Answer:
Role of Na+ in the Generation of Action Potential When a stimulus is applied to a nerve, the membrane of the nerve becomes freely permeable to Na+. This leads to a rapid influx of Na+ followed by the reversal of the polarity at that site, i.e., the outer surface of the membrane becomes negatively charged and the inner side becomes positively charged. The electrical potential difference across the plasma membrane at the membrane is called the action potential, which is in fact termed as a nerve impulse. Thus, this shows that Na+ ions play an important role in the conduction of nerve impulse.
(b) Mechanism of Generation of Light-Induced Impulse in the Retina Light induces dissociation of the retinal from opsin resulting in changes in the structure of the opsin. This causes membrane permeability changes. As a result, potential differences are generated in the photoreceptor cells. This produces a signal that generates action potentials in the ganglion cells through the bipolar cells. These action potentials (impulses) are transmitted by the optic nerves to the visual cortex area of the brain, where the nerve impulses are analysed and the image formed on the retina is recognized.
(c) Mechanism through which a Sound Produces a Nerve Impulse in the Inner Ear In the inner ear, the vibrations are passed through the oval window on to the fluid of the cochlea, where they generate waves in the lymphs. The waves in the lymphs induce a ripple in the basilar membrane. These movements of the basilar membrane bend the hair cells, pressing them against the tectorial membrane. As a result, nerve impulses are generated in the associated afferent neurons. These impulses are transmitted by the afferent fibres via auditory nerves to the auditory cortex of the brain, where the impulses are analysed and the sound is recognised.
You need to login to perform this action.
You will be redirected in
3 sec
