Static equilibrium is due to -
Ans. is 'a' i.e., Macula o Static equilibrium is the special sense which interprets the position of the head permitting the CNS to maintain stability and posture when the head and body are not moving,o It is detected by mechanoreceptors in the utricle and saccule, which each contain a macula with the receptors for static equilibrium.o When head moves in reference to gravity, it is detected by mechanoreceptors in the macula and information is transmitted along the vestibular nerve to the brain for interpretation,Vestibular systemo Vestibular system is responsible for the maintainance of equilibrium.o The vestibular system can be divided into the vestibular apparatus and the central vestibular nuclei.Vestibular apparatus (Peripheral part of vestibular system)o The vestibular apparatus within the inner ear detects head motion and position and transduces this information to a neural signal. The vestibular apparatus has following parts1) Peripheral receptors in membranous labyrinthA) Utricle and sacculeo These are also called otolith organs or macula. Otolith organ acts as stretch receptors Q and gravity acts as a stimulus Q. It has two main parts, i) Sensory neuroepitheliumSensory neuroepithelium contains sensory cells, i.e. Type I (flask shaped) and Type II (cylindrical) cells. The sensory receptors (hair of sensory cells) respond toLinear acceleration QGravity QChange in position of headii) Otolith membraneIt is a gelatinous mass with embedded otoliths.Otolith/otoconia is made of crystals of calcium carbonate Q.B) Semicircular canalo It contains cristae at ampullated end of the ducts which intum contains sensory cells (Type I and Type II cells). The sensory receptor (kinocilium) of sensory cells respond to Angular Q /rotational accelerationQ and deacceleration.2) Vestibular nerve : -Central vestibular nucleio The fibres of vestibular nerve end in vestibular nuclei and some go to the cerebellum directly.
Macula
Cupula
End organ ofcorti
Cristae ampulla
Special Senses: Hearing and Equilibrium