14.4: Receptors Flashcards
Pacinian corpuscle
A sensory receptor that responds to changes in mechanical pressure
Two features of sensory reception as illustrated by the Pacinian corpuscle
- specific to a single type of stimulus
- produces a generator potential by acting as a transducer
Transducer
Converts the change in a form of energy by a stimulus into a form that the body can understand eg: into nerve impulses.
The stimulus always involves…
… a change in some form of energy
For example: heat, light, sound, mechanical
Receptors (therefore) convert…
Receptors convert/ transduce one form of energy into another.
Generator potential
Depolarisation of the membrane of a receptor cell as a result of the stimulus.
How does the pacinian corpuscle act as a transducer
Transduces the mechanical energy of the stimulus into a generator potential.
Stretch-mediated sodium channel
A sodium channel in the plasma membrane of the sensory neurone in the pacinian corpuscle that changes its permeability to sodium when its deformed by stretching.
Where is the stretch-mediated sodium channel
In the membrane of the sensory neurone ending at the centre of the pacinian corpuscle
Transducer cells
Cells that convert a non-electrical signal
such as light or sound into an electrical (nervous) signal and vice versa.
Two main types of light receptor cells in the retina
Rod cells
Cone cells
Both rod and cone cells act as…
…transducers by conserving light energy into the electrical energy of a nerve impulse.
Rod cells
Can’t distinguish between different wavelengths of light and therefore lead to images being seen only in black and white , more numerous than cone cells.
Many rod cells are connected to…
A single sensory neurone in the optic nerve
Rod cells use
To detect light of very low intensity.
Which cells are rod cells connected to where a generator potential can be created
Bipolar cells
Retinal convergence
And means that
Why?
A number of rod cells are connected to a single bipolar cell.
There is a much greater chance of the threshold value being exceeded.
Due to summation
What must happen in order to create a generator potential
Break down of the pigment in rod cells (rhodopsin)
Consequence of many rod cells linking to the same bipolar cell
Light received by rod cells sharing a neurone will only generate a single impulse regardless of how many of the neurones are stimulated. Therefore the brain can’t distinguish between separate source of light that stimulated them so rod cells have low visual acuity .
Cone cells respond to
High light intensity
The pigment in cone cells requires…
High light intensity to be broken down
Iodopsin
Each cone cell is sensitive to…
…a different specific range of wavelengths
Each cone cell has its own…
Therefore
…connection to a single bipolar cell.
Therefore cone cells have good visual acuity .
Distribution of rod and cone cell is
Uneven
Fovea
Point on the retina that the lens focuses light on opposite the pupil.
The fovea receives the…
High intensity of light
Which rod/ cone cells are found at the fovea and why
Cone cells
As the fovea receives the highest intensity of light
The concentration of cone cells diminishes away from…
…the fovea
Where are rod cells found
At the peripheries of the retina where light intensity is the lowest
