Receptors Flashcards
What does the Pacinian corpuscle detect?
Changes in pressure
What are the layers around the Pacinian corpuscle called?
Lamellae
Explain how a Pacinian corpuscle produces a generator potential in response to external pressure.
- Pressure on the skin stretches the membrane
- Causes stretch-mediated sodium ion channels to open
- Sodium ions diffuse in down a concentration gradient causing depolarisation (generator potential)
Explain the effects of a greater pressure on the Pacinian corpuscle.
Greater pressure, more stretch-mediated sodium ion channel proteins open, larger generator potential is produced.
Where are the rods distributed?
Throughout the macula
Where are the cones distributed?
Densely packed in the fovea
What is the photosensitive pigment in rod cells called?
Rhodopsin
Which wavelengths of light are rod cells sensitive to?
All wavelengths of light
How many types of cone cells are there?
3 - Red, Blue, Green
What does each cone detect?
A specific wavelength of light
What is the photosensitive pigment in cone cells called?
Iodopsin
What do rod cells have high visual sensitivity to?
Low levels of light intensity
Why do rod cells have a low visual acuity?
- Retinal convergence (leads to spatial summation)
- Several rods share a single bipolar neurone
- Light that falls on several rod cells only generates one impulse to the brain
- The brain can’t distinguish between the separate light sources that generated them
Why do cone cells have a high visual acuity?
- Each cone cell synapses with a single bipolar neurone
- Cones send separate sets of impulses to the brain
- The brain can distinguish between the light sources that generated them
Why do cone cells have a low sensitivity to low levels of light intensity?
Iodopsin is less sensitive than rhodopsin so requires a higher light intensity of photons per second. Only releases enough neurotransmitter to reach threshold in high light intensities.
