus into?

Answer 13

nervous impulse known as generator potential

Question 14

What does the Pacinian corpuscle transduce?

Answer 14

mechanical energy of stimulus into generator potential

Question 15

Where do Pacinian corpuscles occur?

Answer 15

deep in skin

Question 16

Where are Pacinian corpuscles most abundant in? (3)

Answer 16

most abundant on fingers, soles of feet and external genitalia

Question 17

Where else do Pacinian corpuscles occur?

Answer 17

joints, ligaments and tendons

Question 18

What do Pacinian corpuscles do in joints, ligaments + tendons?

Answer 18

enable organism to know which joints changing direction

Question 19

Where is the single sensory neurone of a Pacinian corpuscle?

Answer 19

at centre of layers of tissue, each separated by gel

Question 20

What does the sensory neurone ending at the centre of the Pacinian corpuscle have?

Answer 20

special type of sodium channel in its plasma membrane

Question 21

What is the sodium channel in the plasma membrane of the sensory neurone ending at the centre of the Pacinian corpuscle called?

Answer 21

stretch-mediated sodium channel

Question 22

Why are stretch-mediated sodium channels called so?

Answer 22

as their permeability to sodium changes when they’re deformed

Question 23

How are the stretch-mediated sodium channels of membrane around the neurone of a Pacinian corpuscle in its normal (resting) state?

Answer 23

too narrow to allow sodium ions to passing along them

Question 24

What potential does the neurone of the Pacinian corpuscle have at normal (resting) state?

Answer 24

resting potential

Question 25

What happens when pressure is applied to the Pacinian corpuscle?

Answer 25

it's deformed + membrane around its neurone becomes stretched

Question 26

What does the stretching of the membrane when pressure is applied to the Pacinian corpuscle cause?

Answer 26

widens sodium channels in membrane + sodium ions diffuse into neurone

Question 27

What does sodium ions diffusing into the neurone cause?

Answer 27

influx of sodium ions changes potential of membrane (becomes depolarised) thereby producing generator potential

Question 28

What does the generator potential create?

Answer 28

creates action potential that passes along neurone + then, via their neurones, to CNS

Question 29

Where is the light receptor cells of the mammalian eye found?

Answer 29

on its innermost layer, the retina

Question 30

What are the two types of light receptor cells?

Answer 30

rod and cone cells

Question 31

What do rod and cone cells act as?

Answer 31

transducers

Question 32

How do rod and cone cells act as transducers?

Answer 32

by conserving light energy into electrical energy of nerve impulse

Question 33

What colour images do rod cells produce?

Answer 33

black and white

Question 34

Why do rod cells produce images in black and white?

Answer 34

as rod cells cannot distinguish different wavelengths of light

Question 35

Comparison of numbers of rod cells and cone cells?

Answer 35

rod cells more numerous than cone cells

Question 36

How many rod cells are connected to a single sensory neurone in the optic nerve?

Answer 36

many rod cells

Question 37

At what light intensity are rod cells used to detect light?

Answer 37

rod cells used to detect light of very low light intensity

Question 38

What must be exceeded before a generator potential is created in bipolar cells?

Answer 38

certain threshold value

Question 39

What is it called when a number of rod cells are connected to a single bipolar cell?

Answer 39

retinal convergence

Question 40

As there are many rod cells connected to a single bipolar cells, what does this increase the chance?

Answer 40

greater change that threshold value will be exceeded than if only single rod cells were connected to each bipolar cell

Question 41

As there are many rod cells connected to a single bipolar cell and so there is a greater chance of exceeding the threshold value, what does this mean? (hint- light intensity)

Answer 41

rod cells allows us to see in low light intensity

Question 42

In order to create a generator potential, what happens in the rod cells?

Answer 42

pigment in rod cells (rhodopsin) must be broken down

Question 43

What is a consequence of many rod cells linking to a single bipolar cell?

Answer 43

light received by rod cells sharing same neurone will only generate single impulse travelling to brain regardless of how many of the neurones stimulated

Question 44

What is the visual acuity of rod cells like?

Answer 44

low visual acuity

Question 45

What does it mean for rod cells to have a low visual acuity?

Answer 45

brain cannot distinguish between separate sources of light that stimulated them two dots close together cannot be resolved + so will appear as single blob

Question 46

How many different types of cone cells are there?

Answer 46

three different types

Question 47

What does each type of cone cell respond to?

Answer 47

each respond to different range of wavelengths of light

Question 48

How many cone cells are connected to a a bipolar cell connected to a sensory neurone in the optic nerve?

Answer 48

own separate bipolar cell connected to sensory neurone in optic nerve

Question 49

As each cone cell is connected to its own separate bipolar cell, what does this mean?

Answer 49

means stimulation of number of cone cells cannot be combined to help exceed threshold value + so create generator potential

Question 50

As a number of cone cells cannot combine to exceed the threshold value, what does this mean? (hint- light intensity)

Answer 50

cone cells only respond to high light intensity and not to low light intensity

Question 51

What is the pigment in cone cells?

Answer 51

iodopsin

Question 52

What light intensity does iodopsin require for it to be broken down?

Answer 52

higher light intensity

Question 53

How many different cone cells are there and what is each pigment like?

Answer 53

three different types of cone cell, each containing specific type of iodopsin

Question 54

As there are three different types of cone cells, each containing a specific type of iodopsin, what does this mean? (hint- wavelength)

Answer 54

each cone cell sensitive to different specific range of wavelenghts

Question 55

How many cone cells are connected to a single bipolar cell?

Answer 55

each cone cell has its own connection to single bipolar cell

Question 56

As each cone cells has its own connection to a single bipolar cell, what happens if two adjacent cone cells are stimulated?

Answer 56

brain receives two separate impulses

Question 57

When two adjacent cone cells are stimulated and the brain receives two separate impulses, what does this show?

Answer 57

brain can distinguish between two separate sources of light that stimulated the two cone cells

Question 58

What is the visual acuity of cone cells like?

Answer 58

good visual acuity

Question 59

What is the distribution of rod and cone cells described to be like?

Answer 59

uneven

Question 60

How is light focused in the eye?

Answer 60

focused by lens on part of retina opposite pupil

Question 61

What is the part of the retina opposite the pupil known as?

Answer 61

fovea

Question 62

What intensity of light does the fovea receive?

Answer 62

high intensity of light

Question 63

As the fovea receives a high intensity of light, what cells are present?

Answer 63

cone cells, but not rod cells found in fovea

Question 64

How does the concentration of cone cells change further from the fovea?

Answer 64

conc. of cone cells diminishes further away from fovea

Question 65

What is the light intensity at the peripheries like?

Answer 65

light intensity lowest

Question 66

What cells are found at the periheries?

Answer 66

only rod cells