In more advanced animals, the senses area unit perpetually at work, creating the animal responsive to stimuli—such as lightweight, or sound, or the presence of a chemical substance within the external surroundings—and watching info concerning the organism’s internal environment. All isobilateral animals have a sensory system, and therefore the development of any species’ sensory system has been driven by natural selection; so, sensory systems take issue among species per the strain of their environments. The shark, not like most fish predators, is electrosensitive—that is, sensitive to electrical fields created by different animals in its surroundings. whereas it’s useful to the current underwater predator, electrosensitivity may be a sense not found in most land animals.
Senses offer info concerning the body and its surroundings. Humans have 5 special senses: olfaction (smell), gustation (taste), equilibrium (balance and body position), vision, and hearing. in addition, we tend to possess general senses, conjointly referred to as somatosensation, that answer stimuli like temperature, pain, pressure, and vibration. proprioception sensation, that is Associate in Nursing organism’s sense of spatial orientation and balance, interoception (position of bones, joints, and muscles), and therefore the sense of limb position that’s wont to track somatic sense (limb movement) area unit a part of somatosensation. though the sensory systems related to these senses area unit terribly totally different, all share a typical function: to convert a stimulant (such as lightweight, or sound, or the position of the body) into Associate in Nursing electrical signal within the system. This method is termed sensory transduction.
There area unit 2 broad forms of cellular systems that perform sensory transduction. In one, a nerve cell works with a organ, a cell, or cell method that’s specialised to interact with and find a selected stimulant. Stimulation of the organ activates the associated neuron, that carries info concerning the stimulant to the central system. within the second style of sensory transduction, a nerve ending responds to a stimulant within the internal or external environment: this nerve cell constitutes the organ. Free nerve endings is stirred up by many totally different stimuli, so showing very little receptor specificity. for instance, pain receptors in your gums and teeth could also be stirred up by temperature changes, chemical stimulation, or pressure.