Receptors Flashcards
(16 cards)
What are receptors?
Receptors only respond to specific stimuli and come in different types: mechanoreceptors detect pressure, photoreceptors detect light, and chemoreceptors detect certain chemicals. They may be cells, or proteins specific to a type of molecule.
An example of a receptor is the Pacinian Corpuscle, describe this.
The Pacinian Corpuscle is a type of mechanoreceptor found in the skin which detects mechanical stimuli.
A pacinian corpuscle contains a sensory neuron ending which is wrapped in layers of connective tissue called lamellae.
How does the pacinian corpsucle work?
1) Pressure causes the lamellae to be deformed and press on the sensory neuron ending.
2) This increase in pressure deforms the stretch-mediated Na+ ion channels.
3) Na+ ion channels open and Na+ ions diffuse into the sensory neuron ending.
4) This depolarises the cell, creating a generator potential.
5) When the generator potential reaches the threshold, an action potential is triggered.
What is the resting potential?
The resting potential is the potential difference when the cell is at rest.
What is the generator potential?
The generator potential is the change in potential difference.
How are electrical impulses (action potentials) generated?
There is a potential difference between the inside and outside of the cell. When a stimulus is detected, the membrane becomes more permeable so ions diffuse across increasing the potential difference. If the generator potential is large enough, an action potential is triggered (an electrical impulse along a neuron).
How is the strength of a stimulus measured?
The strength of a stimulus is measured by the frequency of action potentials because action potentials are all the same size.
How do receptors work in the retina?
Light is detected by photoreceptors and absorbed by light-sensitive optical pigments. Then, the light bleaches the pigments, altering the membrane permeability to Na+ ions.
A generator potential is created. If it’s large enough and over the threshold, an action potential is created (an electrical impulse is sent along a bipolar neuron). The bipolar neuron connects to the optic nerve which takes impulses to the brain.
What are the two types of photoreceptors?
Rods, and cones.
What is the sensitivity to light levels of rods?
Rods have a high sensitivity to light levels because many rods connect to 1 bipolar neuron, so many weak generator potentials combine to reach the threshold and trigger an action potential, this is known as summation.
What is the sensitivity to light levels of cones?
Cones have a low sensitivity to light levels because only 1 cone connects to 1 bipolar neuron so it takes more light to reach the threshold and generate an action potential.
What is the sensitivity to colour of rods?
Rods have a low sensitivity to colour as rods are only sensitive to light levels.
What is the sensitivity to colour of cones?
Cones have a high sensitivity to colour because there are 3 different types of cones (red, green, and blue), each containing a different optical pigment. When they’re stimulated together in different proportions, you see different colours.
What is the visual acuity of rods?
Rods have a low visual acuity because many rods connect to 1 bipolar neuron meaning light from 2 points close together can’t be distinguish so a single impulse is sent.
What is the visual acuity of cones?
Cones have a high visual acuity because 1 cone connects to 1 bipolar neuron so separate impulses are sent. Many action potentials are triggered and the brain receives many impulses.
Where are rods and cones found?
There is a high concentration of rods in the peripheral parts of the retina, and there is a high concentration of cones in the fovea.
