Unit 2: Role of Receptors Flashcards
What are pacinian corpuscles?
mechanoreceptors found in skin or joints.
What do pacinian corpuscles do?
they detect strong pressure and vibrations
How is the pacinian corpuscle specific?
It only response to mechanical pressure and not to any other stimuli.
How does the pacinian corpuscle act as a transducer?
it converts energy from the stimulus into a nervous impulse known as a generator potential. It transduces mechanical energy of the stimulus into a generator potential.
How do receptor cells pass on the information to sensory neurones?
It can synapse with the sensory neurone or sometimes the receptor cell is a sensory neurone itself.
Where are pacinian corpuscles found?
deep in the skin as well as in ligments and joints
Describe the structure of a pacinian corpuscle
a single sensory neurone at the centre surrounded by layers of flattened schwann cells and fluid called lamellae
What type of channel are present in the plasma membranes of pacinian corpuscles?
Stretch mediated sodium channels.
When do stretch mediated sodium channels change shapes?
When the permeability of sodium in the membrane changes.
What is the permeability of the stretch mediated sodium channels like at resting potential and why?
no permeable to sodium ions because the membrane around the neurone is too narrow for the ions to pass through
What happens when pressure is applied to the stretch mediated sodium channels? What does this cause?
the membrane changes shape and becomes stretched. Strecthing causes the sodium channels to widen, allowing Na+ to diffuse in.
When pressure is applied to pacinian corpuscle, the sodium channels stretch, allowing sodium ions to diffuse in. What does this cause?
A generator potential to be produced.
How is an action potential triggered?
When the generator potential reaches threshold potential
How is the eye a complex sense organ?
Because no only does it detect light, but it also regulates the intensity and focuses it to form sharp images.
Which part of the eye detects light?
photoreceptors in the retina
What are the two types of photoreceptors in the eye?
Rod cells and cone cells.
What is the name of the interneurones that rod and cone cells synapse with?
Bipolar neurones.
What cells do bipolar neurones synapse with?
ganglion cells and rod and cone cells.
The axons of which cells cover the inner surface of the retina?
ganglion cells.
What is the optic nerve made up of?
millions of ganglion axons.
What does the optic retina do?
connects the retina to the brain.
How many cone cells connect to one bipolar neurone?
one
How many rod cells connect to one bipolar neruone?
groups of up to 100 rod cells.
What is the linkage called between a bipolar cell and a photoreceptor (rod and cone cells)?
retinal convergence
Which part of the eye is referred to as the blind spot?
the optic nerve.
Why is it called the blind spot?
because it contains no photoreceptors.
Which part of the eye does light pass through?
the pupil
Which muscles control the amount of light entering the eye?
iris
What do the lens in the eye do?
focus light onto the retina
Which part of the eye contains lots of photoreceptors?
fovea
How is the eye an example of a transducer?
it converts light energy into a nerve impulse
What colour images do rod cells produce?
black and white
Why are black and white images produced in rod cells?
because rod cells cannot distinguish between the different wavelengths of light
Which part on the photoreceptor cells detcts light?
the membrane discs on the outer segment
What is rhodopsin?
a photoreceptor protein, pigment in rod cells.
In which photoreceptor cell is rhodopsin found?
rod cells
What happens when rhodopsin becomes illuminated?
the rhodopsin molecule changes shape and so is able to bind with sodium channels in the receptor cell membranes
What happens when rhodopsin binds to sodium channels?
allows sodium ions to diffuse in causing local depolarisation.
When is threshold potential reached in a rod cell?
When sufficient number of sodium channels open.
What happens when an action potential is triggered in a rod or cone cell?
the action potential is passed to the bipolar neurone and then to the ganglion cells in the retina.
How come rod cells are able to responds to low intensity light?
because many rods connected one bipolar cell so greater chance of exceeding generator potential to reach threshold potential.
Why do rod cells have a low visual acuity?
because many rod cells to one bipolar means the the light received by the rod cells will only generate one impulse. Unable to distinguish between separate light source.
How many types of cone cells are there?
3 types
Why are there three different types of cone cells?
because each one responds to a different wavelength of light
Why do cone cells only respond to high intensity light?
because only one cone cell to one bipolar so cannot use retinal convergence to exceed threshold potential.
What is the pigment in cone cells called?
iodopsin
What happens when two adjacent cone cells are stimulated?
two separate impulses are generated
Why do cone cells have high visual acuity?
because there is a high density of cone cells in the fovea and the 1:1 connections with the bipolar cells mean that it is able to tell the difference between separate impulses.
