Receptors
- Sensory receptors are specialised cells in the nervous system that detect physical stimuli and convert them into electrical signals (the generator potential)
- Sensory receptors tend to be specific to one type of stimulus because they have specialised structures that are specific to one type of physical property
- Pacinian corpuscles detect changes in pressure in the skin.
- Increases in pressure cause a deformation of the concentric rings of the Pacinian corpuscle, opening stretch-mediated sodium channels in the membrane. Sodium ions enter the sensory neuron, causing a generator potential which can trigger an action potential
Photoreceptors
- The retina contains photoreceptors which detect light- rods and cones.
Rods cells | Cones cells |
Detect light across the middle of the visible light spectrum | Three types of cone cells, which respond to red, green, and blue light |
More sensitive to low light intensities than cones | Comparing the responses from each type of cone receptor allows for colour vision |
Use the pigment rhodopsin to detect light | Use the pigment iodopsin to detect light |
More abundant than cone cells | Fewer numbers than rod cells |
Located more towards the periphery of the retina. Not present at the fovea | Concentrated at the fovea. Fewer at the periphery of the retina |
Multiple rod cells connect to a single bipolar cell | Cone cells connect to their own bipolar cell |
Provide poor visual acuity | Provide good visual acuity |