Receptors

Question 1

generating a generator potential in a pacinian corpuscle

Answer 1

1) mechanical stimulus (pressure) deforms the lamellae and stretch mediated sodium ion channels
2) sodium ion channels open → sodium ions diffuse into the sensory neurone → more pressure → more sodium ion channels open → more sodium
ion in
3) if generator potential reaches threshold, action potential is triggered

Question 2

what does the pacinian corpuscle illustrate?

Answer 2

receptors only respond to one type of stimuli

Question 3

Rods and cones: fovea

Answer 3

RODS: absent at fovea, more at periphery of retina
CONES: concentrated at fovea, fewer at periphery of retina

Question 4

Rods : visual acuity

Answer 4

lower visual acuity
rods connected in groups to one neuron (retinal convergence)
spatial summation
many neurones stimulate one impulse
can’t distinguish between separate sources of light

Question 5

Cones : visual acuity

Answer 5

-cones have higher visual acuity
-one cone connects to one neurone
-two adjacent cone cells are stimulated, brain receives two separate impulses
-can distinguish between two separate light sources

Question 6

Rods : light sensitivity

Answer 6

• rods are more sensitive to light
• many rods are connected to one neurone (retinal convergence)
• spatial summation
• stimulation of each cell alone is insufficient whereas cells connected in groups mean threshold is more likely to be met

Question 7

Cones : light sensitivity

Answer 7

• cones are less sensitive to light
• one cone connects to one neurone
• no spatial summation

Question 8

Cones : sensitivity to colour

Answer 8

• allows colour vision
• 3 different types of cones
• has different optical pigments which absorb different wavelengths of light

Question 9

Rods : sensitivity to colour

Answer 9

• rods allow black and white vision
• only one type of pigment