Receptors are specific....
- only detect 1 particular stimulus.
- some receptors are cells e.g. photoreceptors.
- some receptors are proteins on cell surface membranes e.g. glucose receptors.
- mechanorepectors- pick up mechanical stimuli e.g. pressure.
- contain en of a sensory neurone wrapped in layers of lamellae.
- Pressure squashes the lamellae & presses on the neurone ending.
- Sodium channels open, sodium diffuses into cell, & a generator potential is produced.
- If this gets to be larger than the threshold value, an action potential is produced.
- Light enters eye through pupil (iris muscles control the amount let through).
- The lens focuses the rays onto the retina at the back of the eye.