The sense of sight constitutes our visual system. Photoreceptors pick up light impulses which – transformed into bioelectric signals – are relayed to the visual center in the brain. Disorders of the sense of sight are of a various nature, such as hyperopia, myopia or presbyopia or restriction of the field of vision caused by stroke, corneitis or retinopathy.
The sense of hearing
The sense of hearing or auditive system functions via acoustic sensors in the form of hair cells. Sound waves are caught by the auricle and directed into the cochlea in the internal ear. Here hair cells project into the cochlear duct, pick up the vibrations and relay them. About 90% of all information reaches the brain via the eyes and ears.
The sense of smell
To enable smelling, the nasal mucous membrane is equipped with olfactory epithelium in the upper part of the nasal cavity. The odorous substances are dissolved by the mucous and then excite the sensory cells. The sense of smell, the olfactory system, has a great influence on perception because many smells are immediately connected with experiences.
The sense of taste
The receptors for the perception of the tastes sweet, sour, bitter and salty are the taste buds of the tongue which relay the stimuli via different nerves to the brain. The sense of taste, the gustatory perception, is often impaired particularly in old age, which can influence the selection and intake of food and thus the nutritional state.
The skin
The skin is the largest sense organ and controls primarily important sensations with protective functions. Accordingly it has different receptors e.g. for the perception of pressure and vibration, of pain and temperature. As the integument and barrier against the environment it is however also susceptible to many diseases and injuries.
Receptors in muscles and joints
The classic five senses are not the sole methods of perception. Bit by bit it was discovered that existential information is taken in via receptors in muscles and joints as well as in inner organ systems such as the cardiovascular system, pulmonary system, gastro-intestinal tract, or renal system (visceral sensitivity).
