Answer: Touch.
Step-by-step explanation:
Cilia are short, mobile prolongations which contain a central structure made up of microtubules and proteins, enveloped by the cytosol and the plasma membrane. They are involved in cell movement, transport of materials, displacement of fluids, among others. Cilia are important for many biological processes, such as the senses of taste, hearing, smell, sight and balance.
For example, each taste bud of the tongue is made up of a set of cells, among which are the taste cells that have cilia that come into contact with the substances dissolved in the mouth by saliva. As for the sense of hearing, when there is a sound, the endolymph in the cochlea moves and this stimulates the cilia of the internal sensitive cells, which communicate with the acoustic nerve that informs the brain of what the sound is like. In the sense of smell, the receptors are the olfactory cilia of the olfactory neurons, which are located in the mucosa of the upper portion of the nostril, above the level of the superior concha. In the sense of vision, cones and rods are the two types of photoreceptor cells that capture light energy and convert it into electrical signals. They are highly specialized cells and can be differentiated into several regions: an outer segment, an inner segment containing the nucleus and a synaptic terminal. The outer segments are modified cilia and consist of flattened membranous sacs or disks. As for the balance system, the vestibular system consists of the utricle and the saccule, which are chamber-shaped organs filled with endolymph. The maculae of the saccule are located in a vertical plane and effectively capture the accelerations of the upward and downward movements of the head, and therefore of the gravitational forces. The hair cells of the maculae are responsible for transforming the mechanical energy produced by movement into nerve signals. The activity of these cells is determined by their morphofunctional polarization or ciliary organization, which is different in the utricle and in the saccule.
Thus, the only sense that does not depend on cilia to transmit stimuli is touch. The skin contains nerve endings, as well as glands, blood vessels and hair follicles. These nerve endings detect pain, touch, pressure and temperature.