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oThese mammals emit sounds and wait to see how long until the waveshit objects and return to the animal to determine their location: echolocation.oSonar and radar are based on echolocation. Body positions and movement are detected by systems associated with hearing systems: using calcium carbonate crystals to detect vibrations also helps other organs detect body positions in space and movement such as acceleration. Statocyst is a structure that allows more invertebrates to align themselves with gravity. Stathocysts contain ciliated hair cells with cilia attached to gelatinous membranes with crystals of calcium carbonate.oThe stones/statholiths increase the mass of the gelatinous membranes so it will be able to bend the cilia when direction changes.
A similar structure is found in the inner ear of vertebrates: the labyrinth is surrounded by bone and perilymph.Structure of the labyrinth and semicircular canals: the receptors for gravity in the membranous chambers of the labyrinth are the utricle and the saccule. Within these structure are the hair cells with stereocilia and kinocillium (like in the lateral line of fish): the hair like processes are embedded in the gelatinous material, the otolith membrane containing calcium carbonate crystals. oThe utrical is more sensitive to horizontal movement and the saccule to vertical movement. In both cases the acceleration cause the stereocilia to bend and produce action potentials in the associated neuron. The membranous labyrinth of the utricle and saccule are continued over to the semicircular canals that are oriented in three different planes so that angular acceleration from any direction can be detected. At the ends of the canals are swollen chambers called ampulae and the cilia of another group of hair cells protrude. The tips of the cilia are embedded with gelatinous material called cupula that protrude into the endolymph fluid of each semicircular canal. When the head rotates the fluid in the semicircular canal pushes against the cupula and causes the cilia to bend. Depending on the direction the cilia are bent it causes a depolarization or hyperpolarization.Vestibular apparatus is the saccule, utricle, and semicircular canals. Saccule and utricle provide a sense of linear acceleration and the semicircular canal provides a sense of angular acceleration.oThe brain uses info from the vestibular apparatus to know about the body’s position and to maintain equilibrium. 43.4 Chemoreceptors: taste, smell, and pHChemical receptors bind to chemicals or ligands in the extracellular fluid. The response to the chemical signals is that they produce action potentials, which is because of stimulation that associated neurons cause depolarization.Taste (gustation) is a combination of physical and psychological factors. There are five categories: sweet, sour, umami (glutamate and other amino acids), bitter, and salty.