The perceived information can be divided into groups; corresponding to the receptors that respond to these stimuli:
- Mechanoreceptors respond to mechanical stimuli, ie pressure, contact, strain or vibration. They convey the tactile perception (sense of touch) and - together with the sense of balance in the inner ear - the proprioception, ie the position and movement of the limbs in space (posture and sense of power). Also, the blood pressure measuring baroreceptors in the body and the hairs of the auditory cells in the inner ear (which respond to their bending as a result of sound waves) belong to the mechanoreceptors.
- Thermoreceptors detect temperature differences, with special probes for both cold and heat.
- Chemoreceptors measure the concentration of dissolved substances in body fluids. Known representatives of this group are the taste or olfactory receptors, others play an important role in the regulation of respiration (by measuring the oxygen or carbon dioxide distribution) or, as osmoreceptors, in the hormone, water and salt balance.
- Photoreceptors respond to light - especially important are the rods and cones in the retina that mediate vision.
- Pain receptors are present in the body almost everywhere and react quite nonspecifically to various stimuli such as heat, strong mechanical effects on body tissue (for example, bruising) or toxic chemical substances. They convey the sensation of pain (nociception).
At the headquarters - processing in the brain
Once the signals have been recorded, they are relayed via associated nerve pathways to the corresponding sensory centers in the brain. This first works as a filter to direct the vortex of information rushing in on sensible paths: Only a few sensory impressions pass through this sieve and are further processed. When you imagine how many blades of grass move in the wind on a meadow where you only notice the colorful butterfly, it becomes clear how important this selection is.
The perception arises regardless of the angle of view, the weather, the shape and color of the butterfly or whether we are 20 centimeters or 20 meters away - this shows the complex power behind these first steps. The remaining stimuli must be processed and interpreted.
Our brain also uses memory - have I ever seen such a rocking fluttering thing? Is it a pair of pants on a leash, a balloon at the fair, a child on a wooden board?
It creates an image of the environment
Until the butterfly is recognized as such (and perhaps even as a peacock's eye determined), the brain has to work pretty well again. For this purpose, the stimuli arriving from the various sensory organs are coordinated and assembled into an overall view:
- Is the butterfly far away or can I hunt for it?
- Is he tall or short, red or yellow?
- Does he smell something, does he make noises when flapping his wings?
Perhaps one feels a pleasant feeling at his sight, because he evokes the memory of shared excursions with Grandpa.
So what ultimately emerges is an image of the environment, albeit one that shows only a small section and is subjectively shaped. To do this, the work of the brain depends not only on the experience, but also on the state of the organism (for example, hunger, fatigue, mood).