Receptors Flashcards
How is a generator potential generated in the Pacinian corpuscle
Pressure deforms lamellae and stretch-mediated sodium ion channels open
Sodium ions diffuse into sensory neurone
greater pressure causes more channels to open and more sodium ions to enter
Causes depolarisation, leading to a generator potential
If generator potential reaches threshold it triggers an action potential.
Differences between rods and cones
-More rods at periphery of retina and absent in fovea whereas cones are more concentrated at Fovea and fewer at periphery of retina
-One type of rod containing one pigment whereas Cones have 3 types of cones containing different pigments
-Rods connected in groups to one bipolar cell while only one cone joins one neurone.
-Rods very sensitive to light while cones less sensitive to light.
-Rods have low visual acuity whereas Cones have high visual acuity.
-Rods black and white while cones see colour.
explain the differences in sensitivity to light by rods and cones
Rods more sensitive
-as they are connected to one bipolar cell
-there is spatial summation
-so stimulation of each individual cell alone exceeds to generate action potential
Cones are less sensitive
-as one cone joins to one neurone
-so no spatial summation
Explain differences in visual acuity of cones and rods
Cones have high visual acuity
- as one cone joins to one neurone
-if two cones are stimulated brain receives 2 separate impulses so it can distinguish between 2 separate sources of light
Rods have lower visual acuity
-as rods connected in groups to one bi-polar cell
-more spatial summation
-due to many neurones generating impulses it cannot distinguish between separate sources of light
explain differences in sensitivity to colour
Cones allow colour vision
-as there are 3 types of cones
-different optical pigments absorb different wavelengths
-so stimulation of cones gives a range of colour perception.
Rods allow monochromatic vision
-as only have one type of cone
